Evaluation of disease and pest damage on soybean cultivars released from 1923 through 2008 under field conditions in central Illinois

Diseases and pests of soybean [Glycine max (L.) Merr.] often reduce soybean yields. Targeted breeding that incorporates known genes for resistance and non-targeted breeding that eliminates susceptible plants in breeding populations reduces the impact of soybean pathogens and pests. Maturity group (MG) III soybean cultivars released from 1923 through 2008 were grown in three field environments to determine if disease and insect ratings were associated with year of cultivar release. Disease and pest ratings were evaluated on 40 soybean cultivars at one location (Urbana, IL) planted in two rotation treatments in 2010 and on 59 cultivars in two locations (Urbana and Arthur) in 2011. During the season, foliar disease symptoms and insect foliar feeding damage were recorded. At harvest maturity, stem diseases were assessed. In at least one environment, foliar incidence reached 100% for bacterial diseases, brown spot (Septoria glycines Hemmi), and insect foliar feeding damage and 100% incidence for anthracnose [Colletotrichum truncatum (Schwein.) Andrus & W.D. Moore], Cercospora stem blight (Cercospora kikuchii T. Matsumoto & Tomoy.), and charcoal rot [Macrophomina phaseolina (Tassi) Goid.] on stems for all cultivars. For the nine different disease and pest severity assessments in 2010, seven had a significant (P < 0.05) negative correlation to year of cultivar release indicating that cultivars more recently released had lower severity ratings than cultivars with older release dates. This study demonstrated that incidence and severity of diseases were less pronounced on more newly-released soybean cultivars, showing that decades of breeding has resulted in increased disease resistance in modern soybean cultivars.