Summary An accession-based study carried out on Anthoxanthum odoratum from Kullu district revealed a tetraploid chromosome count of n=10 and the presence of multiple chromosomal associations of up to 10 chromosomes due to structural heterozygosity for reciprocal translocations. Owing to the presence of multivalents, the individuals showed considerable amounts of non-viable male gametes. Structural heterozygosity in the species has also been detected to affect the chiasma frequency significantly, thereby increasing the variability. Similar effects of translocations in increasing chiasma frequency and affecting pollen fertility have been reported by workers in other species.

-Present work pertains to the cytological investigations performed in Ranunculus laetus for the fi rst time from Indian cold deserts and adjoining high hills of North-west Himalayas which covers Chamba, Kinnaur, Kullu and Lahaul-Spiti districts of Himachal Pradesh. We here also report for the fi rst time the presence of 1 B-chromosome in two accessions studied from Dalhousie hills. Twelve accessions scored presently from these regions uniformly shared the same meiotic chromosome number, n=14 and existed at tetraploid level (based on x=7). Of these, eight accessions showed abnormalities during male meiosis, such as pollen mother cells (PMCs) involved in chromatin transfer at different stages of meiosis, chromosome stickiness, pycnotic chromatin material, out of plate bivalents at metaphase-I, nonsynchronous disjunction of some bivalents, and laggards at anaphases/telophases. Consequent to these meiotic irregularities, microsporogenesis in meiocytes is abnormal characterized by the presence of dyads, polyads, and micronuclei and included micronuclei in sporads. These irregularities during meiotic course resulted into varying percentage of pollen sterility (9-31%) and pollen grains of heterogeneous sizes. The remaining four accessions showed regular meiotic course, normal microsporogenesis and nearly cent percent pollen fertility (97.90-100%).