Cytogeography and phenomenon of cytomixis in Silene vulgaris from cold regions of Northwest Himalayas (India).

Silene vulgaris is an important ethnobotanical species, but so far no thorough meiotic analysis has been performed, despite its wide occurrence in temperate and alpine Himalayas, this prompted us to undertake present study. We investigated original meiotic chromosome number and effect of cytomixis on meiotic course, microsporogenesis and pollen grain size and fertility. The paper also summarizes the previously published chromosome counts in the species and cytogeography of 2 x and 4 x cytotypes in the Indian Himalayas and elsewhere. Meiocytes preparations were made through standard squashed technique in 1 % acetocarmine. Two ploidy levels have been determined during the cytomorphological surveys, diploid (2 n = 2 x = 24) and tetraploid (2 n = 4 x = 48). Most of the presently scored populations were found to be diploid (2 n = 2 x = 24). Morphologically 2 x and 4 x individuals were indistinguishable from each other. Meiosis was perfectly normal in 4 x cytotype. However, some of the 2 x plants showed the phenomenon of cytomixis and associated meiotic abnormalities. Consequent to cytomixis, hypo-, hyperploid and enucleated pollen mother cells (PMCs) were resulted. Such PMCs combined with other meiotic abnormalities yielded sterile and variable sized pollen grains. On the basis of overall information, it is clear that 2 x cytotype is the most widely distributed cytotype in the Indian Himalayas as well as elsewhere. On the other hand, the 4 x cytotype seems to be less frequently present in the Indian Himalayas and outside of India. [ABSTRACT FROM AUTHOR]