SEROLOGICAL STUDIES ON THE ACCUMULATION AND LOCALIZATION OF 3 TOMATO LEAF CURL GEMINIVIRUSES IN RESISTANT AND SUSCEPTIBLE LYCOPERSICON SPECIES AND TOMATO CULTIVARS

Accessions of wild Lycopersicon spp. and selected F1 hybrid tomato cul tivars were compared for their resistance to three whitefly-transmissi ble geminiviruses: Indian tomato leaf curl virus (ITmLCV) and tomato y ellow leaf curl viruses from Sardinia (TYLCV-Sar) and Senegal (TYLCV-S en). The resistance of different plant lines was expressed in differen t ways but in most instances a given line reacted similarly to graft i noculation with the three viruses. L. pimpinellifolium LA1478 produced as much virus antigen, assessed by triple antibody sandwich-ELISA, as the susceptible cv. Moneymaker but developed only very mild symptoms and is therefore tolerant of infection. in L. hirsutum LA1777 and L. p eruvianum CMV-INRA, very mild or no symptoms developed but antigen con centrations were substantially less than in Moneymaker. L. chilense LA 1969 remained symptomless and its antigen concentration was <1% of tha t in Moneymaker. Symptoms were mild or barely evident in the Fl hybrid cultivars. Cultivars Tyking and Fiona had antigen concentrations abou t 5-10% of those of Moneymaker, whereas TY20, Top 21 and Tyger had int ermediate antigen concentrations. In a few instances, the extent to wh ich virus accumulation was restricted depended on the challenge virus. Accumulation of TYLCV-Sen in TY20, Top 21 and Tyger was less affected than that of the other two viruses, and accumulation of TYLCV-Sar in accessions LA1777 and CMV-INRA was less affected than that of TYLCV-Se n or ITmLCV.Tissue-printing tests showed that ITmLCV and TYLCV-Sen ant igens were confined to phloem tissue. In Tyking, the number of virus a ntigen-containing phloem traces and the antigen content of individual traces were less than in Moneymaker but the partitioning of antigen be tween internal and external phloem was unaffected.