A HIGHLY EFFICIENT REGENERATION SYSTEM FOR WATERMELON (CITRULLUS LANATUS THUNB.)

Abstract

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.