Cytogenetical Studies in Some Triploid Mulberry Varieties (Moraceae)

The mulberry is an economically important crop, cultivated for its foliage to rear the silkworm Bombyx mori L. Its chromosome number varies from 2n = 28 to 2n = 308 with ploidy level from x to 22x. In the present investigation, three triploid mulberry varieties, namely, S41, S1635 and BC2–59, have been analyzed for detailed meiotic studies. Based on the chromosome configuration and other meiotic behaviour, x = 14 has been considered as the basic number of the genus. Meiosis was highly irregular. Various anomalies, such as the occurrence of two nucleolus, association of single trivalent with nucleolus, unequal separation and precocious movement of chromosomes, laggards, and occurrence of multivalents, have been observed. The low pollen fertility and seed set may be due to genic or physiological causes.