Cytogenetical Studies on Some Members of the family Asteraceae of Nepal

Abstract

Karyotypic studies of 45 taxa belonging to 33 genera in 10 tribes of the family Asteraceae are reported from Nepal. Chromosome number in somatic cells are recorded to be 2n=20 in Ageratum conyzoides and Taraxacum officinale ; 2n=18 in Ageratum houstonianum, Blumea lacera, Blumea laciniata, Dichrocephala integrifolia, Rhynchospermum verticillatum, Sonchus asper and Sonchus arvensis; 2n=32 in Artemisia indica, Blumea lacera var. glandulosa and Xanthium strumarium ; 2n=34 in Artemisia vulgaris, Cirsium arvense, Parthenium hysterophorus; 2n=36 in Artemisia abronatum, Aster ageratoids, Bidens pilosa var. minor, Chrysanthemum morifolium, Spilanthes acmella, Spilanthes calva, and Senecio laetus; 2n=28 in Anaphalis triplinervis var. triplinervis, Calendula officinalis and Gnaphalium purpureum ; 2n=16 in Crepis japonica, Erigeron annuus, Galinsoga parviflora and Ixeris Polycephala ; 2n=14 in Gnaphalium affine; 2n=22 in Blumea fistulosa, Blumea mollis, Conyza canadensis, Eclipta prostrata and Stevia rebaudiana; 2n=40 in Aster barbellatus, Aster peduncularis subsp. nepalensis and Crassocephalum crepidioides, 2n=26 in Coreopsis grandiflora and Tridax procumbens ; 2n=24 in Tagetes patula, Centaurea cyanus and Zinnia elegans ; 2n=50 in Eupatorium adenophorum and 2n=30 in Wedelia wallichii. Meiotic studies are done in floral buds of 20 species. Lowest haploid chromosome in Crepis japonica ( n=8) and highest in Crassocephalum crepidioides (n=20) are found in present study. The highest pollen stainability was found in Galinsoga parviflora (98.9 %) and lowest in Stevia rebaudiana (61.3%). Chromosome number for the four taxa Aster peduncularis subsp. nepalensis, Aster barbellatus , Artemisia indica and Senecio laetus are reported for the first time in this study. For the eleven taxa viz. Ageratum conyzoides, Ageratum houstonianum, Blumea fistulosa, Blumea lacera var. glandulosa, Cirsium arvense, Erigeron annuus, Eupatorium adenophorum, Spilanthes acmella, Spilanthes calva and Xanthium strumarium new chromosome number have been added. The chromosome counts for 41 taxa in this study are new for the flora of Nepal.