Relationship among severity of late leafspot, canopy reflectance, healthy leaf area duration and pod yield in two peanut cultivars
1991
Aquino, V.M. | Shokes, F.M. (Philippines Univ., Los Banos, College, Laguna (Philippines). Inst. of Plant Breeding)
Field studies were conducted in Marianna, Florida [USA] in 1988 and 1989 to study the relationships among severity of late leafspot (caused by Cercosporidium personatum), canopy reflectance, healthy leaf area duration (HAD) and pod yield in two peanut cultivars. Spray treatments of chlorothalonil were applied to establish different levels of disease. Leaf area index (LAI) was measured eight times during the season and disease progression and canopy reflectance were monitored. Percent canopy reflectance at 800 nm was measured using a hand-held multispectral radiometer. Healthy leaf area duration and green leaf area were calculated from LAI and the total amount of disease. Pod yield for Florunner, a cultivar susceptible to late leafspot, decreased as the duration of healthy leaf area decreased. The percent canopy reflectance at 800 nm decreased as the disease severity and defoliation increased. Linear relationships were obtained between green leaf area and percent canopy reflectance for both cultivars. Using a model developed earlier for Florunner, pod yield of Florunner was adequately predicted from HAD for all treatments. However, the yield for Southern Runner, a partially resistant cultivar, was overestimated by the model for Florunner. Results support the concept that HAD can be used to predict yield, and to determine yield loss due to late leafspot disease.
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