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Potato grown for early or off-season production plays a crucial role in the economy of several areas in the Mediterranean countries. Irrigation is important for determining yield and earliness, thus a better investigation of plant response under various pedo-climatic conditions can help to improve resource use efficiency and farmer income. A two-year field research (2009-2010) was carried out in Apulia region, southern Italy, on cv Spunta grown under three irrigation regimes: full irrigation (I-100), 50% of full irrigation (I-50) and rainfed (I-0). Treatments were arranged in a randomized complete block design with three replicates. Plant water status, plant growth and, at harvesting, water use efficiency, yield and quality parameters were quantified. Water stress significantly affected yield response: as an average of the two years, a marketable yield decrement of 25.9 and 63.6% was observed in I-50 and rainfed compared with I-100 treatment, respectively. On the contrary, tuber dry matter and specific gravity increased moving from irrigated treatments to the rainfed one and varied also as a function of experimental year. The results confirmed that irrigation is required for early potato cultivation because rainfall is not sufficient to meet crop water needs. In addition, the study indicated that the irrigation regime reduced by 50% of crop water requirements was able to furnish satisfactory yield, with tuber quality characteristics similar or even better than those obtained under full irrigation.