Root mass and depth, stolons and roots formed on stolons in four cultivars of potato under water stress

Four potato cultivars (Solanum tuberosum L.) differing in their precocity and contrasted for their drought tolerance were investigated in the field and two of them in the greenhouse. They were subjected to two water treatments, well irrigated and droughted. We followed the evolution of stolon number, stolon length, mass of roots and the adventitious roots which are formed on stolons. Our objective was to check the response of those characters to water shortage throughout the cycle, and examine if they could have, especially the adventitious roots on stolons, contributed to drought tolerance. All physiological and agronomical studied parameters were sensitive to drought. Maximum root dry mass was reduced by drought. Stolon number was enhanced by drought but the total length of stolons, was reduced. The number of the adventitious roots on stolons was reduced by drought and negatively related to root dry mass of the plant. Fresh tuber yield was significantly correlated to root dry mass in the field and drought tolerance index was significantly associated to root depth in the field, but in stressed conditions only.