Browsing by Subject "Spot blotch"
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Item Genetic characterization of multiple disease resistance and agronomical/nutritional traits in hordeum(2013-08) Mamo, Bullo ErenaBarley 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 F2:3 families derived from these accessions revealed that a single gene that maps to chromosome 5HL — at or in close proximity to the complex stem rust resistance locus rpg4/Rpg5 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.Item Genetics of Resistance to Fusarium Head Blight and Spot Blotch in Hordeum(2016-05) Haas, MatthewFusarium head blight (FHB) and spot blotch are two important diseases of barley (Hordeum vulgare) in the Upper Midwest. FHB is caused by Fusarium graminearum which produces deoxynivalenol (DON), a toxin harmful to humans and animals. To characterize the genetic architecture of resistance to FHB and DON accumulation, two wild barley (PI 466423 and W-365) accessions with partial resistance were used as donor parents in advanced backcross populations with six-rowed Minnesota malting barley cultivars. The largest effect quantitative trait locus (QTL) identified in the populations was mapped at or near the photoperiod response gene Ppd-H1, which affects heading date and plant height. This result suggests that the QTL for reduced FHB and DON are a pleiotropic effect of that locus. For over 50 years, spot blotch, caused by Cochliobolus sativus, has been controlled in the Upper Midwest through the deployment of durable resistance derived from the breeding line NDB112. Recently, C. sativus isolates (e.g. ND4008) with virulence for the NDB112 resistance have been reported in the region. PI 466423 is resistant to isolate ND4008; therefore, the Rasmusson/PI 466423 population was used to map QTL for resistance to virulent isolate. Four resistance QTL were identified in chromosomes 1H, 2H, 4H, and 5H. The QTL on chromosomes 1H, 4H, and 5H were contributed by PI 466423, while the one on chromosome 2H was contributed by Rasmusson. A gamma radiation-induced susceptibility mutant from cultivar Morex was used in an RNAseq experiment to study the early infection response of barley to C. sativus. Differential expression analysis between the two genotypes revealed a role for lipid signaling in the resistance response, which may activate the jasmonic acid pathway.