Powdery mildew of wheat (Triticum aestivum), caused by Blumeria graminis f.sp. tritici (Bgt), is a destructive disease that seriously threatens the yield and quality of its host. Identifying resistance genes is the most attractive and effective strategy for developing disease-resistant cultivars and controlling this disease. In this study, a wheat breeding line Yannong 99102-06188 (YN99102), an elite derivative line from the same breeding process as the famous wheat cultivar Yannong 999, showed high resistance to powdery mildew at the whole growth stages. Genetic analysis was carried out using Bgt isolate E09 and a population of YN99102 crossed with a susceptible parent Jinhe 13–205 (JH13–205). The result indicated that a single recessive gene, tentatively designated pmYN99102, conferred seedling resistance to the Bgt isolate E09. Using bulked segregant exome capture sequencing (BSE-Seq), pmYN99102 was physically located to a ~33.7 Mb (691.0–724.7 Mb) interval on the chromosome arm 2BL, and this interval was further locked in a 1.5 cM genetic interval using molecular markers, which was aligned to a 9.0 Mb physical interval (699.2–708.2 Mb). Based on the analysis of physical location, origin, resistant spectrum, and inherited pattern, pmYN99102 differed from those of the reported powdery mildew (Pm) resistance genes on 2BL, suggesting pmYN99102 is most likely a new Pm gene/allele in the targeted interval. To transfer pmYN99102 to different genetic backgrounds using marker-assisted selection (MAS), 18 closely linked markers were tested for their availability in different genetic backgrounds for MAS, and all markers expect for YTU103-97 can be used in MAS for tracking pmYN99102 when it transferred into those susceptible cultivars.

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a serious fungal disease that critically threatens the yield and quality of wheat. Utilization of host resistance is the most effective and economical method to control this disease. In our study, a wheat breeding line ShiCG15–009, released from Hebei Province, was highly resistant to powdery mildew at all stages. To dissect its genetic basis, ShiCG15–009 was crossed with the susceptible cultivar Yannong 21 to produce F1, F2 and F2:3 progenies. After genetic analysis, a single dominant gene, tentatively designated PmCG15–009, was proved to confer resistance to Bgt isolate E09. Further molecular markers analysis showed that PmCG15–009 was located on chromosome 2BL and flanked by markers XCINAU130 and XCINAU143 with the genetic distances 0.2 and 0.4 cM, respectively, corresponding to a physic interval of 705.14–723.48 Mb referred to the Chinese Spring reference genome sequence v2.1. PmCG15–009 was most likely a new gene differed from the documented Pm genes on chromosome 2BL since its different origin, genetic diversity, and physical position. To analyze and identify the candidate genes, six genes associated with disease resistance in the candidate interval were confirmed to be associated with PmCG15–009 via qRT-PCR analysis using the parents ShiCG15–009 and Yannong 21 and time-course analysis post-inoculation with Bgt isolate E09. To accelerate the transfer of PmCG15–009 using marker-assisted selection (MAS), 18 closely or co-segregated markers were evaluated and confirmed to be suitable for tracing PmCG15–009, when it was transferred into different wheat cultivars.

Powdery mildew of wheat, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease that seriously reduces yield and quality worldwide. Utilization of plant resistance genes is an attractive and effective strategy for controlling this disease. Among the reported powdery mildew (Pm) resistance genes, Pm2 exhibits a diverse resistance spectrum among its multiple alleles. It has been widely used in China for resistance breeding for powdery mildew. To mine more Pm2 alleles and clarify their distribution, we screened 33 wheat cultivars/breeding lines carrying Pm2 alleles from 641 wheat genotypes using diagnostic and Pm2-linked markers. To further investigate the relationships within the Pm2 alleles, we compared their resistance spectra, polymorphism of marker alleles and gene sequences, and found that they have identical marker alleles and gene sequences but diverse resistance spectra. In addition, the diagnostic kompetitive allele-specific PCR (KASP) marker, YTU-KASP-Pm2, was developed and was shown to detect all the Pm2 alleles in the different genetic backgrounds. These findings provide valuable information for the distribution and rational use of Pm2 alleles, push forward their marker-assisted breeding (MAS), and hence improve the control of wheat powdery mildew.

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease worldwide. Host resistance is the preferred method for limiting the disease epidemic, protecting environment, and minimizing the economic losses. In the present study, the reactions to powdery mildew for a collection of 600 wheat cultivars and breeding lines from different wheat growing regions were tested using the Bgt isolate E09. One hundred and sixteen resistant genotypes were identified and then crossed with susceptible wheat cultivars/lines to produce segregating populations for genetic analysis. Among them, 87, 19, and 10 genotypes displayed single, dual, and multiple genic inheritance, respectively. To identify the Pm gene(s) in those resistant genotypes, 16 molecular markers for 13 documented Pm genes were used to test the resistant and susceptible parents and their segregating populations. Of the 87 wheat genotypes that fitted the monogenic inheritance, 75 ones carried the Pm2a allele. Three, two, one, and two genotypes carried Pm21, Pm6, Pm4, and the recessive genes pm6 and pm42, respectively. Four genotypes did not carry any of the tested genes, suggesting that they might have other uncharacterized or new genes. The other 29 wheat cultivars/lines carried two or more of the tested Pm genes and/or other untested genes, including Pm2, Pm5, Pm6, and/or pm42 . It was obvious that Pm2 was widely used in wheat production, whereas Pm1, Pm24, Pm33, Pm34, Pm35, Pm45, and Pm47 were not detected in any of these resistant wheat genotypes. This study clarified the genetic basis of the powdery mildew resistance of these wheat cultivars/lines to provide information for their rational utilization in different wheat growing regions. Moreover, some wheat genotypes which may have novel Pm gene(s) were mined to enrich the diversity of resistance source.

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