Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/9/2005
Publication Date: 2/1/2006
Citation: Santra, D.K., Watt, C., Little, L.M., Kidwell, K.K., Garland Campbell, K.A. 2006. Comparison of a modified assay method for the endopeptidase marker ep-d1b with the sts marker xustssr2001-7dl for strawbreaker foot rot resistance in wheat. Plant Breeding 125:13-18. Interpretive Summary: The most effective resistance gene (Pch1) has been used to develop strawbreaker foot rot (also known as foot rot or eyespot) disease resistant wheat cultivars world wide during past 20 years. An isozyme marker endopeptidase and a DNA marker were reported to be closely associated with Pch1. Because of this close association wheat breeders have used endopeptidase marker as indirect selection tool to identify plants carrying Pch1. Thus breeders selected resistant plants indirectly without doing disease evaluation in the field which resulted foot rot resistant wheat cultivars in less time and more efficiently. The objectives of this report were to: (1) develop an efficient assay method for endopeptidase marker in wheat; (2) correlate endopeptidase banding pattern to foot rot reactions of various wheat cultivars and breeding lines; and (3) compare the utility of endopeptidase and DNA marker for predicting disease response. A faster and improved method of assaying endopeptidase marker was developed, which is 2.5 fold improvement over the previous method. Six distinct endopeptidase banding patterns were identified among 38 wheat cultivars and breeding lines tested for the marker and three of these patterns were novel. The endopeptidase marker was 100% accurate for predicting foot rot disease response, whereas the DNA marker predicted the correct phenotype with approximately 90% accuracy. The endopeptidase marker Ep-D1b was more effective and was more economical for use in marker-assisted selection strategies for Pch1 compared to the DNA marker. This improved method for Pch1 linked enedopeptidase marker assay will help wheat breeders to identify resistant plant at early generation in their breeding program which will lead to develop foot rot resistant wheat cultivars quicker and more efficiently.
Technical Abstract: The endopeptidase marker Ep-D1b and STS marker XustSSR2001-7DL were reported to be closely associated with the most effective resistance gene (Pch1) in wheat (Triticum aestivum L.) for strawbreaker foot rot [Pseudocercosporella herpotrichoides (Fron) Deighton]. Our objectives were to: (1) develop an efficient assay method for Ep-D1b in wheat; (2) correlate endopeptidase zymograms to strawbreaker foot rot reactions of various wheat genotypes; and (3) compare the utility of Ep-D1b and XustSSR2001-7DL for predicting disease response. An improved method of assaying for the Ep-D1b marker using roots from a single seedling was developed, which is 2.5 fold improvement over the previous method. Thirty-eight wheat genotypes with known reactions to strawbreaker foot rot were analyzed for Ep-D1b and the STS marker. Six distinct endopeptidase zymograms were identified among these 38 genotypes tested, and three of these patterns were novel. The endopeptidase marker was 100% accurate for predicting strawbreaker foot rot disease response, whereas the STS marker predicted the correct phenotype with approximately 90% accuracy. The endopeptidase marker Ep-D1b was more effective and was more economical for use in marker-assisted selection strategies for Pch1 in our laboratory compared to the STS marker.