Abstract
The majority of rapeseed cultivars shatter seeds upon maturity especially under hot-dry and windy conditions, reducing yield and gross margin return to growers. Here, we identified quantitative trait loci (QTL) for resistance to pod shatter in an unstructured diverse panel of 143 rapeseed accessions, and two structured populations derived from bi-parental doubled haploid (DH) and inter-mated (IF2) crosses derived from R1 (resistant to pod shattering) and R2 (prone to pod shattering) accessions. Genome-wide association analysis identified six significant QTL for resistance to pod shatter located on chromosomes A01, A06, A07, A09, C02, and C05. Two of the QTL, qSRI.A09 delimited with the SNP marker Bn-A09-p30171993 (A09) and qSRI.A06 delimited with the SNP marker Bn-A06-p115948 (A06) could be repeatedly detected across environments in a diversity panel, DH and IF2 populations, suggesting that at least two loci on chromosomes A06 and A09 were the main contributors to pod shatter resistance in Chinese germplasm. Significant SNP markers identified in this study especially those that appeared repeatedly across environments provide a cost-effective and an efficient method for introgression and pyramiding of favorable alleles for pod shatter resistance via marker-assisted selection in rapeseed improvement programs.
Highlights
Rapeseed (Brassica napus L., 2n = 4× = 38, genome AACC) is the third largest oilseed crop produced in the world after oil palm and soybean (USDA FAS, 2015)1
Identification of loci via genome wide association study (GWAS) and classical quantitative trait loci (QTL) analyses, and SNP marker significantly associated with pod shatter resistance may facilitate a costeffective marker assisted selection of favorable alleles in rapeseed breeding programs
We identified six QTL associated with pod shatter resistance which accounted for up to 50% the phenotypic variation in pod shatter resistance index (PSRI) in doubled haploid (DH) and inter-mated F2 (IF2) mapping populations
Summary
Many plant species including rapeseed dehisce seeds upon maturity for dispersal and survival in subsequent generations. This phenomenon is one of the major bottlenecks in rapeseed production on a commercial scale. In recent years, farmers prefer to use combine harvesters, as this operation is less-labor intensive and cheaper compared to windrowing and manual harvesting. The latter is not an option for many western countries where rapeseed is often used as a broad-acre crop and harvested under very hot and dry conditions. Developing pod shatter resistant varieties suitable for combine harvesting has become one of the main breeding objectives of rapeseed improvement programs
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