Morphological and Chromosomal Characterization of Diploid and Colchicine Induced Autotetraploid Plants of <i>Commelina benghalensis</i> L. (Commelinaceae)

Abstract

Induced polyploidy is well known to enhance the genetic architecture of plants that confers better survivorship to them in various agro-climatic conditions than their respective diploids. In this regard, the present study was aimed to obtain the autotetraploid of Commelina benghalensis through antimitotic agent colchicine in order to increase its commercial, ornamental, and medical value. For tetraploidy induction, ungerminated seeds and tips of cotyledon-stage seedlings of the plant were treated with various concentrations of colchicine (0.1, 0.15, 0.2, and 0.25%). Experiments carried out on ungerminated seeds were unsuccessful in generating stable polyploids as it causes the death of germinated seedlings at the very earliest stage. Conversely, applying aqueous colchicine solution constantly on tips of seedlings for 6-8 h per day for three consecutive days was found significant in producing stable tetraploids. Putative tetraploids were subjected to chromosomal, morphological, and palynological observations for their exact confirmation. Out of total 120 seedlings treated, six plants (5%) were found polyploid in C 0 generation with the highest frequency (10%) observed in 0.2% colchicine. During meiosis, the PMCs of tetraploid plants exhibited 44 chromosomes in different associations like quadrivalent, trivalent, bivalent and univalent, while that of the control diploid plants showed regular 11 bivalents. Meiotic analysis showed a constant decrease of quadrivalent frequency and the increasing number of bivalents from C 0 to C 2 for better fertility. Furthermore, differences in vegetative and ornamental characteristics between diploid and polyploid plants were significant. The size of pollen grains, capsules, and seeds were significantly greater than those of diploid plants.