A. Nachmias et al. (1993) Phytoparasitica 21(3):245-255 Effects of Salinity and Its Interactions with Disease Incidence on Potatoes Grown in Hot Climates A. Nachmias, 1 Z. Kaufman, 1 L. Livescu, 1 L. Tsror, 1 A. Meiri 2 and P.D.S. Caligari 3 The interaction of two diseases - Verticillium wilt, caused by Verticillium dahliae, and early blight, caused by Alternaria solani - with salinity was investigated. The use of a system of two overlapping overhead irrigation lines enabled results to be obtained under a continuous gradient of salinity. Three cultivars were investigated, namely, Cara, D6sir& and Nicola. The results illustrate the increase in symptom expression of the two diseases, as well as in associated characters such as height and maturity, in the presence of salt. Differences existed between cultivars in their response to the diseases in the presence of varying levels of salt. KEY WORDS: Potatoes; irrigation water, salinity of; semi-arid conditions; VerticiUium wilt; early blight; Verticillium dahliae; Alternaria solani. INTRODUCTION The potato (Solanum tuberosum) is a vegetable crop which is moderately sensitive to salinity in water and soil (7,13). In the past few years reports appeared on the responses of commercial potato cultivars (2,3) and wild potato species (11,12) to saline water in glasshouse experiments with pot-grown plants. There are, however, few reports of experiments under field conditions, particularly any relating the effect of salinity to disease incidence. Potatoes are cultivated in hot climates, under irrigation, in a number of countries. This is most successful when the water and fertilizers applied to the crop are carefully controlled. However, even under these conditions the maximum yield obtained is not as high as the maximum potential yield. This is a result of a number of limiting factors which generally take the form of stresses such as heat, drought (which can even be present under irrigated conditions, at certain times or periods) and, in many cases, diseases. VerticiUium wilt and early blight, caused by Verticillium dahliae and Alternaria solani, respectively, are diseases which can be major limiting factors to potatoes growing Received March 11, 1993; received in final form June 30, 1993. ~Gilat Experiment Station, ARO, M.P. Negev 2, 85280, Israel. [Telefax: 972-57-926485] 2Dept. of Environmental Physiology and Irrigation, ARO, The Volcani Center, Bet Dagan 50250, Israel. 3Dept. of Agricultural Botany, School of Plant Sciences, University of Reading, Reading RG6 2AS, UK. Phytoparasitica 21:3, 1993 245