Collinearity Analysis and High-Density Genetic Mapping of the Wheat Powdery Mildew Resistance Gene Pm40 in PI 672538

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.

Identification and Cloning of a CC-NBS-NBS-LRR Gene as a Candidate of Pm40 by Integrated Analysis of Both the Available Transcriptional Data and Published Linkage Mapping

“…At present, although Pm21 is still effective and the most widely applied Pm gene in the country [ 16 ], some newly emerged and virulent isolates have been reported to overcome Pm21 resistance in various regions [ 17 , 18 ]. We found that Pm40 still confers strong resistance to powdery mildew in various regions [ 2 , 19 , 20 ]. It was also effective against nearly all isolates collected from the main Chinese wheat growing regions, which indicated that Pm40 could have a large potential role in the improvement in resistance against powdery mildew in China in the future, especially in the post- Pm21 era [ 7 ].…”

“…In 2007, we first identified PmE controlling resistance to powdery mildew in the wheat line YU25 by genetic analysis [ 38 ], which was consequently mapped to chromosome 7B and formally named Pm40 [ 19 ]. In a later study, Pm40 was further mapped to a short chromosomal region of 7BS flanked by Xwmc335 (with distances of 0.58 cm) and BF291338 (with distances of 0.26 cm) [ 20 ]. With the release of the Chinese spring reference genome sequence, it was feasible and workable to identify the effective candidate gene of Pm40 because the high-quality reference genome information was available.…”

“…intermedium because it had Line Yu25 conferring Pm40 resistance in its pedigree [ 19 ]. Subsequent evidence, including the uniformity of agronomic traits and the good genetic stability of powdery mildew resistance in many years [ 2 , 7 ], the genetic behavior as a normal Mendelian factor [ 19 , 20 , 38 ], the wheat-specific amplicons produced by polymerase chain reaction (PCR) amplification, and the similar marker order with the similar total length of the linkage mapping of Pm40 [ 19 , 20 ], supported the view that Pm40 may result from DNA sequence change or chromosomal rearrangement of wheat self-genome during the wild cross process rather than direct transfer from Th. intermedium.…”

“…In this study, we had the following objectives: to further test the resistance of Pm40 by inoculation with Bgt race E20; to identify candidate resistance genes by comprehensive analysis using gene annotation data from the IWGSC RefSeq v1.0 in the physical region flanked by two EST markers, BF478514 and BF291338 [ 20 ], on chromosome 7B and both sequence and expression differences in the available transcriptome data; to clone the TraesCS7B01G164000 sequence and further confirm the sequence differences between L658 carrying Pm40 and L958 lacking Pm40 ; and to validate the candidate gene TraesCS7B01G164000 by cosegregation and qRT-PCR analyses. Comprehensively, all results supported TraesCS7B01G164000 as a potential candidate gene of Pm40 .…”

Comparative Proteomic Analysis of Wheat Carrying Pm40 Response to Blumeria graminis f. sp. tritici Using Two-Dimensional Electrophoresis

“…The resistance gene Pm40 was transferred from Elytrigia intermedium into wheat line GRY19 and mapped on chromosome arm 7BS [ 21 ]. 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 [ 22 ]. Wheat line L699 , which is the high generation of wheat line GRY19 , carries the resistance gene Pm40 and confers resistance to all available isolates of Bgt in China [ 23 ].…”