Cytogenetical Studies in Some Diploid Mulberry Varieties (Moraceae)

Abstract

Most Morus species are diploid, having 28 chromosomes, but a few species, specifically, M. tiliafolia Makino, Morus cathyana and M. nigra L., are higher polyploidy. In these species, the chromosome number varies from 2n=28 to 2n=308, with ploidy level from x to 22x. In the present study, three diploid mulberry varieties, namely, V₁, S₁₃ and S_34, have been analyzed for detailed meiotic studies. Based on chromosome configuration and other meiotic behaviour, x=14 has been considered as the basic number of the genus. Meiosis shows marginal differences. Various meiotic abnormalities, such as the occurrence of one large chromosome at metaphase I, unequal separation at anaphase I, the presence of laggards and precocious movement of chromosomes at anaphase II, and two micronuclei at tetrad, have been observed. The low pollen fertility and seed sets may be due to irregular chromosomal pairing and separation rather than due to genetic or physiological causes.