Identifying beneficial traits for heat stress around reproductive phases of growth in wheat

There is a need for heat tolerant traits in wheat to be identified in order to maintain and increase yields in future climates. The aim of this project was to assess genotypic variation in crop response to heat stress by comparing a southern European wheat genotype (Renesansa; Rht-D1a, Rht8, Ppd-D1a) with a UK genotype (Savannah; RhtD1b, Ppd-D1b, 1BL/1RS) and their doubled haploid progeny. This would allow for the identification of traits and alleles that would benefit UK and European wheat production under climate change scenarios through the use of a combination of phenotyping, genotyping and crop modelling. Heat stress experiments were conducted in controlled environments to identify the most susceptible growth stages to heat stress within the population and to identify potentially tolerant traits. An appraisal of the crop model SIRIUS and how it simulates heat stress was undertaken. Finally, a field trial was conducted to identify which traits perform well in UK field conditions. Two periods of susceptibility in Savannah and Renesansa were identified as susceptible to heat stress, through reductions in grain number. The first period was identified around booting, with the second being identified one day before mid anthesis. The period around heading was found to be relatively tolerant. Compensation of reduced grain numbers through increases in grain size was limited and variable. Rht8 was not found to influence heat stress tolerance. The photoperiod insensitivity allele Ppd-D1a was found to increase susceptibility to heat stress, while the semi dwarfing allele Rht-D1b was found to confer tolerance to it. Rht8 was associated with reduced yield in UK field conditions. Simulations from SIRIUS suggest that yield loss due to heat stress could increase by three fold in central Europe by 2090, though it is not expected to be a major issue in the UK.