1. Traditional and in vitro propagation of a genetically diverse collection of Juglans species including creation and characterization of an enhanced mapping population from Juglans microcarpa x J. regia crosses. 2. Genotypic description of genetic loci which mediate disease resistance. 3. Genetic, physical, and functional mapping of disease resistance genes and deployment of molecular markers for rapid screening/identification of resistant genotypes. 4. Outreach and development of new, and existing, field trials examining performance of elite rootstock germplasm.