Abstract
Karyotype studies of ten exotic cultivars namely, Kosen, Kokuso-13, Kokuso-21, Kokuso-27, Roso and Rokokuyso belonging to Morus latifolia Poir., Kenmochi, Mizusawa and Ichihei belonging to Morus bombycis Koidz. and Chinapeking belonging to M. alba L. were reported for the first time. Of the ten cultivars, five are diploids (2n=28), two are triploids (2n=3x=42) and remaining three are aneuploids (2n=28+2). Chromosomes are generally small with an average length of 1.16μ and length ranges from 0.62μ to 1.70μ in all the cultivars studied. Relative length ranges from 96 to 131μ. In most of the cases, complement consists of only two types of chromosomes with median and submedian centromeres resulting in bimodal karyotypes. As a whole, frequency of median chromosomes is more than submedian ones. Of the ten strains, two strains namely Kokuso-13 and Mizusawa bear satellite chromosomes. Morphological variation and evolution of taxa were attributed to structural changes in the karyotype and an attempt has been made to study the phylogenetic relationship among the varieties of each species based on their karyotype. Vegetative propogation seems to have played a major role in maintaining the taxa at different ploidy level.
