Inheritance of Resistance to Purple Seed Stain Caused by Cercospora kikuchii in PI 80837 Soybean

Abstract

Purple seed stain (PSS) of soybean [Glycine max (L.) Merr.], caused by Cercospora kikuchii (T. Matsu. & Tomoyasu) Gardner, is favored by high moisture and warm temperatures during early pod development. PSS can significantly reduce seed and grain quality. Characterizing genetic resistance to PSS would be valuable in the development of resistant lines and varieties. PI 80837 has a high level of resistance to PSS and also good resistance to Phomopsis seed decay (PSD) caused primarily by Phomopsis longicolla Hobbs. Resistance to PSD in PI 80837 is conferred by a single dominant gene. The research reported here genetically characterizes PSS resistance in PI 80837 and examines if genes for PSS and PSD resistances are linked. Crosses were made between PI 80837 and ‘Agripro 350’ (AP 350) (susceptible to PSS and PSD), PI 91113 (susceptible to PSS and PSD), and line MO/PSD‐0259 (susceptible to PSS but resistant to PSD). Populations and lines were grown in the field and C. kikuchii infection was assayed by plating seed. Cercospora seed infection of F1 plants from reciprocal crosses of AP 350 × PI 80837 was not significantly different from that of PI 80837, indicating that resistance is under nuclear control. Segregation data from each of four F2 populations fit a single dominant gene model for resistance. Data from F2:3 lines of AP 350 × PI 80837 and PI 80837 × MO/PSD‐0259 fit the model for a single dominant gene for PSS resistance. A linkage test for reaction to Cercospora and Phomopsis seed infection in F2:3 lines of AP 350 × PI 80837 showed that the genes for PSS and PSD resistances in PI 80837 are not linked.