Association Analysis of Response to Bacterial Leaf Spot with Single Nucleotide Polymorphism Markers in Lettuce

Bacterial leaf spot (BLS) of lettuce, caused by Xanthomonas campestris pv. vitians, is an economically important disease of lettuce worldwide. Since there are no chemicals available for effective control of the disease, host-plant resistance is highly desirable to protect lettuce production. In the present study, 179 lettuce germplasm lines were evaluated for their response to BLS in the greenhouse. Disease severities ranged from 0 to 4 on the 0 to 4 scale, with 1 line being less than 0.9, 5 lines being 1.0 - 1.9, 62 lines being 2.0 - 2.9, 109 lines being 3.0 - 3.9, and 2 lines being 4. One germplasm line was ranked as BLS resistant and five as moderately resistant. The germplasm lines have been fingerprinted with 384 single nucleotide polymorphism (SNP) markers with the high-throughput GoldenGate assay. An association study is being conducted to determine the relationship between response of lettuce to BLS and SNP markers. Discovering BLS resistance in lettuce and identifying molecular markers associated with resistance will accelerate incorporation of BLS resistance into lettuce cultivars, which will benefit the lettuce industry in USA.