Our research is aimed at generating transgenic pistachio using Agrobacterium-mediated transformation. While previous studies have reported low transformation efficiencies in pistachio, questions remained regarding its susceptibility to Agrobacterium infection and which strains might facilitate successful transformation. Given that Agrobacterium strains differ in virulence across plant species and genotypes, we screened 23 diverse strains to identify those capable of infecting pistachio. These strains, representing various Ti-plasmid types and chromosomal backgrounds, were sourced from the J. Chang Lab at Oregon State University and the USDA’s local collection - primarily isolates from walnuts in California’s Central Valley. We inoculated in vitro-grown pistachio plantlets by wounding stems with blades saturated with each strain. Gall formation was observed in response to 16 strains in UCB-1 (Pistacia atlantica female × P. integerrima male) and 20 strains in Pistacia vera ‘Golden Hills’. These results demonstrate that pistachio is susceptible to infection by diverse Agrobacterium strains, with C58 being one of the most virulent.
