Drought-tolerant coffee plants display increased tolerance to waterlogging and post-waterlogging reoxygenation

Abstract

Soil waterlogging negatively impacts plants due to reduced oxygen availability in the rhizosphere. Here we selected two Coffea canephora clones with contrasting tolerance to drought and oxidative stress to test whether they would also exhibit contrasting tolerance to waterlogging and post-waterlogging reoxygenation. Plants were exposed to six days of waterlogging followed by 40 days of reoxygenation. During waterlogging, both clones exhibited lower leaf gas exchange rate, electron transport rate and photochemical quenching as well as increased non-photochemical quenching; overall, these changes were stronger in the drought tolerant (DT) clones over the drought sentitive (DS) ones. Photosynthetic limitations were essentially linked to diffusional constraints regardless of clone. In both clones, declines in stomatal conductance were not associated with foliar ABA or ethylene levels, however stomatal conductance correlated with the plant hydraulic conductance. After reoxygenation, DT plants mostly recovered leaf function and plant mortality was less than 10%. Conversely, DS plants displayed very low water potentials after reoxygenation, which was accompanied by photosynthetic and membrane damage and 40% plant mortality. Our findings confirmed that the DT clone is less impaired by soil waterlogging and reoxygenation than the DS one. The differences between clones were more evident during the reoxygenation than during waterlogging, likely due to the drought experienced by the DS but not DT plants. Collectively, this information leads us to a common path to find new coffee genotypes with increased tolerance to both drought and waterlogging aiming at increased coffee sustainability under an ongoing climate changing scenario.