The use of molecular and biochemical tools to assist in the breeding of hazelnuts (Corylus spp.)

Hazelnuts rank 6th in world tree nut production, with approximately 800,000 metric tons produced per year. Commercial hazelnut production in the United States (the third largest producer of hazelnuts in the world) has been limited, due to the fungal pathogen Anisogramma anomala, the causal agent of eastern filbert blight (EFB). Interestingly, A. anomala is most deadly to the European hazelnut species (Corylus avellana), the only species used for commercial production, but is harbored by and does not cause symptoms in the native American species (C. americana). This fungal pathogen invades the vascular system of hazelnuts, girdles branches, and ultimately leads to death of the tree. Control measures to combat EFB are expensive and labor intensive, thus the most cost effective means of combating this disease is the use of disease resistant plant material. The Corylus genus holds 10 additional species, many of which carry EFB resistance. Over the past 15 years, extensive germplasm collection trips have been made to develop a broad hazelnut germplasm collection at Rutgers University, the entirely of which has been screened for resistance to EFB. The purpose of this study was to genetically characterize the novel collection of largely EFB resistant germplasm at Rutgers University using simple sequence repeat (SSR) markers. In addition, these same tools were used to further enhance the utility and better direct the use of this germplasm in the breeding program by performing a population structure analysis of A. anomala isolates collected from the United States and Canada. The final aspect of this dissertation investigates additional Corylus species by conducting a lipid content and profile analysis of four hazelnut species and interspecific hybrids to determine if there is a species effect on important kernel characteristics. Both the hazelnut germplasm collection and A. anomala isolate collection were found to be highly genetically diverse, and the analysis resolved 11 and 22 genetic populations, respectively. It was also found that the lipid content and profiles of hazelnuts will likely not be negatively affected by the introgression of different species into the breeding program. This work has demonstrated that there are a number of diverse sources of resistance in the Rutgers University hazelnut germplasm collection to the exceedingly genetically diverse fungus A. anomala, and introgression of sources of resistance in non C. avellana species will likely not effect commercially important kernel characteristics.

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