Assessment of the efficacy of amino acids and polyamines on regeneration of watermelon (Citrullus lanatus Thunb.) and analysis of genetic fidelity of regenerated plants by SCoT and RAPD markers

A simple and efficient regeneration protocol was developed for watermelon from cotyledonary node explants excised from 7-day-old in vitro grown seedlings. This study describes the effect of amino acids and polyamines (PAs) along with plant growth regulators (PGRs) on multiple shoot induction and rooting. The highest number of multiple shoots (46.43 shoots/explant) was obtained from cotyledonary node and they were also elongated (6.3 cm/shoot) on MS medium supplemented with 1 mg l(-1) N-6-Benzyladenine (BA), 5 mg l(-1) leucine, and 10 mg l(-1) spermidine. The elongated shoots developed profuse roots (23.03 roots/shoot) in MS medium containing 1 mg l(-1) indole-3-butyric acid (IBA), 5 mg l(-1) isoleucine, and 10 mg l(-1) putrescine. All the rooted plantlets were successfully hardened and acclimatized in the greenhouse with a survival rate of 98%. The present study described an efficient method to obtain a 1.5-fold increase in the number of shoots, compared with the available regeneration protocols for watermelon. The plants developed in this study showed fivefold higher photosynthetic pigments compared to the control plants. The genetic fidelity of the regenerated plants was evaluated by SCoT and RAPD marker analyses, and banding patterns confirmed the true-to-type nature of in vitro regenerated plants.