Drought resistance of nine maize cultivars released from the 1970s through the 2010s in China

Problem:Water scarcity has become a limiting factor for increasing crop production. Yield losses due to drought stress can best be resolved by breeding new, drought-tolerant cultivars, however, the genetic gains in drought resistance of different maize cultivars especially under precise water control conditions were not systematically studied. The objectives of this study were to assess 1) the change in yield and WUE of different cultivars from the 1970s through the 2010s under precise water control conditions and 2) find out the main factors affecting the yield and WUE change of different cultivars. Methods:We selected nine hybrids from different eras for a detailed field study under three different water treatments (full irrigation, moderate drought, and intense drought) in a rainout shelter at Hengshui (115 degrees 40 & PRIME;E, 37 degrees 44 & PRIME;N) in southern Hebei province in 2018 and 2019. We compared the grain yield and water use efficiency (WUE) of different cultivars from the 1970s through the 2010s under drought-stress (moderate drought and intense drought) and fully-irrigated conditions. Results:The maize yield and WUE showed a significant linear increase with the year of release. The average yield gains were 111, 113.4 and 121.3 kg ha- 1yr- 1 under fully-irrigated, moderate and intense drought conditions while the WUE gains were 0.31, 0.38 and 0.72 kg ha-1 mm-1 yr- 1 respectively. The yield reduction ratio showed a significant linear decrease from the 1970 s through the 2010s under both moderate water deficit and intense water deficit which were 0.51 % and 0.99 % yr- 1, indicating that modern cultivars had better drought resistance than older ones. With increased water stress, the yield gap and yield reduction ratio between full irrigation and drought treatments (moderate drought and intense drought) increased significantly. The significant increase in the number of ears per hectare and the number of kernels per ear was the main reason for maize yield increase with the year of release from 1970s to 2010s under drought treatments. Under drought stress, the uniformity of yield component decreased significantly compared to the fully-irrigated treatment. In addition, an overly large leaf area was not conducive to drought resistance. Conclusions:Modern cultivars had better drought resistance than older ones. Selecting hybrids with higher uniformity and smaller leaf area was beneficial to improve the maize drought resistance. Implications: The results of this study will be beneficial for the breeding and selecting drought-resistant cultivars.

Automated summary

This study aims to assess the change in yield and water use efficiency (WUE) of different maize cultivars under precise water control conditions. The results showed that modern cultivars had better drought resistance than older ones. Selecting hybrids with higher uniformity and smaller leaf area was beneficial to improve the maize drought resistance.