characterization of phytoplasmas associated with tomato big bud disease, using single-tube nested pcr

tomato is an important vegetable crop in iran. recently symptoms associated with phytoplasma disease were observed in tomato cultivars in karaj vicinity. the phytoplasmas were detected and characterized using single-tube nested pcr and rflp. the universal primer pairs amplified the target dna with expected sizes from symptomatic samples in direct pcr and single-tube nested pcr. the patterns of rflp analysis obtained from plants with symptoms of yellowing and showing a bushy aspect corresponded to the profile of tomato big bud phytoplasma–subgroup 16sri, and those detected from plants with symptoms of shoot proliferation and swollen and virescent buds belonged to tomato big bud phytoplasma–subgroup 16srvi. mobeen was the most susceptible cultivar with 23% natural infection, and alex, raha, sadeen 21, and sadeen 95 cultivars showed no symptoms of disease. lack of symptoms in the latter cultivars might be due to inefficient transmission of phytoplasma by vectors or their resistance or tolerance to disease.