phenotypic and molecular screening of tomato germplasm for resistance to tomato yellow leaf curl virus

tomato yellow leaf curl virus (tylcv) is a major tomato virus in tropical and subtropical regions. in this study, 134 accessions of solanum lycopersicum and six accessions of solanum peruvianum were assessed for resistance to an iranian isolate of tylcv. plants were inoculated using whiteflies (bemisia tabaci) and the reaction of plants was evaluated based on either disease symptoms or viral dna amplification. all accessions of s. lycopersicum had demonstrated various degrees of disease symptoms. however, all six accessions of s. peruvianum were resistant and remained symptomless. phenotypic evaluation was confirmed by amplification of a 670bp tylcv dna fragment in all tested accessions of s. lycopersicum. based on both phenotypic and molecular evaluations, no accession provided complete resistance to tylcv, whereas nine accessions were assessed as tolerant. the high level of resistance noted in whitefly inoculated accessions of s. peruvianum was not observed in graft inoculated plants of these accessions. the tylcv dna fragment was detected five weeks post-inoculation when plants were inoculated by grafting. these results suggested that accessions of s. peruvianum may be merely resistant to vector inoculation of tylcv.