Variability in Alternaria brassicae: Response to host genotypes, toxin production and fungicides
2002
S.J. KOLTE, VISHWANATH and
Laboratory and glasshouse experiments were conducted to study the variability among 3 (A, C and D) isolates of Alternaria brassicae, causal agent of Alternaria blight of Brassica spp., in relation to host genotypes, toxin production and fungicides. True leaf inoculation on pot-grown plants of 14 genotypes of 5 different Brassica species revealed differential infection responses to the 3 isolates. Isolate A was more virulent than isolates C and D. Isolate C was rated as moderately virulent and the Disolate as an avirulent type. A similar trend was recorded with bioassays of toxins produced by the 3 isolates on excised leaves of the 14 Brassica genotypes. Seed germination and seedling growth were inhibited by all 3 toxins, the greatest inhibition produced by the isolate A toxin, and differential responses occurred with the different genotypes. The effect of 4 fungicides (mancozeb, iprodione, ziram and metalaxyl) on the growth of the isolates was studied in vitro. Isolate C exhibited maximum sensitivity to ziram at 50 ppm followed by metalaxyl at 100 ppm. Iprodione completely inhibited growth of all the 3 isolates even at the lowest concentration of 5 ppm.
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