Submitted to: International Conference on Legume Genomics and Genetics
Publication Type: Abstract Only
Publication Acceptance Date: September 15, 2008
Publication Date: December 5, 2008
Citation: Upchurch, R.G. and Ramirez, M.E. 2008. Defense gene induction in the compatible interaction of soybean with Cercospora kikuchii and Diaporthe phaseolorum. International Conference on Legume Genomics and Genetics.
We examined the compatible interaction of soybean [Glycine max (L.) Merr.] cultivar Dare with fungal pathogens Cercospora kikuchii (CK), a hemibiotroph, and Diaporthe phaseolorum (DP), a biotroph, in order to gain insight into basal host defense. Expression of defense genes in pathogen-, mock-, or chemically-treated leaves was measured over a 48 h post-treatment period using gene-specific primers and real time, quantitative RT-PCR. For CK treated leaves, expression as mean fold increase over the control (FIOC) of pathogenicity-related proteins PR3 and PR10 was strongly induced (FIOC ca. 17 and 16) within 24 h as was omega-3 fatty acid desaturase GmFAD7 (FIOC ca.12) within 12 h post-inoculation. For DP treated leaves, defense gene induction was lower for PR3, PR10 and GmFAD7, but PR1 (FIOC ca. 9) was strongly induced within 12 h post-treatment. Soybean defensin expression was moderately induced by DP treatment (FIOC ca. 5), but not by CK treatment. PR genes were moderately induced by salicylic acid (SA) or methyl jasmonate (MeJA) treatment with PR1 levels higher (FIOC ca. 4) with SA treatment and PR3, PR4, and PR10 higher (FIOCs ca. 6, 6, and 3) with MeJA treatment. For soybean defensin, no induction was detected with either chemical treatment. In contrast, induction of GmFAD7 was rapid, within 4 h of treatment with either SA or MeJA, but more strongly induced (FIOC ca. 15) by MeJA. Results show that soybean leaf defense mediated through PR and defensin gene expression have pathogen-specific differences in induction pattern but share a similar GmFAD7 induction response.