Leaf photosynthetic performance related to higher radiation use efficiency and grain yield in hybrid rice

Yield potential of hybrid rice has been increased by approximately 10% through breeding super hybrid rice. It is well documented that the yield superiority of super hybrid rice is related to higher radiation use efficiency (RUE). However, limited information is available on the factors that contribute to the higher RUE in super hybrid rice. In this study, field and pot experiments were conducted in 2012-2014 to compare yield attributes, RUE and leaf photosynthetic traits between a super hybrid rice cultivar Y-liangyou 087 and an ordinary hybrid rice cultivar Teyou 838. In the field experiments, Y-liangyou 087 produced 11% higher grain yield than Teyou 838. Total biomass was higher in Y-liangyou 087 than in Teyou 838, whereas the difference in harvest index was not significant. The difference in intercepted radiation was insignificant between Y-liangyou 087 and Teyou 838, while RUE was 14% higher in Y-liangyou 087 than in Teyou 838. Y-liangyou 087 had higher net photosynthetic rate than Teyou 838, especially at the late growth stages (heading and milking). In the pot experiment, higher net photosynthetic rate was also observed in Y-liangyou 087 than in Teyou 838. There were no significant differences in stomatal conductance and intercellular CO2 concentration between Y-liangyou 087 and Teyou 838. Y-liangyou 087 had higher chlorophyll a content and equal chlorophyll b content than Teyou 838. Efficiency of excitation capture by open photosystem II (Fv/Fm) and quantum yield of photosystem II (ΦPSII) were higher in Y-liangyou 087 than in Teyou 838, while the difference in photochemical quenching coefficient was insignificant. Y-liangyou 087 had higher Rubisco content than Teyou 838. These results suggest that higher RUE and grain yield can be achieved by improving leaf photosynthetic traits including chlorophyll a content, Fv/Fm, ΦPSII and Rubisco content in hybrid rice.