Determination of the Panicle Differentiation Stage by tne Visual Observation of Plant Shapeof Rice

摘要

The panicle differentiation (P.D.) is at the emergence of 4thleaf (bL4) counted downward from the flag leaf (bLl). Leaf number index and complimentary age-scale has been developed to specify each stage of the panicle development. Those approaches canfacilitate the determination of the P.D. stage of photosensitivity variety along the cultivation calendar under controlled water condition such as irrigated rice cultivation in Japan. However, rice cultivation in Africa is mainly under rainfed condition(rainfed upland and lowland is representing 47% and 34% respectively of total rice area in West Africa) with thermosensitive variety. Under the rainfed ecosystem, the development of the plant age in leaf number (leaf age) of the individual plant varies compared to irrigated field due to the unstable water condition. Thus, the determination by visual observation has large potential to contribute for increasing rice yield in sub-Saharan Africa through appropriate timing of the fertilizer application at Panicle Initiation (P.I.) stage. JICA has implemented a project for development of rainfed upland rice cultivation in Cameroon since 2011. In the project fields, the remarkably long leaves from the canopy of the community have been frequently observed around the P.D. stage (Fig.1and 2). In this study, the possibility of determining the P.D. stage by the visual observation of plant shape is discussed in terms of leaf age and development.