Genetic characterization of multiple disease resistance and agronomical/nutritional traits in hordeum

Abstract

Barley is an economically important crop plant whose yield and quality is affected by multiple diseases. Landrace and wild barley gene pools can be utilized to enhance disease resistance and nutrition in cultivated barley. To identify and map resistance loci for three important diseases (stem rust, spot blotch and Fusarium head blight [FHB]), and enhanced accumulation of two vital micronutrients (zinc and iron), genetic mapping was employed. The genetics of resistance to stem rust race TTKSK in Swiss landrace and wild barley accessions at the seedling stage was conducted through bi-parental mapping. Genetic analysis of F_2:3 families derived from these accessions revealed that a single gene that maps to chromosome 5HL &mdash; at or in close proximity to the complex stem rust resistance locus <italic>rpg4/Rpg5</italic> confers resistance. An association mapping approach was utilized to identify Quantitative Trait Loci (QTL) associated with disease resistance and zinc and iron concentration in 298 Ethiopian and Eritrean barley landraces genotyped with 7,842 single nucleotide polymorphism (SNP) markers. For stem rust race TTKSK, five seedling resistance loci were identified: one each on chromosome 2HS, 2HL, 3HL, 4HL, and 5HS. The ones on chromosomes 2HL and 4HL are novel, whereas the other three mapped to regions coincident with previously reported stem rust resistance QTL. For stem rust race MCCFC at the adult plant stage, one locus coincident with a known race TTKSK resistance QTL was identified on chromosome 5HL. For spot blotch, SNP markers located in close proximity with known adult plant spot blotch resistance QTL were found on chromosomes 2HL and 4HS in six-rowed barley landraces. For FHB, one common resistance QTL on chromosome 2HL, also associated with deoxynivalenol (DON) concentration, was identified. A locus mapping to a region of chromosome 4HL, known to contain QTL associated with DON, also was detected. The loci identified on chromosomes 2HL and 4HL associated with FHB and/or DON were not associated with heading date or plant height. Two novel loci associated with grain zinc concentration were identified on chromosomes 4HS and 6HL. For kernel weight, a known QTL region on chromosome 2HL was detected.