Ginzberg, I., Agricultural Research Organization, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Minz, D., Agricultural Research Organization, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Faingold, I., Agricultural Research Organization, Gilat Research Center, D.N. Negev 2, Negev 85280, Israel
Soriano, S., Agricultural Research Organization, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Mints, M., Agricultural Research Organization, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Fogelman, E., Agricultural Research Organization, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Warshavsky, S., Hevel Maon Enterprises, M.P. Hanegev, Negev 85465, Israel
Zig, U., Hevel Maon Enterprises, M.P. Hanegev, Negev 85465, Israel
Yermiyahu, U., Agricultural Research Organization, Gilat Research Center, D.N. Negev 2, Negev 85280, Israel

Russeting of smooth-skinned potato varieties affect the protective characteristics of the skin against water loss and pathogens invasion. A distinctive russeting disorder, differs from previously reported tuber blemishes, has been observed in the Negev area of Israel and was named 'Magen russeting' after one of the repeatedly affected plots. The russeted skin appears as protruding dark-brown patches on the surface of the tubers. Histological studies identified the russet as old skin cells that remain adhered to the newly formed skin layers below them. Phytopathological tests and rDNA pyrosequencing analysis for whole bacterial community suggested that 'Magen russeting' is a physiological disorder. Mineral analysis of isolated pure skin samples indicated that russeted skin areas have higher concentrations of Ca and lower concentrations of K than the smooth skin of normal tubers, irrespective of CaCl 2 or KCl fertilization of the soil prior to sowing, or of the irrigation regime during the growing season. Nevertheless, application of CaCl 2 prior to tuber-seed sowing reduces the rate of affected mature tubers and the severity of the russeting. © 2012 Potato Association of America.