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Genome-wide Association Study Identifies New Loci for Resistance to Sclerotinia Stem Rot in Brassica napus.

ABSTRACT: Sclerotinia stem rot (SSR) caused by the necrotrophic fungus Sclerotinia sclerotiorum is a major disease in rapeseed (Brassica napus) worldwide. Breeding for SSR resistance in B. napus, as in other crops, relies only on germplasms with quantitative resistance genes. A better understanding of the genetic basis for SSR resistance in B. napus thus holds promise for the genetic improvement of disease resistance. In the present study, a genome-wide association study (GWAS) for SSR resistance in B. napus were performed using an association panel of 448 accessions genotyped with the Brassica 60K Infinium^® single-nucleotide polymorphism (SNP) array. A total of 26 SNPs corresponding to three loci, DSRC4, DSRC6, and DSRC8 were associated with SSR resistance. Haplotype analysis showed that the three favorable alleles for SSR resistance exhibited cumulative effects. After aligning SSR resistance quantitative trait loci (QTL) identified in the present and previous studies to the B. napus reference genome, one locus (DSRC6) was found to be located within the confidence interval of a QTL identified in previous QTL mapping studies and another two loci (DSRC4 and DSRC8) were considered novel loci for SSR resistance. A total of 39 candidate genes were predicted for the three loci based on the GWAS combining with the differentially expressed genes identified in previous transcriptomics analyses.

SUBMITTER: Wu J

PROVIDER: S-EPMC5028409 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Genome-wide Association Study Identifies New Loci for Resistance to Sclerotinia Stem Rot in Brassica napus.

Wu Jian J Zhao Qing Q Liu Sheng S Shahid Muhammad M Lan Lei L Cai Guangqin G Zhang Chunyu C Fan Chuchuan C Wang Youping Y Zhou Yongming Y

Frontiers in plant science 20160920

Sclerotinia stem rot (SSR) caused by the necrotrophic fungus Sclerotinia sclerotiorum is a major disease in rapeseed (Brassica napus) worldwide. Breeding for SSR resistance in B. napus, as in other crops, relies only on germplasms with quantitative resistance genes. A better understanding of the genetic basis for SSR resistance in B. napus thus holds promise for the genetic improvement of disease resistance. In the present study, a genome-wide association study (GWAS) ...[more]

PMID: 27703464

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Project description:BackgroundOilseed rape (Brassica napus L.) is known as one of the most important oilseed crops cultivated around the world. However, its production continuously faces a huge challenge of Sclerotinia stem rot (SSR), a destructive disease caused by the fungus Sclerotinia sclerotiorum, resulting in huge yield loss annually. The SSR resistance in B. napus is quantitative and controlled by a set of minor genes. Identification of these genes and pyramiding them into a variety are a major strategy for SSR resistance breeding in B. napus.ResultsHere, we performed a genome-wide association study (GWAS) using a natural population of B. napus consisting of 222 accessions to identify BnaA08g25340D (BnMLO2_2) as a candidate gene that regulates the SSR resistance. BnMLO2_2 was a member of seven homolog genes of Arabidopsis Mildew Locus O 2 (MLO2) and the significantly SNPs were mainly distributed in the promoter of BnMLO2_2, suggesting a role of BnMLO2_2 expression level in the regulation of SSR resistance. We expressed BnMLO2_2 in Arabidopsis and the transgenic plants displayed an enhanced SSR resistance. Transcriptome profiling of different tissues of B. napus revealed that BnMLO2_2 had the most expression level in leaf and silique tissues among all the 7 BnMLO2 members and also expressed higher in the SSR resistant accession than in the susceptible accession. In Arabidopsis, mlo2 plants displayed reduced resistance to SSR, whereas overexpression of MLO2 conferred plants an enhanced SSR resistance. Moreover, a higher expression level of MLO2 showed a stronger SSR resistance in the transgenic plants. The regulation of MLO2 in SSR resistance may be associated with the cell death. Collinearity and phylogenetic analysis revealed a large expansion of MLO family in Brassica crops.ConclusionOur study revealed an important role of BnMLO2 in the regulation of SSR resistance and provided a new gene candidate for future improvement of SSR resistance in B. napus and also new insights into understanding of MLO family evolution in Brassica crops.

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Genome-wide Association Study Identifies New Loci for Resistance to Sclerotinia Stem Rot in Brassica napus.

Publications

Genome-wide Association Study Identifies New Loci for Resistance to Sclerotinia Stem Rot in <i>Brassica napus</i>.

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