Fusarium head blight (FHB) is a devastating disease that causes extensive yield and quality losses to wheat and barley. In durum wheat, the pathogen-produced toxin deoxynivalenol (DON) is retained in semolina at ˜50%, and the causal agent of FHB, Gibberella zeae, has a strong adverse effect on pasta color. Two bacteria and two yeast strains with known efficacy against G. zeae on hexaploid wheats were produced in liquid culture and assayed on two cultivars of durum wheat in greenhouse bioassays. All antagonists reduced FHB severity on cultivar Renville, and three of the four reduced severity on cultivar Ben, with Bacillus subtilis strain AS 43.3 decreasing FHB severity by as much as 90%. In separate greenhouse bioassays, the car-bon:nitrogen ratio of the medium used to produce antagonists did not consistently influence antagonist efficacy. All antagonist/production medium combinations but one were effective in reducing disease on both durum cultivars. Of six antagonists tested at field sites, Cryptococcus sp. OH 71.4 and C. nodaensis OH 182.9 reduced disease severity by as much as 57% in Peoria, IL, while Cryptococcus sp. OH 181.1 reduced disease severity by as much as 59% in a trial at Langdon, ND. Antagonists did not influence the DON content of grain in the Peoria trial. Relative performance indices for four antagonists calculated from greenhouse and field results on the two durum cultivars demonstrated that the bioassay location, but not the cultivar of durum, influenced the relative performance of antagonists. Yeast antagonists OH 71.4, OH 181.1, and OH 182.9 appear to have the highest potential for contributing to the reduction of FHB on du-rum wheat in the field.

Gibberella zeae incites Fusarium head blight (FHB), a devastating disease that 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 nonutilizing strains reduced FHB in initial tests and were selected for further assays. Antagonists were effective against three different isolates of G. zeae when single wheat florets were inoculated with pathogen and antagonist inoculum. All seven antagonists increased 100-kernel weight when applied simultaneously with G. zeae isolate Z3639 (P ≤ 0.05). Bacillus strains AS 43.3 and AS 43.4 and Cryptococcus strain OH 182.9 reduced disease severity by >77, 93, and 56%, respectively. Five antagonists increased 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. zeae 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 disease severity, regardless of the sequence, timing, and concentration of inoculum application (P ≤ 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 ≤ 0.05, χ-square test of goodness of fit), demonstrating the potential benefit of prescreening candidate antagonists of FHB for their ability to utilize tartaric acid. Biological control shows promise as part of an integrated pest management program for managing FHB.

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The influence of autoclaved fungal materials such as culture filtrate, freeze-dried mycelium (FDM), mycelium suspension, and spore suspension (SS) on the growth, morphogenesis, and carvone production of spearmint (Mentha spicata L.) plants was studied. Fungal materials were either applied as a drench or spray on the plants. Spearmint plants (cv. "294099") drenched with SS (1 x 10(8) spores/ml) of Trichoderma reesei showed no significant differences in leaf numbers, root numbers, or shoot numbers compared with nontreated controls. However, significantly higher fresh weights and carvone levels were observed in plants drenched with T. reesei SS compared with the untreated controls. Fungal materials derived from Aspergillus sp., Fusarium graminearum, F. sporotrichoides, Penicillium sp., P. acculeatum, Rhizopus oryzae, and T. reesei were sprayed on spearmint foliage. F. graminearum, F. sporotrichoides, or R. oryzae elicited no enhanced growth, morphogenesis, or secondary metabolism responses. The best growth and morphogenesis responses were obtained employing Aspergillus sp., Penicillium sp., or T. reesei foliar sprays. For example, spearmint cv. "557807" plants sprayed with 100 mg/l FDM T. reesei isolate NRRL 11460 C30 stimulated higher fresh weights (75%), shoot numbers (39%), leaf numbers (57%), and root numbers (108%) compared with untreated plants. This effect was not dose-dependent because similar growth and morphogenesis responses were obtained by testing 10, 100, or 1000 mg/l FDM concentrations. Carvone levels in fungal-treated foliar-sprayed plants were comparable to nontreated controls. However, total carvone levels per plant were higher in fungal-treated plants because of their increased fresh weight.