Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/1998
Publication Date: N/A
Interpretive Summary: Sclerotinia stem rot is a severe soybean disease that ranked as the second most important soybean disease in the United States in 1994. Information about the differences in soybean varietal response to the fungal pathogen that causes the disease in relation to soybean yields is lacking. This paper is the first to show that soybean varieties can be tolerant and partially resistant to the disease, which means that they can yield well despite being infected. Yield losses due to this disease ranged from 0 to nearly 100% depending on the level of infection. The importance of this study is to show that yield data taken from plots in the field with different levels of disease can be used to measure tolerance to this disease. This technique may be used by field researchers to evaluate varietal responses to this disease, and could be used widely by most soybean seed companies that are interested in developing tolerance to this disease.
Technical Abstract: Sclerotinia stem rot (SSR) of soybeans is emerging as an important disease in some northern soybean production areas in the U.S. Five Maturity Group III cultivars, Asgrow A3304 STS, Pioneer Brand 9342, Pioneer Brand 9381, Probst, and Yale were planted in East Central Illinois and subdivided into plots based on SSR incidence levels. For each cultivar, at least 23 plots were harvested. Data recorded were yield, 100 seed weight, seed protein and oil content, visual seed quality, seed germination,and the number of sclerotia in a 300 g sample. All cultivars had significant (P<0.05) yield reductions, and for every 10% increase of SSR incidence, there was an average of 277 kg/ha loss over the five cultivars combined. Probst had the lowest yield reduction (15 kg/ha), and the smallest incidence range (2 to 45%). Using the case price of $.26/kg ($7.15/bu) of soybeans at a 15% SSR incidence point, Yale, P9342, P9381 had a $7.54, $140.40, and $197.34/ha advantage over Probst. For all cultivars and cultivars combined, there were some significant (P<0.05) correlations between SSR incidence and yield, 100 seed weight, seed protein and oil content, visual seed quality, and seed germination. Results show that both tolerance and partial resistance are present in some of these cultivars. Although some cultivars show tolerance and partial resistance, other cultivar have greater yields at SSR severity levels