OCCURRENCE OF EXSEROHILUM-TURCICUM ON MAIZE IN UGANDA

Incidence and severity of northern leaf blight were assessed 3-4 wk after mid-silking on 20 maize plants in each of 115 maize fields in Uganda in 1989. Sampling dates for the maize fields ranged from 6 November to 31 December. Northern leaf blight was prevalent in all 115 fields but was most severe in the wet and humid zones around Lake Victoria. Maize differentials containing Ht1, Ht2, Ht3, or HtN genes were used to identify races of Exserohilum turcicum present in Uganda. Maize inbred lines containing Ht1, Ht2, Ht3, or HtN genes were resistant to 215 isolates tested, whereas those without Ht genes showed necrotic susceptible reactions, a virulence pattern recently designated as race 0. Results indicate that race 0 is in Uganda. The mating type (MAT) of the Ugandan isolates was determined by pairing the isolates from Uganda with tester isolates of the known mating types, A or a. Forty-four of the 189 isolates studied formed fertile pseudothecia, 36 were MATa and eight were MATA.