Effect of Cold Stress on Field Performance, Chlorophyll Fluorescence, Electrolyte Leakage and Leaf Gas Exchange Parameters of Potato (Solanum tuberosum L.) Genotypes

North-western parts of the Indo-Gangetic Plains are prone to occasional frost incidences which may result in 40-60% loss of tuber yield in potato. The overall aim of this study was to identify the morpho-physiological responses of two frost tolerant (Kufri Anand, J/2-19) and two susceptible (Kufri Pukhraj and MS/7-645) genotypes of Solanum tuberosum to cold stress. Plants were grown in vivo and in vitro under controlled conditions. In the seasons of natural frost occurrence, 2016-2017 and 2020-2021, Kufri Anand (20.4%) and J-2/19 (10.5%) recorded less foliage damage as compared with MS/7-645 (29.7%) and Kufri Pukhraj (40.2%). The genotypes also exhibited variations in fatty acids and.-sitosterol compositions. The in vitro grown plants were acclimated at 4 +/- 2 degrees C for 10 days before their exposure to freezing temperature (-2 degrees C) for 1.0 and 1.5 h of time durations. Electrolyte leakage, chlorophyll fluorescence and leaf gas exchange were measured. Acclimation treatment did not improve the freezing tolerance behaviour of potato genotypes. However, the frost tolerant genotypes, Kufri Anand and J/2-19, recorded 7.7% and 14.2% less electrolyte leakage at 1.5 h of treatment time span as compared to that of Kufri Pukhraj. Furthermore, post 15 days of recovery after freezing treatment, the non-acclimated J/2-19 plants maintained 16.9% and 9.1% higher net photosynthetic rate and stomatal conductance values than those of Kufri Pukhraj, indicating the ability of the tolerant genotype to recover faster. Overall, although the cold acclimation did not enhance freezing stress endurance in potato, yet the genotypes exhibited differential responses to freezing treatments. Moreover, the fatty acid composition, chlorophyll fluorescence and leaf gas exchange can potentially be utilized for assessing the frost tolerance ability of potato genotypes.