The use of multivariate analysis of karyotypes to determine relationships between species of Opuntia (Cactaceae)

Somatic chromosomes were studied from roots from seven species and two vari eties of the genus Opuntia collected from different localities in Eastern I ndia. 2n = 22 chromosomes were observed in four, 2n = 44 in two and 2n = 55 chromosomes in one population. The total chromosome length is maximum in O . Ficus-indica (2n = 55) and minimum in O. microdasys var. lutea (2n = 22). The karyotypes show a similarity in basic number x = 11, except for the ho rticultural variety, O. monocantha variegata with 2n = 34. The chromosome s izes range from very small (0.97 mum) to medium (3.46 mum); the primary con striction varies from nearly submedian to median and the numbers of chromos omes with secondary constrictions are from four to six. Numerical analysis of data indicates a general similarity of the karyotypes, with O. Ficus-ind ica occupying a separate position.