QTL Analysis of Sclerotinia sclerotiorum Head Rot Resistance in Sunflower

Dissecting the genetic basis of agronomic traits is of primary importance in plant breeding. In this study, we combined an association mapping (AM) approach with biparental QTL mapping to study the genetic basis underlying natural resistance to Slerotinia sclerotiorumhead rot (SHR) in sunflower, an important fungal disease affecting commercial sunflower production.

A total of 137 inbred lines belonging to the breeding program of the National Institute of Agricultural Technology of Argentina (INTA), and a public recombinant inbred line (RIL) population comprising 94 lines from a cross of PAC2 (moderately resistant) and RHA266 (susceptible) were genotyped with an Illumina 384-plex oligo pool assay representing putative candidate genes (CG) for stress resistance responses. In the association mapping approach, population structure was estimated using 42 SSR markers. Both populations were evaluated for disease incidence, severity and incubation period (PI) after assisted inoculation with the pathogen across four campaigns in replicated field trials. A total of four CGs were found to be associated with a reduction in SHR incidence, and one CG with diminished disease severity (p<0.01). Three of these CGs were mapped on linkage groups (LGs) 10, 14, and 15, in the proximities of described QTL that account for a reduction in SHR incidence.

This work allowed the identification of new genomic regions involved in SHR resistance, contributing to the generation of useful tools for sunflower molecular breeding.