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Field Evaluations of Leaf Spot Resistance and Yield in Peanut Genotypes in the United States and Bolivia

March 2011 , Volume 95 , Number  3
Pages  263 - 268

S. K. Gremillion, Department of Biology, Armstrong Atlantic State University, Savannah, GA 31419; A. K. Culbreath, Department of Plant Pathology, University of Georgia Coastal Plain Experiment Station, Tifton 31793; D. W. Gorbet, Agronomy Department, University of Florida North Florida Research and Education Center, Marianna 32446; B. G. Mullinix, Jr., Research Statistician, Texas A&M University, Lubbock 79424; R. N. Pittman, United States Department of Agriculture–Agricultural Research Service, University of Georgia Agricultural Experiment Station, Griffin 30223; K. L. Stevenson, Department of Plant Pathology, University of Georgia Coastal Plain Experiment Station, Tifton 31793; J. W. Todd, Entomology Department, University of Georgia Coastal Plain Experiment Station, Tifton; and R. E. Escobar and M. M. Condori, Asociacion de Productores de Oleaginosas y Trigo, Cas. 2305, Complejo Semillero, Km. 8½ Santa Cruz, Bolivia

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Accepted for publication 1 October 2010.

Field experiments were conducted in 2002 to 2006 to characterize yield potential and disease resistance in the Bolivian landrace peanut (Arachis hypogaea) cv. Bayo Grande, and breeding lines developed from crosses of Bayo Grande and U.S. cv. Florida MDR-98. Diseases of interest included early leaf spot, caused by the fungus Cercospora arachidicola, and late leaf spot, caused by the fungus Cercosporidium personatum. Bayo Grande, MDR-98, and three breeding lines, along with U.S. cvs. C-99R and Georgia Green, were included in split-plot field experiments in six locations across the United States and Bolivia. Whole-plot treatments consisted of two tebuconazole applications and a nontreated control. Genotypes were the subplot treatments. Area under the disease progress curve (AUDPC) for percent defoliation due to leaf spot was lower for Bayo Grande and all breeding lines than for Georgia Green at all U.S. locations across years. AUDPC for disease incidence from one U.S. location indicated similar results. Severity of leaf spot epidemics and relative effects of the genotypes were less consistent in the Bolivian experiments. In Bolivia, there were no indications of greater levels of disease resistance in any of the breeding lines than in Bayo Grande. In the United States, yields of Bayo Grande and the breeding lines were greater than those of the other genotypes in 1 of 2 years. In Bolivia, low disease intensity resulted in the highest yields in Georgia Green, while high disease intensity resulted in comparable yields among the breeding lines, MDR-98, and C-99R. Leaf spot suppression by tebuconazole was greater in Bolivia than in the United States. This result indicates a possible higher level of fungicide resistance in the U.S. population of leaf spot pathogens. Overall, data from this study suggest that Bayo Grande and the breeding lines may be desirable germplasm for U.S. and Bolivian breeding programs or production.

© 2011 The American Phytopathological Society