A. Nouri - Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
A. Nezami - Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
M. Kafi - Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
D. Hassanpanah - Ardabil Agricultural and Natural Resources Research Station, Ardabil, IRAN

In Ardabil region potato crop needs several irrigation, however ground water supplies arebeing exhausted due to reduced precipitation and intensive irrigation. In this research droughttolerance of 10 commercial potato cultivars was studied at three irrigation treatments (100%,80% and 60% of required irrigation water) in Ardabil in a two years field study, 2013-2014.At harvest, marketable tuber yield, tuber weight per plant, mean tuber weight, tuber number perplant, percent tuber dry matter, plant height and the main stem diameter were measured. Alsothe stress indices such as water stress susceptibility (SSI), tolerance (TOL), mean productivity(MP), geometric mean productivity (GMP) and stress tolerance (STI) were determined and usedto select the tolerant cultivars to water deficit. There were significant differences amongirrigation treatments, cultivars and cultivars × irrigation treatments for all studied traits; betweenyears and interaction of years × cultivars for marketable tuber yield, tuber weight per plant,mean tuber weight and tuber numbers per plant. The cultivar Satina produced the highestmarketable tuber yield, tuber weight per plant, mean tuber weight and plant height and also hadhigher MP, GMP and STI indices in all three irrigation treatments, therefore, it can berecommended for cultivation under water deficit condition. Cultivar Caesar showed the lowestSSI and TOL indices under both mild and severe water deficit conditions, therefore it can beused in breeding programs for developing drought–tolerant potato cultivars. Under both mildand severe stress conditions a high correlation was found between marketable tuber yield andplant height, but a negative correlation existed between mean tuber weight and tuber number perplant. Cultivar Savalan showed the highest tuber dry matter content.

Potato cultivars, Water deficit, Yield, Stress indices