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Comparative Analysis of Cylindrocladium Black Rot Resistance in Peanut: Greenhouse, Microplot, and Field Testing Procedures. J. K. Pataky, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650, Present address of the senior author: Department of Plant Pathology, University of Illinois, Urbana 61801; M. C. Black(2), M. K. Beute(3), and J. C. Wynne(4). (2)(3)Research assistant, and professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650; (4)Associate professor, Department of Crop Science, North Carolina State University, Raleigh 27650. Phytopathology 73:1615-1620. Accepted for publication 15 June 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1615.

Two promising advanced generation Virginia-type peanut breeding lines, NC 18016 and NC 18229, and two commercial Virginia-type cultivars, NC 8C and Florigiant, were evaluated for Cylindrocladium black rot (CBR) resistance in greenhouse, microplot, and field trials. The overall evaluation of results indicated that NC 18016 was slightly more resistant than NC 18229; NC 8C was intermediate in resistance between the highly susceptible cultivar, Florigiant, and the resistant breeding lines, NC 18229 and NC 18016. Interpretations of results were slightly different when greenhouse, microplot, and field testing procedures were compared. In greenhouse and microplot evaluations, substantial differences in CBR resistance among cultivars Florigiant and NC8C, and the two breeding lines were apparent, but the more subtle difference between NC 18016 and NC 18229 was not detected. In field evaluations, NC 18016 was observed to be more resistant than NC 18229 when the data were categorized by inoculum density. Results from field trials suggested that much of the variation in field evaluations of CBR resistance is due to the clustered spatial distribution of microsclerotia of Cylindrocladium crotalariae in naturally infested soils. Evaluations of microsclerotial production in roots of infected plants were highly variable. In general, numbers of microsclerotia per gram of root increased with root rot rating; however, it appears that reduced microsclerotia production would be an extremely difficult trait for which to select in a breeding program.

Additional keywords: Arachis hypogaea, Calonectria crotalariae, groundnut.