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Pathogenicity of Biochemical Mutants of Colletotrichum lagenarium

1960; University of Chicago Press; Volume: 121; Issue: 3 Linguagem: Inglês

10.1086/336062

1940-1205

S. K. Dutta, C. V. Hall, E. G. Heyne,

Plant-Microbe Interactions and Immunity

1. Biochemical mutants were induced by treating microconidia from a monosporic isolate of Race 2 of Colletotrichum lagenarium (Pass.) Ell. & Halst. with ultraviolet light. 2. Mutants requiring leucine, isoleucine, serine, lysine, histidine, proline, alanine, valine, inositol, or pyrimidine were avirulent, and those requiring glycine or methionine were virulent for Black Diamond and Charleston Gray watermelons and H.B. 36 variety of muskmelon; the mutant requiring pyridoxine was moderately virulent for Black Diamond watermelon and H.B. 36 muskmelon and avirulent for Charleston Gray watermelon. 3. Most avirulent mutants become pathogenic, producing anthracnose symptoms within 7-10 days, when the respective supplements were supplied in aqueous solution to the surface of leaves of inoculated Black Diamond watermelon seedlings; the avirulent mutants requiring pyrimidine did not become pathogenic when so treated. 4. Aqueous extracts of squash epidermal tissue did not support the growth of any mutant; extracts from a cucumber variety supported the growth of proline-requiring mutant; extracts from Charleston Gray watermelon supported the growth of an inositol-requiring mutant; and extracts from Black Diamond watermelon supported the growth of several biochemical mutants. 5. In general, mutants displayed better growth responses in whole-tissue extracts than in epidermal tissue extracts; mutants requiring pyrimidine did not grow in whole-tissue extracts. 6. The four races of the pathogen which have no apparent nutritional deficiencies displayed poorer growth in epidermal tissue extracts than in wholetissue extracts; the four races displayed only trace growth in epidermal tissue extract of the resistant Butternut squash and good growth in comparable extract from the susceptible Black Diamond watermelon. 7. The nature of resistance to the pathogen is briefly discussed, and an inhibition in the epidermal cells is proposed as a possible mechanism for resistance against the natural isolates of C. lagenarium.