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Modern hexaploid wheat differs from diploid and tetraploid ancestors in the importance of stress tolerance vs. stress avoidance
High temperature and weak radiation stress negatively influences wheat production. Yet, related eco-physiological mechanisms across wheat species of different genetic background are not well documented. A pot-culture experiment was conducted in growth chambers to analyse the prevailing strategies of wheat genotypes with different ploidy levels under combined high temperature and weak radiation (30/25℃; 200 PAR) stress, in comparison with normal growth conditions (20/15℃; 400 PAR). The results showed better avoidance ability by the diploid and tetraploid wheat genotypes to the high temperature and weak radiation stress. These diploids and tetraploids produced high vegetative biomass under control but reduced it substantially under the stress. The adaptive response to avoid heat/radiation overload was the strong reduction in these organs, mainly leaf area. As a consequence, these genotypes produced lower yields. In contrast, modern hexaploid wheat varieties displayed a stronger tolerance to the stress and produced greater yields. This was due to a larger green leaf area, higher relative leaf water content, and higher proline and soluble sugar contents. The relative importance of these tolerance and avoidance strategies was estimated to account for 60% and 22%, respectively, of the variations in grain yield. Our study demonstrated that modern hexaploid wheat has acquired a greater proportion of tolerance rather than avoidance strategy in response to high temperature and weak radiation stress.
CP17224 Accepted 15 December 2017
© CSIRO 2017