APS Homepage

Poster: Biology & Disease Mgmt: Mycology


Genetic mapping of pathogenesis in the northern corn leaf blight fungus
S. MIDEROS (1), C. Chung (2), J. Poland (3), G. Turgeon (4), R. Nelson (4) (1) University of Illinois at Urbana Champaign, U.S.A.; (2) National Taiwan University, Taiwan; (3) Kansas State University, U.S.A.; (4) Cornell University, U.S.A.

Setosphaeria turcica (=Exserohilum turcicum) causes northern leaf blight (NLB) of maize (Zea mays). Identification of genes associated with pathogenesis/virulence suggests possible targets for control, generates molecular tools to characterize populations of the pathogen, and provides valuable information to breeders and maize geneticists. In this study we used a forward genetics approach to i) identify fungal genes that determine race-specific reactions with two maize resistance genes, and ii) determine the genetic regions for other virulence mechanisms in the pathogen. We generated a cross between a race 1 and a race 23N strain and collected 220 single-ascosporic progeny. The ability of each progeny to cause disease on maize lines with or without the Ht1 and Ht2 genes was evaluated in greenhouse experiments. Mycelial abundance, radial growth, sporulation and melanin content were visually evaluated on artificial media. Genotyping-by-sequencing generated 2,078 single nucleotide polymorphic markers (SNPs). Using 310 high-quality SNPs we calculated a genetic map composed of 22 linkage groups spanning 1981.1 cM. Genetic mapping pinpointed regions of interest for the avrHt1, avrHt2, and the melanin biosynthetic locus, as well as quantitative trait loci for mycelial abundance, speed of growth, and sporulation. Molecular markers for the identification of fungal strains capable of causing disease in maize plants with Ht1 and Ht2 genes are being validated.