Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 5/1/2008
Citation: Smith, S., Fenn, P., Chen, P., Jackson, E.W. 2008. Inheritance of resistance to Phomopsis seed decay in PI 360841 soybean. Journal of Heredity. Interpretive Summary: In the southern United States, Phomopsis seed decay is the major cause of post harvest seed losses and reductions in seed quality. Scientists from the University of Arkansas and the United States Department of Agriculture, Agricultural Research Service studied the resistance to this disease in a plant introduced from China designated PI 360841. Together they determined the number of genes involved. This work has now led to ongoing research to map these important genes and breeding efforts by the University of Arkansas to develop a new variety with resistance to the disease.
Technical Abstract: Phomopsis longicolla Hobbs is the primary cause of Phomopsis seed decay (PSD) in soybean. Infection may result in moldy seed and poor germination. The objective of this study was to conduct inheritance studies to characterize resistance to PSD in plant introduction (PI) 360841. Crosses were made between PI 360841 and two PSD-susceptible genotypes, Agripro (AP) 350 and PI 91113, to determine the number of genes for resistance. Additionally, crosses were made between PI 360841 and Phomopsis resistance parents MO/PSD-0259 and PI 80837 to test the allelism of the resistance genes. Seed infection assays were done using seed from parent plants and F2 populations. Chi-square analysis of the resistant x susceptible F2 data fit to a 9R:7S model for 2 complementary dominant genes conferring PSD resistance in PI 360841. Segregation for reaction in the F2 of MO/PSD-0259 x PI 360841 exhibited a good fit to a 57R:7S model for 2 complementary dominant genes from PI 360841 and a different dominant gene from MO/PSD-0259. There was no apparent segregation in the F2 population from PI360841 x PI 80837 except one suspicious susceptible plant, suggesting one of the genes in PI 360841 is the same gene in PI 80837 for PSD resistance.