Loss of endogenous carbon by conidia of Cochliobolus sativus Exposed to soil and its effect on conidial germination and pathogenic aggressiveness

Abstract

Cochliobolus sativus conidia progressively lost endogenous carbon when exposed to nonsterile or sterile soil at − 1 and − 10 kPa matric potential for 50 days. Loss of 14C was detected mainly as 14CO 2 evolved from soil and conidia and as residual 14C in soil. Conidia lost more carbon on sterile soil ( ca 25% of total label) than on nonsterile soil ( ca 12% of total label), but there were no differences in residual 14C, evolved 14CO 2 and total 14C loss between the two matric potentials in either nonsterile or sterile soil. On sterile soil evolved 14CO 2 increased over time from 27.6% of the total 14C lost on day 1 to 76.6% on day 50, with conidial respiration accounting for 100% of the 14C evolved. On nonsterile soil evolved 14CO 2 also increased over time, from 10.4% of the total 14C lost on day 1 to 64.1% on day 50; the estimated contribution of conidial respiration to 14C loss ranged from 6.2% on day 1 to 38.5% on day 50. Conidia germinated on sterile but not on nonsterile soil. Conidia did not lose nutrient independence on either sterile or nonsterile soil. Pathogenic aggressiveness of conidia exposed to sterile or nonsterile soil did not decline as compared to conidia not exposed to soil until 50 days of exposure.