Genome-Wide Association Study of Septoria tritici Blotch Resistance in Ethiopian Durum Wheat Landraces

Abstract

Septoria tritici blotch (STB) is a devastating fungal disease affecting durum and bread wheat cultivation worldwide. The identification, development, and employment of resistant wheat genetic material is the key to overcoming costs and limitations of fungicide treatments. The search for resistance sources in untapped genetic material may speed up the deployment of STB genetic resistance in the field. Ethiopian durum wheat landraces represent a valuable source of such diversity. In this study, 318 Ethiopian durum wheat genotypes, for the most part traditional landraces, were phenotyped for resistance to different aspects of STB infection. Phenology, yield and yield component traits were concurrently measured the collection. Here we describe the distribution of STB resistance traits in modern varieties and in landraces, and the relation existing between STB resistance and other agronomic traits. STB resistance sources were found in landraces as well as in modern varieties tested, suggesting the presence of alleles of breeding relevance. The genetic material was genotyped with more than 16 thousand genome-wide polymorphic markers to describe the linkage disequilibrium and genetic structure existing within the panel of genotypes, and a genome-wide association (GWA) study was run to allow the identification of genomic loci involved in STB resistance. High diversity and low genetic structure in the panel allowed high efficiency GWA. The GWA scan detected five major putative QTL for STB resistance, only partially overlapping those already reported in the wheat literature. We report four putative loci for Septoria resistance with no match in previous literature: two highly significant ones on Chr 3A and 5A, and two suggestive ones on Chr 4B and 5B. Markers underlying these QTL explained as much as 10% of the phenotypic variance for disease resistance. We found three cases in which putative QTL for agronomic traits overlapped marker trait association deriving from STB GWA. Our results show that the Ethiopian untapped allelic diversity bears a great value in studying the molecular basis of STB resistance and in breeding for resistance in local and international material.

Molecular identification of blast resistance genes in rice genotypes using gene-specific markers

“…Although the markers used in the current study were previously reported to be tightly linked to the blast resistance genes (Srivastava et al, 2017), the association analysis demonstrated the possible effect of these markers on the agro-morphological traits. These results were in accordance with those reported by a genome-wide association study conducted in wheat (Kidane et al, 2017). In their study, the authors pointed out that the presence of putative quantitative trait loci (QTL) is associated with blotch resistance, which were also found to be overlapped with the QTL associated with different agronomic traits.…”

“…In this context, DNA markers serve as significant tools to identify the resistance genes in rice breeding programs without the need for conventional inoculation methods (Hayashi et al, 2010). Although the resistance genes mainly confer resistance to a pathogen, in some instances, they also cosegregate with other marker genes associated with quantitative traits (Kidane et al, 2017;Zhang et al, 2017). Therefore, it is of high interest to understand other putative roles, if there are any, of DNA markers associated with disease resistance.…”

A large nested association mapping population for breeding and quantitative trait locus mapping in Ethiopian durum wheat

“…Thousands of FVs evolved in Ethiopia with the simultaneous contribution of natural and artificial selection, following a complex pattern of trait selection and amplification (Kidane et al, 2017b;Mancini et al, 2017). Therefore, the Ethiopian durum wheat is a source of several adaptive traits of breeding relevance, including disease resistance alleles to rusts and Septoria (Kidane et al, 2017a;Liu et al, 2017;Zhang et al, 2017).…”

Unraveling diversity in wheat competitive ability traits can improve integrated weed management

“…GWAS has been widely adopted in different plant species to overcome some of the constraints inherent to bi-parental linkage mapping, such as the limited genetic diversity explored (Barabaschi et al 2016). GWAS has been successfully used in both durum and common wheat, mainly focused to resistance to pathogens (e.g., Kidane et al 2017), grain yield, heading date, plant height, number of fertile tillers, biomass, and number of seeds per spike (Zanke et al 2014a(Zanke et al , b, 2015Mengistu et al 2016).…”