_??_1989 by Cytologia, Tokyo Cyt ologia 54: 51-64, 1989

Chromosomal Evolution in

G. C. Bairiganjan and S. N. Patnaik

Cytogenetics Laboratory, Post-Graduate Department of Botany , Utkal University, Bhubaneswar-751004 ,

Accepted November 12 , 1987

Fabaceae (Papilionaceae), on the world basis , stand third in the number of genera and species, exceeded only by Asteraceae (Compositae) and Orchidaceae . The family comprise of more than 500 genera and 12,000 species in the world flora even after the splitting of the large family Leguminosae (Heywood 1971). In India Fabaceae are represented by about 100 genera and over 750 species (Babu 1977). Cytological study, compared to the number of species in the family, is rather limited specially in respect of karyotypic analysis . Fedorov (1969) and Love (1967-83) reviewed the chromosome numbers of about 2,000 species from different parts of the world. With a view to reckon the potentiality of the wild relatives of the pulses and to collect the germplasms, a survey was undertaken and incidentally 152 species belonging to 60 genera of the family were collected from different parts of Orissa State (India). The survey of literature and specimens at different Indian herbaria along with the present col lections revealed the occurrence of 235 species belonging to 75 genera in this part of the country (Bairiganjan et a!. 1985). Cytological investigation was carried out to determine chromosome numbers with the help of mitotic and meiotic counts and to undertake karyotypic analysis of large number of wild and cultivated species of the family.

Materials and methods

Plants collected during the present survey have been preserved in the Herbarium of this Department. Flower buds fixed in acetic alcohol (1:3) in the field and transferred to 70% ethyl alcohol after 12 hours of fixation could be stored in the refrigerator (ca. 10•Ž) for a long time and the anthers from these buds could be squashed at convenience. Similarly, seeds collected from the field were suitably preserved to protect against pests and were germinated in the petridishes over moist filter paper prior to mitotic study. Simple aceto-carmine squash technique was followed for the study of meiosis. Root tips from the germinated seeds (when 2-3mm. in length) were pretreated in p-dichloro benzene for 4 hours and then fixed in acetic alcohol (1:3) for over-night. Then the roots were transferred to 70% ethyl alcohol and stored in refrigerator. At the time of study the root tips were hyd rolysed in 1N HCl for 3 minutes, warmed in few drops of 2% aceto-orcein and then squashed in a fresh drop of aceto-orcein which yielded in most cases cells with well spreading of chromo somes. Both pollen mother cell and root-tip preparations were temporarily sealed, observed and photographed before the slides were made permanent. Karyotypes were constructed according to the morphology of the chromosomes and idiogram of the chromosome complement for each species was made by representing each chromosome by its proportion to the total chromosome length (TCL) of the complement. The nomenclature system for chromsome type was adopted from Leven et al. (1964) except for SAT chromosomes or those with special structures. A satellite was considered part of the chromosome and thus included in the total length. Four types of centromeric regions were observed taking the value of chromosome index (S/L) into consideration: when this value 52 G. C. Bairiganjan and S. N. Patnaik Cytologia 54

Table 1. Chromosome number in Fabaceae 1989 Chromosomal Evolution in Fabaceae 53

Table 1. Contd. 54 G. C. Bairiganjan and S. N. Patnaik Cytologia 54

Table 1. Contd.

* new reports ** number in case of discrepancies + SAT bearing chromosome is exactly 1, it is median point (M); less than I but more than 0.66; median region (m); less than 0.66, but more than 0.33-sub-median (sm); less than 0.33-subterminal (st).

Observations and discussion

Chromosome numbers of 118 species belonging to 57 genera of Fabaceae could be deter mined through mitotic and meiotic analyses which are presented in Table I. Gametic and somatic chromosome numbers in respect of each species are recorded in column 3 and 4 re spectively. Chromosome number in respect of 16 species, 1 sub-species and 1 variety (*) are 1989 Chromosomal Evolution in Fabaceae 55

Table 2. Distribution of genera of Fabaceae under different basic chromosome numbers (Fedorov 1969) 56 G. C. Bairiganjan and S. N. Patnaik Cytologia 54

Table 2. Contd. 1989 Chromosomal Evolution in Fabaceae 57

Table 2. Contd.

