TITLE:
Adaptability of High-Yielding Rice Cultivars in Relation to Biomass Productivity under Moderately Water Stressed Upland Conditions
AUTHORS:
Tomohiro Hyoda, Koki Homma, Tatsuhiko Shiraiwa, Keisuke Katsura, Takeshi Horie
KEYWORDS:
Intercepted Radiation, Radiation Use Efficiency, Root Length Density, Leaf Water Potential, Temperature Difference between Canopy and Air
JOURNAL NAME:
Agricultural Sciences,
Vol.6 No.3,
March
20,
2015
ABSTRACT: Recent studies have focused on the improvement of rice productivity under aerobic conditions for times when water resources and food production are limited. This study aimed to evaluate the adaptability of high-yielding rice cultivars to moderately water-stressed upland conditions in order to contribute breeding. A three-year field experiment in the temperate climate of Kyoto, Japan, indicated that the decrease in yield was mainly derived from a decrease in above-ground total dry matter (TDM) rather than a decrease in harvest index (HI). Although the decrease in TDM was mostly caused by a decrease in radiation use efficiency (RUE), we determined that the key to adapting high-yielding cultivars to upland conditions is intercepted radiation per day (IRPD), governed by leaf area index (LAI). Although the effect was not robust, LAI growth under upland conditions was associated with root length density. RUE was dependent on leaf water potential (LWP), indicating that a plant’s ability to maintain LWP under water-stressed conditions is important. The results also suggest the necessity of a canopy analyzer to evaluate LAI, as well as an infrared radiation thermometer to evaluate RUE. Performing such measurements during breeding efforts allows us to select for genotypes that are suitable for less stressed aerobic conditions.