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United States Department of Agriculture

Agricultural Research Service

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Research Project: Identify Apple Genes Associated with Apple Replant Resistance

Location: Physiology and Pathology of Tree Fruits Research

Project Number: 2094-21220-001-09-T
Project Type: Trust Fund Cooperative Agreement

Start Date: May 1, 2014
End Date: Apr 30, 2016

Identify apple candidate genes that are robustly associated with resistant phenotype among rootstock genotypes. This will permit development of DNA markers to improve the breeding efficiency as well as provide new information on the nature of resistance to Apple Replant Disease (ARD). Targeted utilization of innate apple rootstock resistance could provide a cost-effective, durable and environment-friendly disease control strategy.

1. The selection of apple genes, for validating their potential association with resistance to ARD, will be based on two large-scale molecular and genetic studies in the labs of the PI and collaborator. About 35-40 groups (families) of candidate gene which are involved in the synthesis of anti-microbial compounds and other defense responses will be investigated in the first year using core resistant and susceptible rootstock genotypes. Based on the first year’s results, 8-12 candidate genes which demonstrate consistent association with resistance phenotypes will be further tested across an expanded rootstock breeding population. 2. The behavior of these candidate genes under pathogen pressure will be studied by quantitative reverse transcription PCR procedure, which offers reliable and accurate data for candidate gene based studies. 3. The core apple rootstock genotypes consist of tolerant (G41, CG4214 and G935) and susceptible (Bud9 and M26) rootstocks. Both tissue culture generated seedlings and commercially available one-year old rootstock liners will used for study. The expanded rootstock germplasm includes over 90 genotypes from a rootstock breeding population from the Fazio program. 4. The primary ARD pathogens Phytophthora, Pythium, Rhizoctonia and Cylindrocarpon, which are commonly isolated from Washington State orchards, will be used to inoculate apple rootstock using established procedures.

Last Modified: 07/26/2017
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