Association mapping in sunflower for sclerotinia head rot resistance

Abstract

Background: Sclerotinia Head Rot (SHR) is one of the most damaging diseases of sunflower in Europe, Argentina, and USA, causing average yield reductions of 10 to 20 %, but leading to total production loss under favorable environmental conditions for the pathogen. Association Mapping (AM) is a promising choice for Quantitative Trait Locus (QTL) mapping, as it detects relationships between phenotypic variation and gene polymorphisms in existing germplasm without development of mapping populations. This article reports the identification of QTL for resistance to SHR based on candidate gene AM. Results: A collection of 94 sunflower inbred lines were tested for SHR under field conditions using assisted inoculation with the fungal pathogen Sclerotinia sclerotiorum. Given that no biological mechanisms or biochemical pathways have been clearly identified for SHR, 43 candidate genes were selected based on previous transcript profiling studies in sunflower and Brassica napus infected with S. sclerotiorum. Associations among SHR incidence and haplotype polymorphisms in 16 candidate genes were tested using Mixed Linear Models (MLM) that account for population structure and kinship relationships. This approach allowed detection of a significant association between the candidate gene HaRIC_B and SHR incidence (P < 0.01), accounting for a SHR incidence reduction of about 20 %.

The control of sclerotinia stem rot on oilseed rape (Brassica napus): current practices and future opportunities

“…As opposed to biparental mapping techniques, these studies are not limited by the genetic diversity restricted within two individual canola plants and therefore represent a more comprehensive way of identifying QTLs for SSR resistance in B. napus. Genome-wide association studies (GWAS) have been performed for resistance to SSR in soybean (Bastien et al, 2014) and sunflower (Fusari et al, 2012), as well as pod shatter resistance in canola (Raman et al, 2014). The recently developed B. napus GWAS ERANET-ASSYST population could be used for future SSR resistance studies (Schiessl et al, 2014).…”

Population structure and genetic diversity characterization of a sunflower association mapping population using SSR and SNP markers

“…Association mapping (AM) is a relatively recent quantitative trait loci (QTL) mapping approach, that has the potential for resolution to the level of individual genes (alleles) [ 8 ]. In contrast to classical QTL mapping techniques used in the analysis of complex traits, AM is a method that detects relationships between phenotypic variation and gene polymorphisms in existing germplasm collections, without development of mapping populations [ 9 , 10 ]. Until now, only four AM studies have been reported for sunflower.…”

“…Until now, only four AM studies have been reported for sunflower. The first one was conducted by Fusari et al [ 9 ] using a set of inbred lines from the breeding program of the National Institute of Agricultural Technology (INTA, Argentina), whereas the remaining three were based on germplasm collections from the USDA North Central Regional Plant Introduction Station (NCRPIS), the French National Institute for Agricultural Research, INRA and the USDA-ARS, Northern Crop Science Laboratory [ 11 - 13 ].…”

Comparison of GWAS models to identify non-additive genetic control of flowering time in sunflower hybrids

“…The impact of environmental cues on flowering time is well documented in the model plant Arabidopsis thaliana where a study (Li et al, 2010) identified SNPs that can explain up to 45% of the phenotypic variation of flowering time in a large panel of natural accessions. In sunflower, GWAS are more recent: Fusari et al (2012) on disease resistance, and Nambeesan et al (2015) on branching performed their GWAS with data collected on inbred lines, whereas Cadic et al (2013) studied the genetic control of FT in a panel evaluated in 15 environments as hybrids.…”