Pathogenicity, Synergism, and Control of Xanthomonas Translucens and Septoria Avenae f. sp. Triticea on Spring Wheat in South Dakota

Abstract

During the 1969 growing season an unusual leaf disease developed extensively on spring and winter wheats (Triticum aestivum L.) in experimental plots at Brookings. This disease was characterized by symptoms somewhat similar to those of three common but relatively minor wheat diseases; Septoria leaf blotch, bacterial blight and Helminthosporium leaf spot. Though similar to each, symptoms were not truly typical of any one disease. Symptoms similar to those observed at Brookings had been observed elsewhere in South Dakota prior to 1969. A fungus tentatively identified as Septoria avenae Frank f. sp. triticea Johnson and a bacterium designated as Xanthomonas translucens Dowson were observed. in, or isolated from, many such lesions. The abundant atypical symptoms and the presence of both pathogens suggested. The possibility of a synergistic relationship between the two organisms. Since relatively little was known about the nature of the Septoria species or about its relationship to X. translucens, this study was conducted to answer several questions relating to the problem: 1. What is the prop.er identity of the Septoria species? 2. Is there a synergistic relationship between this Septoria and X. translucens? 3. Do spring wheat cultivars currently grown in South Dakota have resistance to this disease complex? 4. What available pesticides, if any, will control this disease-complex