Studies on floral characters and pollen behaviour at different levels of ploidy in mulberry (Marus spp.)

Abstract

Mulberry (Morus spp.) is generally a diploid, mono-genous, heterozygous tree belonging to the family Moraceae having 28 chromosomes (2n = 28). It has 24 species and one sub-species and distributed in wide area of tropical, sub-tropical, temperate and sub-artic zones [1]. It is rich in ploidy and a lot of triploid varieties have been found especially among Morus bombysis Koidz. In M. cathayana Hems/. tetraploid, pentaploid and hexaploid varieties are present. M. serrata Roxb., indigenous to India, and M. tiliaefolia Makino, originally from Japan and Korea, are known to be hexaploids. M. nigra L. is a decosaploid (2n = 22x = 308), with the largest number of chromosomes among phanerogams indicating a lot of variation in chromosome numbers as well as level of ploidy in mulberry [2]. These variations in ploidy and geographical diversity have resulted in plasticity of mulberry for many characters. Distingnishing ploidy by pollen fertility, pollen size, stigma length and other characters has been well correlated with the cytological confirmation [3]. The present communication deals with floral morphology and pollen behaviour related to ploidy.