Selection and evaluation of microorganisms for biocontrol of Fusarium headblight of wheat incited by Gibberella zeae

Gibberella zeae incites Fusarium head blight (FHB), a devastating disease t hat causes extensive yield and quality losses to wheat and barley. Of over 700 microbial strains obtained from wheat anthers, 54 were able to utilize tartaric acid as a carbon source when the compound was supplied as choline bitartrate in liquid culture. Four tartaric acid-utilizing and three nonuti lizing strains reduced FHB in initial tests and were selected for further a ssays. Antagonists were effective against three different isolates of G. ze ae when single wheat florets were inoculated with pathogen and antagonist i noculum. All seven antagonists increased 100-kernel weight when applied sim ultaneously with G. zeae isolate Z3639 (P less than or equal to 0.05). Baci llus strains AS 43.3 and AS 43.4 and Cryptococcus strain OH 182.9 reduced d isease severity by > 77, 93, and 56%, respectively. Five antagonists increa sed 100-kernel weight of plants inoculated with G. zeae isolate DAOM 180378 . All antagonists except one increased 100-kernel weight, and four of seven antagonists reduced disease severity (P : 0.05) when tested against G. zea e isolate Fg-9-96. In spray-inoculation experiments, Bacillus strains AS 43 .3 and AS 43.4 and Cryptococcus strains OH 71.4 and OH 182.9 reduced diseas e severity, regardless of the sequence, timing, and concentration of inocul um application (P less than or equal to 0.05), though 100-kernel weight did not always increase when antagonists were applied 4 h after inoculum of G. zeae. Overall, 4 of 54 isolates that utilized tartaric acid in vitro were effective against G. zeae versus only 3 of 170 isolates tested that did not utilize tartaric acid (P less than or equal to 0.05, chi -square test of g oodness of fit), demonstrating the potential benefit of prescreening candid ate antagonists of FHB for their ability to utilize tartaric acid. Biologic al control shows promise as part of an integrated pest management program f or managing FEB.