Cytomorphological investigations in colchicine-induced polyploids of Lablab purpureus (L.) Sweet

Successful induction of autotetraploidy by seedling treatment of colchicine has been achieved in Lablab purpureus (L.) Sweet. Young'seedlings were treated with different concentrations of aqueous colchicine (0.2, 0.3, 0.4 & 0.5%) using the cotton-swab' method, each for different durations. Morphological and cytological variations were studied for C sub(1) and C sub(2) generations. In C sub(1) generation, 4 autotetraploids were obtained with 0.5% colchicine treatment for 6 and 9 h. The tetraploid plants were, morphologically different as compared to diploids. Meiosis was irregular and average number of associations per cell ranged from 1.8+ or -0.83 to 2.2+ or -0.44 among quadrivalents and 24.00+ or -0.00 to 19.6+ or -0.89 in bivalents. Bivalent chromosome associations were observed more frequently than quadrivalent associations. Chiasma was not clearly seen. Seeds (10) from suspected tetraploids were used to raise the next generation to evaluate their stability. Only 5 plants were survived up to maturity and of these, one plant was suspected triploid and another plant monosomie. Thus morphological and cytogenetical changes in the polyploidy of L. purpureus, as a result of colchicine treatment, could not be significantly inherited in next generation and successful induction of stable tetraploids in next generation is a challenge for the researchers.