Morphological and physiological responses of different wheat genotypes to chilling stress: a cue to explain yield loss

Chilling stress is one of the limiting factors inhibiting crop growth and development, resulting in the loss of grain yield. Plants tend to undergo innumerable changes in morphological, biochemical and physiological characteristics under chilling stress. In most cases, chilling stress can markedly decrease the viable leaf area and the carbohydrate production and accumulation, eventually negatively affecting the final yield. Chilling stress-induced photosynthetic inhibition might lead to photo oxidation damage, as photosystem I and II are particularly sensitive to temperature stress, and the inhibition on some components is irreversible. Is the source or the sink is restricted by chilling stress? Which factor would play a critical role to affect the yield loss? The two questions remain unclear in the anti-chilling physiology.

We hypothesized that imbalanced source-sink process could be predicted to have a large impact on yield formation in different wheat genotypes under chilling stress. In the present study, we selected six different genotypes of wheat to test this hypothesis under environment-controlled growth conditions. The objectives were: 1) to investigate morphological, physiological and biochemical responses of contrasting wheat genotypes to chilling stress; and 2) to reveal the eco-physiological mechanism of yield loss across wheat genotypes under chilling stress.

Better understanding on the eco-physiological mechanisms of yield formation under chilling stress is a fundamental issue. The present study showed that diploid and tetraploid wheat genotypes obtained larger leaf areas and relatively high photosynthetic rates but eventually showed no or low yield under chilling stress. While in hexaploid genotypes, leaf areas and photosynthetic rates were remained at a low level, and water soluble carbohydrates can be stored substantially. This phenomenon help exhibit an unimpeded sink, and ensure the supply of current photosynthesis assimilates, the transportation from source to sink and sink demand, allowing these genotypes to achieve relatively stable grain yields under chilling stress. Thus, these results illustrated that the communication of source to sink was a key factor to guarantee a high and stable grain yield under chilling stress in modern wheat genotypes.