Characterization and identification of the powdery mildew resistance gene in wheat breeding line Jimai 809

Abstract Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a severe disease that seriously affects the yield and quality of wheat. Using resistant cultivars in the production is the preferred strategy to control this disease. In the current study, the wheat breeding line Jimai 809 from Shandong Province of China showed high resistance to powdery mildew at the whole growth stage. To dissect the genetic basis for this resistance, Jimai 809 was crossed with the susceptible wheat cultivar Junda 159 to produce F1, F2 and F2:3 populations. Genetic analysis showed that a single dominant gene, temporarily named PmJM809, conferred the resistance to the Bgt isolate E09. Further molecular markers analysis showed that PmJM809 was located on chromosome 2BL and flanked by the markers CISSR02g-1 and CIT02g-13 with the genetic distances 0.4 and 0.8 cM, respectively, corresponding to a physical interval of 704.12-708.24 Mb referred to Chinese Spring reference genome sequence v1.1. PmJM809 differed from the Pm genes previously reported on chromosome arm 2BL in origin, resistance spectrum, physical position and genetic diversity of the interval, and hence was most likely a novel Pm gene or new allele of these reported Pm genes. To analyze and screen the candidate genes of PmJM809, six genes related to disease resistance in the candidate interval of PmJM809 were evaluated their expression pattern using an additional set of wheat samples and time-course analysis post-inoculation of Bgt isolate, and among them, three genes were locked as the key candidate genes. To efficiently transfer and track PmJM809 in different wheat genetic backgrounds, 13 of 19 closely linked/co-segregated markers were selected to be suitable for marker-assisted selection.