Inheritance of Reaction to Stem Canker in Soybean¹

Abstract

There are no known published reports concerning the inheritance of reaction to the disease stem canker [caused by the fungus Diaporthe phaseolorum (Cke. & Ell.) Sacc. var. caulivora Athow & Cald.] in soybean [ Glycine max (L.) Merr.]. Because stem canker has become a serious soybean disease in the southern United States, and because a source of resistance has been identified, information on the inheritance of reaction to this disease is needed. The objective of this study was to determine the inheritance of resistance to stem canker found in the soybean ‘Tracy‐ M.’ Crosses were made between Tracy‐M and a very susceptible line, J77‐339. The disease reactions of parental, F 1 , F 2 and F 3 populations from that cross to stem canker were studied under field conditions to determine the genetic basis for resistance. All F 1 plants were resistant and the F 2 generation fit a 15 resistant:1 susceptible ratio (✕ 2 probability = 0.75 to 0.90). The 199 F, families fit a ratio of 7 resistant:8 segregating:! susceptible (X 2 probability = 0.25 to 0.50). These results indicate that stem canker resistance in Tracy‐M is controlled by two major dominant genes.