Verticillium wilt of tomato. II. Pathogenic variability of Verticillium dahliae and behavior of varieties

Abstract

The pathogenic variability of 22 isolates of Verticillitum dahliae obtained from eggplant, okraplant, strawberry and tomato cultures in several places of São Paulo State was studied in a climatizated room. Isolates were inoculated on 13-15 days-old seedlings of tomato varieties Angela Hiper (susceptible) and Marmande VR (race 1 - V. dahliae resistant) by root-dip for 15 minutes into inoculum suspensions containing about 10⁶ conidia/mL. The disease severity evaluation was done 28 days after inoculation through observations of leaves yellowing and wilting or vascular discoloration symptoms to determine the level of vimen colonization. Besides differences on aggressiveness of isolates the occurrence of more than one physiological race of V. dahliae was observed. So, T-1335, T-1103, T-1098, T-1104-a, T-1289, T-1237 and BE-318 isolates were classified as race 1 because they did not affect Marmande VR variety, and BE-1430, T-1378, M-38, Q-322-a, T-1439, BE-1431, T-1481, Q-320-a, T-1089, M-1099, T-1480, BE-1043 and T-1386 as race 2, for which ''Marmande VR» and «Angela Hiper» were susceptible. Some of the most important fresh-market and canning tomato varieties cultivated in Brazil have shown different behavior depending on the isolate inoculated. While fresh-market varieties Santa Adélia, Príncipe Gigante, Santo Antonio, São Francisco and Santa Clara, and canning tomatoes Agrocica 4, 8, 16, 33 and 72, Ontário 7710 and Rio Grande were resistant to the race 1 isolate (T-1335); the same varieties were susceptible to the race 2 isolate (T-1386). The breeding line Ohio 12 and the tomato variety Petomech VF₁₊₂ have shown the lowest level of disease when inoculated with the race 2 isolate.