| Maize gray leaf spot (GLS) is a world important disease caused by Gercospora zeae-maydisTehon&Daniels. Since the 1990's, with the widely planting of susceptible varieties, the disease occurred seriously year by year and becomes the main disease in northeast China maize spring-sowing area. It is well-known that development and cultivation resistant varieties is the most effective way to control gray leaf spot. The effect of resistant breeding depends on the selection and identification of resistant sources and the understanding of the genetic rule of resistant genes. In this pape, the preliminary study of maize gray leaf spot was carried out from three ways: evaluation of resistant respone of germplasm, identification and validation disease resistant gene loci by backcrossing lines and development of molecular markers linked to disease resistance. The main results are as following:(1) The evaluation of 66 maize inbred lines for resistance to GLS was carried out at three locations in one year under the natural conditions. After disease evaluation, we identified 2 (3.1%), 15 (22.7%) and 13(19.7%) lines offering from high, moderate and low resistance to GLS, respectively. Comprehensive differences were observed on the mean of GLS disease scale among the six groups (PA, Lüda Red Cob, BSSS, PB and Lancaster) with the highest scale of 8.00 for Lüda Red Cob, and 7.52, 6.96, 6.87, 5.67, 3.00 for Sipingtou, PA, BSSS, Lancaster and PB, respectively. The PB group was identified as the important source of resistance to GLS.(2) Six GLS resistant plants were selected from BC4F4 lines of (Ye478×SH15)×Ye478 with artificial inoculation. It was verified that methods of the GLS pathogen culturing on the medium of maize flour CaCO3 agar and the artificial injection of spore suspension were feasible.Genotypes of 6 resistance individuals were analyzed with SSR markers. Using linkage disequilibrium mapping method, three chromsome regions respectively on 3(3.08), 5(5.03) and 8(8.05-8.06) related to GLS resistance were detected, and expressed additive effects.(3) By using BSA method, resistant and susceptible bulks were constructed with 10 resistant and 10 susceptible inbred lines, respectively. 54 polymorphic AFLP primers were selected between two bulks from 100 pairs of AFLP primers. 8 polymorphic AFLP markers were verified among 20 maize inbred lines. The polymorphic fragments were cloned and sequenced, and furthermore the AFLP marker (P51M38-200) was converted into SCAR marker (Scar-100) sucessfully. Genotype of 66 inbred lines was analyzed using SCAR marker (Scar-100). Association analysis of marker genotype with resistance phenotype showed that Scar-100 marker was highly correlated with gray leaf spot resistance. The Scar-100 marker genotypes of 6 resistant plants from BC4F4 lines of (Ye478×SH15)×Ye478 were high consistent with that of resistant parental line. Using Mo17×HZ4 (190 F2 individuals) and X178×B73 (181 F8 family lines), Scar-100 makrer was mapped on chromosome 3 (umc1399- bnlg1754/umc1320-bnlg1754). Scar-100 marker shows the potential utilization in marker-assisted breeding for gray leaf spot resistance in maize.
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