Comparative Cytogenetics. 2008. 2(1): 85-92.
Cytomixis during microsporogenesis in the diploid and tetraploid cytotypes of Withania somnifera (L.) Dunal, 1852 (Solanaceae)
Singhal V.K., Kumar P.
Abstract. Withania somnifera (L.) Dunal, 1852, popularly known as “Ashwagandha” shows considerable morphogenetic diversity in Indian populations. Both the diploid (n=12) and tetraploid (n=24) cytotypes presently reported in the populations from Punjab, Rajasthan and Himachal Pradesh show the phenomenon of cytomixis which is a first record for the species. The inter PMC (Pollen mother cell) transfer of chromatin material in the diploid cytotype is present in 40.76% PMCs involving 2-6 PMCs. However, among tetraploids frequency of cytomixis is much less (15.80-24.32%) and involves only 2-3 PMCs. Chromatin transfer is noticed during the first and second meiotic division in the diploid as compared with the tetraploid where it is observed only during the first meiotic division. The percentage of meiotic abnormalities such as chromosome stickiness, lagging of chromatin material during anaphases and telophases is also higher in the diploid compared with the tetraploid. The microsporogenesis is also abnormal in the diploid resulting into the formation of polyads and tetrads with micronuclei whereas it is normal in the tetraploid. Cytomixis also seems to have had a greater effect on the apparent pollen fertility in the diploid compared with the tetraploid. Furthermore, cytomixis have also resulted into pollen grains of three different sized in the diploid and only of two sizes in the tetraploid.