Abstract
Seed potatoes of seven cultivars grown in the Kingdom have been used in the study: 'Mondial', 'Sandy', 'Hermes', 'Rosetta', 'Victoria', 'Asterix' and 'Safrane'. Plantlets of 6-8 cm long and 4-6 leaflets were transferred to the greenhouse where each one was planted in a pot containing peat moss: sand (2:1) growing media. Acclimatization was carried out for two weeks and water stress treatments were started as irrigation of 20, 40, 60, 80 and 100% of water depletion by evaporation (WDE). Potato drought tolerance was evaluated by taking growth measurements (plant height, number of branches, leaf area, proline content, tuber number and weight) at 0, 30, 60 and 90 days after treatment (DAT). Significant differences have been reported among cultivars and between irrigation treatments in most traits. In general, as water stress increased, vegetative growth and tuber yield decreased. Proline content increased as water stress increased. Significantly higher tuber weight was measured in Rosetta plants at 60 DAT. Whereas at 90 DAT, both Rosetta and Sandy plants had higher tuber weight followed by Hermes, Safrane, Asterix and Mondial plants, respectively. Accordingly, three cultivars have been selected based on their tuber weight response at the 20% WDE. These cultivars were 'Rosetta' (drought tolerant), 'Sandy' (moderately drought tolerance) and 'Asterix' (drought sensitive).