Identify Commercial and Public Varieties of Soybeans to Frogeye Leaf Spot
Crop Genetics Research Unit
2013 Annual Report
1a.Objectives (from AD-416):
1. Evaluate commercial and public varieties for resistance.
2. Characterize prominent pathotypes of Cercospora (C.) sojina.
1b.Approach (from AD-416):
Field and greenhouse evaluation of varieties.
Foliar diseases of soybean reduce yield by an estimated 70 million bushels annually in the United States. This estimate only takes into consideration the direct yield loss and not the additional costs associated with managing diseases with foliar-applied fungicides. Among the various foliar diseases, frogeye leaf spot is unique in that both chemical and host resistance strategies are available. However, this disease is caused by a highly variable pathogen with many races and this adds difficulty to deploying resistant varieties. Currently, fungicide resistant isolates of the frogeye leaf spot pathogen are being detected further complicating fungicide recommendations. The goal of this seven state, multi-institutional program is to develop management options for major foliar diseases of soybean. This goal will be accomplished by gaining a better understanding of the epidemiology of foliar diseases which can be used to optimize disease management strategies, identifying disease-resistant varieties, assisting in the development of resistant germplasm, and refining management recommendations based on results generated from this research. These efforts will provide immediate-term benefits and long-term solutions. In Tennessee, the test was initiated in 2011 to screen and identify soybean lines with resistance under natural field environment. In 2013, 366 soybean lines are being screened. The field used for screening is well infested and has a history of good infection every year on susceptible controls. Thus there was no need to artificially inoculate the lines. The plots are also irrigated during the season. Among the lines tested in 2012, forty-five had no frogeye leaf spot symptoms. These lines and the additional lines included in the 2013 test should continue to be evaluated to ensure that they are resistant.