Study on the optimization of transformation systems in watermelon

To date,the genetic transformation system of watermelon has remained inefficient.In this study,the genetic transformation system of watermelon mediated by Agrobacterium tumefaciens was optimized,including different seedling ages,strains of Agrobacterium tumefaciens,concentrations of acetosyringone infected solution,co-culture time,selection pressure of antibiotics timentin and glufosinate,and concentrations of hormones 6-benzylaminopurine,indoleacetic acid and naphthylacetic acid in the corresponding culture medium.Our results suggested that cotyledons would be used as explants,disinfected with 6%sodium hypochlorite for 12 min,cultured for 3 d,and then infected with Agrobacterium inoculum(Agrobacterium EHA105)containing 200μM acetosyringone and 0.02 of final OD_(600).The explants differentiated into adventitious shoots in the medium with 1.5 mg/L 6-benzylaminopurine and 200μM timentin.Positive adventitious shoots were obtained through further screening by 1.4 mg/L herbicide glufosinate-ammonium,and were induced by 0.1 mg/L naphthalene acetic acid into independent plants.Our system improves the genetic transformation efficiency of watermelon and provides a technical basis for continuous acquisition of watermelon transgenic plants.