Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 30, 2011
Publication Date: April 15, 2012
Citation: Li, Y., Culbreath, A.K., Chen, C.Y., Knapp, S.J., Holbrook Jr, C.C., Guo, B. 2012. Variability in field response of peanut genotypes from the U.S. and China to tomato spotted wilt virus and leaf spots. Peanut Science. 39:30-37. Interpretive Summary: Tomato spotted wilt is a serious problem in the southeastern U.S. Two of other most prevalent and severe foliar diseases of peanut worldwide are early leaf spot and late leaf spot. In the U. S., most of the peanuts are grown in the southern states where environmental conditions are often favorable for leaf spot epidemic development. One or both of the leaf spot diseases occurs in all peanut producing states, and multiple applications of fungicides are necessary for control of the diseases. The development and use of resistant cultivars is one of the most desirable ways to manage both leaf spot diseases and TSWV. Field selection for resistance to leaf spot pathogens and TSWV requires considerable space, and a relatively large number of plants. Development of molecular markers for assisting in selection for resistance to TSWV and the leaf spot pathogens could increase the efficiency of breeding programs. The results in this study indicated a wide range of field reactions to peanut foliar diseases among the tested lines. We found 3 cultivars and 3 breeding lines classified as resistant to both TSWV and leaf spots, and 3 genotypes from China susceptible to both TSWV and leaf spots. Based on the results of these field trials, the parents, NC 94022 and SunOleic 97R differ markedly in their field resistance to TSWV, while the other pair of parents Tifrunner and GTC-20 differs greatly in field resistance to both TSWV and leaf spots. Information from the combination of the field and genetic characterization of these genotypes could be useful in development of mapping populations and construction of genetic linkage map for identification of markers associated with disease resistance.
Technical Abstract: Tomato spotted wilt, caused by tomato spotted wilt virus (TSWV) and transmitted by thrips, and early leaf spot (Cercospora arachidicola) and late leaf spot (Cercosporidium personatum) are among the most important diseases of peanut (Arachis hypogaea) in the southeastern United States. The objective of this study was to compare field susceptibility of diverse peanut lines to TSWV and leaf spot pathogens for decision making of selecting lines for mapping population development. In field trials in 2007 and 2008, 22 genotypes, were evaluated for reactions to TSWV and leaf spots. Early leaf spot was predominated in both years. There was a near-continuous range of final incidence of spotted wilt from 18% to 79% for the total incidence of spotted wilt with 1 or greater for severity rating. In general, NC94022, ‘Georganic’, C689-6-2, ‘Georgia-01R’, C724-19-25, TifGP-1, C11-154-61, C12-3-114-58, and ‘Tifguard’ were among the most resistant genotypes to TSWV, whereas GTC-20, GTC-9 and PE-2 were the most susceptible ones. Final percentage of defoliation by leaf spots ranged from 10% to 97% for both years. In average, genotypes C689-2, Georgia-01R, C12-3-114-58, C11-154-61, Tifguard and Georganic showed resistance to leaf spots, whereas ‘NC-6’, ‘Spancross’, GTC-9, GTC-20 and PE-2 are susceptible to leaf spots. There were 3 cultivars and 3 breeding lines classified as resistant to both TSWV and leaf spots; and there were 3 genotypes from China susceptible to both TSWV and leaf spots. These phenotypic disease reaction data can be used in conjunction with genetic characterization of these genotypes for development of recombinant inbred line (RIL) populations in efforts to develop markers for resistance to TSWV and leaf spots.