Submitted to: ARS Sclerotinia Initiative Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: 12/31/2004
Publication Date: 1/1/2005
Citation: Clough, S.J., Vuong, T., Diers, B., Hartman, G.L. 2006. Genomic responses in soybean stem tissue to sclerotinia. Proceedings of the International Sclerotinia Workshop. p. 22.
Technical Abstract: We are using cDNA microarrays to aid in the search for genes related to defense against Sclerotinia sclerotiorum in soybean. The susceptible cultivar Williams 82 and the resistant plant introduction PI194639 were inoculated by applying agar plugs containing a fresh culture of S. sclerotiorum to freshly cut stems. The top 1.5 inches of inoculated or mock inoculate stems were collected at 0, 6, 18, and 48 hours post inoculation (hpi). This short time course indicated that the activation of enzymes involved in pathogen defense, such as phytoalexin production, had occurred within 18 hours. To identify differential expression at 18 and 48 hpi we used average fold change values of two biological repeats. Because differential gene expression at 6 hour was somewhat weak and less consistent, we increased our number of biological repeats to three independent inoculations and involved a statistical ANOVA calculation to assist in the identification of genes that were most significantly up or down regulated upon pathogen infection. The ANOVA of the 6 hour time point data revealed that about 100 genes out of 9,264 screened were significantly (p </> 0.01) differentially expressed between PI194639 and Williams 82 including many with no known function. At 18 and 48 hpi we again noticed that a high percent (approximately fifty) of the differentially expressed genes had no known function. Select genes that showed a correlation with resistance, such as several signal transduction related genes including calcium associated and LRR containing, will be converted into molecular markers to determine if they are associated with known QTLs for resistance.