534-17 Genotypic Variation of Yield Enhancement of Rice Cultivars with Different Maturity Group of Exposure to Free-Air CO2 Enrichment (FACE).

Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E
Hiroyuki Shimono1, Masumi Okada2, Yasuhiro Yamakawa2, Hirofumi Nakamura2, Kazuhiko Kobayashi3 and Toshihiro Hasegawa4, (1)Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
(2)National Agricultural Research Center for Tohoku Region, Morioka, Iwate, Japan
(3)Dept. Global Agri Sci. U. of Tokyo, Bunkyo-ku, Tokyo, Japan
(4)National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki, Japan
Adequate N status in plants is a critical factor for ensuring their ability to respond positively to elevated atmospheric CO2 concentrations ([CO2]).  A cultivar with higher N concentration might thus respond better to elevated [CO2].  To test this hypothesis, we examined four rice cultivars with different times to maturity in a 2-year free-air CO2 enrichment (FACE) experiment.  Plant N concentration at the heading stage differed significantly between cultivars but without any significant [CO2] ´ cultivar interaction; cultivars that matured earlier had higher N concentrations.  Grain yield was significantly increased by elevated [CO2] (by up to 23%), but the magnitude differed among the cultivars due to a significant [CO2] ´ cultivar interaction; two cultivars (one with early and one with late maturity) responded more strongly to elevated [CO2] than those with intermediate maturity dates, resulting from increased spikelet density.  Biomass and N uptake at the heading stage were closely correlated with grain yield and spikelet density.  Our 2-year field trial rejected the N-response hypothesis and showed that the magnitude of the growth enhancement before heading rather than plant N concentration is a useful criterion for selecting cultivars capable of adapting to future elevated levels of [CO2].