Survival of submerged rice in a flood-prone region of West Africa
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Because of natural disasters caused by a heavy rain and change of precipitation pattern, rice production in West Africa is often unstable, whereas rice is an important food crop. Reports of flooding damage to rice plants have been increasing with the expansion of rainfed lowland rice cultivation there since 1988. This report reviews recent environmental changes that have occurred in a flood-prone region of West Africa, and the eco-physiological survival strategies used by rice plants under flooding stress. We identify the flooding status in West Africa, with flood-prone areas that are classifiable into three types: floating, deepwater, and flash flood areas. Most rice cultivars show shoot elongation in response to submergence. Shoot elongation during long-term submergence is an' escape strategy', which enables rice to resume functioning when again in aerobic conditions. However, some rice genotypes can survive in flash flood areas due to tolerance to short-term submergence. The ecological and physiological traits of flash flood-tolerant rice include less chlorosis and high carbohydrate reserve storage, although shoot and leaf elongation are slow during submergence. Especially for flood-prone areas, we report the potential adaptability of Oryza glaberrima Steud., one cultivated species of rice originating from Africa, which has unique traits of increased biomass production through high photosynthesis by newly developed leaves under prolonged submergence. We conclude that stable agricultural systems with useful tolerance to flooding stress should be improved grain yield to mitigate submergence damage to rice crops in West Africa.
Tropics 20(2), 55-66, 2011
JAPAN SOCIETY OF TROPICAL ECOLOGY