Unveiling the Impact of Growth Traits on the Yield of Bread Wheat Germplasm Subjected to Waterlogging

Changes in the climate have led to the occurrence of extreme events that threaten the production of major crops, namely that of bread wheat ( Triticum aestivum L.). Waterlogging imposed at the tillering stage can severely affect the yield, but several genotype features may counterbalance the negative impacts on yields. The aim of this work was to evaluate the effect of waterlogging on the number of fertile spikes, kernels per plant, and single kernel weight, as well as to assess the main culm and tiller participation in yields. We also investigated if the growth stages affected by stress would influence such traits. The study was conducted in climatized growth chambers using 23 genotypes from five distinct germplasm groups (Portuguese landraces, varieties with the introduced Italian germplasm, post-Green Revolution varieties with the introduced CIMMYT germplasm, advanced lines from the Portuguese wheat breeding program, Australian varieties). Variability was observed between and within the groups. Ten genotypes performed well under waterlogged conditions, showing promising results. Among these, GR-2 showed a rise in tiller yield, AdvL-3 in both the main culm and tiller yield, and the remaining ones displayed unaltered values in both the main culm and tillers. PL-1, PL-5, GR-1, GR-3, AdvL-2, Austrl-2, and Austrl-4 were able to compensate for the decreases observed for several traits, reaching harvest yield values that were unaffected in both the main culm and tillers. Rises in the tiller yield or in the tillers and main culm, GR-2 and AdvL-3 exhibited either stability or increases in all the studied parameters. Results also suggest a negative correlation between the growth stage reached during waterlogging and the effect of this stress on the number of spikes per plant, plant and tiller yield, kernel per spike (tillers), and single kernel weight (tillers). Our findings may contribute to a better understanding of wheat responses to waterlogging and to the development of solutions that mitigate the socio-economic impacts of 20–50% wheat yield reductions, thereby preserving the daily 20% supply of energy and protein required for human nutrition and global food security.