Comparison of a modified assay method for the endopeptidase marker Ep-D1b with the Sequence Tag Site marker XustSSR2001-7DL for strawbreaker foot rot resistance in wheat

The endopeptidase marker Ep-D1b and Sequence Tag Site (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: (i) develop an efficient assay method for Ep-D1b in wheat; (ii) correlate endopeptidase zymograms to strawbreaker foot rot reactions of various wheat genotypes; and (iii) 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 a 2.5-fold improvement over the previous method. Thirty-eight wheat genotypes with known reactions to strawbreaker foot rot were analysed 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 with the STS marker.