Occurrence and impact of polyploidy in dicotyledonous plants from Kinnaur, Himachal Pradesh (India)

Polyploidy, the condition of having multiple sets of genome, has been analyzed in 200 species from Kinnaur district of Himachal Pradesh, India. Among presently studied species, 50 species have been recorded at different polyploid levels. Out of different polyploid cytotypes, the tetraploid cytotype is more frequently found (68.0%) while the higher levels like 8x and 10x are rather less represented. Unreduced gametes might be the first cause of polyploidy which impacts the species distribution, morphological characteristics, plant habit, chromosome pairing, meiotic course, and pollen fertility. Three species, Spergularia diandra (2x, 4x), Indigofera heterantha (2x, 6x), and Veronica anagallis-aquatica (2x, 4x) with intraspecific diploid and polyploid cytotypes showed the variation in the morphological characters and distribution pattern. Four polyploids Erigeron annuus (2n= 27; 3x), Carduus nutans (2n= 40; 4x), Geranium pratense (2n= 56; 4x), and Taraxacum officinale (2n= 32; 4x) showed nonhomologous chromosome pairing and went through a disturbed course of cell division. Overall, 38% of polyploid species exhibited irregular events during meiosis, resulting in low fertility in gametes. The production of 2n gametes through meiotic aberrations might be responsible for the origin of polyploid taxa and also due to the tendency of harsh environmental conditions prevailing in the area. Finally, these species adopt the alternate mode of reproduction to produce new offsprings for the next generations.