VEGETATIVE PROPAGATION OF LIME (Citrus
aurantifolia Swingle) BY STEM CUTTINGS
By Eiman Ahmed Swelih B.Sc. (Agric.) Honours (1999) University of Khartoum
A thesis submitted to the University of Khartoum in partial fulfillment of
the requirements for the degree of Master of Science in Agriculture
Supervisor Prof. Abdelghafar El Hag Saeed
Department of Horticulture Faculty of Agriculture University of Khartoum
September - 2005
DEDICATION To my parents For lightening up the way To my sisters and brothers For the advice, consolation and fun To my nieces and nephews For a better future To my friends For wonderful memories to keep. To you all I dedicate this work
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Acknowledgement
Thanks are due forth and forward to Allah for easing my way towards knowledge and education.
Iam grateful to my supervisor, Prof. Abdel-Gaffar El Haj Said who never hesitated to share his time, knowledge and effort with me.
I would like to thank Dr. Ahmed Jamal, General Manager at the
River Nile State’s, Ministry of Agriculture and Mr. Mohammed Ahmed
Ibrahim, Manager of Horticultural Department at the same Ministry.
Both persons exerted enough time and effort to my work easier, Iam ever grateful to them.
Iam also thankful to the cheerful, faces of the family of School of
Gardening and Nutrition Education Department, namely Mr. Abdallah
Osman Nour Eldin, head of Department and Mr. Mohamed Majzoub,
Mr. Suliman Selmi Suliman and Mr. Hasson Ahemd Alballa.
Thanks are also due to Mr. Ali Yousif, Words will never describe how grateful Iam.
Finally, Iam thankful for every other person who made this work asuccess, Dr. Mubarak Sir Elkhatim, Mr. Abdelnasir and Haitham and
Mss. Lila Mohamed Khair.
ABSTRACT
Three experiments were conducted in this study to investigate the effect of seasons, girdling and sowing interval after girdling on rooting of lime stem cuttings.
In the first experiment, 3 type of stem cuttings non girded, basal and Apical cuttings were taken from lime at summer season in different weeks interval (2, 4, 6, 8 and 10) weeks after girdling. All cuttings were planted in sand soil in plastic trays and then kept under plastic covered frames under lathe- house conditions.
In this experiment, basal cuttings resulted in better values of percentage, number of roots, length of roots, number of new roots and growth vigor compared to non girdling and apical cuttings.
Percentage of rooted cuttings and other parameters measured were influenced by time in which cuttings were taken. The highest percentage of rooted cuttings was obtained with cuttings taken 10 weeks after girdling and this may be attributed to the increase in quantity of carbohydrates and other rooting cofactors with the gradual increase in sowing interval after girdling.
In the second experiment, the same procedures above in experiment (1) was repeated during autumn. The results showed that apical cuttings resulted in betters values of all parameters measured except number of new roots where basal cuttings gave better values of number of new roots.
The highest values of root length, number of new roots and growth vigor were obtained from cuttings taken 2 weeks after girdling while cuttings taken 10 weeks after girdling gave better value of percentage of rooted cuttings. On the other hand the greatest number of roots was obtained with cuttings taken 6 weeks after girdling.
In the third experiment which is the last one, the above procedures was repeated again during winter. The results revealed that apical cuttings resulted in better values of all parameters measured while cuttings taken 4 weeks after girdling gave better values of all parameters measured except percentage of rooted cuttings where cuttings taken 8 weeks after girdling gave the highest percentage of rooted cuttings.
The highest percentage of rooted cuttings of lime was obtained in autumn (46.2%) followed by winter (44.2%) and then summer (4.7%).
اﻟﺨﻼﺻﺔ
أﺟﺮﻳﺖ ﺛﻼﺛﺔ ﺗﺠﺎرب ﻓﻲ هﺬﻩ اﻟﺪراﺳﺔ ﻟﻤﻌﺮﻓﺔ ﺗﺄﺛﻴﺮ ﻓﺼﻮل اﻟﺴﻨﺔ، اﻟﺘﺤﻠﻴﻖ وﻓﺘﺮة
اﻟﺰراﻋﺔ ﺑﻌﺪ اﻟﺘﺤﻠﻴﻖ ﻋﻠﻰ إﻣﻜﺎﻧﻴﺔ اﻟﺘﺠﺬﻳﺮ ﻓﻲ اﻟﻌﻘﻞ اﻟﺴﺎﻗﻴﺔ ﻟﻠﻴﻤﻮن اﻟﺒﻠﺪي.
ﻓﻲ اﻟﺘﺠﺮﺑﺔ اﻷوﻟﻲ ﺗﻢ ﺗﺠﻬﻴﺰ ﺛﻼﺛﺔ أﻧﻮاع ﻣﻦ اﻟﻌﻘﻞ اﻟﺴﺎﻗﻴﺔ ، ﻋﻘﻞ ﻏﻴﺮ ﻣﺤﻠﻘﺔ ، ﻋﻘﻞ
ﻗﺮﻳﺒﺔ ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ ، ﻋﻘﻞ ﺑﻌﻴﺪة ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ ﻓﻲ ﻣﻮﺳﻢ اﻟﺼﻴﻒ وﺗﻤﺖ اﻟﺰراﻋﺔ ﺑﻌﺪ
أﺳﺎﺑﻴﻊ ﻣﺨﺘﻠﻔﺔ (2 ، 4 ، 6 ، 8 و 10) أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ. ﺟﻤﻴﻊ اﻟﻌﻘﻞ زرﻋﺖ ﻓﻲ ﺗﺮﺑﺔ رﻣﻠﻴﺔ
ﻓﻲ أوﻋﻴﺔ ﺑﻼﺳﺘﻴﻚ ﻣﻐﻄﺎة ﺑﻐﻄﺎء ﺑﻼﺳﺘﻴﻜﻲ ﺛﻢ وﺿﻌﺖ ﻓﻲ اﻟﻤﺸﺘﻞ.
أﻇﻬﺮت ﻧﺘﺎﺋﺞ هﺬﻩ اﻟﺘﺠﺮﺑﺔ أن اﻟﻌﻘﻞ اﻟﻘﺮﻳﺒﺔ ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ أﻋﻄﺖ أﻋﻠﻰ اﻟﻘﻴﻢ ﻓﻲ
ﻧﺴﺒﺔ اﻟﻨﺠﺎح ، ﻋﺪد اﻟﺠﺬور ، ﻃﻮل اﻟﺠﺬور ، ﻋﺪد اﻟﺠﺬور اﻟﺠﺪﻳﺪة، وﻗﻮة اﻟﻨﻤﻮ ﻣﻘﺎرﻧﺔ ﻣﻊ اﻟﻌﻘﻞ
ﻏﻴﺮ اﻟﻤﺤﻠﻘﺔ واﻟﻌﻘﻞ اﻟﺒﻌﻴﺪة ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ.
أﺛﺒﺘﺖ اﻟﺘﺠﺮﺑﺔ أن ﻧﺴﺒﺔ ﻧﺠﺎح اﻟﻌﻘﻞ وﺑﺎﻗﻲ اﻟﻘﺮاءات اﻟﺘﻲ أﺧﺬت ﺗﺘﺄﺛﺮ ﺑﺰﻣﻦ أﺧﺬ اﻟﻌﻘﻞ
ﺣﻴﺚ أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ 10 أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻋﻠﻰ ﻧﺴﺒﺔ ﻧﺠﺎح وهﺬا رﺑﻤﺎ ﻳﻌﺰى إﻟﻰ
إزدﻳﺎد آﻤﻴﺔ اﻟﻜﺎرﺑﻮهﻴﺪرﻳﺘﺎت وﻋﻮاﻣﻞ اﻟﺘﺠﺬﻳﺮ اﻷﺧﺮى ﺑﺎﻹزدﻳﺎد اﻟﺘﺪرﻳﺠﻲ ﻓﻲ ﻓﺘﺮة اﻟﺰراﻋﺔ
ﺑﻌﺪ اﻟﺘﺤﻠﻴﻖ.
ﻓﻲ اﻟﺘﺠﺮﺑﺔ اﻟﺜﺎﻧﻴﺔ ﺗﻢ ﺗﻜﺮار ﻧﻔﺲ اﻟﺨﻄﻮات اﻟﺘﻲ اﺟﺮﻳﺖ ﻓﻲ اﻟﺘﺠﺮﺑﺔ اﻷوﻟﻲ ﻓﻲ ﻓﺼﻞ
اﻟﺨﺮﻳﻒ. أﻇﻬﺮت اﻟﻨﺘﺎﺋﺞ أن اﻟﻌﻘﻞ اﻟﺒﻌﻴﺪة ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ أﻋﻄﺖ ﻗ ﻴ ﻤ ﺎً أﻋﻠﻰ ﻓﻲ آﻞ اﻟﻘﺮاءات
اﻟﺘﻲ أﺧﺬت ﻣﺎﻋﺪا ﻋﺪد اﻟﺠﺬور اﻟﺠﺪﻳﺪة ﺣﻴﺚ أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﻘﺮﻳﺒﺔ ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ ﻗ ﻴ ﻤ ﺎً أﻋﻠﻰ.
أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ إﺳﺒﻮﻋﻴﻦ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻓﻀﻞ اﻟﻨﺘﺎﺋﺞ ﻓﻲ ﻃﻮل اﻟﺠﺬور ،
ﻋﺪد اﻟﺠﺬور اﻟﺠﺪﻳﺪة وﻗﻮة اﻟﻨﻤﻮ، ﺑﻴﻨﻤﺎ أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ 10 أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻋﻠﻰ
ﻧﺴﺒﺔ ﻧﺠﺎح واﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ 6 أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻋﻄﺖ أﻓﻀﻞ اﻟﻘﻴﻢ ﻓﻲ ﻋﺪد اﻟﺠﺬور. ﻓﻲ اﻟﺘﺠﺮﺑﺔ اﻟﺜﺎﻟﺜﺔ واﻷﺧﻴﺮة ﺗﻢ ﺗﻜﺮار ﻧﻔﺲ اﻟﺨﻄﻮات أﻋﻼﻩ ﻓﻲ ﻓﺼﻞ اﻟﺸﺘﺎء أﻇﻬﺮت
اﻟﻨﺘﺎﺋﺞ أن اﻟﻌﻘﻞ اﻟﺒﻌﻴﺪة ﻣﻦ ﻣﻨﻄﻘﺔ اﻟﺘﺤﻠﻴﻖ أﻋﻄﺖ أﻓﻀﻞ اﻟﻨﺘﺎﺋﺞ ﻓﻲ آﻞ اﻟﻘﺮاءات اﻟﺘﻲ أﺧﺬت
ﺑﻴﻨﻤﺎ أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ 4 أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻋﻠﻰ اﻟﻘﻴﻢ ﻓﻲ آﻞ اﻟﻘﺮاءات اﻟﻤﺄﺧﻮذة
ﻣﺎﻋﺪا ﻧﺴﺒﺔ اﻟﻨﺠﺎح ﺣﻴﺚ أﻋﻄﺖ اﻟﻌﻘﻞ اﻟﺘﻲ أﺧﺬت ﺑﻌﺪ 8 أﺳﺎﺑﻴﻊ ﻣﻦ اﻟﺘﺤﻠﻴﻖ أﻋﻠﻰ ﻧﺴﺒﺔ ﻧﺠﺎح.
أﻋﻠﻰ ﻧﺴﺒﺔ ﻧﺠﺎح ﻟﻌﻘﻞ اﻟﻠﻴﻤﻮن اﻟﺒﻠﺪي أﺧﺬت ﻓﻲ ﻓﺼﻞ اﻟﺨﺮﻳﻒ (46.2%) ﻳﻠﻴﻪ ﻓﺼﻞ
اﻟﺸﺘﺎء (44.2%) ﺛﻢ ﻓﺼﻞ اﻟﺼﻴﻒ (%4.7).
