Characterization of Stem Canker Resistance in ‘Hutcheson’ Soybean

Abstract

Stem Canker caused by Diaporthe phaseolorum (Cooke & Ellis) Sacc. f. sp. meridionalis Morgan‐Jones (Dpm) can cause significant yield losses in soybean [Glycine max (L.) Merr.] in the southern USA. Some cultivars are known to be resistant to the disease; however, the parental donor, level, and inheritance of stem canker resistance for most of those cultivars is unknown. The objective of this study was to characterize stem canker resistance in ‘Hutcheson’, a widely used parent in breeding programs. To determine the inheritance of resistance and allelic relationships with known genes, Hutcheson was crossed with susceptible genotypes ‘Hartwig’ and J77‐339 and four lines carrying Rdcl, Rdc2, Rdc3, or Rdc4. Crosses were made in the field at Stoneville, MS, in 1993. The parents of Hutcheson and the six F2 populations were toothpick inoculated in the field in 1993 and 1994, respectively. In 1994, Hutcheson and 29 other soybean genotypes were inoculated with four isolates of Dpm and external lesion length was recorded as a measure of level of resistance. Genetic ratios from F2 populations indicate that resistance in Hutcheson is conferred by a single dominant gene that is allelic with Rdc4. ‘York’ was determined to be the parental donor of resistance carried by Hutcheson. Isolates differed in virulence. Hutcheson and several other genotypes were highly resistant to all isolates. Hutcheson should continue to be an excellent source of stem canker resistance.