Abstract
Rapeseed contains glucosinolates, a toxic group of sulfur-containing glucosides, which play critical roles in defense against herbivores and microbes. However, the presence of glucosinolates in rapeseed reduces the value of the meal as feed for livestock. We performed association mapping of seed glucosinolate (GS) content using the 60K Brassica Infinium single nucleotide polymorphism (SNP) array in 520 oilseed rape accessions. A total of 11 peak SNPs significantly associated with GS content were detected in growing seasons of 2013 and 2014 and were located on B. napus chromosomes A08, A09, C03, and C09, respectively. Two associated regions of GS content covered by these markers were further verified, and three B. napus homologous genes involved in the biosynthesis and accumulation of GS were identified. These genes were multigene family members and were distributed on different chromosomes. Moreover, two genes (BnGRT2 and BnMYB28) associated with GS content were validated by the qRT-PCR analysis of their expression profiles. The further identification and functionalization of these genes will provide useful insight into the mechanism underlying GS biosynthesis and allocation in B. napus, and the associated SNPs markers could be helpful for molecular maker-assisted breeding for low seed GS in B. napus.
Highlights
Glucosinolates, a group of sulfur-containing glucosides, are secondary metabolites uniquely detected in Brassicaceae and provide protection against plant pest and pathogens
Quantitative trait locus (QTL) mapping based on molecular markers is an effective method for identifying candidate alleles involved in a complex trait, by which method numerous markers associated with total GS content have been mapped using different populations of B. napus [3,4,5,6,7]
The total GS content of 520 rapeseed accessions were measured with three repeats using near infrared reflectance spectroscopy (NIRS), and the phenotypic variation recorded were observed (Figure 1 and Table 1)
Summary
Glucosinolates, a group of sulfur-containing glucosides, are secondary metabolites uniquely detected in Brassicaceae and provide protection against plant pest and pathogens. It is desirable to reduce the glucosinolate content of seeds, but to maintain a high level of glucosinolates in other tissues to prevent herbivore damage and pathogenic microbes. Rapeseed (Brassica napus L., genome AACC, 2n = 38) is an important source of edible oil for humans and protein for live-stock [2]. Selecting double-low rapeseed, i.e., with seeds lacking erucic acid (another toxic compound produced by rapeseed) and containing only low levels of glucosinolate in seeds, has been an important objective of rapeseed breeding programs globally. Quantitative trait locus (QTL) mapping based on molecular markers is an effective method for identifying candidate alleles involved in a complex trait, by which method numerous markers associated with total GS content have been mapped using different populations of B. napus [3,4,5,6,7]
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