LIST OF CONTENTS
Page
Dedication………………………………………………………………………………….. i
Acknowledgement ………………………….…………………………………………… ii
Abstract ……………………………………………………………………………………… iii
Arabic Abstract …………………………...……………………………………………… v
List of Contents ………………………..………………………………………………… vii
List of Tables………………………………….…………………………………………… xii
List of Figures …………………………..………………………………………………… xiii
1. Introduction…………………………………….…………….……………………… 1
2. LITERATURE REVIEW…….………………………………………………… 7
2.1. Cultural practices.………………………………………….……………………… 8
2.1.1. Planting.…………………………………………………………..………………… 8
2.1.2. Fertilization.……………………………………………..………………………… 10
2.1.3. Irrigation.…………………………………………………………………………… 11
2.1.4. Pruning.……………………………………………………………………………… 11
2.1.5. Harvesting.……………………………………….………………………………… 12
2.1.6. Propagation.…………………………………….………………………………… 13 2.1.6.1. Seed propagation of citrus trees.……………………………………… 14
2.1.6.2. Vegetative propagation of citrus trees.……………………………… 16
2.1.6.2.1. Propagation on a root stock.…………………………………..……… 18
2.1.6.2.2. Own – rooted trees.…………………………….………………………… 21
3. MATERIALS AND METHODS.…………………………………………… 30
3.1 Experimentation.……………………………………………….…………………… 30
3.2 Plant materials.……………………………………………………………………… 30
3.3 Experiment No. 1. Summer Experiment.…………………….…………… 30
3.4 Experiment No. 2. Autumn Experiment.………………………………… 31
3.5 Experiment No. 3. Winter Experiment.…………………………………… 31
3.6 Planting media.………………………….……………..…………………………… 31
3.7 Incubation conditions.………………..…………………………………………… 32
3.8. Parameters measured.……………………………….…………………………… 32
3.9 Experimental design and data analysis.………………………………… 33
4. RESULTS.………………………………………………………..…………………… 34
4.1. Summer experiments……………………………………………..……………… 4.1.1 Effect of girdling and sowing interval on percentage of rooted 34 lime stem cuttings…………….…………………………………………………..………
4.1.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings…………………………………………………..…………………… 37 4.1.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings………………………….…………………………………………… 40
4.1.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings…………………………………………………………… 40
4.1.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings………………………………………..……………………………… 45
4.2. Autumn experiments……………………………..……………………………… 48
4.2.1. Effect of girdling and sowing interval on percentage of rooted lime stem cuttings………………………………….………………………… 48
4.2.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings………………………………………..……………………………… 48
4.2.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings………………………………………...……………………………… 50
4.2.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings…………………………………………………………… 53
4.2.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings………………………………………...……………………………… 53
4.3. Winter experiments………………………………..……………………………… 57
4.3.1. Effect of girdling and sowing interval on percentage of rooted lime stem cuttings…………………………..………………………………… 57
4.3.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings……………………...………………………………………………… 57
4.3.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings……………………………..………………………………………… 59
4.3.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings…………………………….……………………………… 62
4.3.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings………………………………….…………………………………… 62
4.4. Effect of seasons, girdling and sowing interval on percentage of rooted lime stem cuttings………………………….……………………………… 66
4.4.1. Seasons……………………………………………………………………………… 66
4.4.2. Girdling…………………………………………..………………………………… 66
4.4.3. Sowing intervals………………………………………………………………… 66
4.5. Effect of seasons, girdling and sowing interval on number of roots of lime stem cuttings…………………………………………………………… 67
4.5.1. Seasons…………………………………………..………………………………… 67
4.5.2. Girdling………………………………………….………………………………… 67
4.5.3. Sowing intervals………………………………………………………………… 67
4.6. Effect of seasons, girdling and sowing interval on length of rooted lime stem cuttings……………………………………………………………… 70 4.6.1. Seasons………………………………………………………………………… 70
4.6.2. Girdling…………………………………………………………..………………… 70
4.6.3. Sowing intervals………………………………………………………………… 70
4.7. Effect of seasons, girdling and sowing interval in number of new roots of lime stem cuttings…………………………………………………… 72
4.7.1. Seasons……………………………………………………………………………… 72
4.7.2. Girdling…………………………………..………………………………………… 72
4.7.3. Sowing intervals………………………………………………………………… 72
4.8. Effect of seasons, girdling and sowing interval on growth vigor of lime stem cuttings…………………………………………………………………… 74
4.8.1. Seasons……………………………………………………………………………… 74
4.8.2. Girdling………………………………………………………………………… 74
4.8.3. Sowing intervals………………………………………………………………… 74
5. DISCUSSION………………………………………………………………………… 76
5.1 Effect of girdling on rooting of lime stem cuttings…….…………… 76
5-2 The effect of time of severing and planting lime cuttings on percent rooting…………………………………………….………………………….…… 78
5-3 The effect of shoot position……………………………….…………………… 82
REFERENCES………………………...………………………………………………… 86
LIST OF TABLES
Table Title No.
1a, b. Effect of seasons, sowing interval and girdling on percent
rooted lime stem cuttings………………………………. 35
2a, b. Effect of seasons, sowing interval and girdling on number
of roots of lime stem cuttings………………………… 38
3a, b. Effect of seasons, sowing interval and girdling on length
of root of lime stem cuttings…………………………… 41
4a, b. Effect of seasons, sowing interval and girdling on number
of new roots of lime stem cuttings………………… 43
5a, b. Effect of seasons, sowing interval and girdling on growth
vigor of lime stem cuttings……………………………… 46 LIST OF FIGURES Fig. Title No.
1. a Effect of girdling on percent rooted lime stem cuttings 36
b Effect of sowing interval on percent rooted lime stem
cuttings…………………………………………………………………… 36
2. a Effect of girdling on number of roots of lime stem
cuttings…………………………………………………………………… 39
b Effect of sowing interval on number of roots of lime
stem cuttings…………………………………………………………… 39
3. a Effect of girdling on length of roots of lime stem
cuttings…………………………………..……………………………… 42
b Effect of sowing interval on length of roots of lime
stem cuttings…………………………………..……………………… 42
4. a Effect of girdling on number of new roots of lime stem
cuttings…………………………………..……………………… 44
b Effect of sowing interval on number of new roots of
lime stem cuttings………………………..……………………..…… 44
5. a Effect of girdling on growth vigor of lime stem
cuttings…………………………………….……………..……………… 47
b Effect of sowing interval on growth vigor of lime stem
cuttings……………………….…………………..……………… 47
6. a Effect of girdling on percent rooted lime stem cuttings 49
b Effect of sowing interval on percent rooted lime stem
cuttings……………………………………..……………..……………… 49
7. a Effect of girdling on number of roots of lime stem
cuttings…………………………………..………………..……………… 51
b Effect of sowing interval on number of roots of lime
stem cuttings………………………….………………..……………… 51
8. a Effect of girdling on length of roots of lime stem
cuttings……………………………………….…………..……………… 52
b Effect of sowing interval on length of roots of lime
stem cuttings…………………………….……………..……………… 52
9. a Effect of girdling on number of new roots of lime stem
cuttings………………………………..…………..……………… 55
b Effect of sowing interval on number of new roots of
lime stem cuttings……………………..……………..……………… 55
10. a Effect of girdling on growth vigor of lime stem
cuttings…………………………………………….……..……………… 56
b Effect of sowing interval on growth vigor of lime stem
cuttings…………………………..………………..……………… 56
11. a Effect of girdling on percent rooted lime stem cuttings 58
b Effect of sowing interval on percent rooted lime stem
cuttings…………………………………………..………..……………… 58
12. a Effect of girdling on number of roots of lime stem
cuttings…………………………………………….……..……………… 60
b Effect of sowing interval on number of roots of lime
stem cuttings……….………………….………………..……………… 60
13. a Effect of girdling on length of roots of lime stem
cuttings……………………………………..……………..……………… 61
b Effect of sowing interval on length of roots of lime
stem cuttings………………………..…………………..……………… 61
14. a Effect of sowing on number of new roots of lime stem
cuttings………………………………………..…………..……………… 64
b Effect of sowing interval on number of new roots of
lime stem cuttings…………………………………..……………… 64
15. a Effect of girdling on growth vigor of lime stem
cuttings ……………………………………….…………..……………… 65
b Effect of sowing interval on growth vigor of lime stem
cuttings………………………….………………..……………… 65
16. a Effect of seasons on percent rooted lime stem cutting 68
b Effect of girdling on percent rooted lime stem
cuttings……………………………….…………………..……………… 68
c Effect of sowing interval on percent rooted lime stem
cuttings………………………..………………………………………….. 68
17. a Effect of seasons on number of roots of lime stem
cuttings……………………………………..……………..……………… 69
b Effect of girdling on number of roots of lime stem
cuttings………………………………….………………..……………… 69
c Effect of sowing interval on number of roots of lime
stem cuttings………………………..…………………..……………… 69
18. a Effect of seasons on length of roots lime stem cuttings 71
b Effect of girdling on length of roots lime stem cuttings 71
c Effect of sowing interval on length of roots lime stem
cuttings……………………………………….…………..……………… 71
19. a Effect of seasons on number of new roots of lime stem
cuttings………………………………….…..……………..……………… 73
b Effect of girdling on number of new roots of lime
stem cuttings……………………………..……………..……………… 73
c Effect of sowing interval on number of new roots of
lime stem cuttings………………..…………………..……………… 73
20. a Effect of seasons on growth vigor of lime stem
cuttings ……………………………….…………………..……………… 75
b Effect of girdling on growth vigor of lime stem
cuttings…………………………………..………………..……………… 75
c Effect of sowing interval on growth vigor of lime stem
cuttings……………………………………………………..……………… 75
1. INTRODUCTION
Lime (Citrus aurantifolia “Christm.” Swingle) a member of the
Rutaceae is extensively cultivated for its fresh juice and as flavouring for many foods of all citrus fruits lime is highest in percentage composition for acid in the juice ranging from 7 to 8 per cent (calculated as citric).
Much the greater part of the crop is marketed and consumed fresh. Other important commercial products include frozen limeade, carbonated beverages, marmalade, pickling, citric acid and lime oil from the peel being the principal by-product. Sour lime juice have been used in many place in the treatment and the prevention of scurvy.
Lime cultivation is confined to hot tropical, semi-tropical and sub tropical regions of the world where it is the most commonly cultivated species of the acid group of Citrus spp. being considered the most tropical of the commercially produced citrus fruits.
Limes can survive on poor soil and under neglected conditions and are thus widely grown in schools, hospitals and other government premises in Sudan. They succeed much better than lemons in humid climate. The fruits of limes are picked to size and hence largely immature. They require comparatively low heat to attain acceptable maturity during the summer month coinciding with the period of great market demand and thus high revenues. The tree of “Baladi lime” is fine–stemmed, thorny, with small leaves of distinct pale colour. It is markedly cold-sensitive and has a high total heat requirement for the production of fruit of good size.
Generally citrus trees are produced in most citrus growing areas by budding the scion of the desired variety onto the chosen seedling root-stock. Other methods of propagation used to a relatively limited extent in some areas include grafting, layering and cuttings. These methods are successfully practical under some conditions though they are more difficult, laborious, tedious and time consuming. They do not differ greatly from those usually used for the propagation of other fruit trees. Certain details, however, are unique and apply only to citrus.
In budding, the most important single factor that affect the production of vigorously growing citrus trees is the scion selection.
Primary emphasis is placed on selecting and using scion obtained from healthy mother trees (Optiz, 1960; Garnsey and Jones, 1967), that are know to be true – to – type and are of high yields in the areas where they are planted. The budding process and time of budding vary with locality.
In Sudan the eye or shield method is used and budding is usually done in
March and early May when the cambium is actively dividing.
Budding allows the use of a root-stock of a species or a variety different from the scion. The root stock in a budding tree is chosen for its tolerance to diseases, better adaptation to adverse temperature conditions or to certain soil types in addition to its effects on both fruit quantity and quality. Furthermore large numbers of trees can be obtained from a small amount of vegetative material and this is of utmost importance where sources of vegetative material is limited.
