B. Bandyopadhyay et A. Sharma, The use of multivariate analysis of karyotypes to determine relationships between species of Opuntia (Cactaceae), CARYOLOGIA, 53(2), 2000, pp. 121-126
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.