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Disease Detection and Losses

Effects of Cassava Mosaic Disease on Certain Leaf Parameters of Field-Grown Cassava Clones. D. K. G. Ayanru, Senior lecturer, Department of Biological Sciences, University of Benin, Benin City, Nigeria; V. C. Sharma, senior lecturer, Department of Physics, University of Benin, Benin City, Nigeria. Phytopathology 72:1057-1059. Accepted for publication 13 November 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1057.

Mature leaves of 14 field-grown 8-mo-old cassava clones with (diseased) and without (healthy) symptoms of cassava mosaic disease (CMD) were assessed comparatively for concentrations of chlorophylls (chl) a and b, leaflet surface area, leaflet dry weight, and petiole dry weight. Ratios of chl a and chl b were similar in diseased and healthy leaves (1.762.23 and 1.902.20, respectively). Concentrations of chl a and chl b were between 1.352.38 and 0.671.19 mg/g dry wt, respectively, in healthy leaves, and 0.841.42 and 0.400.72 mg/g dry wt, respectively, in diseased leaves. Concentrations of chl a and chl b, as well as leaflet surface area, leaflet dry weight, and petiole dry weight of diseased leaf samples were reduced significantly (P <0.01) by 3262, 3757, 2148, 2554, and 2751%, respectively, compared with corresponding data from healthy leaves. It is suggested that the bulk of CMD-induced heavy yield reductions in cassava can be explained on the basis of the diminished chlorophyll content, leaflet size, and (possibly) other aspects of photosynthetic carbohydrate production.