NEW VARIANTS OF VERTICILLIUM DAHLIAE CAUSING SUNFLOWER LEAF MOTTLE AND WILT IN ARGENTINA
G.E. Clemente, M.E. Bazzalo, A.R. Escande
The sunflower leaf mottle and wilt caused by Verticillium dahlie Kleb. is a major disease of the crop. The populations of V. dahliae are variable and physiological races of the pathogen have been reported in lettuce, pepper, spinach, sunflower and tomato. The classification of V. dahliae isolates based on their pathogenicity in differential sunflower genotypes to determine races of the pathogen gives useful information for growers and breeding programmes. Two new Verticillium dahliae races causing sunflower leaf mottle and wilt in sunflower hybrids previously known as resistant were recognized. The sunflower inbred lines ADV29 and ADV53 allowed to differentiate specific pathogenicity patterns. One isolate that affected both genotypes was postulated as race VArg3, and another group that did not cause disease on either genotypes was described as race VArg4. Sunflower genotypes showing inverse differential reactions to races VArg3 and VArg4 were not found. However, the observed pathogenicity patterns could be considered a phenotypic marker useful to identify the V. dahliae races VArg3 and VArg4 in monitoring studies. The current presence of four races of V. dahliae affecting sunflower in Argentina is discussed.