Effects of Weak- and Semi-Winter Cultivars of Wheat on Grain Yield and Agronomic Traits by Breaking through Traditional Area Planting

Global warming has changed the suitability of areas traditionally planted with crops, raising concerns about cereal security. To investigate the possibilities and constraints of increasing yields by breaking through traditional area plantings of wheat cultivars, a two-year field experiment was conducted in southern and northern locations in the Yangtze River basin (YRB), China (separated by approximately 180 km), with seven weak-winter types and six semi-winter types, respectively, bred for the two regions. The movement of weak-winter-type cultivars to the north increased or did not change grain yield and their grain yields were not significantly higher than those of local semi-winter-type cultivars. The movement of semi-winter-type cultivars to the south significantly decreased their yields. Thus, breaking through traditional area plantings did not significantly increase grain yields compared with those of local wheat cultivars. Grain yield of wheat planted in the northern YRB was higher by 5 to 20% than that in the southern YRB because of an increase in spikes that resulted from a longer spike formation phase. In addition, the post-anthesis leaf area declined more slowly in the northern YRB because of higher main stem and tiller survival. High-yielding cultivars always had more spikes and larger photosynthetic areas after anthesis than those of low-yielding cultivars regardless of the planting locations, which led to increases in post-anthesis biomass. However, the grain yield of different cultivars was highly variable under different environmental conditions. The coefficient of variation (CV) of grain yield in different cultivars was significantly positively correlated with the CV of spike number and post-anthesis biomass, implying that flexibility spike number and post-anthesis biomass in response to environmental changes can maximize release of yield potential. Therefore, improving main stem and tiller survival can increase spike number and maintain post-anthesis photosynthetic areas and help to establish a large, highly stable, and productive population with a high level of suitability and production through effectively utilizing the resources during the late growth phase. Valuable suggestions for breeding high-yield and -stability cultivars and confirming their planting range in the future are given.