|Talukder, Zahirul -|
|Pegadaraju, Venkatramana -|
|Mcphee, Kevin -|
|Gulya Jr, Thomas|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2013
Publication Date: January 1, 2014
Citation: Talukder, Z.I., Hulke, B.S., Qi, L., Scheffler, B.E., Pegadaraju, V., McPhee, K., Gulya, T.J. 2014. Candidate gene association mapping of Sclerotinia stalk rot resistance in sunflower (Helianthus annuus L.) uncovers the importance of COI1 homologs. Theoretical and Applied Genetics. 127:193-209. Interpretive Summary: Sclerotinia stalk rot is one of the most destructive diseases in sunflower. This study used field based studies and molecular markers from the sunflower genome to find the chromosomal location of genes that are important in resistance to Sclerotinia, using a candidate gene approach. The candidate gene approach is used when there is evidence of a gene being involved in a plant trait, and a scientist wants to test whether or not the evidence is true. For two genes we studied, which are from the same gene family, COI1, we found correlation with resistance to Sclerotinia. This means that the genes are likely giving the plant resistance. This information can be used by geneticists and breeders to improve resistance in sunflowers grown in producer’s fields.
Technical Abstract: Sclerotinia stalk rot is one of the most destructive diseases of sunflower (Helianthus annuus L.) worldwide. Markers based on the Sclerotinia disease resistance gene will enable efficient marker-assisted selection (MAS). We sequenced eight candidate genes homologus to Arabidopsis thaliana defense genes known to associate with Sclerotinia disease resistance, in a set of sunflower genotypes of an association mapping population evaluated for Sclerotinia stalk rot resistance in two-year multilocation trials. The total candidate gene sequence regions analyzed covered a concatenated length of 3,791bp per individual. A total of 187 polymorphic sites were detected for all candidate gene sequences, 149 of which were SNPs (single nucleotide polymorphisms) and 38 were InDels (insertions/deletions). Fifteen SNPs in the coding regions led to changes in amino acid codons. LD decay throughout the candidate gene regions declined to an r2 = 0.2 for genetic intervals as long as 150 bp, but extended up to 500 bp with r2 = 0.1. A GLM (general linear model) with modification to account for population structure was found the best fitting model for this population and followed for association mapping. Both the paralogs of the HaCOI1 candidate gene was found strongly associated with Sclerotinia resistance and explained 7.4% of phenotypic variation in this population. The set of SNP markers associated to the Sclerotinia stalk rot resistance can potentially be applied for the selection of genotypes which will significantly improve the efficiency of MAS during the development of stalk rot resistant cultivars.