Race Variation Of Exserohihun Turcicum, Causal Agentof Northern Leaf Blight In China

Northern corn leaf blight or Turcicum leaf blight is the most serious disease in the maize growing areas all over the world. The occurrence and epidemics of this disease are affected by the composition and variation of Exserohilum turcicum population. This paper focuses on identifing in pathogenic variation to different Ht resistance gene and the population structure of the pathogen based on AFLP. The results are of significane to the resistant-breeding as well as to control variation of physiological races of Northern corn leaf blight.One hundred isolates of Exserohihun turcicum, collected from 23 provinces or cities in 2005 and 2006 were identified in pathogenic variation to different Ht resistance gene in chamber. The results showed that composition of the physiological races was complex in above 23 provinces or cities. There were 15 different races in the 100 isolates tested. Race 1, 0, N showed the higher frequency of 21%, 18%, 13%, followed by 13, 1N, 2, 123, 3N, 2N, 3, 23, 123N, 12, 12N, 23N with frequencies of 2%～8%. At the same time, physiological race variations in the North areas are higher than in the South areas.An AFLP protocol for analyzing Exserohilum turcicum was established after selecting the condition of react systems.The six isolates collected from different provinces were amplified with"1+1","1+2","2+2","2+3","3+3"primers complications.Twenty-six pairs of primers are polymorphic amplification in the strains of Exserohilum turcicum.Eleven pairs of primers were used for amplifying 90 isolates in above aeras. The results showed that there were no direct correlation among physiological races,genetic diversity and DNA polymorphism of the pathogen.