Screening Potato Cultivars and Wild Species to Abiotic Stresses Using an Electrolyte Leakage Bioassay

Ten Solanum tuberosum cultivars and accessions from 11 wild Solanum species were evaluated for their tolerance to salt (200 mM NaCl or 100 mM Na2SO4), drought (35% PEG), cold (-4ºC) and heat (37ºC). Evaluation was based on electrolyte leakage from detached leaves of in vitro plantlets. Testing involved a rinsing treatment with three changes of distilled water to remove electrolytes from leaf and petiole surfaces, an exposure period of 24 hours for salt and PEG stress and four hours for temperature stress and a rehydration period of 24 hours in distilled water followed by measurement of electrical conductivity into distilled water to determine the effects of stress. Significant differences were observed between Solanum genotypes for all types of stresses. Among the S. tuberosum cultivars, stress tolerance was great to NaCl and PEG in Alpha and Bintje; to Na2SO4 in Agria and to heat and cold in Norland. Among the wild species, tolerance to all stresses was great in S. demissum, to all stresses except heat in S. acaule and to heat and cold in S. commersonii. The correlations among types of stress tolerance were significant for all stresses except for heat and drought. The level of tolerance in some wild species was significantly greater compared with the cultivars tested. There appears to be a wide genetic base available to improve the stress tolerance of cultivated potato