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A Seedless Fruit: Less Is Better in Quality

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A Seedless Fruit: Less Is Better in Quality Food and Scientific Reports ISSN 2582-5437 A Seedless fruit: less is better in quality Sajana S, Jagadeesha Mulagund and Prashanth Kalal PhD scholars, Division of Fruit crops, ICAR-IIHR, Bengaluru ABSTRACT Seed formation and development of fruit are closely related mechanisms governed by internal signals and environmental conditions. Consumers and producers usually desire seedlessness because it improves fruit quality and shelf-life. Seedless fruits can be produced by developing plants which will be able to show fruiting without pollination and subsequent fertilization. Hormones produced by plants regulate development of fruits. Studies in the recent years have enormously contributed to demonstrate the role of plant hormones in controlling initiation of fruits and simultaneously developing genetic methods for incorporating seedlessness in horticultural crops. Seedlessness is a relative phenomenon where it may be Low pollen viability- Pollen viability is reported to be due to occurrence of the following situations namely low in late flowering genotypes of apricot compared to reduction in size of the seed, number of seeds per fruit, early flowering ones. (Ruiz and Egea, 2008) presence of soft/ semi soft (Mellowness), Rudimentary/papery seed. Seedlessness may be due to Pollen sterility - Large proportion of sterile pollens are genetic/other factors like incompatibility, triploidy, reported in cv. J.H.Hale and many Olive cultivars gynoecy or due to cultural and environmental (Besnard et al., 2000) conditions. Genetically seedless fruits are produced as a Sterile ovule - The share of sterile ovules varies from result of Parthenocarpy. Parthenocarpy is a phenomenon 22% in apricot and 98% in avocado (Verma and Jindal, where fruits are produced without fertilization. It is a 1997). Trevatt blue, a clone of Trevatt variety in apricot phenomenon which is common in fruits having inferior showed very small multiple ovules, retarded ovary. Noll (1902) proposed the term Parthenocarpy development in flower, anthers and degenerated when he observed formation of seedless fruits in micropores which is the first report of simultaneous absence of functional pollination. mutation in both female and male function (Lillecrapp 2. Types of parthenocarpy: et al., 1999). a. Stimulative parthenocarpy: Pollination stimulus is Poorly developed embryosac- At anthesis, embryosac necessary for development of fruit. e.g grapes development is poor in large percentage of ovules in Olive cv. Swan Hill (Rallo, 1981) b. Vegetative parthenocarpy: Fruits are developed without pollination stimulus. e.g. Pineapple, banana, Aborted pollen grains - In cashew nut, 22.5 to 46.8% of Washington Navel orange, apple, pear, fig, date and pollen grains were found to be aborted and it showed an bread fruit. increase in this proportion with the age of the plant (Bhattacharya, 2005) c. Parthenogenesis: The condition in which viable seeds are produced without pollination (development of Self incompatibility - Many of Pear cultivars show embryo from egg cell). e.g. mangosteen and some improper fruit set which is due to prevention of self- varieties of strawberries. pollination by gametophytic self incompatibility system (Sanzol, 2007). In loquat varieties such as golden d. Seedless fruits are also produced due to sterility yellow, pale yellow and improved golden yellow the which may be because of the following reasons: pollen tube penetrated 1/4 to 1/3rd of the length of stylar canal and did not proceed further even at 72 h Defective pollen - In Muscadine grapes, sterile pollen after pollination which suggested self incompatibility in forms as a result degeneration processes in the loquat (Singh and Rajput, 1964). Apart from this generative nucleus or development will stop in condition, a true seedless fruit cannot be possible in microspore nucleus before mitosis (Samson et al., 2001) crops like custard apple, pomegranate where the seed coat serve as edible part. April 2020 │Volume 1: Issue 4 │Page 25 Food and Scientific Reports ISSN 2582-5437 3. Characteristics of seedless fruit 6. Seedlessness in fruit crops Sl. Crop Seedless Particulars a. Seedless fruits in general are smaller in size No Variety 1. Grapes- stimulative Perlette and Produce compared to their seeded counterpart (eg: Grape- pathenocarpy Pusa Urvashi rudimentary seed exogenous GA can give elongated berry). due to temperature b. In Seedless fruits, other forms like reduced seed fluctuation in sub- tropical conditions. number, soft seed, Hollow seed (floater) in grape can also be noted. Venus when grown in temperate region, c. Thickened pedicel in case of pear considered as d. Fruit surface is normally very smooth except in seedless