reported here for the first time and different chromosome numbers than those reported earlier (within parentheses) are recorded for 6 species (**). Genera representing larger number of species during the present study are Crotalaria, , Indigofera, Sesbania, Tephrosia and Vigna. Basic chromosome numbers in different genera studied range from x=6 to x=11 from which few representative ones are illustrated (Figs. 1-2). Detailed karyotypic analyses in respect of 95 taxa belonging to 44 genera could be carried out (Figs. 3-5) which would re veal phylogenetic relationships between genera and species. The karyotypic formula for each species studied is given in column 5 (Table I). Genera characterised by x=6 are Rothia, Sesbania and Vicia. Rothia, a small genus, comprising of only two species in the world flora is represented in India by only one species viz. R. indica, which is a diffuse annual herb growing widely in sandy beds. The present find ing of chromosome numbers of 2n=12 is in contradiction to the earlier report of 2n=14 (Rao 1950). Species of Sesbania range from prostrate herb to medium sized trees and seven out of eight species reported from India have been cytologically studied. Out of these, five species are diploids and two are tetraploids. Chromosomes in the two tetraploid species viz. S. cannabina and S. grandiflora are considerably smaller and variable in size than those of the diploid species. However, in total chromatin length S. grandiflora (40.79 ,u) stands out dis tinct from all other species (ranging from 17.35 y to 22.40,u) including the tetraploid S. can nabina. Three species of Vicia were studied which are chromosomally well known. There is considerable variation in chromosome size between these species. Genera characterised by x=7 are Cyamopsis, Lathyrus, Pisum, Galactia and Erythrina. Of these, the first three genera possess haploid chromosome number of n=7. Lathyrus and Pisum have large sized chromosomes and in size range they are next to Vicia.faba. Galactia tenuiflora with somatic chromosome number of 28 is comparatively more uniform in its chro mosome size. The whole genus Erythrina is at higher polyploid level based on x=7 and all the species so far studied by various workers were found to be characterised by somatic chro mosome number of 42. During the present study, both E. fusca and E. variegata var. ori entalis conformed to the earlier findings. Seven genera viz. Alysicarpus, Cicer, Clitoria, Crotalaria, Indigofera, Melilotus and Tri gonella are characterizsed by x=8. Crotalaria is a large genus having mostly diploid species. All the 13 species studied here were characterised by 2n= 16 and there was not much variation in chromosome size between the species. Both the cultivated species of Trigonella were studied confirming the earlier reports of 2n=16. Seven species of Indigofera could be worked out in which I, glandulosa and I. tinctoria are found to possesss comparatively larger sized chro mosomes where as I. trita has conspicuously smaller chromosomes. Other four species are with medium sized chromosomes. Two species of Melilotus were studied which are mor phologically allied and sometimes taxonomically confused. Both the species were reported earlier to possess chromosome number of 2n=16. In the present study while M. alba was found to be characterised by 2n-16, M. indica proved to possess 2n= 18. Therefore, cyto typic variation is suspected to exist in different biotypes of M. indica which need further study. One species each of Alysicarpus, Cicer, Clitoria showed 2n=16 confirming the earlier resports. 58 G. C. Bairiganjan and S. N. Patnaik Cytologia 54

Of the genera studied presently, Butea is the only one based on x=9. Both B. mono sperma, a moderate sized tree and B. superba a woody climber were found to be diploid species with n=9. Karyotypic analysis of B. superba shows very little difference in the size of the chromosomes in the complement.

Fig. 1. (a) motorius 2n=22; (b) Dysolobium pilosum 2n=22; (c) Cyamopsis tetrag onoloba 2n=14; (d) Crotalaria ramosissima 2n=16; (e) Dunbaria rotundifolia 2n=22; (f) Dolichos trilobus 2n=20. 1989 Chromosomal Evolution in Fabaceae 59

Genera with basic chromosome number of x=10 are Aeschynomene, Arachis, Dalbergia, Dolichos, Glycine, Macrotyloma, Psophocarpus and Zornia. Of the three species of Aeschy nomene studied, two Indian species are tetraploids while A. americana, possibly a new intro duction to this country, is a diploid species. The karyotype of A. americana is more asym metrical than those of the two tetraploid species. Arachis and Glycine are two genera with pre dominantly tetraploid species and two strains of the cultivated G. max and one strain of Arachis

Fig. 2. (a) Macroptilium lathyroides var. semierectum 2n=22; (b) Pisum arvense 2n=14; (c) Sesbania javanica 2n=12; (d) Trigonella corniculata 2n=16; (e) Mucuna nivea 2n=22; (f) Sesbania cannabina 2n=24. 60 G. C. Bairiganjan and S. N. Patnaik Cytologia 54 hypogea studied presently were with mitotic counts of 40 chromosomes. The heavy deposits of oil globules in root tip cells of both the species make the mitotic counts difficult. The only diploid species G. javanica with 2n=20 could not be collected for study. Three species

Fig. 3. Idiograms of species in different genera of Fabaceae.

of Dalbergia and one species each from Dolichos, Macrotyloma and Zornia were studied,all of which were with diploid chromosome number of 2n=20. The basic chromosome number of x=11 is the most frequent and 28 genera studied here viz. Abrus, Atylosia, Cajanus, Canavalia, Codariocalyx, Dendrolobium, Derris, Desmodium, 1989 Chromosomal Evolution in Fabaceae 61

