Genotypic Variation in, and Effects of N on, Sensitivity to a Wave of High Temperatures during Wheat Grain Filling.

It is urgently required to substantially increase wheat yields, with at least no reductions in grain quality, during the next decades. Fulfilment of this requirement is challenging as projections suggest that wheat will be concurrently exposed to both higher mean temperatures and more frequent events of heat shocks, both potentially penalizing crop yields (and perhaps also quality). It seems necessary to identify agronomic and breeding alternatives to minimize this penalty. We conducted two field experiments comparing the response of different commercial cultivars of wheat to a high-temperature wave of 10 days (increasing the maximum while unaffecting the minimum), under high soil N in the first year and under contrasting soil N levels in the second season.

We found that, in average, yield and grain weight were reduced by heat stress. However, the magnitude of the penalty imposed by the heat was dependent on both the genotype and the soil N availability. Genotypes exhibit large variation in sensitivity, and high-N plots were more sensitive to heat than plots under relatively low N availabilities. Thus, we showed that modern Spanish cultivars vary in sensitivity which is essential for breeding for improved tolerance to heat through conventional procedures; and that high N availability increased the sensitivity to heat. This is relevant as it means that fertilization strategies may need to be revised to balance the yielding benefits of high N availability and the detrimental effect high levels of soil N when the crop is exposed to the event of a heat stress.