Study On Inducing Watermelon Tetraploid By Tissue Culture

Mini-diploid watermelon inbred-line 21, 90, 141, 149, 157 were used for inducing tetraploid in vitro culture. The effect on inducting rate of colchicine concentration and treating time and regenerating way, simple way to identificating ploidy. the optimum concentration of PVA to resist vitreous plantlets, the effect on rooting of hormone varieties and concentration were studied. Conclusions were drawed as followed:1.Middle immature cotylelons in 20 ~ 23 days were used for inducing tetraploid. The inducting rate was high and it was not likely to be mosaic.The doubling rate was different from different genetype , treating concentration and time, regenerating way . Treated by 0.03%~ 0.07% colchicines in 4~9 days was the optimal induction extent. Line 21,90,141,149,157 attained the highest doubling rate, they were 37%,50%,17%,43%,37% respectively. The doubling rate from callus was higher than from buds and crowed buds.2.Mature cotyledon tips were used for inducing tetraploid. When colchicine was 0.05% ,treated in 36~48 hours was the optimal induction extent. The highest doubling rate of line 149,157 was 13%, 17% respectively.3.Watermelon tetraploid plantlets were shorter, leaf lengh to width ratio was smaller, stomas were bigger, density of stoma was smaller, choltoplasts in guard cell were more, diameter of nucleus was longer, the resistance to vitreous plantlets was stronger than that of diploid. They could be used for identificating ploidy early.4.PVA could resist diploid watermelon plantlets to be vitreous , the optimum concentration was 2.5g/L.5.Each of IAA,IBA and NAA could make the tetraploid watermelon plantlets root. IBA was the best.When IBA was 0.2~0.3mg/L , inoculated about l~2cmhigh stem with shoot tip ,the rooting rate , No. of root and morphology of root were good , it was suitable to transplant.6.The doubling rate of seedling dropped was low . When treated by 0.2% colchicines in 4 days , the doubling rate of line 21,90,141,149,157 was 2.8%, 0%, 5.1%, 4.7%, 13.2% respectively. In the first period ,fruit rate and seed rate were very low.