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United States Department of Agriculture

Agricultural Research Service

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Research Project: Development of Management Strategies for Bacterial Leaf Spot

Location: Crop Improvement and Protection Research

2013 Annual Report


1a.Objectives (from AD-416):
Objective 1. Provide BLS phenotype evaluations Lettuce Breeding objectives. Objective 2. Screen bacterial strains available in our collection for their ability to overcome BLS resistance currently deployed. Objective 3. Monitor strains of Xcv isolated from diseased lettuce throughout California for ability to overcome resistance.


1b.Approach (from AD-416):
We will conduct laboratory and greenhouse experiments of lettuce to advance disease resistance breeding, understanding of mechanisms involved in resistance and to understand how pathogen diversity influences disease.


3.Progress Report:

This project relates to objective C: Identify emerging diseases and their etiology and evaluate resistant germplasm for diseases of strawberry, lettuce, and vegetables.

Bacterial leaf spot of lettuce caused by the pathogen Xanthomonas campestris pv. vitians (Xcv) results in significant losses throughout California the US. Genetic diversity of over 100 strains collected world-wide was described. Pathogen genotypes present in California elicited a hypersensitive response within 24 hours on host cultivars previously identified as resistant. In contrast, other genotypes of the pathogen from other geographic regions did not. Disease progress was significantly reduced in resistant cultivars compared to disease progress in susceptible cultivars inoculated with the California strains. The relationships between virulence and genotype are being further explored. In order to find sequences useful for the specific detection and quantification of the pathogen, whole genomes of ten strains of the pathogen and related organisms were sequenced.


Last Modified: 12/17/2014
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