Heat stress rather than drought will hit yields in the future, says researcher

Breeding for drought tolerance or heat stress was under the spotlight at a Rothamsted Research/HGCA workshop. Mike Abram reports

Wheat breeders will need to focus on overcoming heat stress rather than improving drought tolerance as a result of climate change, according to modelling by Rothamsted Research‘s Mikhail Semenov.

Currently the environment was not changing rapidly as a result of climate change, he told a HGCA/Rothamsted Research Association water use workshop at Broom’s Barn Research Station.

But the latest Intergovernmental Panel of Climate Change assessment predicted climate would change much more rapidly in the future, and that could mean new varieties wouldn’t be adapted to the new environment after their 10-year development period, he explained.

Climate change models were giving hints for what to breed for, he said. The UK would have wetter winters, and drier, hotter summers, according to the Met Office’s Hadley Centre predictions for the 2050s.

That meant drought could potentially be a big problem, but so could heat stress, as the UK would experience more heatwaves, which if they coincided with vulnerable stages of wheat growth, particularly flowering, can severely hit yields, he suggested.

wheat spraying T3 
Heat stress during flowering will cause more yield loss than drought stress in the future, according to Rothamsted’s Mikhail Semenov.

To help determine which would have greater impact on wheat yields he had used a Rothamsted model which predicted wheat performance under different climates.

The results were quite surprising. Yield losses for the variety modelled, Avalon, from severe droughts – the kind that happened once every 20 years – in 2050 would actually be less than for the reference period of 1960-1990.

The reason was the crop would develop more quickly because of the higher temperatures, Dr Semenov explained. He suggested maturity might be up to three weeks sooner by 2050, so drier summers would have less affect, while wetter winters would provide water for the growing crop.

But yield losses from heat stress would be much more severe, the model predicted. Days with temperatures of over 30C at flowering would be much more likely, even if flowering moved two weeks earlier, hitting yields, he said.

Later flowering varieties would be hit even harder than the relatively early flowering Avalon, he added.

He had also run the model for 2020, he said. “It looks similar. Drought won’t be a problem but heat stress will become more of a problem. So the answer to what wheat breeders should be looking to breed for is heat stress. It is going to be a problem in the future.”

But Broom’s Barn director Bill Clark wasn’t convinced. He suggested that with crops maturing earlier, growers would drill earlier so crops might flower even earlier than what Dr Semenov predicted. That could alleviate some of the heat stress problems, he suggested.

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