Physiological races ofExserohilum turcicum in Israel

A set of differentials of corn plants(Zea mays L.) containing Ht1, Ht2, Ht3 or HtN genes was used to identify races ofExserohilum turcicum in Israel. Plants were inoculated with 14 isolates ofE. turcicum collected from various regions in Israel (from Ayyelet HaShahar in the north to Sa’ad in the south). Differentials containing Ht1, Ht2, Ht3 or HtN genes were resistant to the 14 isolates tested, whereas the inbred lines without Ht genes were highly sensitive. Resistance was characterized by the formation of non-sporulating chlorotic lesions. When plants containing Ht1, Ht2 or Ht3 genes were inoculated with relatively high inoculum concentrations (over 50 conidia/drop), chlorotic lesions were associated with necrosis in the center of the lesions. Sporulation of the fungus in the necrotic parts of the lesions was significantly less than on plants without Ht genes. No necrosis was observed in plants with the HtN gene. Our results indicate that the physiological race ofE. turcicum in Israel is race 1.