but when shifted to case of guava where the surface is warty. tropical/sub tropical e. Seedless fruits in general mature later than their produced hard seed counter parts. (floater) 2. Mango- due to Sindhu Developed from embryo (Ratna x FRS, Vengurla 4. Need for Seedless fruits abortion/vegetative Alphonso) Parthenocarpy a. Seedlessness is a desirable trait for preference by 3 Banana- Vegetative even in the BB wild parthenocarpy in banana genotype consumers & buyers owing to improvement in cultived types seeds are formed, eating quality. they are hardly seed fertile owing to the b. Seedless fruits are preferred by processors so that complex cytological there is less waste generation. factors. c. It improves the acceptability / creates the novelty 4. Citrus- triploidy Sweet seedlessness can also in fruit crops. through orange - result due to self natural/induced Hamlin, incompatibility mutation washington (summer fruiting 5. Reasons/ Causes for formation of Seedlessness in navel, pera, Kagzi Kalan), fruit crops valencia, reduced pollen Shamouti. fertility, embryo 1. Evolution caused due to spontaneous mutation in Mandarin- abortion and Satsuma, chromosomal ploidy nature clementine variation. 2. Genetic makeup Grapefruit- Marsh, 3. Hybridization & complex nature (due to several Thompson, processes/ existence of extra chromosomes- Redblush Lime-Tahiti satellite chromosomes) 4. Induced mutations/ Isolation of natural bud/limb 5. Guava- spray of Pusa Srijan they will not sports auxins (few seeds germinate. 10-15) 5. Polyploidy (Accessions of triploids- Apple, pear, Seedless It is made to develop Tahiti: All aneuploids) clone into natural fruit identified at when some growth 6. Parthenocarpy Taiwan regulator was 7. Incompatibility owing to pollen deformity, sterility (VNR-clone) sprayed during fruit development. The (Self-sterility in Litchi) fruits are unique with 8. Climatic conditions (Fig) almost negligible 9. Location (Latitudinal changes- Eg: Grapes) seed coat and the pulp never ripens. 10. Chromosomal imbalances due to polyploidal The ripening in such crosses fruits can be induced by spraying of ethrel. 11. Other factors: Damage by insects, 6. Ber with the application abnormal/unseasonal adverse weather condition of EMS (0.01 %) with lanolin on small growth tensions and plant growth conditions like developing fruits. excessive vegetative growth reduced crop density, The fruits are found root destruction, tree injury may also lead to seedless with formation of central Seedlessness. notch. April 2020 │Volume 1: Issue 4 │Page 26 Food and Scientific Reports ISSN 2582-5437 7. Difficulties in developing Seedless varieties in fruit characterised by its seedless core, delicate fragrance and crops: firm, full-flavoured pulp. Even after it is sliced, the fruit i. In conventional breeding, only seeded maintains its excellent consistency for a long time. genotypes can be used as seed parents, hence there is lot of limitation. Conclusion ii. When seedless genotypes are used as male Development of fruits without seeds may or parents, the pollen quality, viability etc. vary may not alter the original characters of the fruit. Seed is considerably and hence the results are variable. a part in fruit which aids in utilizing energy and iii. The average frequency of seedless progeny in a essential nutrient elements for changing characteristics cross involving seedless parent can only give of the fruit like levels of sugar and nutrients, size of the rise to 15 % (on avg.) seedless progeny which fruit, maturity time etc. Breeders and horticulturists is further reduced by poor germination. have done an appreciable job by applying standard iv. Lack of availability of morphological marker breeding methods and production strategies to surpass for adjudging seedlings at the early age. these barriers. v. In the present day, the traditional breeding involves use of genotypes with high seed index References namely Hur, Anngurkala, Kattakurgan, which are expected to give high proportion of Besnard, G., Khadari, B., Villemur, P.(2000). Cytoplasmic seedless progeny. male sterility in the olive (Olea europaea L.). Theor vi. Introgression breeding to transfer berry quality Appl Genet 100, 1018–1024. and seedlessness and an alternative approach Bhattacharya, A (2005). Age dependent pollen abortion in cashew. Curr. Sci. 88 (7) : 1169-1171. involving different crosses (A x B and A x C) Lillicrapp, A.M, Wallwork, M.A and Sedgley, M. (1999). vii. In-ovulo embryo rescue and use of marker : In Female and male sterility cause low fruit set in a clone present day, several grape breeding of the ‘Trevatt’ variety of apricot (Prunus armeniaca). programmes globally following in-ovulo Scientia. Hort. 82 : 255-263. embryo rescue followed by recovery of Noll, F., 1902. Fruchtbildung ohne vorausgegangene seedless progeny from crosses
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