Yazar "Peever, T. L." seçeneğine göre listele

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    Contrasting species boundaries between sections Alternaria and Porri of the genus Alternaria
    (Wiley, 2018) Ozkilinc, H.; Rotondo, F.; Pryor, B. M.; Peever, T. L.
    The fungal genus Alternaria comprises a large number of asexual taxa with diverse ecological, morphological and biological modes ranging from saprophytes to plant pathogens. Understanding the speciation processes affecting asexual fungi is important for estimating biological diversity, which in turn affects plant disease management and quarantine enforcement. This study included 106 isolates of Alternaria representing five phylogenetically defined clades in two sister sub-generic groups: section Porri (A.dauci, A.solani and A.limicola) and section Alternaria (A.alternata/tenuissima and A.arborescens). Species in section Porri are host-specific while species in section Alternaria have wider host ranges. For each isolate, DNA sequences of three genes (Alt a1, ATPase, Calmodulin) were used to estimate phylogenies at the population and species levels. Three multilocus haplotypes were distinguished among A.dauci isolates and only one haplotype among A.solani and A.limicola isolates, revealing low or no differentiation within each taxon and strong clonal structure for taxa in this section. In contrast, 37 multilocus haplotypes were found among A.alternata/tenuissima isolates and 21 multilocus haplotypes among A.arborescens isolates, revealing much higher genotypic diversity and multiple clonal lineages within taxa, which is not typical of asexual reproducing lineages. A species tree was inferred using a Yule Speciation model and a strict molecular clock assumption. Species boundaries were well defined within section Porri. However, species boundaries within section Alternaria were only partially resolved with no well-defined species boundaries, possibly due to incomplete lineage sorting. Significant association with host specificity seems a driving force for speciation.
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    Population structure and reproductive mode of Didymella fabae in Syria
    (Wiley, 2015) Ozkilinc, H.; Thomas, K.; Abang, M.; Peever, T. L.
    Didymella fabae is a highly destructive fungal pathogen of faba bean (Vicia faba) that represents a significant yield-limiting biotic constraint in all locations where the crop is grown. However, nothing is known about the population structure of this pathogen anywhere in the world. Population genetic analyses employing 18 sequence-tagged microsatellite (STMS) markers covering eight genetic linkage groups and a PCR-based mating type marker were used to elucidate the genetic structure and reproductive mode of the pathogen in three populations in Syria. High gene diversity within populations but low genetic differentiation among populations was observed and the entire collection of isolates was assigned to a single genetic population using a Bayesian clustering algorithm. Independent analyses were performed based on four unlinked sets of STMS markers to infer reproductive mode. A simulation approach was used to estimate which of the repeated multilocus genotypes were probably the result of asexual reproduction and should be clone-corrected. A 1:1 ratio of mating types could not be rejected in any clone-corrected population, probably due to small sample sizes. Likewise, frequency of clones and sample size, but not marker linkage, had strong effects on multilocus gametic disequilibrium. The null hypothesis of random mating was rejected in the majority of populations for both non-clone-corrected and clone-corrected samples and with four sets of unlinked markers indicating a predominance of asexual reproduction in these populations. This represents the first detailed screening of clonal and genetic composition of D. fabae populations in Syria.