title: Lack of Population Structure and Mixed Reproduction Modes in Exserohilum turcicum from South Africa.
abstract: Exserohilum turcicum is the causal agent of northern corn leaf blight, a destructive foliar disease of maize that results in yield losses worldwide. In South Africa, typical yield losses range from 15 to 30%. Previous studies found high haplotypic diversity with evidence for sexual recombination in E. turcicum populations from tropical climates such as Kenya. However, the population genetic structure and method of reproduction of E. turcicum in South Africa is unknown and, therefore, was investigated. Twelve polymorphic microsatellite markers were screened on 258 E. turcicum isolates from maize collected during 2012 and 2013 from three maize fields in South Africa. A multiplex polymerase chain reaction assay amplifying both mating type idiomorphs was applied to investigate the distribution of mating types. No distinct genetic clusters were observed. Shared haplotypes were identified between isolates separated by distances of up to 762 km, which provided evidence of migration. High haplotypic diversity indicated that sexual reproduction is occurring among E. turcicum isolates, although mating type ratios and linkage disequilibrium analyses did not support the hypothesis of random mating. The population genetic structure of E. turcicum in South Africa is likely due to the direct movement and spread of isolates undergoing a mixed reproductive lifecycle.
authors.affiliation: First and fourth authors: Department of Plant and Soil Sciences, and second author: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa; and third author: Agricultural Research Council-Grain Crops Institute, Potchefstroom, 2520, South Africa.
authors.forename: Maria Petronella
authors.identifier: 0000-0002-0155-289X
authors.initials: MP
authors.lastname: Human
authors.affiliation: First and fourth authors: Department of Plant and Soil Sciences, and second author: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa; and third author: Agricultural Research Council-Grain Crops Institute, Potchefstroom, 2520, South Africa.
authors.forename: Irene
authors.initials: I
authors.lastname: Barnes
authors.affiliation: First and fourth authors: Department of Plant and Soil Sciences, and second author: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa; and third author: Agricultural Research Council-Grain Crops Institute, Potchefstroom, 2520, South Africa.
authors.forename: Maryke
authors.initials: M
authors.lastname: Craven
authors.affiliation: First and fourth authors: Department of Plant and Soil Sciences, and second author: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa; and third author: Agricultural Research Council-Grain Crops Institute, Potchefstroom, 2520, South Africa.
authors.forename: Bridget Genevieve
authors.initials: BG
authors.lastname: Crampton
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000302:isolation & purification; D049770:Genes, Mating Type, Fungal / Q000235:genetics; D008040:Genetic Linkage; D040342:Genetic Structures; D005828:Genetics, Population; D005843:Geography; D006239:Haplotypes; D018895:Microsatellite Repeats / Q000235:genetics; D010935:Plant Diseases / Q000382:microbiology*; D013019:South Africa; D003313:Zea mays / Q000382:microbiology*