Location: Crops Pathology and Genetics Research
2013 Annual Report
This is the first year of our USDA, National Institute of Food and Agriculture (NIFA) Specialty Crops Research INitiative (SCRI) supported project during which we established five Assistance Type Cooperative Agreements (ATCA’s) with university collaborators across the country. In addition we conducted four Principal Investigator (PI) research progress meetings and one industry oversight committee meeting in conjunction with the Walnut Research Conference in Bodega Bay, California. Initial steps in this project have focused on the generation of a genetically diverse walnut germplasm collection which is being propagated using a variety of traditional and in vitro techniques. Using embryo rescue techniques, we have been able to place recalcitrant walnut species into in vitro culture from which we have generated clonal copies. Clonal material from all our propagation efforts have resulted in the generation of thousands of trees which are currently being examined for resistance to crown gall, Phytophthora spp., lesion nematodes and Armillaria. All initial disease resistance screening is being conducted under greenhouse conditions with the exception of our screen for lesion nematode resistance which is occurring in the field. In addition to walnut (Juglans) evaluations, we generated and screened Chinese wingnut species (a distant walnut relative) obtained from open pollinated seeds for resistance to crown gall. The attractiveness of numerous Juglans species to the 10,000 cankers walnut twig beetle is being assessed under field conditions. In addition, we have screened target Juglans species for their susceptibility to the walnut twig beetle under both laboratory and field conditions. A statewide survey of the sensitivity of walnut rootstock Paradox clones to 10,000 (10K) cankers disease is under way. Genetic characterization of the 10K cankers disease causing agent, Geosmithia morbida, is being conducted along with an analysis of its interaction with the walnut twig beetle during transmission. We have isolated and identified a number of potential phytopathogenic agents which are associated with the newly emergent disease of Paradox walnut rootstocks known as lethal canker disease. Experiments to confirm Koch’s Postulates of these isolates are in progress at a field location in the state.