Identification and characterization of fungicide-resistant strains of Parastagonospora nodorum in Kentucky

Parastagonospora nodorum (formerly known as Stagonospora nodorum and Septoria nodorum) causes both Stagonospora leaf blotch and glume blotch. Stagonospora leaf blotch is one of the most common foliar diseases observed in Kentucky. When flag leaves are affected by leaf blotch, yield losses generally occur. Glume blotch also is a common disease in Kentucky, and can reduce yields and test weight. One of the most common ways to manage these diseases is through application of foliar fungicides. The strobilurin fungicide class is one of the most common fungicide classes applied to wheat and other field crops. This class of fungicides contains active ingredients that control a wide spectrum of diseases, but has a high risk of selecting for fungicide-resistant strains of fungal pathogens. A non-funded preliminary research trial that was initiated in Dr. Bradley’s research program at the University of Illinois and recently initiated at the University of Kentucky indicates that strobilurin fungicide-resistant strains of Parastagonospora nodorum are present in both Kentucky and Illinois (Table 1). Based on these preliminary results, it is important to know how wide-spread these strobilurin fungicide-resistant strains are in Kentucky, so that the best management recommendations can be developed for both leaf blotch and glume blotch. The objective of the proposed research are: 1. Collect isolates of P. nodorum throughout Kentucky and evaluate their sensitivity to strobilurin fungicides 2. Characterize the mechanism of P. nodorum’s resistance to strobilurin fungicides 3. Develop an efficient method to identify strobilurin fungicide-resistant strains of P. nodorum