1969 213

Chromosome Numbers in

K. Ramachandran

University Department of Botany, Kerala University, Trivandrum, India

Received April 12, 1968

Introduction The family Zingiberaceae consists of 45 genera and about 800 species distributed mostly in tropical Asia (Willis 1960). The family contains several useful genera. Many species are used as spices, a few have fleshy rhizomes which yield starch and several others are used in medicine. Holttum (1951) has listed the useful genera of the family and has also suggested possible lines of artificial hybridization for the improvement of the various cultivated species of the family. Cytological observations on some cultivated and related wild of the family are given in this paper.

Materials and methods

Cytological investigations of 26 species coming under 11 genera were carried out during the present study (Table 1). Most of the species in vestigated were collected from the different parts of Kerala State. Boesenbergia longiflora and Zingiber roseum were obtained from Nepal and Hitchenia caulina from Maharashtra State.

Root tips for somatic chromosome studies were chilled for an hour at

6-10•Ž in water before fixation in Carnoy's fluid (alcohol, acetic acid and chloroform, 3: 1 : 1). Anthers were dissected out from buds and fixed in alcohol-acetic acid (3: 1). Acetocarmine smears were made according to the usual procedure.

Observations The chromosome numbers of 26 species determined in the present study and numbers reported previously for the same species are listed in Table 1 (The genera are arranged in the order given in Hutchinson's (1934) classi fication). Some interpretations of the data presented in Table 1 are given below.

Costus C. speciosus. This is a polymorphic species complex (Simmonds 1954) having a very wide distribution range. All the South Indian plants of this species examined showed 36 somatic chromosomes. Meiosis was regular. 214 K. Ramachandran Cytologia 34

Table 1. Chromosome numbers in the Zingiberaceae 1969 Chromosome Numbers in Zingiberaceae 215

Table 1 (Contd.)

Eighteen bivalents were regularly observed in pollen mother cells (Fig. 1). The showed good pollen and seed fertility. Sato (1948) reported a somatic chromosome number of 18 in this species from Japan and, therefore, the South Indian plants examined in the present study are tetraploids. The same number has been reported previously in plants from Eastern and Central India (Banerji 1940, Raghavan and Venkatasubban 1943, Venkatasubban 1946, Chakravorti 1948, Sharma and Bhattacharyya 1959). Simmonds (1954) reported from Trinidad a triploid (2n=27) showing 9II 9I at metaphase I, suggesting allotriploidy, resulting from hybridization between distinct tetraploid and diploid species. Hedychium H. coronarium. A clone of this common garden plant showed 2n=34 and n=17, as reported previously (Sharma and Bhattacharyya 1959). Another clone possessing 51 somatic chromosomes (Fig. 2) was also found in the present study. The latter showed a maximum of 17 trivalents (Fig. 3), suggesting 216 K. Ramachandran Cytologia 34

Figs. 1-10. •~1000. 1, metaphase I in a pollen mother cell of Costus speciosus showing 18 bivalents. 2, Hedychium coronarium (triploid form) 2n=51. 3, metaphase I in pollen mother cell of triploid H. coronarium showing 17 trivalents. 4, metaphase I in pollen mother cell of Boesenbergia longiflora showing 25 bivalents. 5, Kaempferia rotunda, 2n=44. 6, Kaempferia galanga, 2n=54. 7, Hitchenia caulina, 2n=42. 8, metaphase I in a pollen mother cell of H. caulina showing 21 bivalents. 9, Globba ophioglossa, 2n=22. 10, metaphase I in pollen mother cell of G. ophioglossa showing 11 bivalents. 1969 ChromosomeNumbers in Zingiberaceae 217 that the plant is possibly an autotriploid. The triploid shows gigas characters such as larger stature of the plant and larger size of leaves and flowers. The plants examined by Raghavan and Venkatasubban (1943) and Chakravorti (1948) possessing 54 chromosomes are possibly hypertriploids. Boesenbergia B. longiflora. The chromosome number of B. longiflora has been determined from meiosis only. At metaphase I, 25 bivalents have been ob served (Fig. 4). Two to four secondarily associated pairs of bivalents have also been found in most pollen mother cells. The plant showed regular meiosis and good seed setting. Kaempferia K. rotunda showed 44 somatic chromosomes (Fig. 5) and is a tetraploid on the basic number 11. In K. galanga root tip cells showed 54 chromo somes (Fig. 6). The latter is presumably an aneuploid pentaploid. Hitchenia H. caulina showed a somatic complement of 42 chromosomes (Fig. 7). Meiosis was regular. Twenty one rod bivalents were regularly observed at metaphase I (Fig. 8). This suggests a high Easic number of 21 for the genus. The cytology of 6 species and several varieties of Curcuma was reported earlier (Ramachandran 1961). Diploid, triploid and tetraploid numbers on the basic number 21, were observed in this genus.

