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Single and Combined Effects of the Lesion Nematode and Colletotrichum graminicola on Growth and Anthracnose Leaf Blight of Corn. R. L. Nicholson, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907; G. B. Bergeson(2), F. P. DeGennaro(3), and D. M. Viveiros(4). (2)(3)(4)Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 75:654-661. Accepted for publication 3 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-654.

Corn plants were grown to maturity in the greenhouse in the presence or absence of the lesion nematode (Pratylenchus hexincisus) (initial soil populations of 89.6 and 0.6 nematodes per 50 cc, respectively), and leaves were inoculated with the fungus at 14, 35, or 55 days after planting. The effects of the nematode, the fungus and the nematode ? fungus interaction were assessed by measuring disease development, leaf senescence, and various aspects of plant growth. Anthracnose leaf blight severity increased significantly in plants that were also infected with the nematode. Plants grown either in the presence of the nematode or inoculated with the fungus at all times also senesced faster than the controls, and the nematode and fungus together caused an even greater rate of individual leaf senescence. Dry root weight, but not shoot weight, was significantly reduced by nematodes. Plants inoculated with the fungus at the seedling stage had significantly lower root and shoot dry weights. The fungus, but not the nematode, significantly reduced extended leaf height and stem circumference. The results demonstrate that nematode infection in corn can cause earlier appearance and increase the severity of anthracnose symptoms.

Additional keywords: pathogen interactions, susceptibility, Zea mays.