Abstract:

【Objective】 To make a survey of the advances of maize breeding efforts in north China and find the strategies to continuously improve the yields of maize hybrids in the future, the regression of maize hybrid agronomic traits on year of introduction was calculated. 【Method】 The regression of agronomic traits in yields of hybrids, which was based on the split-spot experimental design with 25 hybrids released during 1970s-2000s eras in north China as sub-plot and population density as main plot, was carried out in Xinjiang and Beijing in 2005 and 2006, respectively. 【Result】 By means of comprehensive analysis on response between yields and eras from 1980s to 2000s, it showed that the yield response of medium density was higher than that of high density in Xinjiang, and the response of medium density was also not significant compared with that of high density in Beijing. It indicated that higher yield response of high density had not been achieved between 1980s and 2000s. In addition, increasing improvement of 1000-kernel weight and rows per ear was the major positive factor that enhances yield of hybrids between 1980-2000 while improvements for decreasing barren rate and shelling percentage were the important negative factors. Through the pooled ANOVA, it showed that there were no significant improvements for traits such as ears per plant, stock lodging, barren tip rate which were closely associated with adaptability of high density between 1980s and 2000s. 【Conclusion】 Therefore, it could be concluded that higher density strategy and technology routine of maize breeding activity should be strengthened and improved although some yield response of high density has been achieved in the last few decades. As a result, the future hybrids in China can be developed towards the modern breeding goals such as early maturity, tolerance to high density, higher shelling rate, no bare tip.

Key words: maize (Zea mays L.), single cross, yield, agronomy traits, genetic gains, tolerance to high density, technology strategy for breeding program