Identification Of Races And Induction Of Perfect Stage Of Exserohilum Turcicum

The Northern leaf blight of corn is an important leaf disease in most of the major corn-producing areas in the world caused by the fungus Exserohilum turcicum.47 isolates of Exserohilum turcicum collected from Hebei, Liaoning, Heilongj iang, Shandong, hIm and so on were provided for identification of physiological races of Exserohilum turcicum, induction of perfect stage of Exserohilurn turcicum and CTAB method of isolating DNA from Exserohilum turcicum for RAPD. 40 isolates of Exserohilum turcicum were identified on Huangzao4.. 0H43 OH43HtI Huangzao4Ht2~ Huangzao4Ht3 and Huangzao4HtN in greenhouse collected in 1999. The experimental results showed that 19 isolates were race O,the frequency was 47.5%; 7 isolates were race 1, the frequency was 17.5%;3 isolates were race 12, the frequency was 7.5%;l isolates was race 13, the frequency was 2.5%;2 isolates were race 3, the frequency was 5%;3 isolates were race IN, the frequency was 7.5%;3 isolates were race 23, the frequency was 7.5%;1 isolates was race 2N. the frequency was 2.5%;1 isolates was race 3N, the frequency was 2.5%.The results indicated that the physiologic specialization of these isolates was evident, race 0 was also the dominant race. As for their distribution, different races appear in one province and among provinces the physiologic specialization were different. The results also indicated that the detection of composition distribution and genetic variation of Exserohllwn turcicum was very important, the research of the genetic variation of races further would be the basis of research on toxin of Exse,vhi/u,n turcicum. 42 isolates of Exserohilum turcicum collected during 1999?000 were used to cross in plates. The experimental results indicated that ascocarp?sites of development and pattern of arrange, asci and ascospores were all described simply, and a little of asci with 8 ascosproes were examined; The results also indicated that ascocarps can developed on bare fragments of barley straw, bare fragments of wheat straw and bare corn stalks.As a means of reference, isolate No.99 14 was designated a strain, isolate No.9961 was designated a strain. By the two isolates, 42 isolates were examined for mating types. 24 were MATA, the frequency was 57.14%, 18 were MATa, the frequency was 42.86%.No isolates were examined which failed to mate with either ?or ?mating types.The results indicated that the favorable condition for perfect stage were: Sachs?agar, pH7.0,barley straw for substrate,25C,and with light. The results also suggested mature ascocarps can also develop with light for 12h or 24h without any substrates but in dark ascocarps can develop bu can mature. 14 isolates of Exserohilum turcicum collected in 1999 were cultured in liquid medium, DNA was isolated from the hyphae by CTAB method and were detected on 752-ultravioiet spectrometer then the DNA were amplified on thermal cycler PE-4800.The results showed that the ratios of 0D26010D280 of DNA range from 1 .730 to 1.847, and clear amplification maps was obtained after agarose gel electrophoresis. It concludes that the CTAB method is more effective in isolating DNA from Exserohilum turcicum for RAPD.