Globba G. ophioglossa possesses 22 somatic chromosomes (Fig. 9) which form 11 bivalents (Fig. 10) during meiosis. G. bulbifera showed 96 somatic chro mosomes (Fig. 11), the highest chromosome number observed in any South Indian plant of the Zingiberaceae. This is possibly an octoploid on the basic number 12, since the tetraploid number 48 has been reported for this species from other sources. During meiosis, varying numbers of univalents and multivalents are formed (Fig. 12) and irregular separation of chromo somes occurs at anaphase. Only less than 10 per cent of pollen is well formed. The plant is seed sterile, but has very efficient means of vegetative propagation by means of bulbils. The flowers in the lower bracts of in florescences are replaced by spherical or ovoid bulbils. This genus has two basic numbers 11 and 12. Alpinia The 3 species of Alpinia examined showed 48 somatic chromosomes, which agree with previous observations of numbers for the same species.

Cytologia34, 1969 15 218 K. Ramachandran Cytologia 34

Amomum The 3 South Indian species in which chromosome numbers were de termined in the present study showed 48 somatic chromosomes.

Figs. 11-16. •~1000. 11, Globba bulbifera, 2n=96. 12, metaphase I in a pollen mother cell of G. bulbifera showing univalents and multivalents. 13, metaphase I in a pollen mother cell of Elettaria cardamomum showing 24 bivalents. Figs. 14-16. Stages of division I in pollen mother cells of Zingiber officinale (2n=22). 14, metaphase I showing 11 bivalents. 15, metaphase I showing 9 bivalents and 1 chain quadrivalent. 16, anaphase I showing two bridges and two fragments.

Elettaria

E. cardamomum forms the chief source of the well known spice Carda

moms. In South India, it grows wild in the Western Ghats, and is also 1969 ChromosomeNumbers in Zingiberaceae 219 cultivated on a plantation scale, at elevations of over 900 meters. The cytology of this plant has been previously studied in detail by Gregory (1936). He reported n=24 and 2n=48. Chakravorti (1948), however, reported 2n=52. Forty-eight somatic chromosomes were observed in the present study in 2 varieties of this species. Meiosis was regular and 24 bivalents were observed at metaphase I (Fig. 13).

Zingiber The five species of Zingiber investigated in the present study showed 22 chromosomes in root tip cells. Meiosis in Z. roseum. Z. wightianum and Z. zerumbet was regular and they showed good pollen and seed fertility. Z. macrostachyum showed 1 to 2 bridges with fragments at anaphase I in 11 out of 150 pollen mother cells examined. Sixty per cent of pollen appeared normal in this plant. The locally cultivated clone of the ginger plant (Z. officinale) showed evidence of structural hybridity involving inter changes and inversions. In 32 out of 68 pollen mother cells, 1 or 2 quadrivalents were observed at metaphase I. At anaphase I, 1-3 bridges with fragments were observed in 40 out of 72 pollen mother cells (Figs. 14, 15 and 16). Only 8 per cent of the pollen were well formed.

Discussion The cytology of 27 species, belonging to 11 genera of the Zingiberaceae has been studied. The lowest chromosome number observed in South Indian species is 2n=22 in Globba ophioglossa and Zingiber species and the highest 2n=96 in Globba bulbifera. New basic numbers observed in the present study are 25 for Boesenbergia and 21 for Hitchenia. In the other genera, the basic numbers observed are in agreement with those already known for the respective genera (9, 11, 12, 17 and 21). The high basic num ber 25 in Boesenbergia might have been derived by secondary polyploidy. Hitchenia and Curcuma have the same high basic number of 21. It was proposed earlier (Ramachandran 1961) that the basic number 21 in Curcuma might have been derived either by dibasic amphidiploidy (by combination of lower basic numbers 9 and 12 found in some genera of the family) or by secondary polyploidy. The same might apply to Hitchenia also. It is also possible that these two closely allied genera might have differentiated from the same ancestor. Zingiber officinale is not known to set seeds. East (1940, vide Fryxell 1957) suggested that the failure of seed set in Z. officinale is due to incom patibility. The clone of Z. officinale grown locally has shown evidence of structural hybridity for interchanges and inversions and forms only 8% ap parantly normal pollen. A chromosomal basis for the sterility of Z. officinale is suggested by the present study, though this can be established only by studies of other clones also. 15* 220 K. Ramachandran Cytologia 34

Summary The cytology of 27 species coming under 11 genera of the Zingiberaceae has been investigated. This includes 11 species and 2 genera not previously studied cytologically and 4 species for which the chromosome numbers determined in the present study differ from previous reports. The lowest chromosome number observed in South Indian plants of this family is 2n=22 and the highest 2n=96. New basic numbers observed include 25 for Boesenbergia and 21 for Hitchenia. The locally cultivated clone of the ginger plant (Zingiber officinale) showed evidence of structural hybridity resulting from inversions and inter changes. Zingiber macrostachyum also showed evidence of heterozygosity for inversions.

Acknowledgments The author wishes to express his thanks to Prof. A. Abraham, Head of the Department of Botany and Dean, Faculty of Science, University of Kerala, for guidance and suggestions. Financial assistance from the Indian Council of Agricultural Research is gratefully acknowledged.

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