|WU, LIJUN - OKLAHOMA STATE UNIVERSITY
|DAMICONE, JOHN - OKLAHOMA STATE UNIVERSITY
|DUTHIE, J - OKLAHOMA STATE UNIVERSITY
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/1999
Publication Date: N/A
Interpretive Summary: Initiation and progression of infection by the early leaf spot fungus on peanut is dependent on temperature and wetness duration. This paper describes the three-dimensional aspects of these relationship as affected by peanut genotype. Inoculation experiments were conducted under controlled conditions where several wetness durations and temperatures were created to ostudy the initiation and progression of infection on three peanut genotypes. A Spanish cultivar, Spanco, and two runner type cultivars, Florunner and Okrun, varied in their response to temperature and wetness duration. Cultivar responses to wetness duration varied at a given temperature. At 22.8 deg C, one lesion per leaf was expected following 26, 30, and 36 hours of wetness for Spanco, Florunner, and Okrun, respectively. If temperature was increased to 28 deg C, one lesion per leaf was expected following 36, 44, 54 hours of wetness for the respective cultivars. Overall, severity of disease was greatest for Spanco, intermediate for Florunner, and lowest for Okrun. These data are useful in improving the weather-based advisory programs for managing early leaf spot on runner and Spanish peanut cultivars.
Technical Abstract: Effects of temperature and wetness duration on infection of 3 peanut cultivars by Cercospora arachidicola were determined under controlled conditions. Plants of Spanco, Florunner, and Okrun were exposed to constant temperatures of 18-30 deg C during 12-h periods of wetness each day, totaling 12-84 h following leaf inoculation with conidia. Severity of disease, measured by either lesion density or lesion size, was greatest fo Spanco, intermediate for Florunner, and lowest for Okrun in each of 2 experiments. Leaf density was evaluated further because it indicated both occurrence and degree of infection. Nonlinear regression analysis was employed to evaluate combined effects of temperature and wetness duration on leaf density. Cultivars varied in response to wetness duration at a given temperature. At 22.8 deg C, 1 lesion/leaf was expected following 26, 30, and 36 h of wetness for Spanco, Florunner, and Okrun, respectively. If temperature was increased to 28 deg C, 1 lesion/leaf was expected followin 36, 44, and 54 h of wetness for the respective cultivars.