APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


Evaluating soybean breeding lines developed from different sources of resistance to Phomopsis seed decay
S. LI (1), J. Smith (1) (1) USDA-ARS, Crop Genetics Research Unit, U.S.A.

Phomopsis seed decay (PSD) causes poor soybean seed quality worldwide. The primary causal agent of PSD is Phomopsis longicolla (syn. Diaporthe longicolla). Breeding for PSD-resistance is the most effective long-term strategy to control this disease. To develop soybean lines with resistance to PSD, multiple breeding populations were developed from crosses between PSD-resistant and high-germination lines, as well as between PSD-resistant lines. Based on the seed plating assay, the range of percent seed infected by P. longicolla among all lines tested was from 0 to 52%, with an overall line mean of 7.5. There were significant differences in the reaction to PSD among lines derived from the same source of resistance, as well as among lines from different sources of resistance. More important for making future populations, the mean PSD score of the lines derived from the PI 424324B source was significantly lower than that of those derived from the PI 80837/SS93-6181 source. The PSD of lines from PI 417050 source were not significantly different from those from the other sources. These results indicate an apparent superiority for using the PI 424324B source of resistance for breeding improved lines. Seeds for many of the lines derived from both PI 424324B and PI 417050 had no incidence of PSD. Therefore, it is likely that some of them will be released in the future as resistant to PSD and thereafter utilized in breeding programs to develop PSD-resistant cultivars.