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Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only Publication Acceptance Date: 1/12/2002 Publication Date: 4/12/2002 Citation: HOWELL, C.R. ECOLOGY AND BIOCONTROL OF PRE-EMERGENCE SEEDLING DISEASE PATHOGENS OF COTTON. PROCEEDINGS OF BELTWIDE COTTON CONFERENCES. CD-ROM. MEMPHIS, TN: NATIONAL COTTON COUNCIL. 2002. ABSTRACT. Interpretive Summary: Technical Abstract: Seedling disease incited by cotton pathogens can be controlled with fungicides or by seed treatment with wheat bran and peat moss preparations of the biocontrol fungus Trichoderma virens, including strains that were deficient for antibiotic production, mycoparasitism, and induction of terpenoid synthesis in cotton radicles. Soil amendment with wheat bran negated the protective effect of the biocontrol agents, but not that of th fungicides. Mixture of wheat bran extract, or exudates collected from resistant and susceptible cotton cultivars, with pathogen propagules and culture on Noble agar, showed that wheat bran extract and exudates from susceptible cultivars induced germination and growth of pathogen propagules, while exudates from resistant cultivars did not. These results indicate that disease in susceptible cultivars is induced by compounds in exudates from those cultivars that are released during germination, and which stimulate pathogen propagule germination and growth. Disease resistant cultivars do not emit pathogen stimulants during germination. Disease control by the biocontrol agent Trichoderma virens is effected by metabolism of pathogen propagule germination stimulants emitted by the germinating seed before they can act on the pathogen, thereby rendering the seeds and seedlings resistant to disease. Assay of a number of currently grown cotton cultivars for resistance or susceptibility to pre-emergence damping-off in infested soil has shown that resistance to disease is related to cultivar and, among resistant cultivars, to seed quality. |
