|Schisler, David - Dave|
|Boehm, Michael - The Ohio State University|
|Paul, P - The Ohio State University|
|Rooney, Alejandro - Alex|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2015
Publication Date: 5/1/2015
Citation: Schisler, D.A., Boehm, M.J., Paul, P.A., Rooney, A.P., Dunlap, C.A. 2015. Reduction of Fusarium head blight using prothioconazole and prothioconazole-tolerant variants of the Fusarium head blight antagonist Cryptococcus flavescens OH 182.9. Biological Control. 86:36-45.
Interpretive Summary: This research resulted in the discovery of variants of a yeast biological control agent that demonstrate both enhanced fungicide tolerance and enhanced ability to combat Fusarium head blight (FHB) disease of wheat and barley compared to the parental agent. FHB disease frequently causes severe losses of grain yield and quality in wheat and barley and has proven to be very difficult to control using conventional disease control methods. When we grew our yeast biological control agent (Cryptococcus flavescens) in a liquid medium containing a fungicide commonly used against FHB, we discovered that some antagonist cells were tolerant of the fungicide and possessed greater ability to suppress the disease than the original yeast culture when both were tested on wheat in greenhouse and field experiments. Combinations of fungicide-tolerant variants with the fungicide reduced FHB and the mycotoxin deoxynivalenol (DON) to the greatest extent. If commercially developed, these fungicide tolerant variants with enhanced ability to reduce FHB and DON should provide a significant, new disease management tool that could be used alone or in combination with certain fungicides to reduce the negative impact of FHB on producers, millers, and consumers of wheat and barley products.
Technical Abstract: Integrated disease management strategies utilize a range of measures to prevent or reduce plant diseases. Combining the biological control agent Cryptococcus flavescens OH 182.9 (NRRL Y-30216) with a triazole fungicide such as prothioconazole has potential for significantly contributing to the reduction of Fusarium head blight (FHB) but is complicated by the sensitivity of the yeast to the chemical. Protracted exposure of strain OH 182.9 to gradually increasing concentrations of the fungicide prothioconazole during growth in liquid culture resulted in the selection of stable variants of OH 182.9 with doubling times of 135 to 174 min when grown in the presence of 50 ppm prothioconazole compared to 228 min for the OH 182.9 progenitor strain. Prothioconazole tolerant (PTCT) variants were confirmed to be cospecific with the progenitor strain using Biolog™ YT Microplate™ and phyllogenetic analysis. In greenhouse tests, PTCT variant OH 182.9 4C reduced head blight severity by 83% compared to a 36% reduction for the OH 182.9 wild type (wt) strain (P=0.05, Bonferroni mean separation). All four PTCT variants, prothioconazole applied as Proline® at label rate, and combinations of PTCT variant and fungicide significantly reduced FHB severity and incidence (P=0.05). In two field trials on susceptible winter wheat, variants 3C and 4C reduced severity by 34% and 42% compared to the control (P=0.05) in one trial and 21% and 24% in another (not significantly different at P=0.05) while strain OH 182.9 wt had no consistent positive effect. For both field trials on both wheat varieties, treating flowering wheat heads with prothioconazole and a PTCT variant resulted in the greatest numerical reduction of FHB severity, incidence, and DON relative to the check and the all other treatments. Prothioconazole-tolerant variants of C. flavescens OH 182.9 warrant further study regarding their inclusion in the integrated management of FHB.