VIEW ARTICLE

Ecology and Epidemiology

Influence of Nutrition During Conidiation of Colletotrichum truncatum on Conidial Germination and Efficacy in Inciting Disease in Sesbania exaltata. D. A. Schisler, Plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, Fermentation Biochemistry Research Unit, National Center for Agricultural Utilization Research, Peoria, IL 61604; M. A. Jackson, and R. J. Bothast. Microbiologists, respectively, U.S. Department of Agriculture, Agricultural Research Service, Fermentation Biochemistry Research Unit, National Center for Agricultural Utilization Research, Peoria, IL 61604. Phytopathology 81:458-461. Accepted for publication 4 December 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/Phyto-81-458.

Conidia of Colletotrichum truncatum (NRRL 13737) were produced in semidefined, liquid media, with total carbon concentrations of 4 g/L and carbon/nitrogen ratios of 40:1, 15:1, and 5:1. Conidia produced in 5:1 medium were longer and thinner than conidia from 15:1 and 40:1 media, and a higher proportion contained two, rather than one, nuclei per conidium. After either 6 or 12 hr on cellophane membranes, a greater proportion of conidia produced in the 5:1 medium had germinated compared with conidia from 15:1 and 40:1 media. Germination on attached leaves of Sesbania exaltata was greatest with conidia from 5:1 medium when assayed after either 6 or 24 hr. Equality of variance tests implied that the leaf environment had a greater influence on the germination of conidia from 15:1 medium than conidia from 40:1 or 5:1 media. All conidial treatments caused losses in biomass of seedlings of S. exaltata. Conidia produced from 5:1 or 15:1 media induced greater reduction in shoot height, and conidia from 5:1 medium induced greater reduction in shoot dry weight than did conidia from 40:1 medium. Further research on increasing the efficacy of mycoherbicide conidia by modifying the phyllosphere environment and the nutritional conditions of the conidiation medium is needed.