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ARS Home » Pacific West Area » Pullman, Washington » Plant Germplasm Introduction and Testing Research » Research » Research Project #434357

Research Project: Bacterial Stem Blight Of Alfalfa: Connection with Frost Damage, Development Of Resistant Germplasm, and Mapping Resistance Genes

Location: Plant Germplasm Introduction and Testing Research

Project Number: 2090-21000-036-06-I
Project Type: Interagency Reimbursable Agreement

Start Date: Oct 1, 2017
End Date: Aug 31, 2019

Objective:
Objective 1: Obtain information on the extent of bacterial stem blight (BSB) damage occurring in commercial alfalfa production fields, the association of disease with frost damage, and the relationship of disease with bacterial populations. Objective 2: Identify DNA markers and candidate genes associated with disease resistance loci. Objective 3: Develop germplasm with enhanced resistance to bacterial stem blight.

Approach:
(1) We will conduct a grower survey to gather information on the extent of frost damage and symptoms of bacterial stem blight (BSB) observed and solicit plant samples for symptom evaluation and isolation of the pathogen. (2) We will use an integrated framework that merges a QTL mapping approach called genome-wide association with high-throughput genome sequencing methodologies called genotyping by sequencing (GBS) in order to map traits quickly, efficiently, and in a relatively inexpensive manner. This framework provides a statistical basis for analyzing marker-trait association using linkage disequilibrium. (3) We will use phenotypic recurrent selection to identify plants with resistance to BSB with a target of obtaining germplasm with = 50% resistant plants. Over the course of the grant, we would be able to carry out two cycles of selection and evaluation. Based on results of recurrent selection in alfalfa for resistance to other diseases such as Fusarium wilt, bacterial wilt, anthracnose, and Phytophthora root rot (Elgin et al., 1988), we hypothesize that one cycle of selection may be sufficient to achieve this goal. Beyond the scope of the proposal, we would have the most resistant germplasms increased to produce sufficient seed for field evaluations in locations with high levels of BSB and frost damage to measure progress made to reduce damage from these stresses.