Most citrus cultivars can be propagate by seeds (Hartmann and
Kester, 1983). Seedling trees are found in many tropical countries on small scale planting, but large scale plantation generally use budded trees.
Seedling citrus trees are moderately true – to – type, (because of poly embryony), have many large thorns, grow upright rather than the spreading habit of growth of budded trees and are initially free from virus diseases. The most important disadvantages of seedling citrus trees are that they take longer time to come into bearing, they are susceptible to foot rot and their picking cost is high compared to their budded counter parts. The budded seedling method is usually the most used and most practical methods for the vegetative propagation of large number of trees for commercial citrus plantation.
An unusuall practice of horticultural interest employed in the culture of “Baladi lime” include the almost universal use of seedling rather than budded trees in establishing large scale plantation. Being a very distinct species not closely related to other Citrus spp. (Pursaglove,
1984), no satisfactory rootstock is known for lime. There has been only limited experience with lime on different rootstock, showing in most cases an over growth of the scion or a marked overgrowth of the stock indicating a lack of compatibility.
On the other hand “Baladi lime” has been little used as a rootstock and its suitability and reaction with different citrus varieties are little known. The small size of the tree, its susceptibility to cold injury, the difficulty to slice the eye from the bud wood stick and to bud it onto the rootstock all contribute to sexual propagation of this fruit trees by seeds.
Selection of varieties with known desirable characteristics in lime fruit has thus been hindered. The term “Baladi” when used with fruit tree types denotes seedling fruit trees that are produced sexually by seeds.
Each seedling tree is a variety by itself differing from its mother tree and from sister seedling trees in its genetic make-up.
Own-rooted propagation has been used successfully in many citrus growing countries. Methods of own-rooted lime tree production includes the use of cuttings in the Mediterranean region and in California and layering, was used in tropical and subtropical Asia, Florida and South
Africa (Sutton, 1954). Many Citrus spp. can be propagated by cuttings. The ease of rooting varies with species. In earlier studies Halma (1931) found that members of the acid group root much more readily, sweet orange and grapefruit are intermediate and the mandarin group proved to be most difficult to root.
Own-rooted citrus trees attain orchard planting size eight month after rooting is initiated compared to the two to three years required for budded seedlings. Cuttings also provide a rapid means of obtaining uniform rootstock material for budding especially of selections of short seed supply or varieties producing seeds having low viability or a low percentage of nucellar seedlings (Platt and Opitz, 1973). One of the principal disadvantages of the own-rooted method is that it eliminate the use of a rootstock of a species or variety different from the scion and having desirable characteristics that the scion lack.
Production of large numbers of own-rooted trees by stem cuttings is more difficult because greater amount of vegetative material is required making the method laborious, tedious and expensive.
The objective of this research is to developed and easy, quick and simple method for the clonally multiplication of lime trees in large numbers for evaluation and consequently, distribution to citrus growers.
2. LITERATURE REVIEW
Lime (Citrus aurantifolia “Christm” Swing.) is a member of the
Rutaceae a large family with about 130 genera and 1.500 species mainly trees and shrubs with the largest number in the warmer regions of the world. It is indigenous to the East Indian Archipelago and was taken from there to the mainland. Wild lime trees were also found growing in northern India which may be considered as an indication that lime may have originated there (Purseglove, 1984). It has since then spread throughout the tropics and was taken to Europe about the thirteenth century and by the Spaniards to the American continents early in their colonization.
There is extensive commercial production in Mexico, Dominican
Rebuplic, Pakistan, India and Egypt. The group name for lime in Sudan is “Limoon”, Benzahair in Saudi Arabia and the Gulf States, Nomi
Basra, in Iraq, and lime in Spanish and English. The fruit does not store and transported well and thus limes have been replaced by lemons in temperate regions. There are two natural groups of limes: sour limes and sweet limes.
The Mexican limes also called “West Indian” and “Key” lime is the cultivar most commonly grown in the tropics, is round, small fruited, moderately seedy and highly polyembryonic. It has a thin, smooth rind, greenish pulp. The larger fruited “Tahiti” or “Persian” lime is seedless.
Its flowers have defective pollen and egg cells and is triptoid. It is well adapted to tropical and subtropical humid climate. The later group, sweet limes are only used as root stock on light soils.
Limes are more tender than most other Citrus spp. They can survive on poor soils and often under neglected conditions.
2.1. Cultural practices:
2.1.1. Planting
The field where planting out is to take place must be well prepared, drained and weeded. The planting system may be square, rectangular, triangular or hexagonal. The planting distance depend on the nature and fertility of the soil and the type of rootstock and scion.
Planting in light clay soils with sour orange as rootstock the spacing recommended is 5 x 6m for orange and lemon, 7 x 7m for grapefruit and
4 x 5m for lime and mandarin. Drainage and provision for mechanical cultivation, spraying and irrigation must be taken into consideration.
The field prepared for planting is then lined out and stakes are placed to locate the planting holes. The normal planting holes are 30 x
30 x 30cm in soil where drainage is secured, otherwise the size of these holes should be 50 x 50 x 50cm. Top soil is kept apart and later returned to the top. One kilogram of mixed fertilizer may be applied in the bottom of the hole before planting.
Citrus may be transplanted in the field either bare rooted, or with a ball of earth, or from plastic bags. Bare rooted transplant are easier to handle and transport. They permit inspection for diseases, abnormal growth, nematodes or damage. They must be planted immediately after digging and require careful handling and protection from direct sun and wind injury. Planting with a ball of earth or from plastic bags on the other hand allows for transport over long distances and the transplants may be left out of the ground for a number of days before planting. This method is useful in drier areas but is expensive.
Transplants should be planted on a mound 15cm high. After the soil has settled. They should be more higher than they were in the nursery to avoid infection by foot rot. Planted transplants should be watered immediately. The soil around the transplant must be thoroughly wetted. The direction of the rows is important for high yield. A north – south direction ensure maximal sunlight. Wind breaks are necessary for protection from direct wind damage but shade should be avoided.
Citrus fields are often intercropped with vegetables or other legume fodder crops such as “Berseem”. These cover crops keep the soil cool, being cut only periodically to act as a mulch thus adding organic matter, control weeds, improves structure and fixes nitrogen.
Intercropping have several disadvantages of which is the competition for water during the dry season. Usually the cover crops are mowed at the time of dry periods to lessen the intensity of this competition. Another disadvantage associated with dry period and drought conditions is the hazards of fire. The use of leguminous creepers as cover crops should be avoided since these plants have the tendency to climb the fruit trees and compete for light.
2.1.2. Fertilization:
Crop fertilization is most important in citrus growing. Fertilizer type, amounts and time of application so much depends on the soil type.
Nitrogenous fertilizers are the most important and most usually applied at the rate of 1 – 2 pound (20% N) to young trees and 4 – 10 pounds per mature trees per annum often in two applications, the first at the beginning of autumn and the second 4-5 months after flowering.
Potassium affect fruit quality and 1 pound potassium sulphate per tree annum may be applied. Zinc and magnesium deficiency are quite common in citrus and may be controlled by foliar sprays often together with copper and manganese. Iron deficiency is cured with chelated iron.
Organic manures are beneficial and are strongly recommended where available and economic. 2.1.3. Irrigation:
Citrus trees can withstand a drought of up to four months if grown on deep soils with good water–holding capacity. Irrigation water to be supplied depends on soil type, rootstock, rainfall and temperature. The soil should be kept moist but not wet to a depth of at least 90cm. Too much water is just as harmful as too little. The even distribution of water over the tree area is important. Irrigation following a period of at least six weeks of drought has been found to induce flowering of mature trees.
2.1.4. Pruning:
Pruning is practiced for the first shaping of the trees in the nursery before planting in permanent sites and continues for the first 2 – 3 years after planting. It is essential to remove all suckers particularly those from the rootstock. Some scion suckers if left on the tree will acquire a horizontal habit of growth and may become fruitful. Inward growing sucker, dead wood, nest of ants and termites and bee hives must removed.
Unlike temperate fruit trees citrus trees have a limited reserves of carbohydrates. Very little pruning is done in the tropics and heavy pruning should be avoided since it delays flowering. Only old low fruiting citrus trees are usually severely pruned in what is known as top- working in order to rejuvenate them. 2.1.5. Harvesting:
All citrus fruits should be held on the trees until they are fully mature. Colour is not considered as an indicator of maturity in the tropics as many citrus retain a green colour when fully mature. The colours do not develop unless the temperature has remained below 13º C for several hours. Only limes and lemons are usually picked while still green according to size. Fruits are harvested individually either by clipping off near the calyx with special a clipper or by bending and pulling with a slight twist. For the fresh fruit market the fruits should be picked at the right stage of maturity, should be clean and free from bruises and blemishes and of good color. Orange – yellow colour can be obtained by treating with ethylene gas after harvest. 2.1.6. Propagation:
Sexual as well as asexual methods of propagation are used to raise plants of different species of citrus. Sexual propagation is usually used for breeding purposes and for production of rootstocks for budding and in dioecious plants, such as date palm and papaya, sexual propagation is used for the production of males needed for pollen production. It is also used principally for the production of fruit trees that are difficult to propagated vegetatively such as guava, papaya and annonas. It is easy, cheap, fast and does not need much expertise and technical know-how. It however, results in the production of complex heterogeneous seedling with considerable variation in genetic make up. The unique characteristics of many fruit trees is immediately lost if propagated by seeds (Hartmann and Kester, 1990). Seedling fruit trees tend to be rather more vigorous, more thorony and are slower to come into bearing.
Vegetative propagation, on the other hand, is used for the clonal reproduction of known desired varieties. Genetic variation is eliminated unless a sport or a mutation occurs. It result in the production of uniform plants that are genetically homogeneous and true–to–type. In addition to that fruit trees propagated by vegetative means come into the bearing earlier compared to their seed propagated counterparts.
2.1.6.1. Seed propagation of citrus trees: Citrus spp. have been grown from seeds in many citrus growing countries for long times (Hartmann and Kester, 1990). Seeds of most citrus spp. and cultivars are polyembryonic. A seed may contain a sexual embryo, resulting from a fertilized egg cell and up to 9 or more asexual embryos which develop from the somatic cells of the nucellus.
Pollination is usually necessary for the development of nucellar embryos.
Seedling trees from the sexual embryos do not breed true – to – type and usually result in the reproduction of inferior trees and fruits, while seedlings from nucellar embryos will be the same genetically as the female parent. Nuceller seedlings are thus used both for direct planting as well as for raising uniform rootstock (Singh and Singh,
1955).
The degree of polyembryony vary among citrus species and varieties (Gopalakrishna and Kunte, 1958; Singh, 1965; Motial, 1983;
Prasad and Ravishanker, 1983). Limes, lemons and mandarins usually show a high degree of nucellar embryony (80 – 100%). While pummelos and citrons are monoembryonic. Citrus spp. with relatively high degree of polyembryony seeds give remarkably true-to-type seedlings while pummelo and citron seeds, being monoembryonic, reproduce inferior seedlings. Usually propagation of citrus by seed is cheap and easy and is used where possible.
Presence of a zygotic embryo among the asexual vegetative embryos makes the use of seeds for the propagation of polyembryonic citrus spp. difficult. Nucellar embryos produce seedlings of the same genetic constitution as budding from the same tree but the identification of the single zygotic seedling from nucellar seedlings is still a difficult task. It is important to be able to accurately distinguish between nucellar and zygotic seedlings at an early stage of growth. This has proved to be extremely difficult. Several attempts including the use of a modification of rootstock colour – reaction test (Nishiura et al., 1957), gas chromatography (Pieringer et al., 1964), infrared spectroscopy (Pieringer and Ewards, 1965), isozyme analysis (Anderson et al., 1991) failed to offer a basis for accurately distinguishing zygotic seedlings in progenies where it is also difficult distinguish them on morphological basis.
The use of seeds for the propagation of desired citrus varieties has not been practiced on large scales for the establishment of commercial orchards even in varieties that are known to produce high proportions of asexual seedlings such as mandarins, oranges and grapefruit. Vegetative propagation techniques are thus sought to ensure the clonal status of desired commercially known varieties and cultivars of citrus trees.