Dicerma, Dunbaria, Dysolobium , Flemingia, Gliricidia, Lablab, Macroptilium, Millettia, Mucuna, Pachyrrhizus, Paracalyx , Phaseolus, Phyllodium, Pongamia, Pseudarthria, Rhynchosia , Tadehagi, T ephrosia, Uraria and Vigna are all characterised by this basic number . Of these Vigna and Phaseolus have been karyotypically studied by many earlier workers . During the present study karyotypic analysis of representative species from all these genera except Tephr osia has

Fig. 4. Idiograms of species in different genera of Fabaceae. been carried out. Recently Cajanus-Atylosia complex has been interesting from cytogenetic and phylogenetic stand point. For this reason, comparison of karyotypic details in the mem bers of the genera Atylosia, Cajanus, Dunbaria, Flemingia, Paracalyx, Rhynchosia belonging to the sub-tribe Cajaninae under the tribue Phaseolae will of significance. A review of chromosome numbers (Fedorov 1969) of approximately 2000 species belonging to 271 genera (Table II) of Fabaceae (Papilionacea) shows a broad spectrum of chromosomal 62 G. C. Bairiganjan and S. N. Patnaik Cytologia 54

evolution in the family (Fig. 6). Basic chromosome numbers in the genera range continuously from x=4 to x=26 with only three more numbers x=28, x=30 and x=64, known, each characterising one genus only. Good number of genera show more than one basic chromo

Fig. 5. Idiograms of species in different genera of Fabaceae . some number of which Astragalus is the most conspicuous showing maximum variation with x=8, 10, 11, 12, 13, 14. This is in contrast with the observation of Turner and Fearing (1959) that "chromosome numbers for the species of Leguminosae show a remarkable degree of uniformity for not only genera but often for ... tribes". This is possibly because very limited 1989 Chromosomal Evolution in Fabaceae 63 number of species were chromosomally reported at that point of time. The lowest basic number x=4 has been known for one genus (Indigofera) in only one of its species (n=4). Two genera Vicia and Trifolium have some species conforming to the basic chromosome number of x=5. But at the general basic level very high concentration of genera (195) is seen between base numbers x=6 to x=11. with highest number of genera (47) characterised by x=11. At the next higher level 75 genera range in basic numbers x=12 to x=22 with highest number (17 genera) known for x=16. At still higher level there is a sharp decline and only 17 genera are found between x=23 to x=30. The highest level with one basic number x=64 characteri ses only one genus (Nepa). Thus generalising these observations it could be seen that mono basic polyploidy (72 genera) is much more frequent than dibasic polyploidy and aneuploidy (21 genera) in this family, a finding which is in conformity with the observations of Grant (1983) for angiosperms as a whole. Of the various lines of chromosomal evolution the mono basic line extending from x=4 upto x=64 seems to be much more successful with highest

Fig. 6. Chromosomal evolution in Fabaceae.

number of genera (55) in this line. The basic chromosome number of x=11 has also been equal ly successful as large number of genera (49) are characterised by this basic number. How ever, it is realised that these chromosomal data are not adequate for deriving phylogenetic con clusions and many more number of species of this vast family (550 genera and 12,000 species) need to be cytologically studied before projecting the chromosomal data for drawing a com prehensive phylogenetic picture in the family starting from interspecific to intertribal relations ships. In this context the remark of Darlington (1956) is significant which states that "any diagram of chromosome phylogeny is necessarily of limited value by itself, but as a framework for evolutionary speculations and investigation it is often indispensable".

Acknowledgements

We are grateful to University Grants Commission, India, New Delhi for awarding a Teach 64 G. C. Bairiganjan and S. N. Patnaik Cytologia 54 er Fellowship to one of us (GCB) and providing other financial assistance.

Summary

With a view to collect the germplasms of the pulses and their allies a survey of Fabaceous from Orissa state (India) was undertaken. Through a period of four years (1980-84) 152 species belonging to 60 genera were collected of which 118 species belonging to 57 genera were cytologically studied. While in majority of the species, earlier findings were confirmed, chromosome numbers in 16 species, 1 subspecies and 1 variety are recorded here for the first time and different chromosome numbers than those reported earlier are recorded for six spe cies. In all the genera studied the basic chromosome numbers were found to range from x= 6 to x=11 and maximum number of genera were found to possess x=1 l with larger number of species at the diploid level. Karyotypic analysis in respect of 95 taxa belonging to 44 genera could be carried out during the present investigation. On the basis of a review of num ber of genera under different basic chromosome numbers, chromosomal evolution in the family has been envisaged.

References

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