Population dynamics of the fusarium head blight biocontrol agent cryptococcus flavescens OH182.9 on wheat anthers and heads

Authors: Schisler, David; CORE, AMANDA - The Ohio State University; BOEHM, MICHAEL - The Ohio State University; Horst, Leona; Krause, Charles; Dunlap, Christopher; Rooney, Alejandro - Alex

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2013
Publication Date: 3/3/2014
Publication URL: http://www.sciencedirect.com/science/article/pii/S1049964413002776
Citation: Schisler, D.A., Core, A.B., Boehm, M.J., Horst, L., Krause, C.R., Dunlap, C.A., Rooney, A.P. 2014. Population dynamics of the Fusarium head blight biocontrol agent Cryptococcus flavescens OH182.9 on wheat anthers and heads. Biological Control. 70(1):17-27.

Interpretive Summary: Fusarium head blight is a difficult disease to control and frequently causes severe losses of grain yield and quality in wheat and barley. In previous research, we discovered yeast Cryptococcus flavescens OH 182.9 which reduces Fusarium head blight when sprayed onto heads of wheat at about the time they flower. In these studies, we discovered that after application to wheat, the yeast often grew in population both on anthers and wheat head tissue but that treating wheat too early in head emergence or a prolonged lack of moisture reduced yeast populations which would reduce biocontrol effectiveness. We found that the yeast penetrated inside of wheat florets and, by using scanning electron microscopy, that the yeast colonized additional tissues that normally could be infected by the head blight pathogen. Understanding where and how yeast OH 182.9 colonizes wheat heads over time is information critical to commercially developing this new tool for wheat producers to use in reducing fungicide use and the negative impact of Fusarium head blight.

Technical Abstract: Cryptococcus flavescens OH 182.9 (NRRL Y-30216) reduces Fusarium head blight (FHB) incited by Fusarium graminearum and DON contamination of grain in greenhouse and field settings. Yet little is known about the population dynamics of OH 182.9 on wheat heads and anthers from the time of inoculating heads through kernel development when options for fungicide application can be limited. Whether the growth stage of wheat at the time of application influences the survival and efficacy of OH182.9 also is lacking. Biomass of OH182.9 was produced in liquid culture and applied to greenhouse and field grown wheat prior to and during early anthesis. In greenhouse studies, populations of OH 182.9 were similar on anthers for heads inoculated before (Feekes 10.5) or early in flowering (Feekes 10.5.1) but were 1-3 log units lower in Feekes 10.5 inoculated wheat after eight to ten days. In greenhouse and field studies, OH 182.9 colonized anthers inside florets prior to anthesis. In the field, populations of OH 182.9 on anthers increased or, less frequently, remained steady throughout the 12 day sampling period, regardless of application time and peaked at 1 to 2 log units higher than in the greenhouse. Strain OH 182.9 reduced FHB severity (P<0.05, FPLSD) but not other disease parameters in the same field study. Application of OH 182.9 at split boot (Feekes 10.1) or Feekes 10.5.1 resulted in higher populations on spikelets treated at flowering on a CFU/g fresh weight tissue basis and as a percentage of the total recoverable microbial population in one of two field studies. Throughout a 10 day sampling period after inoculating wheat heads, scanning electron microscopy revealed cells of OH 182.9 in microcolonies, groups of several cells and as individual cells, most frequently on the abaxial surfaces of glume and lemma tissues and near the apex of palea tissues. The survival of yeast OH 182.9 on anthers and wheat heads for 12 days and more suggests the strain has the potential to reduce late kernel infections by F. graminearum that can increase DON.