Abstract
Drought poses a major challenge to the production of potatoes worldwide. Climate change is predicted to further aggravate this challenge by intensifying potato crop exposure to increased drought severity and frequency. There is an ongoing effort to adapt our production systems of potatoes through the development of drought-tolerant cultivars that are appropriately engineered for the changing environment. The breeding of drought-tolerant cultivars can be approached through the identification of drought-related physiological and biochemical traits and their deployment in new potato cultivars. Thus, the main objective of this study was to develop a method to identify and characterize the drought-tolerant potato genotypes and the related key traits. To achieve this objective, first we studied 56 potato genotypes including 54 cultivars and 2 advanced breeding lines to assess drought tolerance in terms of tuber yield in the greenhouse experiment. Drought differentially reduced tuber yield in all genotypes. Based on their capacity to maintain percent tuber yield under drought relative to their well-watered controls, potato genotypes differed in their ability to tolerate drought. We then selected six genotypes, Bannock Russet, Nipigon, Onaway, Denali, Fundy, and Russet Norkotah, with distinct yield responses to drought to further examine the physiological and biochemical traits governing drought tolerance. The drought-induced reduction in tuber yield was only 15–20% for Bannock Russet and Nipigon, 44–47% for Onaway and Denali, and 83–91% for Fundy and Russet Norkotah. The tolerant genotypes, Bannock Russet and Nipigon, exhibited about a 2–3-fold increase in instantaneous water-use efficiency (WUE) under drought as compared with their well-watered controls. This stimulation was about 1.8–2-fold for moderately tolerant genotypes, Onaway and Denali, and only 1.5-fold for sensitive genotypes, Fundy, and Russet Norkotah. The differential stimulation of instantaneous WUE of tolerant and moderately tolerant genotypes vs. sensitive genotypes was accounted for by the differential suppression of the rates of photosynthesis, stomatal conductance, and transpiration rates across genotypes. Potato genotypes varied in their response to leaf protein content under drought. We suggest that the rates of photosynthesis, instantaneous WUE, and leaf protein content can be used as the selection criteria for the drought-tolerant potato genotypes.
Highlights
Potato ranks the first highest produced non-cereal food crops and the fourth highest produced crop after wheat, corn, and rice worldwide (FAOSTAT, 2019)
The drought-induced reduction in tuber yield was associated with decreases in total tuber number for the majority of the potato genotypes under drought (Table 1)
We used 56 potato genotypes including commercial cultivars to assess their tolerance to drought stress. Based on their capacity to maintain tuber yield under drought, potato genotypes differed in their ability to tolerate drought stress (Table 1)
Summary
Potato ranks the first highest produced non-cereal food crops and the fourth highest produced crop after wheat, corn, and rice worldwide (FAOSTAT, 2019). The drought-induced stomatal closure, which is aimed at reducing the transpiration water loss and conserving plant water status, restricts CO2 diffusion in the leaf making the Calvin cycle CO2 substrate-limited (Pinheiro and Chaves, 2011; Dahal et al, 2014, Aliche et al, 2020) This may result in the accumulation of ATP and NADPH since their rates of generation by the photosynthetic electron transport chain exceeds their utilization by the Calvin cycle. There is an energy imbalance in the chloroplast level that favors the generation of reactive oxygen species leading to oxidative stress and damage of cell components Plants experience both stomatal and biochemical limitations of photosynthesis in response to drought stress (Lawlor and Tezara, 2009; Pinheiro and Chaves, 2011; Dahal et al, 2015; Dahal and Vanlerberghe, 2017)
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