Inheritance of resistance to Fusarium head blight in barley

Fusarium Head Blight (FHB) is currently the most important disease of barley in the Midwestern USA. In Chapter I of this thesis the objectives were to investigate the inheritance of resistance to FHB, Deoxynivalenol (DON) production and kernel discoloration (KD) and their association with each other. Four populations resulting from crosses between putative resistant and susceptible parents were evaluated in inoculated and misted nurseries at three locations in Minnesota and China from 1995 to 1997. Estimates of heritability for FHB and KD, obtained with the variance component method, using multiple environment data tended to be intermediate, ranging from 0.48 to 0.76 for FHB and from 0.31 to 0.63 for KD. Heritability estimates from individual environments for FHB and KD ranged from low to high, and for DON from low to intermediate; these estimates were likely inflated by genotype x environment interaction. Resistance near the level of the resistant parent was recovered in most of the populations for FHB, KD and DON. Transgressive segregates toward susceptibility were relatively common and were found in Populations 2 and 3 for FHB and Population 4 for FHB and KD. Positive correlation were found between FHB and KD and between these diseases and DON concentration in the grain. The variable response of the parents and the ever present genotype x environment interactions provided evidence that FHB and DON resistance breeding represent an unusually large challenge.;In Chapter 11 the goals were to investigate Type 11 resistance in barley using the point inoculation technique and to describe the pattern of spread of Fusarium in the barley spike. Three experiments were conducted in the greenhouse with a selected set of eleven six- and five two-row genotypes. Significant genetic differences were found for Type 11 resistance. The limited spread in the head from a single point of infection of about 10% and genotype x environment interaction suggests that screening for Type 11 resistance should be of secondary importance when breeding for resistance to FHB in barley, even though it could be important in determining severity of FHB in the field.