Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/13/2004
Publication Date: 4/1/2005
Citation: Luo, M., Dang, P., Bausher, M.G., Holbrook, C.C., Lee, R.D., Lynch, R.E., Guo, B.Z. 2005. Identification of transcripts involved in resistance responses to leaf spot disease caused by Cercosporidium personatum in peanut (Arachis hypogaea). Phytopathology. 95(4):381-387. Interpretive Summary: Leaf spot diseases are the major destructive diseases of peanut worldwide. Control of leaf spot diseases in the U.S. has depended on multi-applications of fungicide, based either on a calendar schedule or a weather-based spray advisory. The development of resistant cultivars can be effective in decreasing production costs while maintaining good product quality. Because of the economic importance of leaf spot disease in peanut and the concerns regarding chemical control, it is important to understand peanut resistance at the molecular level and it would be useful to develop markers for use in breeding disease resistant cultivars. In this investigation we report the identification and characterization of the expression patterns of the resistant genes or complementary DNAs (cDNAs) related to the resistance/susceptibility to late leaf spot disease using microarray analysis and real-time PCR. The 384 gene clones for spotted microarray were selected for adversity resistant unique DNA sequences from leaf spot disease challenged cDNA libraries. Some genes identified by microarray analysis were validated by real-time PCR, and these genes had significantly higher expression in the resistant cultivar than the expression levels in the susceptible cultivar. Molecular markers could be developed to more rapidly select for these genes in peanut breeding programs.
Technical Abstract: Late leaf spot disease caused by Cercosporidium personatum is one of the most destructive foliar diseases of peanut worldwide. The objective of this research was to identify genes for resistance to leaf spot disease. We used microarray chips containing 384 cDNA unigenes related to adversity resistance genes, which were selected from ESTs (expressed sequenced tags) of two cDNA libraries, to identify transcripts of disease resistance in two peanut cultivars, C34-24 (resistant) and GT-YY20 (susceptible). A total of 112 spots representing 56 genes in several functional categories were detected to be up-regulated genes (Log2 ratio>1). Seventeen of the top 20 genes, each matching known function genes in GenBank, were selected for validation of their expression levels using real-time PCR. These two peanut cultivars, one resistant and one susceptible to late leaf spot disease, were also used to study the functional analysis of these genes and possibly link the genes to these traits of disease resistance. Microarray technology and real-time PCR were used for comparison of gene expression. Some genes identified by microarray analysis were validated by real-time PCR, and these genes had significantly higher expression in the resistant cultivar challenged by C. personatum than the expression levels in the susceptible cultivar. Further investigations are needed to characterize each of these genes for their possible functions in disease resistance. Molecular markers could then be developed to more rapidly select for these genes in peanut breeding programs.