Submitted to: Maydica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2004
Publication Date: 2/2/2006
Citation: Carson, M.L., Goodman, M.M. 2006. Pathogenicity, aggressiveness, and virulence of three species of Cercospora associated with gray leaf spot of maize. Maydica. 51:89-92. Interpretive Summary: Gray leaf spot is considered to be one of the most important diseases of corn in the U.S. At least three species of the fungus Cercospora have been associated with the disease in the U.S. In this study, we tested the ability of these different species to cause gray leaf spot. We also tested whether hybrids resistant to one species of Cercospora were also resistant to the others. Our studies demonstrated that one species previously associated with gray leaf spot, Cercospora sorghi var. maydis, does not cause the disease. Furthermore, we found that hybrids with resistance to gray leaf spot are resistant to both sibling species of Cercospora zeae-maydis. We also demonstrated that more aggressive strains of the two sibling species of Cercospora zeae-maydis should be used when testing corn germplasm for resistance to gray leaf spot. This information will be useful to corn breeders and pathologists in developing hybrids with improved resistance to gray leaf spot.
Technical Abstract: In the eastern United States, three genetically distinct species of Cercospora, the two sibling species of C. zeae-maydis (types I and II) and C. sorghi var. maydis, are routinely isolated from maize leaves exhibiting symptoms of gray leaf spot (GLS). To determine if resistance to GLS is species specific, we conducted field trials comparing four commercially available maize hybrids for resistance to four isolates of C. zeae-maydis type I, three isolates of C. zeae-maydis type II, two isolates of C. sorghi var. maydis, as well as isolates of C. sorghi from Sorghum spp., and C. kikuchii from soybean. Isolates within each of the two sibling species of C. zeaemaydis were highly variable in their aggressiveness on the hybrids. Resistance in maize to GLS appears to be equally effective against both type I and type II of C. zeae-maydis. Neither of the two isolates of C. sorghi var. maydis isolated from maize, the C. sorghi isolates, nor C. kikuchii were pathogenic on maize. These results indicate that aggressive isolates, regardless of which sibling species of C. zeae-maydis, should be used to select for GLS resistance in field trials.