2.1.6.2. Vegetative propagation of citrus trees:
The term vegetative propagation is often used more or less synonymously with asexual propagation which means in its broad sense the detachment or severing of a multicellular mass from the parent plant and its development directly into a new separate individual.
Plants reproduced vegetatively have exactly the same hereditary potentialities as the parents except for rather rare mutations. They may be regarded as extension of the single individual and are referred to as clones.
The most obvious advantage of vegetative propagation as a horticultural practice is that all off springs propagated vegetatively are clonal. A second advantage of vegetative propagation is that plants produced come into bearing earlier (reach maturity early) compared to their seed produced counterparts. Perhaps the most important advantage of vegetative propagation, however, is that it makes possible the propagation of some citrus varieties that have lost their capacity for seed reproduction even though they have flowers such as navels, Bearess lime and Satsuma mandarin. Wherever, a plant can be conveniently and practically be propagated vegetatively, this means of reproduction is used in preference to seeds because of the ease of maintaining desirable combination of hereditary traits. The availability of vegetative propagation for a plant frequently makes plant breeding a simple procedure. The most obvious disadvantage is that it plays an important role in the spread of pests and diseases especially viral diseases.
Various forms of vegetative propagation exist. Any part of a plant whether an organ (stem, root, leaves or flowers), tissues (nucellus), or even a single cell may be involved in vegetative propagation. They all have the ability (totipotency) to form whole individual plants.
The classification of the technique of vegetative propagation among vascular plants is based on the plant part used (the propagule) for propagation such as stem, root, leaf cuttings, rhizome, corm bulb, offshoot, organ tissue or single cell culture.
Citrus can be propagated by various vegetative techniques which can be broadly divided into two forms: propagation on the plants’ own root. This form include cuttings and layering. Plants produced are called own-rooted plants. The other form of vegetative propagation is propagation on a rootstock as in budding and grafting. Plants produced are called budded or grafted plants 2.1.6.2.1. Propagation on a root stock:
Citrus is chievely propagated by budding on seedling rootstocks.
Here the most important single factor that ensure the production of vigorously growing citrus trees is the scion selection. Great emphasis should be placed on selecting and using scions obtained from healthy virus – free mother trees known to be true – to – type and high yielders in areas where they are planted (Optiz, 1960; Garnsey and Jone, 1967).
The time and type of budding vary with locality. In Sudan budding is usually done in late March and early May when the vascular cambium is actively dividing.
The most common method of budding practiced in many citrus growing countries including Sudan is the eye or shield method. Using a special knife, an eye or bud with a shield – shaped piece of bark 2 – 3cm in length is sliced from the budwood stick. A vertical cut through the bark to the wood of the stem of the seedling rootstock is made. This is followed by a horizontal cut at the upper end of the vertical cut to form a
T. This open the bark so that the bud may be inserted at the junction of the two cuts in such away that the bud faces upwards. During the time when the vascular cambium of the seedling rootstock is actively dividing the bark will slip freely. For successful “take” all surfaces of the bud shield must contact the exposed surfaces of the seedling rootstock. The inserted bud is then tied with polythene strips starting at the bottom to ensure a strong contact between the shield bud and the seedling rootstock and to ensure that no water can penetrate and encourage rottening and failure of “bud – take”. The tape should also cover the shield bud to prevent drying but the eye of the shield bud must be left free.
After four to six weeks from budding the seedling rootstock is inspected and if the shield bud is still green, union has probably been effected. Buds that do not “take” turn brown in colour. The rootstock may be used again by rebudding with a new shield bud. Under cases where bud growth is weak or slow after “take” forcing is practiced by either cutting off the top of the seedling rootstock just above the inserted green buds (topping) or by bending or half ringing the seedling rootstock
3 – 10cm above the inserted green bud (lopping)(Nauer and Goodale,
1964; Samson, 1989). Topping effectively destroys apical dominance while lopping breaks apical dominance selectively on the upper side only, mean while allowing continued transport of food and auxins along the lower side to the roots (Samson and Bink, 1975).
The most important and obvious advantage of budding is that it allows the use of a rootstock of a species or variety different from the scion. The rootstock in a budded tree is chosen for its tolerance to diseases, better adaptation to temperature extremes, certain soil types and its effects on fruit quantity and quality. In addition, large numbers of trees are more easy to propagate by budding since it require a small amount of propagules.
Twig grafting (cutting grafts) is a modified form of budding when two leafy twigs are grafted together by means of a whip or tongue grafting. The lower twig is rooted. A small desired tree is thus produced on a desired rootstock. Experience and technical know–how are needed here and successful “take” and rooting are both a must. This form of vegetative propagation is used only for the production of specific clonal material (Ohkawa, 1980).
2.1.6.2.2. Own – rooted trees:
This form of vegetative propagation has been used successfully for citrus propagation in many citrus growing countries. The method of own–rooted tree production include cuttings, a method used in many
Mediterranean countries and in California, layering, mostly used in tropical and subtropical Asia, Florida and in South Africa (Sutton, 1954) and tissue culture which is a newly developed technique, rarely used for citrus propagation (Parntip, 1993, Perez and Ochoa, 1997, Al-Khayri and
Al-Bahlrany, 2001).
Cutting have been used more extensively compared to layering for the vegetative propagation of many Citrus spp., where a species or a variety is raised on its own root system. Wide variation in rooting ability among Citrus species and varieties have been observed. While lime, lemons and citron root much more readily, sweet orange, grapefruit, sour orange are intermediate and mandarin proved to be difficult – to – root
(Sadhu, 1986). Age and the physiological status of the mother plants, type of wood, time of planting and media composition determine the extent of successful rooting (Gangwar and Singh, 1965, Bajwa et al.,
1977).
Leaf – bud cutting have been used as apropagules for Citrus propagation in the late 1930 s when Watkin and Blackman (1939) described this method. The branch is cut above and below each bud so that the cutting consist of only the single leaf attached to a piece of stem
2- 3 cm long containing a single bud. This small cutting is then planted in soil so that the shield of the stem is covered and allowing the lamina of the leaf to lie flat on top of the soil.
The leaf – bud cutting method has been used for the propagation of larger number of Citrus spp. where the parent material is in limited supply (Ford, 1957). A leaf–bud cutting contain only a single bud, similar in that respect to budding, while the standard stem cutting may contain from five to nine buds. Stem cuttings may be hard, semi–hard or of soft– wood according to the type of wood used. Stem cutting have been used for the vegetative propagation of several fruit trees including citrus (Gabricidze, 1970, Platt and Opitz, 1973, El– Tomi and Galal, 1980, Debnath et al., 1986), mango, (Basu et al., 1972), guava (Bhandary and Mukherjee, 1969,
Wally et al., 1981) olive, (Loretti and Hartmann, 1965), grapes, (Goode and Lane 1983), figs, (Aminov, 1972); macademia (James et al., 1970), cashew, (Nageswar et al. 1988), kiwifruit , (Caldwell et. al., 1988), apples, (Howard et al., 1984) and plums (Nahlawi and Howard, 1973) to mention but few.
Several factors have been reported to influence rooting of stem cuttings. The part of the branch used for planting greatly influences percentage of successful rooting. Higher rooting percentage were consistently obtained with basal cuttings while apical cuttings had significantly less rooting ability in various plant species (Shafriz and
Mende1970, Aminov, 1972; Porlingis and Theros, 1976; Hansen, 1986;
Goode and Lane 1983; Thompson, 1986; Samekto et al, 1995).
Girdling (ringing) the branches from which cuttings for rooting are to be taken has also been reported to substantially increase rooting success and improved the quality of the cuttings (Jauhari and Rahman, 1959; Stoltz and Hess, 1966; Basu et al., 1972; Debnath et al., 1986;
Nageswar Rao et al. 1988).
Working with lime leaf– bud cuttings Juma (1994) obtained the highest rooting percentage in cuttings severed from parent plants during the rainy season and no rooting was observed in cuttings taken during winter. Similar observations have been reported by several workers using various plant species (Hartmann and Loretti, 1965; Howard and
Nahlawi, 1969; Anand and Heberlein, 1975; Issell and Chalmer, 1979;
Thomposn, 1986).
Wounding the base of the cutting before planting was also found to be beneficial for rooting of cuttings of several woody species
(Hartmann and Kester 1983; Howard, et al., 1984; Caldwell, et al.,
1988).
The response to timely collection of cuttings from field grown mother trees is species and variety dependent (Sen and Rose, 1966). The dramatic influence of season of the year on successful propagation by other vegetative methods have been observed for layering (Azzouz,
1965; Tingwa and Abbadie, 1968; Chkonkar and Singh, 1972) and for budding and grafting (Platt and Opitz, 1973).
Auxins and phenolic compounds were found to enhance rooting of citrus cuttings to varying degrees (Gibricidze, 1970; Shafriz and Mende 1970; Dhatt and Singh, 1993). The effects of exogenously applied auxin on cuttings of various woody species have also been reported (Sinha et al., 1962; Basu et al., 1972; Porlingis and Theros 1976; Pennock and
Maldonado, 1963).
Tingwa and Abbadi (1968), however were first to use a commercial rooting formulation “Seradix 3” for the induction of rooting guava stem cuttings obtained from limb branches and from suckers.
Some what later Bani (1988) used “Seradix 3” for rooting of stem cuttings of mangoes, guavas, nerium and gardina. The use of auxins in the form of powder has long been practiced for the commercial propagation of citrus where most citrus varieties and species responded to treatments of IBA in talc (Platt and Opitz, 1973). There was much genetic variation with respect to rooting ability of cuttings of various plant species and varieties (Sorensen and Campbell, 1980; Miller et al.,
1982).
Propagation by budding or grafting on genetically different rootstocks is time consuming. In Sudan seedling of sour orange, the main rootstock, takes from 14 to 24 months to be ready for budding or grafting. These techniques need expertise and are thus expensive and the rootstock might have adverse effects on the scion budded or grafted on it. Layering was the principal method of propagation of citrus in
South Africa. Air – layering was much used in the humid regions of tropical and subtropical Asia. A branch is caused to root while still attached to the mother plant. It is then severed from its mother and planted as a separate individual. The method, however, does not allow for the production of large number of trees. It has been used with success for the propagation of Bearess lime (Persian lime) in Southern Florida
(Platt and Opitz, 1973).
The use of cutting as a method of vegetative propagation has many advantages. It is inexpensive, rapid and simple and does not require special technical know – how. In addition, a greater number of plants can be produced in a small space from few mother plants and in a short period of time. But the use of cuttings for the propagation of citrus is still quite limited.
As for limes, the subject matter of this research, seeds have been used as the sole propagation methods throughout Sudan. Because of the relatively high degree of polyembryony exhibited by lime seeds, seedlings come remarkably true–to mother plants. Selection of seeds from high yielding mother trees and roging of off-types may lead to the establishment of nucellar–seedling bud lines which could serve as mother trees for supplying virus–free, vigorously growing, higher yielding trees even thought some problems associated with juvenility still remain to be overcome.
There has been only limited experience with lime trees on different rootstocks. Although lime is known to hybridize with other
Citrus spp., it is a very distinct species not closely related to them
(Purseglov, 1984). When budded or grafted lime may show an overgrowth of the scion or marked overgrowth of the stock indicating a lack of compatibility (congeniality). Sweet orange commonly gives normal bud union with lime but it is highly susceptible to fot rot. It can not be of much use as a rootstock in humid regions. Budded lime trees were found to be short-lived. Orchard trees grow well for a few years and then gradually slowed down in growth and begin to decline.
Budding or grafting of limes can be used only if it is desired for some special purpose as for protection from uprooting by strong winds
(Freeman, 1931) or against cold injury. It is very difficult to handle and bud lime seedlings as they are thorny and small as well as the separation of the bud shield is extremely difficult because of the thorn.
