Studies on the mechanism underlying the reduction of pea wilt by Fusarium solani F. pisi

Abstract

The mechanism underlying the decrease caused by Fusarium solani f. pisi in the severity of pea wilt due to F. oxysporum was studied by examining sites of possible interaction in soil and in host. F. solani produced no substance in vitro that inhibited spore germination or growth of F. oxysporum , and there was no evidence that the two fungi competed to the detriment of F. oxysporum either in the rhizosphere of peas or in the soil. Some water extracts of foot-rot lesions contained a substance inhibitory to the germination of F. oxysporum spores, but it could not always be demonstrated. No inhibition was caused by exudates or extracts of pea roots infected with F. solani . F. solani colonized the epidermis and outer cortex of pea roots more rapidly and more extensively than did F. oxysporum . Three days after inoculation with F. solani , pea roots respired 25% more than uninoculated ones. The physical nature and metabolic activity of the cortex was altered through infection by F. solani , so it is concluded that it was these changes alone that delayed the progress of F. oxysporum to the stele, resulting in a decrease in wilt.