INFLUENCE OF NUTRITION DURING CONIDIATION OF COLLETOTRICHUM-TRUNCATUM ON CONIDIAL GERMINATION AND EFFICACY IN INCITING DISEASE IN SESBANIA-EXALTATA

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.