Lime has been little used as a rootstock and its suitability and reactions with different citrus varieties are little known. They are resistant to drought more than any other citrus species and are well adapted to poor sandy soils. Seedling lime trees shed, most if not all, their flowers if grown in isolated areas in houses, hospitals, schools and other governmental premises in Sudan. Seed propagation of lime trees is not a desirable method since plant raised from seeds vary greatly and many seedling trees have pistils that are regularly under developed or absent in a large part of the flowers (Frost and Soost, 1968). Iwamasa and Iwasaki (1963) also associated low temperature with reduction of pollen viability and fertility of lime. This leads to shedding of flowers due to failures of pollination.
In mixed plantings with other citrus species and varieties pollination occurs and fruits are set since most citrus cultivars are self and cross-compatible. Pollen viability has been a problem in lime culture. Non-viable pollen is common in lime trees and the percent of viable pollen may be very low in same trees. selection of trees with high percent of viable pollen is important. Vegetative propagation is a must for large scale reproduction and release of varieties with high degrees of pollen viability, high yielders and with high fruit quality.
Propagation of limes from cuttings could provide low-cost plants in large numbers and in short period of time for large scale plantation systems as has been shown with other fruit tree species (Erez and
Yablowitz, 1981; Couvillon et al., 1986). Subsequent growth of own – rooted trees was comparable to trees propagated on seedling rootstock
(Couvillon and Erez, 1980) Own-rooted trees were found to be more efficient in absorbing Ca and Mg than the same cultivars budded to seedling rootstock (Couvillon, 1982). Own-rooted trees are being considered as a commercial alternative to budding onto seedling rootstock. Where poor rooting and survival of cuttings have been a problem (Yu and Robitaille, 1979).
3. MATERIALS AND METHODS
3.1 Experimentation:
All experiments were conducted using “Baladi lime” (Citrus aurantifolia L.) to investigate the possibility of its clonal propagation by stem cuttings. The effect of time of the year on rooting of cutting and girdling were studied. The experiments were executed for two consecutive season (2002/2003).
3.2 Plant materials:
The mother plant is a 10 years old “Baladi lime” tree growing in the orchard of the School Gardening and Nutrition Education which belongs to the Ministry of Education, Eldammer (300 km north of
Khartoum).
All cuttings were obtained from this single tree to avoid genetic variability in response to treatments. All cutting were prepared in a similar way for all three experiments.
3.3 Experiment No. 1. Summer Experiment:
Selected branches with uniform, thickness and age were girdled during the summer.
Branches were cut for experimentation above the girdle 2, 4, 6, 8 and 10 weeks after girdling. Cutting of 7cm length containing 1 – 2 lateral buds were used throughout these experiments. Three types of shoot cuttings were tested: The first type consisted of the part of the girdled shoot near to the girdle (basal cutting) and the second type of cutting consisted of the terminal of the girdled shoot
(apical cutting). Also as a control similar shoot cuttings were used from un girdled shoot (non girdled cuttings).
3.4 Experiment No. 2. Autumn Experiment:
The same procedures above in experiment 1 was repeated during
(Autumn).
3.5 Experiment No. 3. Winter Experiment:
The above procedures was repeated again during (Winter) when the last experiment was conducted.
3.6 Planting media:
All cuttings were planted in sand soil. All prepared cuttings were dipped in the commercial rooting compound (Seradix II) which is used in nurseries for the rooting of semi-hard wood shoot cuttings.
Cutting were then planted in plastic trays (half jerrycans ) having a dimension of 27 x 24 x 7cm with nine drainage holes at the bottom. The plastic trays containing the planted cuttings were kept under plastic covered frames under lathe-house conditions. Watering was done once every day by spraying.
3.7 Incubation conditions: Plastic covered frames were structured to create conditions suitable for rooting of the cuttings. The frames were made of wood with the dimensions of 300 x 150 x 23cm and covered with white transparent plastic for the purpose of maintaining high relative humidity around the cuttings. These plastic covered frames were placed under alathe house.
3.8. Parameters measured:
The parameters measured in all experiments included the percentage of rooting, number of roots and length of roots. Data were recorded at the end of the experiment. Growth vigor of rooted cuttings was also recorded by judging by the naked eye where shoot growth, leaves colour and roots branching and length were all used as indicators to growth vigor. 3.9 Experimental design and data analysis:
A completely randomized design was used. The treatments in each experiment were replicated 2 times and each plastic tray consisted of 10 cuttings.
Mean separation was performed using Duncan’s Multiple Range
Test at 5% level. In all experiments three differential treatments were used namely:
1. Cuttings from non-girdled shoot (control “G1”).
2. Basal cuttings (G2).
3. Apical cuttings (G3).
4. RESULTS
4.1. Summer experiments:
4.1.1 Effect of girdling and sowing interval on percentage of rooted lime stem cuttings:
Results shown in (Table 1-a; Fig. 1-a) indicates no significant difference between the different treatments. The highest rooting percentage was associated with basal cutting (8.1%), followed by non girdled cuttings (5.3%) and then apical cuttings (1.8%), while (Table 1- a; Fig. 1-b) show no significant difference in percentage of rooted cuttings among cuttings taken 2, 4, 6 and 8 weeks after girdling.
However, a highly significant difference was observed between these time interval and the 10 weeks interval after girdling.
The highest percentage of rooted cuttings was obtained with cuttings taken 10 weeks after girdling (34.1%) followed by 8 (8.00%) and then 2 weeks after girdling (2.6%). Complete failure was observed in rooting of cutting taken 4 and 6 weeks after girdling. Table (1a): Effect of seasons, sowing interval and girdling on percent rooted lime stem cuttings Non girdled Time Basal cuttings Apical cuttings Avg Seasons cuttings interval/W T P T P T P T P 2 13.57 5.50bc 13.57 5.50bc 0.57 0.00c 9.23 2.6B 4 0.57 0.00c 0.57 0.00c 0.57 0.00c 0.57 0.00B 6 0.57 0.00c 0.57 0.00c 0.57 0.00c 0.57 0.00B Summer 8 9.55 2.70bc 39.11 39.80a 0.57 0.00c 16.39 8.0B 10 42.11 45.00a 28.84 23.30ab 36.22 34.90a 35.72 34.1A Mean 13.27 5.3A 16.53 8.1A 7.70 1.8A 12.50 4.7B 2 39.11 39.80abc 35.78 34.20abc 50.90 60.20a 41.93 44.7A 4 45.0 50.00ab 13.57 5.50c 36.22 34.90abc 31.69 27.5A 6 53.78 65.10a 41.99 44.80ab 51.34 61.00a 49.04 57.0A Autumn 8 22.50 14.60bc 54.22 65.80a 47.89 55.00ab 41.53 44.0A 10 39.23 40.00abc 53.78 65.10a 57.11 70.50a 50.04 58.8A Mean 39.92 41.2A 39.87 41.1A 48.69 56.4A 42.82 46.2A 2 36.22 34.90 25.83 19.00 45.00 50.00 35.68 34.0A 4 36.22 34.90 45.0 50.00 48.01 55.30 43.08 46.7A 6 42.12 45.00 26.56 20.00 53.78 65.10 40.82 42.7A Winter 8 50.80 60.20 25.83 19.00 46.18 81.00 46.97 53.4A 10 53.78 65.10 19.90 11.60 51.34 61.00 41.67 44.2A Mean 43.85 48.0AB 28.62 22.9B 52.46 62.9A 41.64
Table (1b): Effect of seasons, sowing interval and girdling on percent rooted lime stem cuttings Time Non girdled cuttings Basal cuttings Apical cuttings Avg interval/W T P T P T P T P 2 29.63 24.8 25.06 17.9 32.16 28.3 28.95 23.40BC 4 27.26 21.0 19.71 11.4 28.27 22.4 25.08 18.00C 6 32.16 28.3 23.04 15.3 35.23 33.3 30.14 25.20BC 8 27.62 21.5 39.72 40.8 37.55 37.2 34.96 32.00B 10 45.04 50.1 34.17 31.6 48.22 55.6 42.48 45.60A Avg 32.34 28.70A 28.34B 22.50A 36.29 35.00A T: Transformation P: Percentage W: Weeks Mean separation within columns by Duncan’s Multiple Range Test 5% level. 9.00 8.00 7.00 6.00 5.00 4.00 3.00 Rooting % Rooting 2.00 1.00 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments) Fig. 1a. Effect of girdling on percent rooted lime stem cuttings
35 A
30
25
20
Rooting % Rooting 15
10 B
5 B BB 0 246810 Time interval (in weeks) Fig. 1b. Effect of sowing interval on percent rooted lime stem cuttings 4.1.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings:
Significant differences in number of roots were found among basal cuttings and apical cutting. On the other hand, non–girdled cuttings showed no significant difference whether they were basal or apical cuttings. The highest value of number of roots was obtained with basal cuttings followed by non girdled cuttings and the lowest number of roots was obtained with apical cuttings (Table 2-a; Fig. 2-a).
Results in Table 2-a; Fig 2-b, showed that no significant difference in number of roots were found between 2, 4 and 6 weeks after girdling. Significant differences were observed only when data were taken 10 weeks after girdling. On the other hand 8 weeks after girdling showed no significant difference when compared to all other weeks sowing interval.
The highest value of number of roots was obtained with cuttings taken 10 weeks after girdling followed by 8 weeks and then 2 weeks. Table (2a): Effect of seasons, sowing interval and girdling on number of roots of lime stem cuttings
Time Non girdled Basal Apical Seasons Avg interval/W cuttings cuttings cuttings 1.51 1.76 0.01 1.09B 4 0.01 0.01 0.01 0.01B B 6 0.01 0.01 0.01 0.01 8 0.01 3.90 0.01 1.31AB 10 3.25 4.35 1.90 3.17A Mean 0.96AB 2.01A 0.39B 1.12B 2 2.20 2.80 2.40 2.47A 4 1.80 1.01 2.90 1.90A 6 3.00 3.10 2.85 2.98A Autumn 8 1.51 1.11 2.60 1.74A 10 0.16 2.90 1.80 1.62A Mean 1.73A 2.18A 2.51A 2.14A 2 1.00 0.01 1.50 0.84BC 4 1.15 2.90 3.20 2.42A 6 1.20 1.00 2.65 1.62AB Winter 8 1.00 0.01 0.55 0.52BC 10 0.61 0.26 0.16 0.34C Mean 0.99A 0.84A 1.61A 1.15B
Table (2b): Effect of seasons, sowing interval and girdling on number of roots of lime stem cuttings Time Non girdled cuttings Basal cuttings Apical cuttings Avg interval/W 2 1.57 1.52 1.30 1.46A 4 0.99 1.31 2.04 1.45A 6 1.40 1.37 1.84 1.54A 8 0.84 1.67 1.05 1.19A 10 1.34 2.50 1.29 1.71A Avg 1.23A 1.68A 1.50A Mean separation within columns by Duncan’s Multiple Range Test 5% level.
2.50 A 2.00
1.50
AB
Number of roots 1.00
0.50 B
0.00 Non girdled cuttings Basal cuttings Apical cuttings Cutting type and position (treatments) Fig. 2a. Effect of girdling on number of roots of lime stem cuttings
3.50 A 3.00 2.50 2.00
1.50 AB B 1.00 Number of roots roots of Number 0.50 BB 0.00 246810 Time interval (in weeks)
Fig. 2b. Effect of sowing interval on number of roots of lime stem cuttings 4.1.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings:
No significant difference in values of length of roots were noted between the different treatments. The highest value of root length was obtained with basal cuttings and the lowest values were obtained with apical cuttings (Table 3-a; Fig. 3-a).
Results in (Table 3-a; Fig. 3-b) showed that no significant difference was found in root length among 4 and 6 weeks sowing interval, but a significant difference was observed between these two intervals and the 10 weeks after girdling. On the other hand 2 and 8 weeks after girdling showed no significant difference when compared to all other weeks interval.
The highest value of roots length was obtained from cuttings taken
10 weeks after girdling and the lowest one was associated with cutting taken 8 weeks after girdling.
4.1.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings:
No significant difference was observed in number of new roots among the different treatments. The greatest number of new roots was obtained with basal cuttings followed by non girdled cuttings and then apical cutting (Table 4-a; Fig. 4-a).
