Speaker
Description
Introduction
Over the last decades, there has been an increased frequency of intense rainfalls (1). Thus, waterlogging events are becoming and will be more common, jeopardizing the performance of crops. As the higher frequency of storms is associated with increased temperatures (2), the frequency of crops being exposed to both stresses will increase. Wheat is crucial for food security and will be more frequently exposed to waterlogging and heat stress, even in Mediterranean regions (3). The economic damage produced by waterlogging or heat in wheat has been evidenced in many studies (4,5,6). Although most literature assume synergistic interactions among stresses (7), it has not been yet analyzed how these stresses interact on wheat yield: i.e., whether they are synergistic or antagonistic; which is the aim of this study.
Materials and methods
We conducted an experiment involving 3 bread (Artur Nick, Santaella, Acorazado) and 3 durum (Euroduro, Don Ricardo and Athoris) spring wheats grown under 4 treatments (control, waterlogging, heat stress, and combining both stresses). Plants were grown individually in plastic tubes (8.5 cm diameter and 100 cm length) placed outdoors. At the onset of stem elongation (DC30, 8), the tubes designed for waterlogging were placed into waterproof plastic bags and filled with water until covering 3 cm from soil surface for 15 consecutive days. Then, plastic bags were removed, and plants were watered daily. Two days after waterlogging ended (i.e., at booting, DC40, 8), plants assigned to heat stress (heat alone and combined with waterlogging) were placed under portable tents with transparent polyethylene increasing daily temperature (+3ºC daily average at midday) for 15 days. After that, tents were removed, and plants continued growing until maturity, when yield and components (biomass and harvest index; numerical components) were quantified.
Results
As expected, there was genotypic variability in yield responses to the stresses but not related to the different species. Averaging across the 6 cultivars, yield was reduced by all treatments: by 33.7±7.3, 24.7±7.8, and 44.9±6.4%, when affected by waterlogging, heat stress, and both stresses combined, respectively. This means that collectively and considering all genotypes together waterlogging and heat were antagonistic on their effects (i.e., the exposure to waterlogging mitigated the effect of heat, through conferring a sort of general acclimation to the plants that had been stressed before the imposition of the heat). However, this only reflects overall general result. The SEs shown above are relatively large because there was genetic variation in sensitivity, with most cultivars showing the antagonistic effect reflected in the average behavior, whilst one exhibited an additive type of effect and another a synergistic type. The variability in response reflected more intra- than inter-specific variation, the antagonistic effect was dominant in both species. Considering the effects of the individual stresses, yield seemed in general more sensitive in durum than in bread wheat. The effects of treatments on yield operated mainly through affecting grain number (mainly though the number of grains per spike) with more exceptional effects through grain weight. Also, the stresses seemed to have affected more growth of the plants than the partitioning to yield.
Discussion
The responses observed in yield and its components prompt consideration not only of genotypic variability, which serves as a tool for selecting varieties more tolerant to waterlogging and high temperatures, but also of the interactions between these consecutive stresses. Contrary to the expectation that prior stress leads to greater reductions in subsequent stress, most combined stress cases in our study resulted in yield reductions lower than anticipated based on additive responses to individual stresses. The antagonistic interaction between stresses identified in our experiment may offer insights for understanding and mitigating the impact of waterlogging and heat stress occurring concurrently in wheat cultivation scenarios.
References
1. IPCC, 2023
2. Scientific Reports,9, 16063.
3. Journal of Hydrology,590, 125249.
4. Plant, Cell & Environment,39, 1068-1086.
5. Agricultural Water Management,284, 108334.
6. Climatic Change,143, 227-241.
7. New Phytologist, 234, 1161-1167.
8. Weed Research, 14, 415-421.
| Keywords | wheat; waterlogging; high temperatures; stress interactions; yield |
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