Phenotyping Sunflower Genetic Resources for Sclerotinia Head Rot Response: Assessing Variability for Disease Resistance Breeding

Abstract

Sclerotinia head rot (SHR) is one of the most serious constraints to sunflower (Helianthus annuus L. var. macrocarpus) production worldwide. Here, we evaluated the response to SHR in a sunflower inbred panel from a large INTA germplasm collection, consisting of 137 inbred lines (ILs). Field trials were performed over five consecutive seasons using a twice-replicated randomized complete-block design. Disease incidence, disease severity, incubation period, and area under disease progress curve for disease incidence and severity were determined after controlled inoculation with the pathogen. Statistical analysis using mixed-effect models detected significant differences among ILs for all variables (P < 0.001). In addition, principal component analysis (PCA) and distance-based methods were used to classify the ILs according to their response to SHR, with ILs ALB2/5261 and 5383 emerging as the most resistant. Broad-sense heritability estimates ranged from 20.64% for disease severity to 10.58% for incubation period. The ample phenotypic variability of our collection, along with the moderate heritability estimates, highlight the importance of molecular breeding approaches to gain new insights into the genetic basis of sunflower resistance to SHR. The exhaustive phenotypic characterization presented here provides a reliable set of variables to comprehensively evaluate the disease and identifies two new sources of resistance to SHR.

Main and epistatic QTL analyses for Sclerotinia Head Rot resistance in sunflower

“…Filippi et al . [ 30 ], who studied SHR resistance with association mapping in the same location, also observed that the DI and DS values were below the overall mean in an assay conducted in 2011/2012. In agreement with our findings, Abawi and Grogan [ 66 ] found a negative correlation between temperature and SHR disease levels.…”

“…These values are comparable to those obtained by Filippi et al . [ 30 ] using the same approach. The moderate h 2 values suggest that marker assisted selection, using either the AM or the BMP approach, may be the method of choice when breeding for resistance to SHR, instead of conventional phenotypic selection.…”

“…A generalized mixed linear model (GMLM) or a linear mixed-effects model (LMEM) was fitted for each disease variable depending on the variable distribution and according to Filippi et al . [ 30 ].…”

Genetic Diversity, Population Structure and Linkage Disequilibrium Assessment among International Sunflower Breeding Collections

“…These distinct groups of accessions are of particular interest when planning the incorporation of new genetic backgrounds to each breeding collection. Among them, STRUCTURE group 4 contains a mixture of Argentinean HA and RHA inbred lines, bred for traits of agronomic importance such as drought stress tolerance and rust and sclerotinia head rot resistance [4,5,45].…”

Analysis of genetic determination of partial resistance to white rot in sunflower

“…Previous studies have shown a relationship between the values of genotypic variance and those of the phenotypic variance for RIP. In Argentina, Godoy (2001) detected that the genotypic contribution to phenotypic variance in the 49 hybrids evaluated in two localities of southeastern Buenos Aires was of 67%, whereas Filippi et al (2017) showed a contribution of 0-48% (annual) and of 11% (pooled across five years) when 69-137 B and R-lines were tested in Balcarce. Regarding DLG, the only study so far performed showed a relationship between the genotypic and phenotypic variances of 54% when 31 hybrids were evaluated in Balcarce (Castaño and Giussani 2006).…”