Table (3a): Effect of seasons, sowing interval and girdling on length of roots of lime stem cuttings
Time Non girdled Basal Apical Seasons Avg interval/W cuttings cuttings cuttings 4.81 4.41 0.01 3.08AB 4 0.01 0.01 0.01 0.01B B Summer 6 0.01 0.01 0.01 0.01 8 0.01 5.90 0.01 1.97AB 10 4.00 4.50 5.20 4.57A Mean 1.77A 2.97A 1.05A 1.93B 2 4.70 4.10 4.10 4.30A 4 2.00 1.81 5.65 3.15A 6 3.85 4.80 2.30 3.65A Autumn 8 1.76 1.91 4.20 2.62A 10 0.46 3.10 3.40 2.32A Mean 2.55A 3.14A 3.93A 3.21A 2 2.50cde 0.01e 5.15abcd 2.55BC 4 2.95bcde 6.00abc 7.85a 5.60A 6 2.25cde 3.35bcde 6.80ab 4.13AB Winter 8 3.30bcde 0.01e 1.40de 1.57C 10 1.56de 0.16e 0.66e 0.79C Mean 2.51B 1.91B 4.37A 2.93AB
Table (3b): Effect of seasons, sowing interval and girdling on length of roots of lime stem cuttings Time interval/W Non girdled cuttings Basal cuttings Apical cuttings Avg 2 4.00a 2.84ab 3.09ab 3.31A 4 1.65b 2.61ab 4.50a 2.92A 6 2.04b 2.72ab 3.04ab 2.60A 8 1.69b 2.61ab 1.87b 2.06A 10 1.99b 2.59ab 3.09ab 2.55A Avg 2.27A 2.67A 3.12A Mean separation within columns by Duncan’s Multiple Range Test 5% level.
3.00
2.50
2.00
1.50
1.00 Root length
0.50
0.00 Non girdled cuttings Basal cuttings Apical cuttings Cutting type and position (treatments) Fig. 3a. Effect of girdling on length of roots of lime stem cuttings
5.00 A 4.50 4.00 3.50 AB 3.00 2.50 AB Root length Root 2.00 1.50 1.00 0.50 B B 0.00 246810 Time interval (in weeks) Fig. 3b. Effect of sowing interval on length of roots of lime stem cuttings Table (4a): Effect of seasons, sowing interval and girdling on number of new roots of lime stem cuttings
Time Non girdled Basal Apical Seasons Avg interval/W cuttings cuttings cuttings 2 14.01 9.51 0.01 7.84AB 4 0.01 0.01 0.01 0.01B B Summer 6 0.01 0.01 0.01 0.01 8 0.01 14.90 0.01 4.97AB 10 9.45 22.35 8.60 13.47A Mean 4.70A 9.36A 1.73A 4.39A 2 14.20 18.35 12.60 15.05A 4 3.05 7.51 9.05 6.54B 6 9.95 12.40 5.50 9.28AB Autumn 8 6.51 2.41 9.55 6.16B 10 1.55 5.25 7.15 4.65B Mean 7.05A 9.18A 8.77A 8.33A 2 2.85 0.01 9.90 4.25B 4 5.25 17.25 15.60 12.70A 6 1.85 4.25 15.50 7.20AB Winter 8 2.85 0.01 0.86 1.24B 10 3.26 0.01 0.01 1.09B Mean 3.21A 4.31A 8.37A 5.30A
Table (4b): Effect of seasons, sowing interval and girdling on number of new roots of lime stem cuttings Non girdled Apical Time interval/W Basal cuttings Avg cuttings cuttings 2 10.35 9.29 7.50 9.05A 4 2.77 8.26 8.22 6.42A 6 3.94 5.55 7.00 5.50A 8 3.12 5.77 3.46 4.12A 10 4.74 4.87 5.25 4.95A Avg 4.98A 6.75A 6.29A Mean separation within columns by Duncan’s Multiple Range Test 5% level. 10.00 9.00 8.00 7.00 6.00 5.00 4.00
Number of new roots 3.00 2.00 1.00 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments) Fig. 4a. Effect of girdling on number of new roots of lime stem cuttings
14.00 A 12.00
10.00
8.00 AB
6.00 AB
Number of new roots roots new of Number 4.00
2.00
0.00 BB 246810 Time interval (in weeks) Fig. 4b. Effect of sowing interval on number of new roots of lime stem cuttings The effect of sowing interval on number of new roots was illustrated in (Table 4-a; Fig. 4-b). No significant difference was observed between cuttings taken 4 and 6 weeks after girdling. But cuttings taken 10 weeks after girdling showed a high significant difference compared to 4 and 6 weeks interval, while 2 and 8 weeks showed no significant difference compared to all other weeks interval.
The highest value of number of new roots was obtained from cuttings taken 10 weeks after girdling followed by 2 and then 8 weeks. No rooting was noted on cuttings 4 and 6 weeks after girdling.
4.1.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings:
Results in (Table 5-a; Fig. 5-a) showed that no significant difference on growth vigor were found among the different treatments.
The highest growth vigor was recorded with basal cuttings and the lowest growth vigor was obtained with apical cuttings.
No significant difference was found on growth vigor among cuttings taken 4 and 6 weeks after girdling. However, they were significantly different from cuttings taken 10 weeks after girdling. On the other hand, 2 and 8 weeks showed no significant difference compared to all other weeks.
The highest growth vigor was obtained with cuttings taken 10 weeks after girdling and the lowest growth vigor was obtained with cuttings taken 8 weeks after girdling (Table 5-a; Fig. 5-b). Table (5a): Effect of seasons, sowing interval and girdling on growth vigor of lime stem cuttings
Time Non girdled Basal Apical Seasons Avg interval/W cuttings cuttings cuttings 2 1.51 1.26 0.01 0.93AB 4 0.01 0.01 0.01 0.01B B Summer 6 0.01 0.01 0.01 0.01 8 0.51 2.20 0.01 0.91AB 10 1.90 2.00 1.75 1.88A Mean 0.79A 1.10A 0.36A 0.75B 2 2.25 2.05 1.85 2.05A 4 1.40 1.01 2.10 1.50A 6 2.10 2.00 1.35 1.82A Autumn 8 1.50 1.30 1.85 1.55A 10 1.05 1.55 1.35 1.32A Mean 1.66A 1.58A 1.70A 1.65A 2 1.35 1.00 2.00 1.45B 4 1.80 2.30 2.45 2.18A 6 1.10 1.50 2.25 1.62AB Winter 8 1.50 1.00 1.20 1.23B 10 1.35 0.51 1.10 0.99B Mean 1.42AB 1.26B 1.80A 1.49A
Table (5b): Effect of seasons, sowing interval and girdling on growth vigor of lime stem cuttings Time interval/ Non girdled cuttings Basal cuttings Apical cuttings Avg W 2 1.87 1.44 1.29 1.53A 4 1.07 1.11 1.52 1.23A 6 1.07 1.17 1.20 1.15A 8 1.17 1.50 1.02 1.23A 10 1.43 1.34 1.40 1.39A Avg 1.32A 1.31A 1.29A Mean separation within columns by Duncan’s Multiple Range Test 5% level. 1.20
1.00
0.80
0.60
Growth vigor Growth 0.40
0.20
0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 5a. Effect of girdling on growth vigor of lime stem cuttings
2.00 A 1.80 1.60 1.40 1.20 1.00 AB AB 0.80
Growth vigor Growth 0.60 0.40 0.20 BB 0.00 246810
Time interval (in weeks)
Fig. 5b. Effect of sowing interval on growth vigor of lime stem cuttings 4.2. Autumn experiments:
4.2.1. Effect of girdling and sowing interval on percentage of rooted lime stem cuttings:
The effect of girdling on percentage of rooted cuttings, was shown in (Table 1-a Fig. 6-a). No significant difference was observed in rooting percentage between the different treatments. The highest percentage of rooted cuttings was associated with apical cuttings (56.4%) followed by non girdled cuttings (41.2%) and then basal cuttings (41.1%).
Data presented in Table (1-a); Fig. (6-b) showed that no significant difference in percentage of rooted cuttings among cuttings taken at different sowing interval. The highest percentage of rooted cuttings was obtained with cuttings taken 10 weeks after girdling
(58.8%) followed by those taken 6- (57.0%), 2- (44.7%), 8- (44.0%) and then 4-weeks after girdling (27.5%).
4.2.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings:
No significant difference in number of roots among the different treatments was observed. Apical cuttings resulted in the greatest number of roots followed by basal cuttings and then non girdled cuttings (Fig. 7- a, appendix 2-a). 60.00
50.00
40.00
30.00
Rooting % Rooting 20.00
10.00
0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 6a. Effect of girdling on percent rooted lime stem cuttings
60.00
50.00
40.00
30.00
Rooting % Rooting 20.00
10.00
0.00 246810 Time interval (in weeks)
Fig. 6b. Effect of sowing interval on percent rooted lime stem cuttings
The effect of sowing interval is shown in Table (2-a); Fig. (7-b).
No significant difference was found in number of roots of cuttings taken in the different sowing intervals. The greatest number of roots was obtained with cuttings taken 6 weeks after girdling followed by 2, 4, 8 and then 10 weeks after girdling.
4.2.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings:
No significant difference was found in root length among the different treatments. The highest value of roots length was obtained with apical cuttings and the lowest root length was recorded with non girdled cuttings (Table 3-a; Fig. 8-a).
Results in Table (3-a); Fig. (8-b) showed that no significant difference was found in root length among different sowing intervals.
The highest value of root length was obtained from cuttings taken 2 weeks after girdling, and the lowest root length value was associated with cuttings taken 10 weeks after girdling. 3.00
2.50
2.00
1.50
1.00 Number of root root of Number 0.50
0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments) Fig. 7a. Effect of girdling on number of roots of lime stem cuttings
3.00
2.50
2.00
Number of root root of Number 1.50
1.00
0.50
0.00 246810
Time interval (in weeks)
Fig.7b. Effect of sowing interval on number of roots of lime stem cuttings 4.00 3.50 3.00 2.50 2.00 1.50 Root length length Root 1.00 0.50 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments) Fig. 8a. Effect of girdling on length of roots of lime stem cuttings
4.50 4.00 3.50 3.00 2.50 2.00 Root length length Root 1.50 1.00 0.50 0.00 246810 Time interval (in weeks) Fig. 8b. Effect of sowing interval on length of roots of lime stem cuttings 4.2.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings:
No significant difference was found in number of new roots among the different treatments. The highest value of number of new roots was associated with basal cuttings followed by apical cuttings and the lowest root number value was obtained with non girdled cuttings
(Table 4-a; Fig. 9-a).
No significant difference was found in number of new roots among cuttings taken 4, 8 and 10 weeks after girdling. However, cuttings taken 2 weeks after girdling were significantly higher in number of new roots compared to those taken in the former weeks. On the other hand, the 6 weeks interval showed no significant difference when compared to all other weeks interval. The greatest value of number of new roots was associated with 2 weeks followed by 6, 4, 8 and then 10 weeks (Table 4- a Fig. 9-b).
4.2.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings:
Results in Table (5-a); Fig. (10-a) indicated no significant difference in growth vigor among the different treatments. The highest growth vigor was associated with apical cuttings and the lowest was obtained with basal cuttings. The effect of sowing interval on growth vigor was illustrated in
Table (5-a) Fig. (10-b). No significant difference was found among cuttings taken in the different weeks interval. The highest value of growth vigor was obtained 2 weeks after girdling and the lowest was obtained 10 weeks after girdling. 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 Number of new roots new of Number 1.00 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 9a. Effect of girdling on number of new roots of lime stem cuttings
16.00 A 14.00 12.00 10.00 AB 8.00 B B 6.00 B
Number of new roots new of Number 4.00 2.00 0.00 246810 Time interval (in weeks)
Fig. 9b. Effect of sowing interval on number of new roots of lime stem cuttings 1.70 1.68 1.66 1.64 1.62 1.60 Growth vigor Growth 1.58 1.56 1.54 1.52 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 10a. Effect of sgirdling on growth vigor of lime stem cuttings
2.50
2.00
1.50
1.00 Growth vigor Growth
0.50
0.00 246810 Time interval (in weeks)
Fig. 10b. Effect of sowing interval on growth vigor of lime stem cuttings 4.3. Winter experiments:
4.3.1. Effect of girdling and sowing interval on percentage of rooted lime stem cuttings:
The effect of girdling on percentage of rooted cuttings, was illustrated in (Table 1-a; Fig. 11-a). Significant differences were found among basal cuttings and apical cuttings. Non girdled cuttings showed no significant difference when compared to the two other treatments.
