Inter‐annual climate variability constrains rice genetic improvement in China

Abstract

Abstract Yield potential has been significantly increased through hybrid rice breeding in the past, however, the genetic gain in grain yield is becoming marginal in recent years, especially in farmers’ field. The increase in climate variability is one potential reason for the stagnant rice grain yield. Moreover, overuse of nitrogen fertilizer and poor grain quality of hybrid rice reduce its advantage over inbred rice. The present study evaluated seventy‐eight elite hybrid varieties in 2014–2018 aiming to determine the climate variability and its influences on grain yield, nitrogen use efficiency (NUE), and grain protein content of the newly bred rice hybrid varieties simultaneously. It was found that daily maximum and minimum temperature, daily radiation varied significantly across planting years. The extreme differences for Tmax, Tmin, and radiation were 2.0°C, 1.5°C, and 3.6 MJ m−2 d−1, respectively. Overall, grain yield of 22 varieties was significantly increased in comparison to that of the control cultivar Yangliangyou6 (YLY6), which was closely dependent on the planting year. Grain yield of these elite varieties ranged from 9.69 to 11.97 t ha−1, and NUE for grain production (NUEg) from 47.3 to 60.9 kg kg−1. The inter‐annual variation in grain yield, NUEg, and grain protein content was significantly related to the average daily minimum temperature (Tmin), due to its effects on grain filling percentage and harvest index. Moreover, these three properties are mutually correlated for all varieties across five years: grain yield positively correlated with NUEg (R2 = 0.46) and negatively correlated with protein content (R2 = 0.32), whereas NUEg negatively related to protein content (R2 = 0.49). These results suggest that enhancing the adaptation to climate variability in hybrid rice breeding is essential and urgent for sustainable rice production in China.

Keywords

• grain yield
• Green super rice
• nighttime temperature
• NUE