2019 年 63 巻 3 号 p. 140-149
Soil moisture stress is a major constraint of upland rice cultivation under rainfed conditions in Africa. The aim of this investigation was to clarify the effect of soil moisture stress at the panicle development stage on the growth and yield of New Rice for Africa (NERICA) cultivars. In 2012, five upland rice cultivars (NERICA 1 (N1), NERICA 4 (N4), NERICA 7 (N7), WAB56-104 and Yumenohatamochi) were grown in pots with application of soil moisture stress of -20 to -49 kPa for 20 days at panicle formation (PF) or booting (BT) stages. Similar soil moisture stress was imposed on the same cultivars, except WAB56-104, for 15 days at spikelet formation (SF) stage in 2013. Compared to the condition of adequate soil moisture, the number of spikelets and the grain yield of tested cultivars were reduced for application of soil moisture stress in PF, BT and SF. N1 showed less reduction of the number of spikelets than N4 or YHM for stress in BT. In addition, N1 had less decline in net assimilation rate, and tended to have higher increases in leaf nitrogen and chlorophyll contents than the other cultivars for stress in SF. These results suggest that N1 maintains higher net assimilation rate and larger number of spikelets under soil moisture stress applied at SF and BT, respectively, than the other NERICAs.
