Rice yield potential is closely related to crop growth rate during late reproductive period

Yield potential in rice has remained stagnant since the development of IR8 by International Rice Research Institute (IRRI), especially in tropical environments. We conducted field experiments in Kyoto, Japan (temperate climate) in 1999 and 2000 to determine the factors related to yield potential in rice. A rice cultivar Takanari showed the highest grain yield among the genotypes across the 2 years, and successfully produced over 11 t ha(-1) of grain yield in 2000. The genotypic difference in grain yield was most closely related to that in crop growth rate (CGR) during the late reproductive period (14-0 days before full heading). Rice genotypes having higher CGR during this period produced a greater number of spikelets per unit land area. The higher CGR also led to larger accumulation of non-structural carbohydrate (NSC) in the culms and leaf sheaths during the period that was positively correlated with the rapid translocation of NSC to particle in the initial period of grain filling. Solar radiation during grain filling was higher in 2000 than 1999. Therefore, Takanari appeared to have succeeded in over 11 t ha(-1) of grain yield by achievement of both prerequisite biomass production during the late reproductive period and better grain filling. A large genotypic variability in CGR during the late reproductive period was mainly derived from that in radiation use efficiency. These results indicate that improvement of canopy photosynthesis during the late reproductive period may be essential as a first step toward increased yield potential in rice. (c) 2005 Elsevier B.V. All rights reserved.