Characterization of a new Pm2 allele associated with broad-spectrum powdery mildew resistance in wheat line Subtil

Abstract

Wheat powdery mildew is a severe disease affecting yield and quality. Host resistance was proved to be effective and environment-friendly. Wheat line Subtil is an elite germplasm resource resistant to 28 of 30 tested Bgt isolates. Genetic analysis showed that the powdery mildew resistance in Subtil was conferred by a single dominant gene, temporarily designated PmSub. Using bulked segregant analysis, PmSub was mapped to chromosome arm 5DS, and flanked by the markers Bwm16 and Cfd81/Bwm21 at 5.0 and 0.9 cM, respectively. Allelism tests further confirmed PmSub was allelic with documented Pm2 alleles. Then, homologous sequences of Pm2a related sequence was cloned from Subtil and Chinese Spring. It was completely identical to the reported Pm2a sequence, but significantly different from that of Chinese Spring. A marker SWGI067 was developed based on the sequence divergence of homologous sequence in Subtil and Chinese Spring. SWGI067 was closely linked to PmSub, indicating that the gene PmSub itself was different from the cloned Pm2a related sequence. Meanwhile, Subtil produced significantly different reaction pattern compared with other genotypes with Pm genes at or near Pm2 locus. Therefore, PmSub was most likely a new allele of Pm2. PmSub has opportunities for marker-assisted selecting for high-efficiency wheat improvement.

Characterization of the Powdery Mildew Resistance Gene in the Elite Wheat Cultivar Jimai 23 and Its Application in Marker-Assisted Selection

“…Although this locus has been cloned by mutant chromosome sequencing (Sánchez-Martín et al, 2016) and analysis of the annotated genes in the mapping interval using the reference genome of Chinese Spring , no transgenic evidence was provided to confirm that the cloned sequence is the unique functional element conferring resistance to powdery mildew. Additionally, other reports showed that all the homologous sequences in different Pm2 allele donors have the exactly the same sequence, yet these Pm2 alleles exhibit significantly different resistance spectra that cannot be explained by the background differences of the resistant germplasms (Jin et al, 2018;Ma et al, 2018). In this study, the marker order across the PmJM23 interval showed inversion and recombination phenomena (Figure 2 and Table 3).…”

Bulked Segregant RNA-Seq Reveals Distinct Expression Profiling in Chinese Wheat Cultivar Jimai 23 Responding to Powdery Mildew

“…in Jimai 23. In our previous reports, a series of Pm2 alleles with different reaction patterns to Bgt isolates have been identified in various wheat genotypes (Ma et al, 2014(Ma et al, , 2015a(Ma et al, ,b,c, 2016(Ma et al, , 2018Xu et al, 2015;Jin et al, 2018). However, these Pm2 alleles were only characterized at the genetic level.…”

“…Even though a Pm2-related gene was cloned using mutant chromosome sequencing and candidate gene analysis using the reference genome of Chinese Spring (Sánchez-Martín et al, 2016;Chen et al, 2019), there are still aspects of this locus that require further investigation. For instance, while the homologous sequences of different Pm2 alleles are identical to each other, these alleles have significantly different reaction patterns to Bgt isolates with different virulence spectra, something which cannot be explained by the background difference of the wheat genotypes (Jin et al, 2018;Ma et al, 2018).…”

“…In this study we confirmed that a Pm2 allele confers the powdery mildew resistance in Jimai 23. Although a Pm2-related gene has been cloned, the Pm2 locus has been shown to be a complex locus (Sánchez-Martín et al, 2016;Jin et al, 2018;Ma et al, 2018;Chen et al, 2019), and the resistance mechanism of this locus is even less clear during Bgt invasion. In order to dissect the composition of the Pm2 locus and profile the expression of powdery mildew resistance genes in Jimai 23 when subjected to Bgt invasion we: (1) confirmed the candidate interval of the Pm gene by distribution of differential SNPs; (2) identified and classified differentially expressed genes (DEGs) at the whole-genome scale; and (3) selected several key genes mediating powdery mildew resistance in Jimai 23 and profiled their expression following Bgt inoculation.…”

An Analysis of the Genetic Diversity of Bread Wheat x Spelt Breeding Lines in Terms of Their Resistance to Powdery Mildew and Leaf Rust

“…tritici and P. triticina, respectively. To date, more than 77 formal Pm genes and more than 30 temporarily designated genes (such as PmYB or PmWFJ) have been identified in 56 chromosomal loci in bread wheat [12,13]. Most Pm genes are localized on the chromosomes of A-and B-genomes (46.2% and 35.1% of all Pm genes, respectively).…”