Studies on colchicine induced changes in bajra napier hybrid (Pennisetum glaucum × P. purpureum)

An experiment was conducted to estimate the lethal concentration of the polyploidy inducing chemical Colchicine in two genotypes of Bajra Napier hybrid CO 6 and TNCN 1534. Single nodded setts of the genotypes CO 6 and TNCN 1534 were treated with colchicine using two diferent methods viz., whole immersion with concentrations of 0.05%, 0.10%, 0.15%, 0.20% and 0.25% for 3 and 6 hours and the cotton swab method using the same fve diferent concentrations. The LC₅₀ values were observed based on growth reduction of seedlings after the planting of treated setts by the two methods. The sprouting percentage and survival percentage of both genotypes gradually reduced with increasing doses of colchicine and it also difered based on the method used. The LC₅₀ values difered for both the methods used. The cotton swab method had the LC₅₀ value of 0.21% for the genotype CO 6 and 0.19% for TNCN 1534. The whole immersion method had the LC₅₀ value of 0.14% in case of CO 6 and 0.15% colchicine concentration was found to be optimum for TNCN 1534 indicating the diferential response of genotypes for colchicine treatment. Correlation between diferent concentrations and stomatal parameters indicated positive correlation when the varieties were treated for 3 hours duration and a negative correlation was observed when they were treated for 6 hour duration in case of whole immersion method. As the duration of exposure increased, the parameters showed decreased growth. In case of cotton swab method, both the varieties showed positive correlation for stomatal width with the increasing concentration while stomatal length was seen having negative correlation when the concentrations were increased.