Studies on tetraploidization in watermelon, Citrullus lanatus Thunb

Seedless watermelon cultivars are in high demand by consumers not only because their fruits are seedless but also because they are sweeter than the fruits from diploid and seeded cultivars. Diploid watermelon varieties were treated with the chemical mutagen colchicine to develop tetraploid seed parents. Seedlings of different genetic backgrounds (Arka Manik, Arka Muthu, Sugar Baby and IIHR-14) were raised and injected with different treatment combinations of colchicine (0.2, 0.3 and 0.4%) with and without 0.5 per cent PEG. The varieties responded differently for different treatment combinations of colchicine. The treated seedlings were evaluated for the tetraploidy induction on the basis of chloroplast count. The results revealed that the variety Arka Manik was sensitive to the colchicine treatments and among the four varieties  maximum number of tetraploids were identified in the variety Arka Muthu at 0.2 per cent colchicine whereas  0.3 per cent colchicine + PEG was found to be the best for variety Arka Manik and 0.4 per cent colchicine + PEG and 0.4 per cent colchicine  treatments were found to be best for the  Sugar Baby and IIHR-14 respectively. The efficiency rate of tetraploid induction levels in the present experiment varied with the varieties selected even though they belong to same crop.