Differential Responses of Advanced Potato Clones to Primed Acclimation for Drought Tolerance in a Peruvian Potato System: Yield and Physiological Effects of Irrigation Timing.

Despite the fact that potato ranks fourth among the world’s primary crops in production, its cultivation is threatened by its sensitivity to water deficit. Primed acclimation, or the exposure of a crop to a period of mild to moderate water deficit early in the season, may improve the ability of the crop to respond to subsequent or more extreme water deficits. The use of primed acclimation as a management tool in potato is little understood. Therefore, the objective of this study was to determine the physiological effects of a primed acclimation period applied either before or after tuber initiation onset (TIO) in three advanced potato clones grown under field conditions during May-September of 2014 in Lima, Peru. Priming was achieved through the application of controlled deficit irrigation at a rate of 50% of irrigation needed to reach field capacity for a period of two weeks. Both the early and late priming treatments, as well as a third treatment that received no priming were subjected to a more severe drought applied as a complete water deficit beginning three weeks after tuber initiation. Overall, yield was reduced by 39% due to imposed drought in comparison to the production potential, which was determined by a fourth set of plants that received full irrigation for the whole season. Leaf-level measurements (e.g. gas exchange and instantaneous water use efficiency) were taken at TIO and two weeks after the implementation of drought. Both yield and gas exchange data exhibited significant interactions between variety and treatment, indicating that the optimal timing of the priming application (before or after TIO) differs among varieties. For example, the cultivar UNICA showed no difference in yield between non-primed and priming before TIO, while Tacna showed no difference between non-primed and priming after TIO. Consequently, the characterization of these differential, varietal responses will determine the appropriate timing of primed acclimation for inducing drought tolerance.