Genetics of fusarium head blight resistance in wheat

Fusarium head blight (FHB), Fusarium graminearum, affects wheat (Triticum aestivum L. em. Thell) by reducing grain yield and end-use quality worldwide in the humid environments. This dissertation research covered four different studies. The first study was conducted to determine the combining ability and gene effects of FHB in winter and spring wheat. Six parents 'Nekota' (A), '2137' (B), 'Harding' (C), 'Ning 7840' (D), 'ND2710' (E) and 'BacUp' (F) were crossed in a partial diallel mating design (Griffing's method 4, model 1). GGEBiplot analysis showed that E/F was the best hybrid for healthy index and undamaged kernel traits, whereas Line D had the best resistance to DON accumulation. The results indicated that selecting for healthy index might indirectly lead to reduction in DON content. The results also suggested that additive gene effects were more important than non-additive gene effects for healthy index.;The second study was conducted to determine the inheritance of known FHB resistance quantitative trait loci (QTLs;Fhb1 and Qfhs.ifa-5A) in spring and winter growth habits of wheat. Four genotypes consisting of susceptible winter wheats 'Nekota' and '2137' and moderately resistant spring wheats 'ND2710' and 'BacUp' were crossed and populations derived from the crosses were segregated into spring and winter types following cold treatment of seedlings at -7 0C for 1 h. A total of six SSR markers (Fhb1 markers: Xgwm389, Xgwm493 and STS256; Qfhs.ifa-5A markers: Xgwm293, Xgwm304 and Barc186) were used to genotype the F5 populations. Chi-square analysis showed that there were significant differences in the percentage of genotypes containing homozygous marker alleles for Fhb1 and Qfhs.ifa-5A between spring and winter types in the population ND2710/2137, ND2710/Nekota and BacUp/2137. The percentage of genotypes with homozygous marker alleles for Fhb1 was lower in the spring types in the populations ND2710/2137 and ND2710/BacUp. In contrast, the spring types in the population ND210/Nekota had a higher percentage of genotypes containing homozygous marker alleles for Qfhs.ifa-5A. The results indicated that Fhb1 was less inherited in spring growth habit backgrounds whereas Qfhs.ifa-5A was less inherited in winter growth habit backgrounds.;The third study was conducted to identify QTLs linked to FHB resistance in a genotype indigenous to South Dakota---'SD97060'. A cross was made between SD97060 and 'Jagalene' and the single seed descent procedure (SSD) was used to advance the population. The F2:4 and F2:5 populations were evaluated by artificially inoculating disease in a mist-irrigated nursery in 2006 and 2007. Disease incidence, severity, Fusarium damaged kernel (FDK) and deoxynivalenol (DON) content were evaluated in the 115 recombinant inbred lines (RILs). Four QTLs for FHB responses were detected using field and greenhouse phenotypic data. Two QTLs were stable across two environments and were located at 2BL and 4BL. The 2BL QTL conferred resistance, whereas the 4BL QTL contributed to susceptibility to FHB. Two unstable QTLs were detected at the 3BS and 3BSc using field and greenhouse environments, respectively.;The fourth study was conducted to identify QTLs linked to FHB resistance in a Japanese genotype---'Tokai 66'. A cross was made between Tokai 66 and Jagalene and the SSD was used to advance the population. The F2:4 and F2:5 populations were evaluated by artificially inoculating disease in a mist-irrigated nursery in 2006 and 2007. Disease incidence, severity, FDK and DON content were evaluated in the 128 RILs. Four QTLs for FHB responses were detected using phenotypic data from the field trial, of which one QTL each for severity and FDK were stable across two years and were located at the 5B and 3BSc, respectively. Both QTLs conferred resistance to FHB. Two unstable QTLs were detected at the 5B and 3D for FDK and DON content, respectively using the field environment. The 5B QTL for FDK contributed to susceptibility, whereas the 3D QTL for DON content contributed to resistance. The 5B QTL associated with resistance to severity and 3B QTL associated with resistance to FDK could be utilized by winter wheat breeding programs selection to enhance FHB resistance. (Abstract shortened by UMI.)...