Screening of tetraploidy induction methods using anti-microtubule agent colchicine in watermelon (Citrullus lanatus (Thunb.) Matsum & Nakai)

Three distinct watermelon genotypes (Sugar Baby, California Sweet and 5255-1-3-1) were subjected to antimicrotubule agent, colchicine with three different doses (0.1%, 0.2% and 0.3%) to induce tetraploidy using three methods viz. shoot apex, seed soaking and inverted hypocotyl. The experiment was carried out at Vegetable Research Farm and Laboratory, Department of Vegetable Science, Punjab Agricultural University, Ludhiana during the period 2013–2015. The observations were recorded on chloroplast count, palynological and phenotypic traits to confirm the tetraploidy. California Sweet showed the highest rate of efficiencyofgenerating putative tetraploids (6.12%). Amongst the various methods and concentrations of colchicine for induction of tetraploids, 0.2% and 0.3% concentrations of colchicine by inverted hypocotyl and shoot apex method was comparatively more effective. The highest frequency of putative tetraploids (11.55%) was recorded with inverted hypocotyl method @ 0.3% colchicine.