Mapping of Crown Rust (Puccinia coronataf. sp.avenae) Resistance GenePc54and a Novel Quantitative Trait Locus Effective Against Powdery Mildew (Blumeria graminisf. sp.avenae) in the Oat (Avena sativa) Line Pc54

Abstract

The Pc54 oat line carries the crown rust resistance gene ‘Pc54’ and an unknown gene effective against powdery mildew. In this study two recombinant inbred line populations were developed to identify the genomic locations of the two genes and producing lists of molecular markers with a potential for marker assisted selection. The RILs and parents were phenotyped for crown rust and powdery mildew in a controlled environment. They were also genotyped using the 6K Illumina Infinium iSelect oat SNP chip. Multiple interval mapping placed Pc54 on the linkage group Mrg02 (chromosome 7D) and the novel powdery mildew QTL ‘QPm.18’ on Mrg18 (chromosome 1A) both in the mapping and validating population. A total of nine and 31 significant molecular markers were identified linked with the Pc54 gene and QPm.18, respectively. Reactions to crown rust inoculations have justified separate identity of Pc54 from other genes and QTL that have previously been reported on Mrg02 except for ’qPCRFd’. Pm3 is the only powdery mildew resistance gene previously mapped on Mrg18. However, the pm3 differential line, Mostyn was susceptible to the powdery mildew race used in this study suggesting that Pm3 and QPm.18 are different genes. Determining the chromosomal locations of Pc54 and QPm.18 is helpful for better understanding the molecular mechanism of resistance to crown rust and powdery mildew in oats. Furthermore, SNPs and SSRs that are closely linked with the genes could be valuable for developing PCR based molecular markers and facilitating the utilization of these genes in oat breeding programs.

Mapping and identification of molecular markers for the Pc96 gene conferring resistance to crown rust in oat

“…The ruler scale on the left indicates map distances in centiMorgans (cM). * The estimated position of Pc54 on consensus map [ 19 ].…”

“…Other investigations have identified Pc genes in this chromosomal region. Evidence of linkage in the broader Pc96 gene region was reported for Pc35 [ 32 ], Pc38 (chromosome 9D) [ 12 ], and Pc54 [ 19 ]. Segregation analysis has linked Pc38 with Pc62 and Pc63 [ 47 ].…”

“…This position of Pc38 overlaps with the most probable location of Pc96 , and the recombination between Pc38 and Pc96 could be evaluated if this combination of genes is desired. Yimer et al [ 19 ] mapped Pc54 to the same location as Pc96 , in part using the Pc54 × Pc96 population analyzed in this study. A comparison of Pc54 × Pc96 phenotypes from growth chamber screening with NQBK (avirulent on Pc96 ) and LLMG (avirulent on Pc54 ) [ 19 ] indicate that these two genes are linked rather than allelic.…”

“…Yimer et al [ 19 ] mapped Pc54 to the same location as Pc96 , in part using the Pc54 × Pc96 population analyzed in this study. A comparison of Pc54 × Pc96 phenotypes from growth chamber screening with NQBK (avirulent on Pc96 ) and LLMG (avirulent on Pc54 ) [ 19 ] indicate that these two genes are linked rather than allelic. Crossover events produced 2 RILs which were homozygous carriers of both genes and only four RILs carried the susceptible alleles for both Pc54 and Pc96 ( S5 Table ).…”

“…For this reason, incorporation of single gene resistance into cultivated oat germplasm has been a common strategy for managing oat crown rust [ 9 – 11 ]. Oat crown rust qualitative resistance genes with known genomic locations include Pc38 [ 12 ], Pc39 [ 13 , 14 ], Pc45 [ 15 ], Pc48 [ 16 ], Pc50-5 [ 17 ], Pc53 [ 18 ], Pc54 [ 19 ], Pc58 a [ 20 , 21 ], Pc68 [ 22 ], Pc71 [ 23 ], Pc91 [ 24 ], Pc94 [ 25 ] and Pc98 [ 26 ]. Unfortunately, single gene resistance is typically only effective for a few years due to rapid changes in Pca virulence [ 27 – 31 ].…”