Effect of drought acclimation on drought stress resistance in three potato genotypes

Potato crops are generally sensitive to drought. Even a short period of water shortage can affect tuber production and quality. However, field potato crops undergoing mild water deficit conditions may acclimate to subsequent severe water deficits. While responses may be both acclimation and genotype-dependent, few studies have examined whole plant physiological factors leading to enhanced drought stress resistance. Identification of these key factors may increase selection efficiency in breeding programs. This study examined the effects of drought acclimation on drought stress resistance in three potato genotypes [‘Fv12246-6’ (Fv), ‘Vigor’ (V) and ‘Russet Burbank’ (RB)] in a low relative humidity greenhouse. Non-Acclimated and Non-Stressed (NA), Drought Acclimated and Drought Stressed (DAS) and Non-Acclimated and Drought Stressed (NAS) treatments were applied. Tuber yield and number were genetically determined and acclimation had no effect on increasing these components under drought stress. However, water conservation mechanisms based on leaf and stem characteristics were both genotype and treatment-dependent. When leaves were drought stressed while attached to the stem, genotype V and RB maintained a higher percentage of leaf water content (%LWC) than Fv, likely from the greater water stored in their stems that may have been delivered through continued leaf transpiration. Acclimation induced a thicker leaf cuticular layer and partially open stomata under drought stress in both RB and Fv. Nevertheless, Fv was the most drought sensitive potato genotype, displaying the highest degree of leaf wilting and lowest %LWC under drought stress. The observed drought stress-induced smaller stomatal size in Fv did not confer greater resistance. In addition, Fv displayed the lowest percentage shoot water content (%SWC) and slowest recovery time after drought stress. RB underwent the fastest recovery from drought stress, possibly due to its equivalent xylem to pith ratio which might have enhanced greater water uptake in RB than in V and Fv. Finally, compared to application of drought stress directly (NAS), a pre-treatment of drought acclimation cycles followed by drought stress (DAS) reduced leaf wilting, induced thicker cuticular layer and more open stomata under stress. Without a DAS approach, potentially key drought stress resistance mechanisms will be missed. The role of the stem as a potential water reservoir to adapt against drought stress should be examined to further identify key elements for drought stress survival and recovery at the level of the potato whole plant