Cytological studies in two diploid mulberry varieties (Moraceae)

Most of the species of the Morus are diploid having 28 chromosome, but a few species, namely, M. tiliafolia Makino, Morus cathyana and M. nigra L., are higher polyploidy. Chromosome number varies from 2n =28 to 2n = 308 with ploidy level from x to 22x. In the present study two diploid mulberry varieties namely, Kollegal and DD have been analyzed for both mitotic meiotic studies. Based on the somatic chromosome number, ploidy level, chromosome configuration and other meiotic behavior x = 14 have been considered as basic number of the genus. Meiosis showed marginal differences. Various meiotic abnormalities like occurrence of one large chromosome, stickiness and loose association of chromosomes at metaphase I, unequal separation at anaphase I, laggards, precocious movement and unequal separation of chromosomes at anaphase II, have been observed. The low pollen fertility and seed set may be due to irregular chromosomal pairing and separation rather than due to genic or physiological causes.