Interactive effects of host, pathogen and mineral nutrition on grey leaf spot epidemics in Uganda
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Date
2004-02-08
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Publisher
European Journal of Plant Pathology
Abstract
Grey leaf spot incited by Cercospora zeae-maydis is a new devastating foliar disease of maize in East Africa. For
effective control, elucidation of the most critical elements of the grey leaf spot disease pyramid is important. This
study investigated the role of mineral nutrition, pathogen variability and host resistance in the epidemic. Trials
were conducted under field and controlled environments. The 28 isolates used in the controlled environment varied
significantly (P ≤ 0.05) in parasitic fitness measured indirectly as disease efficiency, but no infection pattern
could be attributed to known C. zeae-maydis pathotypes. Data from field trials showed that host resistance and
mineral nutrition significantly (P ≤ 0.05) affected disease efficiency, with highest disease development occurring
in nitrogen-augmented plots. Exclusive phosphorus application had no clear effect on grey leaf spot epidemics
but combined application with nitrogen significantly (P ≤ 0.05) reduced the predisposition effects of nitrogen to
the disease. Overall, treated plots had less disease than unfertilised plots. Fertiliser application had no effect on
sporulation capacity, while cultivars significantly affected it. Geographic differences in amount of disease were
observed, suggesting environment influences on grey leaf spot incidence. The results suggest that the current grey leaf
spot epidemics in East Africa are due to favourable cultivars, poor mineral nutrition and environmental interactions.
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Citation
Okori, P., Rubaihayo, P. R., Adipala, E., & Dixelius, C. (2004). Interactive effects of host, pathogen and mineral nutrition on grey leaf spot epidemics in Uganda. European Journal of Plant Pathology, 110, 119-128.