Abstract

Soybean (Glycine max (L.) Merr.) is an important crop for edible oil and protein in the United States and the world. However, soybean yield productions have been challenged by diseases caused by soil-borne pathogens such as Pythium. The purpose of this case study was to identify the interactions among soybean genotypes, medium of inoculum, and pathogen species on the pathogenicity of Pythium disease on soybean. Three-way ANOVA indicated that the interaction of host genotype, inoculum medium and pathogen species significantly affected the severity of Pythium disease on soybean. There were also significant interactions between inoculum medium and pathogen species. Marginal analysis for inoculum medium indicated that rice may be a better medium used for inoculation for Pythium than millet as it induces higher pathogenicity on soybean plants. Marginal analysis for Pythium species indicated that P. oopapillum was the most aggressive on 6 soybean genotypes evaluated by RR and on 4 genotypes by RW; P. irregulare was the most aggressive on 2 soybean genotypes evaluated by RR, and on 4 genotypes by RW; and P. sylvaticum was the most aggressive on one soybean genotype by both RR or RW.

Keywords: Soybean; Pythium root rot; Medium

Abbreviations: ANOVA: Analysis of variance; RR: Root Rot Rating; RW: Ratio of Plant Fresh Weight