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  • 1
    Electronic Resource
    Electronic Resource
    Molecular marker analysis of European Setosphaeria turcica populations (1998)
    Springer
    European journal of plant pathology 104 (1998), S. 611-617 
    Details
    ISSN: 1573-8469
    Keywords: Exserohilum turcicum ; Johnson grass ; maize ; northern corn leaf blight ; population genetic structure ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Setosphaeria turcica is the causal agent of northern corn leaf blight, a foliar maize disease of worldwide economic importance. In Europe, its severity increases. To investigate the pathogen's population-genetic structure in central Europe, a total of 80 isolates was sampled in Germany, Switzerland, France, Austria, and Hungary and investigated with 52 random amplified polymorphic DNA (RAPD) markers. The mating type of the isolates was determined in testcrosses. Among the 73 isolates from maize there were 26 different RAPD haplotypes. All isolates with identical haplotype are considered clonemates. The haplotype shared by most members was represented by 22 isolates from Germany, Switzerland, and France, indicating high fitness and substantial migration. Only a single clone had members in both southeastern Austria and southwestern Switzerland, suggesting that the Alps constitute a major barrier for this pathogen. Several haplotypes differed by only one or two RAPD bands from the predominant haplotype and may have arisen by mutation. Few other clonal lineages were detected. The evolution of some haplotypes could not be explained by mutation alone. Sexual recombination may rarely occur. In population samples from Germany, Switzerland, and France, mating type MAT2 was predominating, while most isolates from Austria and Hungary had MAT1. Seven isolates from Johnson grass (Sorghum halepense), an alternative host of S. turcica, were clonemates and very different in RAPD haplotypes from all isolates collected from maize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008641920356
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  • 2
    Electronic Resource
    Electronic Resource
    Gametic phase disequilibria in populations of race 2 and race 3 ofCochliobolus carbonum (1995)
    Springer
    European journal of plant pathology 101 (1995), S. 301-310 
    Details
    ISSN: 1573-8469
    Keywords: Bipolaris zeicola ; maize ; multilocus haplotypes ; Northern Corn Leaf Spot ; sexual reproduction ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Over 3 years 15 samples ofC. carbonum were collected from 11 corn fields in North Carolina and Tennessee. Among 514 isolates of race 2 and 319 isolates of race 3, five phenotypic characters (mating type, production of pseudothecia, production of asci and ascospores, tolerance to cycloheximide and carboxin, respectively) that are controlled by single genes at unlinked loci (Mat, Psu, Asc, Cyh, Crb) were examined. Gametic phase disequilibrium (GPD) was analyzed by three methods. First, observed and expected four-locus haplotype frequencies were compared inG-tests for goodness of fit (method 1) and second, four-locus disequilibrium was calculated using an index of association which is based on the variance of the number of loci at which two isolates in a given population differ (method 2). Third, observed and expected frequencies of allele pairs were compared in 2×2 contingency tables (method 3). Each test was performed on individual and pooled samples which also allowed assessment of heterogeneity among samples. In general this heterogeneity was low, i.e. the consistency of associations among samples was high. Four-locus disequilibrium was significant in race 2 with method 1 but not with method 2. In race 3 we found no disequilibrium with any of the two methods. Method 3 indicated that several allele pairs were significantly associated in race 2 but not race 3. Thus GPD was significant in race 2 but not in race 3. Mating type frequencies were close to 0.50 in race 2 and race 3. This and the non-significant index of association indicate that the sexual stage ofC. carbonum is operating within each of the two race populations. It is suggested that selection favours different haplotypes in the asexual than in the sexual stage of the pathogen. Such disruptive selection may have maintained polymorphisms of genes related to sexual fertility and stabilized gene frequencies inC. carbonum over a period of 15 years (1972–1987).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01874786
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