2014 年 58 巻 3 号 p. 109-115
NERICA (new rice for Africa) varieties (Oryza sativa x O. glaberrima x O. sativa), which, with their strong drought tolerance, are expected to promote upland rice cultivation in sub-Saharan Africa, could be grown in lowland conditions. Field experiments were conducted at the experimental farm of National Crop Resources Research Institute in Uganda for four crop seasons in 2010 and 2011 under upland and lowland field conditions using three upland NERICA varieties in order to (i) compare crop performance between upland and lowland rice ecosystems and (ii) identify attributes responsible for the yield gap between upland and lowland ecosystems. Results indicated that on average, the yield under lowland condition was higher than under upland condition by 25%. With favorable rainfall conditions, the yield under upland ecosystem was the same as, or even better than that of lowland ecosystem for the same varieties. Among the yield components assessed, the number of panicle m-2 and the number of spikelets per panicle were key factors that contributed to yield under upland condition, and the number of spikelets per panicle was the single significant factor contributing to yield under lowland condition. The differences in these two yield components, the number of spikelets per panicle in particular, were responsible for the yield gap between lowland and upland. These characteristics are common to Oryza sativa, but more distinct for upland NERICAs.
