A highly efficient regeneration system for watermelon (Citrullus lanatus thunb.)

We developed a high frequency watermelon regeneration system using two inbred lines of watermelon (citrullus lanatus),'w1-4' and 'w1-12'. shoots were induced from cotyledonary nodes cultured on murashige and skoog (ms) basal medium solidified with agar (7.0 g/l) and containing various concentrations of cytokinin (6-benzyladenine; 6-ba) and auxin (indoleacetic acid; iaa). the highest rate of bud organogenesis was on ms medium containing 1.5 mg/l 6-ba + 0.2 mg/l iaa for 'w1-4' and on ms medium containing 1.0 mg/l 6-ba + 0.1 mg/l iaa for 'w1-12'. the regeneration rate was higher in 'w1-12' than in 'w1-4'. the best medium for shoot elongation in both inbred lines was ms containing 0.05 mg/l 6-ba. regenerated plants showed the best rates of root formation on 1/2 ms containing 0.1 mg/l iaa. the rooted plants were carefully washed to remove all medium from the roots,and then transferred to soil in a greenhouse. the plants showed a 100% survival rate when transferred to soil. this highly efficient regeneration system will be useful for regenerating plants in genetic engineering applications,and is a useful tool for further genetic transformation studies on watermelon.