The highest percentage of rooted cuttings was associated with apical cuttings (62.9%) followed by non girdled cuttings (48.0%) and then basal cuttings (22.9%).
No significant difference in percentage of rooted cuttings was found among cuttings taken in the different sowing intervals. The highest percentage of rooted cuttings was obtained 8 weeks after girdling
(53.4%) followed by 4-(46.7%) 10-(44.2%), 6-(42.7%), and then 2- weeks after girdling (34.0%) (Table 1-a; Fig. 11-b).
4.3.2. Effect of girdling and sowing interval on number of roots of lime stem cuttings:
Table (2-a); Fig. (12-a) showed that no significant difference was found in number of roots among the different treatments. The greatest number of roots was obtained with apical cuttings followed by non girdled cuttings and then basal cuttings. 70.00 A 60.00 50.00 AB 40.00 30.00
Rooting % Rooting B 20.00 10.00 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 11a. Effect of girdling on percent rooted lime stem cuttings
60.00
50.00
40.00
30.00 Rooting % Rooting 20.00
10.00
0.00 246810 Time interval (in weeks)
Fig. 11b. Effect of sowing interval on percent rooted lime stem cuttings No significant difference in number of roots between 2, 8 and 10 weeks, between 2, 8 and 6 weeks and between 6 weeks and 4 weeks. The highest value of number of roots was obtained 4 weeks after girdling followed by 6, 2, 8 and then 10 weeks (Table 2-a; Fig. 12-b).
4.3.3. Effect of girdling and sowing interval on length of roots of lime stem cuttings:
The effects of girdling was shown in Table (3-a); Fig. (13-a).
Apical cuttings showed significant differences in roots length when compared to basal cuttings and non girdled cuttings.
The highest value of roots length was associated with apical cuttings and the lowest value was associated with basal cuttings.
Results in Table (3-a); Fig. (13-b) showed that no significant difference was found in root length between 2, 8 and 10 weeks interval, between 2 and 6 weeks and between 6 and 4 weeks interval. The highest value of root length was obtained with cuttings taken 4 weeks after girdling, and the lowest root length value was associated with those taken 10 weeks after girdling. 1.80 1.60 1.40 1.20 1.00 0.80 0.60 Number of roots of Number 0.40 0.20 0.00 Non girdled cuttings Basal cuttings Apical cuttings Cutting type and position (treatments)
Fig. 12a. Effect of girdling on number of roots of lime stem cuttings
A 2.50
2.00 AB 1.50
1.00 BC Number of roots of Number BC 0.50 C
0.00 246810 Time interval (in weeks) Fig. 12b. Effect of sowing interval on number of roots of lime stem cuttings 4.50 4.00 A 3.50 3.00 B 2.50 B 2.00
Root length Root 1.50 1.00 0.50 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 13a. Effect of girdling on length of roots of lime stem cuttings
6.00 A
5.00 AB 4.00
3.00 BC Root length Root 2.00 C
1.00 C
0.00 246810 Time interval (in weeks)
Fig. 13b. Effect of sowing interval on length of roots of lime stem cuttings 4.3.4. Effect of girdling and sowing interval on number of new roots of lime stem cuttings:
No significant difference was found in number of new roots among the different treatments. The greatest number of new roots was obtained with apical cuttings, followed by basal cuttings and then non girdled cuttings (Table 4-a; Fig. 14-a).
No significant difference in number of new roots was noted between cuttings taken 2 weeks after girdling and those taken 6, 8 and
10 weeks after girdling and also among cuttings taken 4, and 6 weeks after girdling. The highest number of new roots was obtained with 4 weeks after girdling followed by 6, 2, 8 and then 10 weeks (Table 4-a;
Fig. 14-b).
4.3.5. Effect of girdling and sowing interval on growth vigor of lime stem cuttings:
The effect of girdling on growth vigor was illustrated in Table 5-a
Fig. (15-a). Significant differences were found among apical and basal cuttings. Non girdled cuttings showed no significant difference compared to the two other treatments. The highest growth vigor was obtained with apical cuttings and the lowest growth vigor value was obtained with basal cuttings. Data presented in Table (5-a); Fig. (15-b) showed that no significant difference on growth vigor was noted between cuttings taken
2, 6, 8 and 10 weeks after girdling and also among cuttings taken 4 and 6 weeks after girdling. The highest value of growth vigor was obtained 4 week after girdling and the lowest value was obtained 10 weeks after girdling. 9.00 8.00 7.00 6.00 5.00 4.00 3.00
Number of new roots roots new of Number 2.00 1.00 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments) Fig. 14a. Effect of sowing on number of new roots of lime stem cuttings
14.00 A 12.00
10.00
8.00 AB 6.00 B 4.00 Number of new roots roots new of Number
2.00 BB 0.00 246810
Time interval (in weeks) Fig. 14b. Effect of sowing interval on number of new roots of lime stem cuttings 1.80 1.60 AB A 1.40 B 1.20 1.00 0.80
Growth vigorGrowth 0.60 0.40 0.20 0.00 Non girdled cuttings Basal cuttings Apical cuttings
Cutting type and position (treatments)
Fig. 15a. Effect of gridling on growth vigor of lime stem cuttings
2.50 A
2.00 AB B 1.50 B B 1.00 Growth vigor vigor Growth
0.50
0.00 246810
Time interval (in weeks)
Fig. 15b. Effect of sowing interval on growth vigor of lime stem cuttings 4.4. Effect of seasons, girdling and sowing interval on percentage of rooted lime stem cuttings:
4.4.1. Seasons: The effect of seasons on percentage of rooted lime stem cuttings was shown in Table (1-a) Fig. (16-a). Cuttings taken in summer showed significant differences in percentage of rooted cuttings compared to those taken in autumn or winter. Cuttings taken in autumn gave the highest percentage of rooted cuttings (46.2%) followed by winter
(44.2%) and then summer (4.7%).
4.4.2. Girdling:
Results in Fig. (16-b), appendix (1-b) showed that basal cuttings showed significant differences in percentage of rooted cuttings compared to apical cuttings and non girdled cutting. The highest percentage of rooted cuttings was associated with apical cuttings (35.00%) followed by non girdled cuttings (28.7%) and then basal cuttings (22.5%).
4.4.3. Sowing intervals: No significant difference in percentage of rooted cuttings were found among cuttings taken 2, 4, and 6 weeks after girdling and also among 2, 6 and 8 weeks after girdling. However, cuttings taken 10 weeks after girdling were significantly different compared to all other weeks. The highest percentage of rooted cuttings was obtained with 10 weeks after girdling (45.6%) followed by 8 (32.00%), 6 (25.2%), 2
(23.4%) and then 4 weeks after girdling (18.00%) (Table 1-b Fig. 16-c). 4.5. Effect of seasons, girdling and sowing interval on number of roots of lime stem cuttings:
4.5.1. Seasons: Results in Table (2-a); Fig. (17-a) showed that cuttings taken in autumn were significantly different in number of roots compared to cuttings taken in summer or in winter.
The highest value of number of roots was obtained in autumn followed by winter and then summer.
4.5.2. Girdling: No significant difference was found in number of roots among the different treatments. The greatest number of roots was obtained with basal cuttings followed by apical cuttings and then non girdled cuttings (Table 2-b; Fig. 17-b).
4.5.3. Sowing intervals:
The effect of sowing interval on number of roots was illustrated in
Table (2-b); Fig. (17-c). No significant difference was observed between cuttings taken in the different sowing interval. The greatest number of roots was obtained with cuttings taken 10 weeks after girdling followed by 6, 2, 4 and 8 weeks after girdling. 50.00 AA 40.00 30.00 20.00
Rooting % 10.00 0.00 B Summer Autumn Winter Seesons
Fig. 16a. Effect of seasons on percent rooted lime stem cutting
A 35.00 30.00 A 25.00 B 20.00 15.00 10.00 Rooting % Rooting 5.00 0.00 Non girdled Basal cuttings Apical cuttings cuttings
cutting type and position (treatments)
Fig. 16b. Effect of Girdling on percent rooted lime stem cuttings
50.00 A 40.00 30.00 B 20.00BC BC C 10.00
Rooting % 0.00 246810 Time interval (in weeks)
Fig. 16c. Effect of sowing interval on percent rooted lime stem cuttings 2.50 A 2.00 1.50 1.00 B B roots 0.50 Number ofNumber 0.00 Summer Autumn Winter
Seesons
Fig. 17a. Effect of seasons on number of roots of lime stem cuttings
2.00 1.50 1.00
of roots 0.50 Number Number 0.00 Non girdled Basal cuttingsApical cuttings cuttings Cutting type and position (treatments)
Fig. 17b. Effect of Girdling on number of roots of lime stem cuttings
2.00 1.50 1.00 roots 0.50 Number of of Number 0.00 246810 Time interval (in weeks)
Fig. 17c. Effect of sowing interval on number of roots of lime stem cuttings 4.6. Effect of seasons, girdling and sowing interval on length of rooted lime stem cuttings:
4.6.1. Seasons:
Significant differences were found in root length among summer and autumn seasons sowings. On the other hand, winter cuttings showed no significant difference compared to these two seasons. The highest value of root length was obtained from cuttings taken in autumn and the lowest value was associated with cuttings taken in summer (Table 3-a;
Fig. 18-a).
4.6.2. Girdling:
No significant difference was found in root length among the different treatments. The highest value of root length was obtained with apical cuttings and the lowest value was associated with non girdled cuttings (Table 3-b; Fig. 18-b).
4.6.3. Sowing intervals:
Results in Table (3-b); Fig. (18-c), showed that no significant difference was found in root length among the different sowing intervals.
The highest root length value was obtained from cuttings taken 2 weeks after girdling, and the lowest value was associated with cuttings taken 8 weeks after girdling. 4.00 A AB 3.00 2.00 B 1.00
Root length length Root 0.00 Summer Autumn Winter Seesons
Fig. 18a. Effect of seasons on length of roots lime stem cuttings
3.50 3.00 2.50 2.00 1.50 1.00
Root length length Root 0.50 0.00 Non girdled cuttings Basal cuttings Apical cuttings Cutting type and position (treatments) Fig. 18b. Effect of girdling on length of roots lime stem cuttings
3.5 3 2.5 2 1.5 1 0.5 Root length length Root 0 246810 Time interval (in weeks)
Fig. 18c. Effect of sowing interval on length of roots lime stem cuttings v 4.7. Effect of seasons, girdling and sowing interval in number of new roots of lime stem cuttings:
4.7.1. Seasons:
No significant difference was found in number of new roots among the different three seasons. The greatest number of new roots was obtained in autumn followed by winter and then summer (Table 4-a; Fig.
19-a).
4.7.2. Girdling:
The effect of girdling on number of new roots was illustrated in
(Table 4-b Fig. 19-b). No significant difference was observed between the different treatments. The highest value of number of new roots was obtained with basal cuttings followed by apical cuttings and then non girdled cuttings.
