Improving physiological N-use efficiency by increasing harvest index in rice: a case in super-hybrid cultivar Guiliangyou 2

Abstract

Field experiments were conducted in 2013 and 2014 to compare grain yield, yield attributes and physiological N-use efficiency between two super-hybrid rice cultivars: (1) with the potential of high harvest index and physiological N-use efficiency (Guiliangyou 2) and (2) a representative super-hybrid rice cultivar (Y-liangyou 1). No significant difference in grain yield was observed between Guiliangyou 2 and Y-liangyou 1, whereas there were obvious differences in yield attributes between the two cultivars. Compared with Y-liangyou 1, Guiliangyou 2 had 8–10% lower biomass production but 14–18% higher harvest index. Consequently, physiological N-use efficiency was 18–20% higher in Guiliangyou 2 than in Y-liangyou 1. The higher harvest index in Guiliangyou 2 was mainly attributed to enhanced remobilization of stored reserves in the growing grain than in Y-liangyou 1. Larger panicle neck diameter and thinner leaves were partially responsible for the enhanced remobilization of stored reserves in Guiliangyou 2 as compared to Y-liangyou 1. Our results suggest that Guiliangyou 2 is a unique super-hybrid rice cultivar that achieves high grain yield by increasing harvest index and N-use efficiency.