Since the discovery of the first powdery mildew resistance gene in wheat, over 130 powdery mildew resistance genes have been identified and mapped in both wheat and its related species. Currently, there are 69 officially named powdery mildew resistance genes (
Pm1–
Pm69), which are distributed across different chromosome loci [
7].
Pm genes are present in different species and genera, including primary, secondary, and tertiary gene banks. In wheat, disease resistance genes of many ancestral and related species have been introduced, such as A genome donor
Triticum Urartu [
28], B genome donor
Ae. speltoides [
29], and D genome donor
Ae. tauschii [
30]. To date, a total of 31
Pm genes have been found in 22 loci of common wheat and local varieties, suggesting that there may be many more unknown
Pm genes in common wheat and local varieties remaining to be discovered [
26]. Wheat landraces are abundant in China, and the desirable traits can be easily transferred from landraces to elite common wheat cultivars. So far, five powdery mildew resistance genes have been identified in Chinese wheat landraces, including
Pm63 (PI628024) [
31].
Pm61 (Xuxusanyuehuang) [
15],
Pm59(PI181356) [
27],
Pm47 (Hongyanglazi) [
26],
Pm24 (Chiyacao/Baihulu) [
32,
33,
34],
Pm11 (Chinese spring) [
35], ,
Pm5e (Fuzhuang 30) [
36,
37],
Pm2c(Laomai) [
38], which were mapped on chromosomal arms of 2BL, 4AL, 7Al, 7BS, 1DS, 6BS, 7BL, and 5DS, respectively. It has been reported that there are three powdery mildew resistance genes on chromosome 1B, namely
Pm28,
Pm32, and
Pm39, and their specific locations are chromosomal arms of 1B, T1BL.1SS, and 1BL, respectively [
39,
40,
41]. The powdery mildew resistance gene
Pm28 of Meri was mapped to chromosome 1B by Peusha et al. [
42] through monosomic analysis, and
Pm32 was identified by Hsam et al. [
38] through multiple identification of wheat-
Ae. parvum translocation line L501. It was found that the resistance gene was located on 1BL.1SS. On the other hand,
Pm39 is a
Lr46/Yr29 locus on chromosome 1BL in the RIL population constructed by Saar and Avocet, which is officially named as
Pm39 [
33]. In this study, we used F
2 population to map
PmCAHM on the chromosome 1BS. We then compared the gene loci and gene origin with those officially named genes, and found that
PmCAHM is a new powdery mildew resistance gene due to its different chromosomal location on chromosome 1BS.
Full exploration and utilization of beneficial genetic resources in wheat local varieties and farm-grown varieties are of great significance for modern wheat disease-resistant breeding and genetic improvement. However, in actual wheat breeding, the utilization efficiency of local varieties is very low due to their inferior agronomic traits (such as low grain yield, lodging), long breeding time, and difficulty in breaking the genetic balance of unfavorable genes[
41,
42,
43,
44]. Most studies of resistance to powdery mildew in local varieties are based on gene localization[
45,
46,
47].
Pm5e,
Pm24,
Pm47 and
Pm61, which are only found in certain Chinese wheat landraces. For example,
Pm24 is the only known wheat powdery mildew resistance locus that was located on chromosome arm 1DS. The markers flanking
Pm24a were
Xgwm789/
Xgwm603 and
Xbarc229 at 2.4 and 3.6 cM, was also near
Xgwm337 and co-segregated with
Xgwm1291.
Pm24b was constructed and markers
Xgwm337 and
Xbarc229 flanked it at genetic distances of 3.7 and 1.0 cM, Xue tested with a differential array of 23
Bgt isolates Baihulu dis-played a response pattern that was clearly distinguishable from that of Chiyacao and varieties or lines possessing documented
Pm genes. Allelism analysis indicated that mlbhl is a new gene, and was designated
Pm24b. Xiao et al. used SSR markers closely linked to the resistance gene for chromosome physical mapping, resulting in the mapping of
Pm47 in the 7BS-1-0.27-1.00 region at the end of the short arm of chromosome 7B from Hongyanglazi[
26]. Molecular marker analysis localized
Pm61 in a 0.46-cM genetic interval on chromosome arm 4AL from Xuxusanyuehuang, and physical mapping of the closest flanking markers
Xgwm160 and
Xicsx79 assigned
Pm61 to a 1.3-Mb physical interval in the chromosome 4AL genomic sequence of Chinese Spring [
15].
Pm59 [
27] and
Pm63 [
31], which are only found in certain abroad wheat landraces. characterization of
Pm59, a novel powdery mildew resistance gene in Afghanistan wheat landrace PI 181356, and mapped in the terminal region of the long arm of chromosome 7A, was mapped to an interval between sequence tag site (STS) markers
Xmag1759 and
Xmag1714 with genetic distances of 0.4 cM distal to
Xmag1759 and 5.7 cM proximal to
Xmag1714.
Pm59 is in the distal bin 7AL 0.99–1.00. Pm59 is a novel powdery mildew resistance gene, and confers resistance to
Bgt isolates collected from the Great Plains and the state of Montana.
Pm63, was identified in Iranian wheat landrace PI 628024 and mapped to the terminal region of the long arm of chromosome 2B. spanning 710.3–723.4 Mb in the Chinese Spring reference sequence. Bin mapping assigned
Pm63 to the terminal bin 2BL6-0.89-1.0, 1.1 cM proximal to STS marker
Xbcd135-2 and 0.6 cM distal to SSR marker
Xstars419. Allelism tests indicated that
Pm63 can be widely used to enhance powdery mildew resistance in the Great Plains, western, and southeastern regions of the USA. So far, the most successful transfer of landrace genes into common wheat was
PmXNM [
48], originated from the Chinese wheat landrace Xiaonanmai, was delimited to a 300.7-kb interval enriched with resistance genes. Bulked segregant analysis and molecular mapping delimited
PmXNM to the distal terminal region of chromosome 4AL flanked by markers
caps213923 and
kasp511718 and contained nine high-confidence genes according to the reference genome sequence of CS. Seven candidate gene-specific markers have proven effective for marker-assisted introgression of
PmXNM into modern elite cultivars Bainong 207, development of breeder-friendly molecular markers to facilitate its utilization in wheat breeding programs.