Effects of Temperature and Wetness Duration on Infection of Peanut Cultivars by Cercospora arachidicola.

ABSTRACT The effects of temperature and duration of wetness (relative humidity >/=95%) on infection of three peanut cultivars by Cercospora arachidicola were determined under controlled conditions. Plants of the Spanish cv. Spanco and the runner cvs. Florunner and Okrun were exposed to constant temperatures of 18 to 30 degrees C during 12-h periods of wetness each day that totaled 12 to 84 h following inoculation of leaves with conidia. Severity of disease, measured by either lesion density (number per leaf) or lesion size (diameter), was greatest for 'Spanco', intermediate for 'Florunner', and lowest for 'Okrun' in each of two experiments. Lesion density was evaluated further because it was an indicator of both the occurrence and degree of infection. Nonlinear regression analysis was employed to evaluate the combined effects of temperature (T) and wetness duration (W) on lesion density (Y). In the regression model, the Weibull function characterized the monotonic increase of Y with respect to W, while a hyperbolic function characterized the unimodal response of Y with respect to T. Parameters for the intrinsic rate of change with respect to W (b), the intrinsic rate of change with respect to T (f), the optimal value of T (g), and the upper limit (e) when T is optimum (T = g) were estimated for each cultivar and experiment. The effect of cultivar was characterized primarily by differences in the upper limit parameter e. In each experiment, e was greatest for 'Spanco', intermediate for 'Florunner', and least for 'Okrun'. The effect of cultivar on b followed a pattern similar to that for e in experiment 1, but not in experiment 2. Differences among cultivars for estimates of f and g were small and inconsistent. Estimates for g were precise for each cultivar and experiment and fell within the range of 22.3 to 23.2 degrees C. Cultivar responses to T and W were further evaluated using data pooled over the two experiments. Parameter e was estimated for each cultivar, but common values of b, f, and g were estimated. At e = 22.8 degrees C, lesion density approached an upper limit of 96, 17, and 6 lesions per leaf for the cvs. Spanco, Florunner, and Okrun, respectively. These fitted values approximated the observed values of 86, 25, and 9 lesions per leaf for the respective cultivars. Cultivars varied in their response to W at a given T. At 22.8 degrees C, one lesion per leaf was expected following 26, 30, and 36 h of wetness for 'Spanco', 'Florunner', and 'Okrun', respectively. If temperature was increased to 28 degrees C, one lesion per leaf was expected following 36, 44, and 54 h of wetness for the respective cultivars.

[1]  J. C. Wynne,et al.  Effects of temperature and relative humidity on expression of resistance to Cercosporidium personatum in peanut , 1988 .

[2]  H. Melouk,et al.  Assessment of resistance to Cercospora arachidicola in peanut genotypes in field plots. , 1984 .

[3]  C. Campbell,et al.  Underestimation of disease progress rates with the logistic, monomolecular, and Gompertz models when maximum disease intensity in less than 100 percent , 1992 .

[4]  G. Shaner.  The Effect of Nitrogen Fertilization on the Expression of Slow-Mildewing Resistance in Knox Wheat , 1977 .

[5]  D. J. Nevill.  Components of resistance to Cercospora arachidicola and Cercosporidium personatum in groundnuts , 1981 .

[6]  A. Jones,et al.  A model for detecting infection periods of Coccomyces hiemalis on sour cherry. , 1981 .

[7]  S. Alderman.  Influence of Temperature, Lesion Water Potential, and Cyclic Wet-Dry Periods on Sporulation ofCercospora arachidicolaon Peanut , 1987 .

[8]  S. Toth,et al.  Evolution of a Weather-Based Peanut Leaf Spot Spray Advisory in North Carolina , 1994 .

[9]  B. Oso.  Conidial germination in Cercospora arachidicola Hori , 1972 .

[10]  R. Rowe,et al.  Effects of temperature and duration of surface wetness on spore production and infection of cucumbers by Didymella bryoniae , 1991 .

[11]  M. Ricker,et al.  Relationship between components of resistance and disease progress of early leaf spot on Virginia-type peanut , 1986 .

[12]  D. R. Butler,et al.  Effects of leaf wetness and temperature on late leaf‐spot infection of groundnut , 1994 .

[13]  C. Campbell,et al.  Components of Resistance in Peanut to Cercospora arachidicola , 1985 .

[14]  J. Parlevliet.  Components of Resistance that Reduce the Rate of Epidemic Development , 1979 .

[15]  H. Melouk,et al.  A Method of Screening Peanut Genotypes for Resistance To Cercospora Leafspot1 , 1978 .

[16]  J. Damicone,et al.  Evaluation of a Weather-Based Spray Advisory for Management of Early Leaf Spot of Peanut in Oklahoma1 , 1994 .

[17]  M. K. Beute,et al.  Evaluation of Resistance to Cercospora Leafspot in Peanut Germplasm Potentially Useful in a Breeding Program1 , 1977 .

[18]  N. L. Powell,et al.  Evaluation of Criteria for the Utilization of Peanut Leafspot Advisories in Virginia , 1984 .

[19]  F. Waliyar,et al.  Components of Resistance to an Indian Source of Cercospora Arachidicola in Selected Peanut Lines , 1993 .

[20]  R. Littrell,et al.  Management of peanut foliar diseases with fungicides. , 1980 .

[21]  J. Santini,et al.  A Model Defining the Relationship Between Temperature and Leaf Wetness Duration, and Infection of Watermelon by Colletotrichum orbiculare. , 1997, Plant disease.

[22]  L. Madden,et al.  Nonlinear Disease Progress Curves , 1990 .

[23]  P. M. Phipps,et al.  Development of a pathogen growth response model for the Virginia peanut leaf spot advisory program , 1993 .

[24]  S. Lim,et al.  Empirical Estimation of the Asymptotes of Disease Progress Curves and the Use of the Richards Generalized Rate Parameters for Describing Disease Progress , 1985 .

[25]  K. Boote.  Growth Stages of Peanut (Arachis hypogaea L.)1 , 1982 .

[26]  H. Melouk,et al.  Sporulation of Cercospora arachidicola as a criterion for screening peanut genotypes for leaf spot resistance , 1983 .

[27]  D. Parvin.  Development and Evaluation of a Computerized Forecasting Method for Cercospora Leafspot of Peanuts , 1974 .

[28]  James A. Duthie,et al.  Models of the response of foliar parasites to the combined effects of temperature and duration of wetness. , 1997, Phytopathology.

[29]  J. Sinclair,et al.  Basic plant pathology methods , 1985 .

[30]  T. Sutton,et al.  Influence of temperature and moisture on germination of ascospores and conidia of Botryosphaeria obtusa , 1989 .

[31]  R. Latin,et al.  A model based on temperature and leaf wetness duration for establishment of alternaria leaf blight of muskmelon , 1992 .

[32]  B. Skovmand,et al.  Evaluation of wheat cultivars for ability to retard development of stem rust , 1975 .

[33]  R. O. Hammons,et al.  Resistance of peanut plant introductions to Cercospora arachidicola. , 1976 .

[34]  M. K. Beute,et al.  Influence of temperature and moisture on germination and germ tube elongation of Cercospora arachidicola , 1986 .

[35]  W. C. Gregory,et al.  Sources and Nature of Resistance to Cercospora Arachidicola Hori and Cercosporidium Personatum (Beck & Curtis) Deighton in Arachis Species1 , 1974 .