Changes in the yield and associated photosynthetic traits of dry-land winter wheat (Triticum aestivum L.) from the 1940s to the 2010s in Shaanxi Province of China

Eight dry-land winter wheat cultivars (Triticum aestivum L), representative of those widely cultivated from the 1940s to the 2010s in Shaanxi Province of China, were grown in plots that could be sheltered from rain. The plots were subjected to irrigation and drought treatments to identify the agronomic and photosynthetic traits associated with yield progress. Plant height at maturity decreased from 140.7 cm to 79.5 cm from the earliest to the most recent studied cultivar. The yield increased significantly with an annual genetic gain of 0.48% and was consistently and positively associated with the grain weight and harvest index. Modern cultivars were more sensitive to drought stress, and no obvious increase in harvest index was found to indicate possible limitations on further yield increase after the 1980s. The mean tilt angle was similar among all of the cultivars. A trend over time towards a high photosynthetic rate of flag leaf and leaf area index at the heading stage was observed. Both trends were significantly related to a yield increase. The post-anthesis photosynthetic traits showed no trend with cultivar replacement or obvious stable relationship with yield. A future challenge for wheat breeding in this region is to increase the genetic gain in grain yield under water deficits, likely through increases in the grain weight and harvest index as well as an improvement of the photosynthetic rate before and after anthesis. (C) 2014 Elsevier B.V. All rights reserved.