Genetic transformation of Persian melon (Cucumis melo L.) via Agrobacterium

A reliable Agrobacterium-mediated transformation and regeneration protocol was developed for commercially important endemic Persian melon cultigens (Cucumis melo L.) comprising ‘Eyvanaki’, ‘Samsoori’, and ‘Khatooni’. The effect of selective Murashige and Skoog (MS) medium containing various concentrations of 6-benzyl adenine (BA) (0, 0.5, 1, and 1.5 mg l-1) and 1 mg l-1 Gibberellic acid (GA3) on regeneration of cotyledon, hypocotyl, and cotyledonary petioles derived from 6-day-old in vitro grown seedlings of the three Persian melons were investigated. For transformation, the sensitivity to kanamycin (Km) concentrations (0, 50, 75, 100, 125 mg l-1 ), the effect of three A. tumefaciens strains (GV3103, LBA4404, and AGL0), inoculation time (0.5, 1, 5, and 30 min), and co-cultivation time (24, 48, and 72 h) on direct shoot regeneration of cotyledonary petiole of ‘Samsoori’ were investigated. Shoot regeneration from cotyledonary petiole explants received the highest attention. Cotyledonary petiole segments of ‘Samsoori’ and ‘Khatooni’ treated respectively with 1.0 mg l-1 and 1.5 mg l-1 BA exhibited the highest potential for shoot multiplication; while the regeneration rate of ‘Eyvanaki’ was drastically lower. Putative transgenic ‘Samsoori’ plantlets selected in 100 mg l-1 Km were subcultured on elongation MS medium composed of 100 mg l-1 Km, 0.1 mg l-1 BA, 1 mg l-1 GA3 plus 400 mg l-1 CTX, and then successfully rooted on growth regulator-free MS medium for two weeks. Using histochemical GUS assay along with genomic PCR screening for GusA and VirG genes, the efficiency of transformation was estimated to be 10% for AGL0 and 6% in LBA4404.