Trends of grain yield and plant traits in Chinese maize cultivars from the 1950s to the 2000s

Retrospective analyses may provide an understanding of unexploited genetic potential and indicate possible pathways for future yield improvement. The objectives of this study were to present maize(Zea mays L.)yield trends and plant traits changes for maize cultivars from the 1950s to the 2000s in China. Trials were conducted at three locations in 2007 and 2008, and at four locations in 2009. Twenty-seven single hybrids, four double-cross hybrids, and four open-pollinated varieties, were grown at three densities at each location each year. 56% of total yield gain was contributed to breeding from 1950 to 2000. New hybrids had more resistance to compound stress. Levels of response of all hybrids to higher-yielding environments were similar, and greater than that of OPVs. All maize cultivars showed morphological changes for all characteristics tested in a volatile manner from 1950 to 2000, except for relatively stable leaf number. ASI decreased and tolerance to root lodging improved, which were enhanced at higher plant densities. There were no trends for other characteristics at higher densities. Shorter maturity, smaller plant size and more tolerance to root and stalk lodging will be required for further yield improvement. Chinese maize yield improvement can benefit from agronomic strategies at higher plant densities.