Genetic progress in wheat yield and associated traits in China since 1945 and future prospects

Genetic progress has brought about a dramatic increase in yield potential per se for almost all production areas around the world. The present study examines the relationship of wheat yield with year of release, yield components, harvest index (HI), biomass production, and plant height. We used aggregative data from 1945 to 2010 to calculate genetic gain in wheat yield across different zones in China. A deeper understanding of these issues facilitates the identification of specific yield-limiting factors that can be used for future breeding strategies. Absolute yield gain for the different zones was found to range from 20 to 103 kg ha(-1) year(-1), whereas relative yield gain ranged from 0.33 to 1.42 % per year. When data from all the Chinese wheat production zones was pooled, yield gain at the national level had an absolute value of 66 kg ha(-1) year(-1) and a relative value of 1 % per year. Grain weight and spike weight, rather than the other yield components, are significantly correlated with year of release for most zones, suggesting that these two were the most promising traits for breeders in the past. These two traits are also responsible for the significant genetic progress in wheat yield in China since 1949. HI and biomass production also showed strong correlation with year of release and grain yield. In China, HI and grain weight have experienced such a substantial increase that both have almost reached their theoretical maxima in the period 1945-2010. Further improvement in the yield potential of wheat will have to involve increase in biomass production and grain number. This paper also reviews cropping systems and technologies as well as improvement in physiological trait from 1945 onwards during the period of genetic gain.