Adaptation of winter crops to high temperature : defining sensitivities, impact and targets

Abstract

Warming trends involve a gradual increase of temperature and higherincidence of heat waves. Working at different scales, from continentaltrial networks to detailed physiological experiments we illustrate thevalue of (i) separating stressful vs. non-stressful temperatures, (ii)identifying sensitive stages for impact on yield and (iii) understandingthe interaction with other weather/soil factors. Using National VarietyTrials across Australia we observed a consistent negative associationbetween maximum temperature and yields in wheat, barley and canolawith clear regional patterns. Days exceeding 30°C were unlikely beforeflowering; while canola and chickpea sampled the highest occurrenceduring grain filling, chickpea was less affected. In addition, a rise inminimum temperature during the critical period can lead to substantialyield reduction linked to a shorter cycle. Our study highlights thattemperature in the non-stressful range can be associated with yieldreduction with crop specific effects. Finally, the interaction betweentemperature and water stress presented a regional pattern. Under aMediterranean rainfall pattern, high minimum temperature beforeflowering was associated with higher yields in wheat, barley, canola andchickpea, possibly promoting early growth and water use and reducingdirect evaporation from the soil. Where crops depend on initial soilmoisture, high yields were associated with lower minimum temperature,possibly slowing growth and early water use, lessening terminal stress.We discuss likely selection targets for temperature responsiveness perse that could add value to adaptation strategies.