| Abstract: | Root rot severity of asparagus plants grown in sterilized field soil inoculated with Fusarium oxysporum f . sp . asparagi (Foa) was reduced by more than 50% when the soil was precolo nized by each of 13 non - pathogenic (np) isolates of F. oxysporum originating from asparagus roots or field soils . In a greenhouse experiment , application of six np isolates to naturally infested field soil was followed by a 23 - 49% decrease of disease severity , depending on the isolate . One of them , Fo47 originating from Fusarium suppressive soil in France , was applied to field plots infested with Foa . Foa root rot was not suppressed in asparagus plants grown for 1 year in these plots . Pathogenic and np isolates extensively colonized the root surface and isolates of both types infected the roots of asparagus plants grown in sterilized field soil , with significant differences among the np isolates . Inoculation of sterilized field soil with np isolates reduced germination of Foa chlamydospores by 43 - 64% depending on the isolate used . It is concluded that np isolates of F. oxysporum can suppress asparagus root rot caused by Foa in naturally infested field soil . The differences for root colonization capacity among the np isolates imply that selection for this trait might reveal isolates that perform better under field conditions . |
