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POSTERS: Biological control

Verticillium klebahnii and V. isaacii isolates exhibit host-dependent biocontrol activity against Verticillium wilt caused by V. dahliae
Krishna Puri - University of California, Davis. German Sandoya- University of Florida, Yuan-yuan Zhang- Inner Mongolia Agric University, Jun Zhao- Inner Mongolia Agric University, Suraj Gurung- Sakata Seed America, Inc., Krishna Subbarao- University of California At Davis, Xiaoping Hu- Northwest A&F Un

The soilborne fungal pathogen Verticillium dahliae causes vascular wilt on a number of economically important crops that results in major yield losses. This pathogen is notoriously difficult to manage as it produces long-lived microsclerotia and there is little or no host resistance. A single nonpathogenic isolate each of V. klebahnii (PD659) and V. isaacii (PD660) were evaluated as potential biocontrol agents (BAs) in eggplant, lettuce, and tomato by pre, post or co-inoculation with virulent isolates of V. dahliae. Initial studies demonstrated biocontrol efficacy of BAs similar to the reference BA-Talaromyces flavus (NRRL 15936) across all hosts (?= 0.05). Modified treatments using isolates from the three hosts- Sm113 from eggplant, Ls17 from lettuce, and Le1811 from tomato demonstrated significant biocontrol efficacy in eggplant (P<0.001) and tomato (P< 0.001) but not in lettuce (P> 0.301), suggesting host-dependent efficacy of these BAs. Competitive exclusion might be a possible biocontrol mechanism as indicated by the limited root colonization by the pathogen in the presence of introduced BAs relative to the pathogen alone. Quantitative expression analysis of defense regulating genes in tomato in the presence or absence of BAs is in progress. Integrated use of nonpathogenic V. klebahnii or V. isaacii isolates reduce Verticillium wilt incidence and severity in a host-dependent manner.