Chromosome count, male meiotic behaviour and pollen fertility analysis in Agropyron thomsonii Hook.f. and Elymus nutans Griseb. (Triticeae: Poaceae) from Western Himalaya, India

Present cytological study records existing chromosome number diversity, their male meiotic course and pollen fertility analysis in the two wheatgrass species of tribe Triticeae Dumort. (Poaceae) from Western Himalaya, India. Agropyron thomsonii Hook. f. is an endemic grass of alpine zones of Western Himalaya and Elymus nutans Griseb., a widely distributed grass in sub-alpine to glacial regions of Himalaya. The gametophytic chromosome number count of n=21 (Jadh Ganga Valley, Uttarkashi) is a pioneer count for A. thomsonii. During the male meiotic course of A. thomsonii, 14.04-16.29% and 2.97-4.17% pollen mother cells, respectively at prophase-I and metaphaseI, observed to be involved in phenomenon of cytomixis. Seven accessions of E. nutans collected from Bhagirathi Valley and Jadh Ganga Valley of Uttarkashi district, and Pangi Valley of Chamba district, recorded with gametophytic chromosome number count of n=21 and record of 1B-chromosome in PUN61958 is a new record for the species. In three accessions 5.56-9.41% and 2.5% pollen mother cells at prophase-I and metaphase-I, respectively were also noted with phenomenon of cytomixis. In addition to phenomenon of cytomixis, during meiotic course of both species pollen mother cells also depicted associated meiotic course irregularities viz. non-synchronous disjunction of bivalents, chromatin bridges, laggards, micronuclei in sporads and shrivelled microspores. These species are growing in cold climatic condition habitats. So, cold stress seems to be a preferential inductor for cytomixis and associated meiotic abnormalities in the gametic cells of stamens of A. thomsonii and E. nutans that ultimately leads to reduction in pollen fertility.