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United States Department of Agriculture

Agricultural Research Service

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Research Project: Development of Disease Resistant Walnut Rootstocks: Integration of Conventional and Genomic Approaches (Thousand Cankers Disease)

Location: Crops Pathology and Genetics Research

2013 Annual Report

1a. Objectives (from AD-416):
Evaluate J. nigra germplasm collection in Missouri for susceptibility to Thousand Cankers Disease.

1b. Approach (from AD-416):
1)screen multiple clonal replicates of each accession (propagated at the University of Missouri) for Thousand Cankers Disease Susceptibility. 2)Establish new J. nigra clonal plantings on sites proximal to know Thousand Cankers Disease outbreaks in Tennessee. 3)Establish new large-scale plantings of J. nigra seedling material representing 33 provenances from 10 different states to quantify the extent of geographic variation associated with Thousand Cankers Disease susceptibility. 4)provide a critical test of whether the innate selectivity of the vector-pathogen complex for certain mature trees noted in the USDA, ARS, National Clonal Germplasm Repository applies to juvenile trees.

3. Progress Report:
This project was established in support of objective #1 of the in-house project, which is to characterize the etiology, biology, and ecology of key phytopathogenic agents and their interactions with economically important tree and grapevine species. The goal of this project is to evaluate the J. nigra germplasm collection in Missouri for susceptibility to Thousand Cankers Disease (TCD). Provenance Tests: Three provenance tests of black walnut were established in Tennessee, Virginia, and Pennsylvania. The Tennessee test has been managed by herbicide and mowing, while the other plantings have not been managed with the exception of herbicide spraying around the trees. The seedlings were measured for height and root collar diameter, prior to planting in an incomplete block, within complete block design using single tree plots. All plantings will be measured in the 2013-2014 dormant season. Grafted Clones: A grafted clone plantation was established in Richmond, Virginia, within the TCD quarantine zone and monitored by a scientist from Virginia Tech. Additional grafts were transferred in 2013 from the University of Missouri to the University of Tennessee. These grafts will be used for field and greenhouse resistance testing. A significant number of grafts also will be transferred in September, 2013. All grafts are produced by a collaborating scientist at the University of Missouri. Field Seedling Planting: A number of black walnut seedlings were field planted to provide rootstock for field grafting in 2014. Approximately 300 seedlings were planted. Raised Nursery Bed Planting: Approximately 800 black walnut Root Production Method (RPMTM) seedlings, grown by Forrest Keeling Nursery, were transported to the University of Tennessee and planted in four 60’L X 4’W raised nursery beds for grafting. After grafting and subsequent growth, the grafts will be challenged with the TCD pathogen to test for resistance. Seedlings planted at the East Tennessee State Nursery: Open-pollinated families from black walnut and butternut trees from various sources were planted. The seeds were collected in different parts of Tennessee from naturally occurring and seed orchard trees. The resulting 1-0 seedlings will be planted on the University of Tennessee, East Tennessee Research and Education Center, Plant Science Unit in early 2014, for eventually resistance testing. Low seedling numbers in many of the families were the result of crow predation at the State Nursery. Although measures were taken to prevent predation, they proved only partially successful. Predation was heavy in some areas and light in other areas. Knoxville, Tennessee Area Black Walnuts – These families came from naturally occurring trees in urban settings. Families D52 and D53 are the trees that originally alerted foresters to the presence of TCD in the Knoxville area. Lakeshore Park Black Walnuts, Knoxville, Tennessee – This location was the second area in Knoxville where TCD was observed. Tree LS1 is half-dead, but produced a large crop. Many trees at this location have died, yet there are surviving trees that appear to be quite healthy. West Tennessee Black Walnuts, Ames Plantation vicinity – This collection was made in southeastern Tennessee, about 60 miles east of Memphis. Tennessee Division of Forestry Seed Orchard, East Tennessee State Nursery – These families were collected from a black walnut seed orchard located at the State Nursery. Butternuts, south-central Tennessee – These families were collected in the Lynchburg, Tennessee area, at the southern limit of the species’ range. These seedlings will be challenged with the TCD pathogen, as well as the pathogen responsible for butternut canker disease.

4. Accomplishments

Last Modified: 06/26/2017
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