Location: Vegetable ResearchTitle: Identification of resistance to bacterial leaf blight in the U.S. Department of Agriculture collard collection
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2018
Publication Date: 6/1/2018
Citation: Branham, S., Farnham, M.W., Robinson, S.M., Wechter, W.P. 2018. Identification of resistance to bacterial leaf blight in the U.S. Department of Agriculture collard collection. HortScience. 53:838-841. https://doi:10.21273/HORTSCI12347-17.
Interpretive Summary: Collard (Brassica oleracea L.) is a leafy green vegetable crop primarily produced in the southeastern United States with a yearly fresh market value of over $125 million. Bacterial leaf blight is currently causing the highest yield losses of leafy green Brassicas in the Southeast. Commercial collard cultivars have all been found to be susceptible to the pathogen and available pesticides for control of this disease appear unable to reduce the disease to acceptable levels. ARS scientists in Charleston, SC, screened 110 U.S. Plant Introductions of leafy green B. oleracea for resistance to this disease in greenhouse assays. Only two accessions, (‘PI662820’ and ‘G33036’), were found to have acceptable levels of resistance to bacterial leaf blight, and these will prove useful as parental lines in the USDA and other breeding programs. Leafy greens growers are especially interested in this work that can ultimately lead to resistant cultivars for their productions and reduce yield losses due to disease.
Technical Abstract: Bacterial leaf blight caused by Pseudomonas cannabina pv. alisalensis (Pca) is a devastating disease with incidence reports worldwide and a wide host range capable of infecting all commercially valuable Brassica crops. With no chemical control options available, the most effective form of disease control is host plant resistance but thus far resistant germplasm has only been identified in Brassica juncea L. (Mustard greens). We report the first screening of Brassica oleracea L. var. viridis germplasm, including leafy green collard and collard-like accessions, for resistance to bacterial leaf blight by artificial inoculation of Pca in greenhouse trials. All commercial cultivars tested displayed an intermediate disease response resulting in leaf lesion development that renders the product unmarketable. Two sources of significant resistance were identified in the USDA viridis collection which provides a valuable source of resistance alleles for collard cultivar development and introgression into other B. oleracea crops.