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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF ALMOND, STONE FRUIT, AND WALNUT ROOTSTOCKS WITH IMPROVED RESISTANCE TO SOILBORNE PATHOGENS
2010 Annual Report


1a.Objectives (from AD-416)
1) Identify and deploy rootstocks with improved resistance/tolerance to the major soil-borne pathogens of almonds, other Prunus spp and walnut rootstocks including: Agrobacterium tumefaciens (crown gall), Phytophthora, Armillaria spp, phytoparasitic nematodes, and orchard replant disorder. 2) ID and map genes/QTLs governing resistance to facilitate marker-based disease screening and selection strategies to rapidly integrate resistance genes into new rootstocks. 3) Develop association mapping populations for mapping and validating genes governing resistance. 4) Propagate and field test resistant rootstock genotypes identified in objective #1.


1b.Approach (from AD-416)
We will use conventional breeding, disease-screening, novel propagation techniques in combination with educational outreach to develop, characterize, and deploy walnut and almond/Prunus rootstocks with to soilborne pathogens. The following material will be examined, NCGRU germplasm, existing rootstocks used as standards, and novel genotypes created from controlled crosses. Promising genotypes will be propagated as seed or as clonal plants and used in replicated evaluations of pathogen resistance. Genetic markers associated with resistance will be exploited in rootstock breeding efforts. Rootstocks with superior resistance/tolerance will be grafted/budded with scion cv's and evaluated in commercial nursery/orchard trials. Documents Trust with CDFA. Log 39947.


3.Progress Report

The agreement was established in support of Objective 1 of the in-house project, the goal being to improve management strategies for key soil borne diseases of tree fruit and nut crops; subobjective 1B-Identify and characterize available walnut and almond rootstock germplasm for resistance to key soil borne pathogens. The goal of this project is to use conventional breeding, disease-screening, novel propagation techniques in combination with educatonal outreach to develop, characterize, and deploy walnut and almond/Prunus rootstocks with resistance to soilborne pathogens. To date we have made 56 interspecific Prunus crosses using the following mother trees; Prunus persica, Prunus dulcis, and the Prunus hybrids ‘Nemaguard’ and ‘Nemared’. We have used 13 different Punus species as pollen donors in these crosses. We have completed the following Juglans crosses: female parents: Juglans microcarpa, Juglans cathyensis, Juglans major. Pollen donor: Juglans regia ‘Serr’. Up to 80 flower clusters were bagged on each mother tree. A large collection of Juglans microcarpa seedlings have been moved from the propagation house to the greenhouses where disease resistance screening will begin. These trees will be inoculated with Agrobacterium tumefaciens and evaluated for crown gall development with 90 days. Even though we were unable to access the grant funds, due to an accounting glitch, we are well on the road to accomplishing the first goal of our project, i.e. development/generation of genetic diversity in our available germplasm.


Last Modified: 11/27/2014
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