Trends in drought tolerance in Chinese maize cultivars from the 1950s to the 2000s

Drought is a key factor that has historically affected maize productivity. Thus, retrospective studies of the performance of cultivars used in China under water- limited conditions may provide some useful information and guidance for the improvement of maize yield. The objectives of the present study were to assess genetic gains in grain yield and the trends in related secondary traits, particularly increased drought-stress tolerance, in cultivars widely used in China from the 1950s to the 2000s. Trials were conducted at two locations (Sanya and Urumchi) under two water regimes per location during the 2010-2011 growing seasons. Results indicated that mean grain yield showed a significant linear increase from the 1950s to the 2000s, and that newer maize cultivars yielded more than older ones under either drought stress or fully irrigated treatments. The average yield gains under water-limited and unstressed environments were 62.6 and 100.3 kg ha−1 yr−1 respectively. Secondary traits associated with drought in maize have been improved over the past 50 years. The ASI and empty ear rate both decreased, while kernels per ear and weight per 100 kernels increased. The latter two parameters were the main sources of yield gain from 1950 to 2000 under drought stress treatment. To further improve yield under drought-stress conditions, the ASI and empty ear rate should both continue to be decreased during maize breeding. Further, genotypes with plant height and ear traits that are less affected by drought stress should be selected.