Coordination of high grain yield and high nitrogen use efficiency through large sink size and high post-heading source capacity in rice

Breeding green varieties that have high yield potential and require less resource input is the ideal way to cope with the challenges that human is facing with respect to food security and environmental pollution. However, few studies have focused on how high yield and high resource use efficiency is coordinated in rice (Oryza sativa L.). Here three varieties with different sink size, namely Yongyou4949 (YY4949) with large sink size, Yangliangyou6 (YLY6) with medium sink size, and Huanghuazhan (HHZ) with small sink size, were used in field and pot experiments in 2015-2017. The objective was to examine how enlarged sink size coordinate high yield and high nitrogen (N) use efficiency (NUE). It was found that YY4949 produced a grain yield of 9.60-11.79t ha(-1) in 2015-2017, which was higher than that of YLY6 by 0.3-1.75t ha(-1), and that of HHZ by 1.3-2.18t ha(-1) . N use efficiency for grain production (NUEg) of YY4949 reached 47.7-58.3 kg kg(-1) depending on the weather condition, which was 5.3-12.8% higher than that of YLY6 and 15.8-20.7% higher than that of HHZ. The concomitantly higher grain yield and NUEg of YY4949 were due to: (1) higher efficiency of spikelet production in respect of dry matter, N, accumulated temperature and radiation; (2) higher biomass production and N accumulation after flowering; (3) higher RUE after flowering due to the better canopy structure. In conclusion, rice breeding in the future should continue to enlarge the sink size especially through the improvement in production efficiency of sink size, while simultaneously increase the post-heading biomass production capacity.