Abstract
The wheat powdery mildew resistance gene Pm40, which is located on chromosomal arm 7BS, is effective against nearly all prevalent races of Blumeria graminis f. sp tritici (Bgt) in China and is carried by the common wheat germplasm PI 672538. A set of the F1, F2 and F2:3 populations from the cross of the resistant PI 672538 with the susceptible line L1034 were used to conduct genetic analysis of powdery mildew resistance and construct a high-density linkage map of the Pm40 gene. We constructed a high-density linkage genetic map with a total length of 6.18 cM and average spacing between markers of 0.48 cM.Pm40 is flanked by Xwmc335 and BF291338 at genetic distances of 0.58 cM and 0.26 cM, respectively, in deletion bin C-7BS-1-0.27. Comparative genomic analysis based on EST-STS markers established a high level of collinearity of the Pm40 genomic region with a 1.09-Mbp genomic region on Brachypodium chromosome 3, a 1.16-Mbp genomic region on rice chromosome 8, and a 1.62-Mbp genomic region on sorghum chromosome 7. We further anchored the Pm40 target intervals to the wheat genome sequence. A putative linear index of 85 wheat contigs containing 97 genes on 7BS was constructed. In total, 9 genes could be considered as candidates for the resistances to powdery mildew in the target genomic regions, which encoded proteins that were involved in the plant defense and response to pathogen attack. These results will facilitate the development of new markers for map-based cloning and marker-assisted selection of Pm40 in wheat breeding programs.
Highlights
Powdery mildew, which is caused by Blumeria graminis f. sp tritici (Bgt), is a globally destructive disease of common wheat (Triticum aestivum L.)
Genetic analysis demonstrated that the resistance to wheat powdery mildew in YU25 was controlled by the genes PmE and PmYU25, which are located on chromosomes 7B and 2D, respectively [21]
To achieve the eventual objective of marker-assisted selection and mapbased cloning, we studied the inheritance of Pm40, constructed a high-density genetic linkage map of Pm40, performed comparative genomics analysis of the regions of Pm40 in PI 672538, and obtained 9 candidate genes related to powdery mildew resistance
Summary
Powdery mildew, which is caused by Blumeria graminis f. sp tritici (Bgt), is a globally destructive disease of common wheat (Triticum aestivum L.). Genetic analysis demonstrated that the resistance to wheat powdery mildew in YU25 was controlled by the genes PmE and PmYU25, which are located on chromosomes 7B and 2D, respectively [21]. To accelerate the application of Pm40 in wheat breeding programs, we have explored the underlying molecular mechanism of resistance to powdery mildew as conferred by the host gene Pm40, including studying the physiological changes and gene expression profile of Pm40 during host-pathogen interaction [27]. To achieve the eventual objective of marker-assisted selection and mapbased cloning, we studied the inheritance of Pm40, constructed a high-density genetic linkage map of Pm40, performed comparative genomics analysis of the regions of Pm40 in PI 672538, and obtained 9 candidate genes related to powdery mildew resistance
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