Effects of Meloidogyne hapla and M. arenaria on Black Rot Severity in New Cylindrocladium-Resistant Peanut Genotypes. A. K. Culbreath, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793-0748. M. K. Beute, B. B. Shew, and K. R. Barker. Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 76:352-357. Accepted for publication 15 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0352.

Greenhouse and microplot experiments were done to determine the effects of Meloidogyne hapla and M. arenaria on the severity of Cylindrocladium black rot (CBR), caused by Cylindrocladium crotalariae, in the peanut (Arachis hypogaea) genotypes Florigiant, NC 10C, NC Ac 18416, and NC Ac 18016. In the greenhouse, severity of black rot was increased in Florigiant by either M. hapla or M. arenaria in treatments with fungal inoculum densities of 0.05 and 0.5 microsclerotia per gram of soil. Severity of black rot was not affected by these nematodes on NC 10C or NC Ac 18016. In microplots, disease ratings of roots from NC 10C, NC Ac 18416, and NC Ac 18016 were higher in plots infested with either nematode species and C. crotalariae than in plots with C. crotalariae alone. In field studies, initial and late-season populations of root-knot juveniles were correlated with incidence of CBR and area under disease progress curves for some genotypes, but results were not consistent from 1986 to 1987.