Karyomorphological observations in some species of Desmodium Desv. (Fabaceae-Papilionoideae)

Abstract

The present paper deals with the chromosome numbers and morphology of thirteen species of the genus Desmodium. Twelve out of thirteen species show 2n=22, while one species (D. salicifolium) shows 2n=20. A review of present and previous chromosome number reports justifies the basic numbers x=11 and 10 for the genus. The karyotype analysis is made for the first time in ten species. In all the species investigated here only nearly median and nearly submediam chromosomes are observed. On the basis of karyomorphology D. salicifolium is relatively primitive compared to D. gangeticum, while D. laxiflorum, D. uncinatum, D. triflorum, D. sandwiscence, D. velutinum, D. distortum, D. ritchiei, D. heterocarpon var. strigosum, D. dichotomum, D. elegans and D. intortum occupy the intermediate position. The interrelationship among the species is reticulate. The minor differences between the karyotypes of different species indicate that structural alterations have played an important role in speciation. Karyornorphological observations are discussed in light of Ohashi's infrageneric classification.