Heat susceptibility of grain filling in wheat (Triticum aestivum L.) linked with rapid chlorophyll loss during a 3-day heat treatment
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Brief heat events (1–3 days, >30 °C) commonly reduce wheat (Triticum aestivum L.) grain size and consequently yield. To identify mechanisms of tolerance to such short heat events, 36 wheat genotypes were treated under day/night temperatures of 37 °C/27 °C for 3-days in a growth chamber, at 10 days after anthesis, and a range of developmental, chlorophyll and yield-related traits monitored. The degree of flag leaf chlorophyll loss during the treatment was the variable that showed the highest correlation to grain weight loss (r = 0.63; p < 0.001), identifying chlorophyll stability during this brief period as a potential determinant or indicator of grain weight stability under heat. Variables summarizing the combined during- and post-heat chlorophyll losses showed similar or lower correlations with heat tolerance of grain filling, despite the fact that genotypes varied in their ability to resume normal chlorophyll loss rates after the heat treatment. Additionally, heat tolerance of grain size showed no correlation with grain filling duration or traits relating to utilization of stem carbon reserves under heat stress. Measurement of chlorophyll loss over a forecasted heat wave was thereby identified as a potential basis for developing tools to help breeders select heat tolerant genotypes.
KeywordsHeat tolerance Senescence Stay-green Chlorophyll content Wheat
This project was funded by the Grains Research and Development Corporation (GRDC; project UA00123), with additional support from the Australian Centre for Plant Functional Genomics (ACPFG). ACPFG is funded mainly by the GRDC, the Government of South Australia and the University of Adelaide and was also supported by the Australian Research Council and the University of South Australia during the time of this study. We thank staff of The Plant Accelerator®, Australian Plant Phenomics Facility, for plant care and growth facilities. The Plant Accelerator® is supported by the Australian Government under the National Collaborative Research Infrastructure Strategy (NCRIS) and the University of Adelaide. We thank Susanne Dreisigacker Gina Brown-Guedira for access to Rht gene KASP assays pre-publication, Kelvin Khoo and Melissa Garcia for assistance with the KASP platform, and the following people for supplying seed: Michael Francki, Dion Bennett, Dan Mullan, Bertus Jacobs, Hugh Wallwork, Brett Lobsey and Livinus Emebiri.
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Conflict of interest
The authors declare that they have not conflict of interest.
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