4.7.3. Sowing intervals:
No significant difference was found in number of new roots among the different sowing interval. The highest value of number of new roots was obtained with cuttings taken 2 weeks after girdling followed by 4, 6, 10, and then 8 weeks after girdling (Table 4-b; Fig. 19-c). 10.00 8.00 6.00 4.00 2.00 new roots Number of 0.00 Summer Autumn Winter Seesons
Fig. 19a. Effect of seasons on number of new roots of lime stem cuttings
8.00 6.00 4.00 2.00 Number of new roots 0.00 Non girdled Basal cuttingsApical cuttings cuttings
Cutting type and position (treatments)
Fig. 19b. Effect of girdling on number of new roots of lime stem cuttings
10 8 6
roots 4 2
Number of new 0 246810 Time interval (in weeks)
Fig. 19c. Effect of sowing interval on number of new roots of lime stem cuttings 4.8. Effect of seasons, girdling and sowing interval on growth vigor of lime stem cuttings:
4.8.1. Seasons:
Results in (Table 5-a; Fig. 20-a), showed that cuttings taken during summer showed significant differences on growth vigor compared to those taken in autumn and winter. The highest growth vigor value was obtained in autumn and the lowest growth vigor value was obtained in summer.
4.8.2. Girdling:
No significant difference was found in growth vigor among the different treatments. The highest growth vigor was obtained with non girdled cuttings and the lowest was obtained with apical cuttings (Table
5-b Fig. 20-b).
4.8.3. Sowing intervals:
Results in (Table 5-b; Fig. 20-c) showed that no significant difference was found on growth vigor among the different sowing intervals. The highest value of growth vigor was obtained from cuttings taken 2 weeks after girdling and the lowest value was associated with cuttings taken 6 weeks after girdling. 2.00 A A 1.50
1.00 B 0.50 Growth vigor 0.00 Summer Autumn Winter
Seesons Fig. 20a. Effect of seasons on growth vigor of lime stem cuttings
1.33 1.32 1.31 1.30 1.29 1.28 Growth vigor 1.27 1.26 Non girdled Basal cuttingsApical cuttings cuttings
Cutting type and position (treatments) Fig. 20b. Effect of Girdling on growth vigor of lime stem cuttings
2
1.5 1 0.5 Growth vigor 0 246810 Time interval (in weeks)
Fig. 20c. Effect of sowing interval on growth vigor of lime stem cuttings 5. DISCUSSION
5.1 Effect of girdling on rooting of lime stem cuttings:
The physical removal of a ring of the phloem (bark) from a branch or stem blocks the downward movement of food materials, hormones and other growth regulators synthesized in the leaves.
Basal stem cuttings of lime taken from girdled shoots gave high rooting percentage compared to similar cuttings taken from non-girdled shoots or apical cuttings taken from girdled shoots during the summer season (Table 1-a). These results are in agreement with those reported by
Debanath et al (1986) for lemons and Nageswar et al. (1988) for sweet lime, suggesting that girdling of shoots prior to severing of cuttings substantially increased rooting percentage of those cuttings.
Perhaps the higher rooting percentage of cuttings obtained from girdled shoots would results from a significant buildup of carbohydrates and other rooting cofactors above the girdle. James et al (1970) attributed the beneficial effect of girdling on rooting of cuttings of macadamia to the possible accumulation of higher levels of carbohydrates, auxin and other endogenous root promoting substances.
Similar explanation for the promotive effect of girdling on rooting has been suggested by Basu et al. (1972) and by Stoltz and Hess, (1965). Basal stem cuttings of lime taken from girdled shoots during winter showed a relatively low rooting percentage in a agreement with previous finding (Cormack and Bate, 1976), that girdling has no effect on rooting of cuttings during the winter. This might be attributable to depletion of carbohydrates and other growth promoters during the flowering and fruiting periods which coincide with the time of branch girdling leaving low levels of these rooting factors and cofactors above the girdle. Cambial activity is also expected to be low indicating that the response of rooting cuttings to girdling is season dependent (Cormack and Bate 1976).
Girdling also greatly improved rooting percentage in response to
Seradix II treatment. Similar observations were reported by Mukherjee
(1972), that girdling improved the influence of 1BA and increased its effect in promoting rooting of mango stem cuttings.
In citrus girdling proved to be effective where greater success in for rooting was recorded for lemon cuttings from girdled shoots compared to those form non- girdled shoots (Debanth et al., 1986).
Complete failure of rooting of cutting from non-girdled shoots of sweet lime was also reported by Jauhari and Rahman (1959).
Girdling increased rooting percentage of cutting through its effects on total sugars concentration in cuttings (Stloltz and Hess, 1965, Evert and Smittle, 1990, Hartmann et al 1990). Starch concentration in cutting from girdled shoots was however unchanged (Evert and Smittle
1990). Only one single report, to my knowledge, that of Evert and
Simttle (1990), reported a decreased rooting and survival percentages of cuttings from girdled shoots.
5-2 The effect of time of severing and planting lime cuttings on percent rooting:
Plant species differ greatly in their response to environmental factors in all their developmental growth phases. Rooting of cuttings for the purpose of propagation is not an exception. Rooting of cuttings seem to be influenced by the time of the year cutting are collected from filed grown mother trees and differences in rooting ability of cuttings of various plant species and varieties have been observed (Issell and
Chalmer, 1979, Nam and Kim 1985).
The data portrayed in table (1-a) shows that best rooting percentage of lime stem cuttings was obtained during Autumn. Percent rooting declined during summer. This data generally concur with previous findings reported by several investigators with different plant species (Sinha et al., 1962, Hartmann and Loretti, 1965; Howard and
Nahlawi, 1969, Issell and Chalmer, 1979, Anand and Hebertein 1975,
Fadl et al., 1979, Costa and Baralidi, 1983, Caldwell et al., 1988). The time of the year that the cuttings were taken had a significant influence on their rooting percentage. The important of cambial activity at the time of cutting preparation and planting has been suggested as a factor determining successful rooting of these cuttings. The association of high rooting percentage with periods of new growth flushes has been reported by Sinha et al (1962), and by Anand and Hebertein
(1975).
The obtenation of high rooting percentage during Spring and
Summer and low rooting percentage during Autumn and Winter may be attributed to temperature degree at the time of planting.
Temperature degrees usually drop below the optimum for rooting thus low rooting percentage or no rooting occur in winter (Tingwa and
Abdadi 1968). The importance of temperature degrees of the planting medium has been sited as the main factor governing rooting of kiwifruit cuttings (Sim and Lawes, 1981). No difference in rooting percentage was found between cuttings collected in January and March if the temperature of the growing medium was maintained at 23±2°C throughout the course of their experiments. Unlike in this study and other studies (Costa and Baraldi, 1983, Caldwell et al., 1988), where planting medium temperature reflected seasonal changes in air temperature. Rate of root formation on cuttings seem to be directly affected by medium temperature, with raised temperature accelerating root initiation and development (Poole and Waters, 1971, Henny, 1984,
Wang, 1988).
Differences in rooting efficacy of lime cutting across dates may be because of physiological changes in the mother tree. And the time of cuttings which is greatly influenced by air and planting medium temperatures.
The result of this study indicates that temperature is the major factor influencing the rooting of lime stem cuttings. The two weeks sowing interval gave high value of rooting in respect to number of newly formed roots, length of roots and growth vigor in the autumn season and in the winter season most parameters measured gave high values in cuttings taken 4 weeks after girdling. This trend in rooting seems to be associated with the gradual decrease in temperature with time. This agrees with the findings of Juma (1994) where he reported complete failure of rooting of lime cuttings during the winter season.
The progressive increase in relative humidity during the rainy season of the year in Sudan may flavour rooting of lime stem cuttings through its effects on water loss from the planted cutting and / or the planting medium. Similar observation have been reported by Chhonkar and Singh (1972) in air– layering of a mango variety where rooting was far better in summer due to increased atmospheric humidity.
It has been observed during the course of this study that cuttings obtained from flowering branches did not root at all. The developmental growth changes of the mother tree may have an influence on rooting of cutting through its effect on mother plant food reserves and on synthesis of growth cofactor. At flowering most tissue food reserves and growth substance in the plant tissue might be directed to the transformation of pre-existing vegetative buds into flower buds. Competition for growth and development between rooting and flowering might be a factor in failure of rooting during flowering. Issel and Chalmer, (1979), and
Thompson (1986), reported lower rooting percentages when cuttings were taken at flowering and fruit set and attributed that to depletion of food and other growth factors stored in the tissue of the donor trees.
Seasonal variation in the rooting promoters (Sinha et al., 1962) and rooting inhibitors (Wally et al 1981) have been sited as the main factor eliciting rooting of cuttings during the different times of the year.
The variation in rooting percentages, obtained in this study may possible be due to alterations in the internal balance of promoters and inhibitors during the different times of the year cuttings were severed from the parent plant which is in accord with findings of other investigators (Fadl and Hartmann, 1967; Robert and Fuchigami, 1973, Miller et al., 1982).
5-3 The effect of shoot position:
Shoot section had a significant effect on rooting of lime stem cuttings. The highest percent rooting was obtained with cuttings taken from the basal portion of current season growth (table 1-a). The terminal section of shoot had lower rooting percentage than the basal section, possibly due to wilting of succulent tissue (higher evaporation loss of water) or low carbohydrate concentration compared to more basal shoot sections. The relationship of rooting ability of cuttings to shoot sections has been reported by many investigators using various plant species
(Bachelard and Stowe, 1963, Aminov, 1963, Wally et al., 1981, Goode and Lane, 1983, Thompson, 1986, Samekto et al., 1995). The influence of shoot section on rooting ability of cuttings was attributed to high carbohydrate concentration in the tissues of basal portions in addition to the presence of preformed root primordia and high levels of auxins and other rooting cofactors compared to terminal portions of the shoot
(Aminov, 1963, Goode and Lane, 1983, Thompson, 1986). The disturbance of the balance between root promoters / inhibiters with distance from the apex has also been suggested as a factor involved in the increase in rooting percentage as the cuttings were taken progressively distal from the apex (Thompson, 1986, Mahgoub, 1990).
The observation by Hans, (1975), Polusen and Anderson, (1980), Goode and Lane (1983), and Hansen (1986) that rooting ability increased with distance from the apex, indicates that auxin, among other endogenously produced substances is an important factor in this gradient rooting effect
Natural auxin (IAA) is known to be basipetally transported from the apical to the basal portion of plants. Equal percentages of rooting were obtained when sub terminal and basal cutting of olive were treated with high concentration (4000mg/l) of the IBA (Loretti and Hartmann. 1965).
Similarily Howard and Nahlawi, (1969) reported equal rooting percentage of plum terminal, median and basal cuttings concluding that auxin was the main limiting factor. Furthermore time of severing cutting seems to have an influence on the relationship of rooting percentage to the shoot sections. Goode and Lane (1983), working with grape cuttings reported higher rooting percentage for basal cuttings than for middle or terminal cuttings on the early cuttings dates of (May 30 and June 15) but rooting percentage became similar or equivalent or better on later cuttings dates (July 13 and August 7) indicating the influence of environmental conditions on promoters/inhibitors balance. In controst to our results apical cuttings were found to be the cuttings of choice where higher rooting percentage were consistently obtained (Marini, 1983, Caldwell et al., 1988, Mahgoub, 1990), still in other plant species shoot section has no effect on rooting efficiency (Mahagoub 1990). This may be due to the fact that the response to shoot position is species depended
(Hans, 1975).
Difference in rooting ability between shoot section has been attributed to differences in concentrations of substances required for rooting. Basal sections had higher rooting percentage because the concentration of these substances is higher compared to median or terminal section.
The finding that basal cuttings were better during the summer while the apical cuttings were best during autumn and winter may be attributed to the cambical activity as well as to the rate of translocation of phytozynthates which both decrease with the gradual decrease in temperature.
Apical cuttings were younger and more juvenile and relatively have a high rate of translocation of phytozynthates and cambial activity.
However Bachelard and Stowe (1963) speculated the involvement of natural GA, produced in the apical tips, in the inhibition of rooting of terminal shoot section where its concentration is expected to be higher compared to basal shoot sections. The increase in rooting ability with distance from the apex has also been attributed to phase change that gradually occur along the stems of shoots of plants (Hackett, 1985)
Henry et al (1992), on the other hand, found no effect of shoot position in 4-year-old trees but cuttings of 30–year-old trees from terminal portions rooted less well than cutting from basal portions.
The balance between the auxin and rooting cofactor throughout the branches of young trees was not yet disturbed in younger trees as in old trees.
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