Stephen Rehner - Academia.edu (original) (raw)
Papers by Stephen Rehner
Biological Control, 2021
Abstract The coffee berry borer Hypothenemus hampei (CBB) is a major pest of coffee, and the ento... more Abstract The coffee berry borer Hypothenemus hampei (CBB) is a major pest of coffee, and the entomopathogenic fungus Beauveria bassiana (Bb) is used worldwide for its biological control. Commercial formulations of Bb are sprayed on coffee, but local isolates of Bb may also provide some level of natural control. We compared selected local Bb isolates from CBB-infested coffee fruits in Puerto Rico against the commercial strain, GHA, derived from Mycotrol®. Isolates were tested for their virulence toward CBB in vitro. Two local isolates and the commercial isolate were sprayed on coffee plants in the field, and percent CBB infected, percent fruits with CBB damage, and number of CBB per fruit were surveyed over eight weeks in three consecutive years. Genotypes of Bb isolates in the field were discriminated with microsatellites to determine if isolates persisted after application. Several local isolates and mixtures of isolates were as virulent in vitro as the commercial isolate. In the field, all isolates significantly reduced CBB damage; one local isolate was more successful than the others. Genetic structure of local Bb populations varied from field to field and from year to year. Local isolates persisted; the commercial isolate did not, except in one plot. The commercial isolate may not be adapted to the warm, humid environment of coffee farms. Local isolates and perhaps combinations of isolates can provide more effective control, although current regulations preclude their use.
Applied and Environmental Microbiology, 2020
Genomic sequence data indicate certain fungi in the genus Metarhizium have the capacity to produc... more Genomic sequence data indicate certain fungi in the genus Metarhizium have the capacity to produce lysergic acid-derived ergot alkaloids, but accumulation of ergot alkaloids in these fungi has not been demonstrated previously. We assayed several Metarhizium species grown under different conditions for accumulation of ergot alkaloids. Isolates of M. brunneum and M. anisopliae accumulated the lysergic acid amides lysergic acid α-hydroxyethyl amide, ergine, and ergonovine on sucrose-yeast extract agar but not on two other tested media. Isolates of six other Metarhizium species did not accumulate ergot alkaloids on sucrose-yeast extract agar. Conidia of M. brunneum lacked detectable ergot alkaloids, and mycelia of this fungus secreted over 80% of their ergot alkaloid yield into the culture medium. Isolates of M. brunneum, M. flavoviride, M. robertsii, M. acridum, and M. anisopliae produced high concentrations of ergot alkaloids in infected larvae of the model insect Galleria mellonella,...
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](IMA fungus, 2017
The ending of dual nomenclatural systems for pleomorphic fungi in 2011 requires the reconciliatio... more The ending of dual nomenclatural systems for pleomorphic fungi in 2011 requires the reconciliation of competing names, ideally linked through culture based or molecular methods. The phylogenetic systematics of and its many genera have received extensive study in the last two decades, however resolution of competing names in has not yet been addressed. Here we present a molecular phylogenetic investigation of that enables identification of competing names in this family, and provides the basis upon which these names can be maintained or suppressed. The taxonomy presented here seeks to harmonize competing names by principles of priority, recognition of monophyletic groups, and the practical usage of affected taxa. In total, we propose maintaining nine generic names, and and the rejection of eight generic names, , , , and . Two new generic names, and , and a new species, , are described. New combinations are also proposed in the genera and
Molecular ecology, Jan 13, 2017
Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (A... more Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (Atta, Acromyrmex) range from Argentina to the USA, with the greatest species diversity in southern South America. We elucidate the biogeography of fungi cultivated by leafcutter ants using DNA-sequence and microsatellite-marker analyses of 474 cultivars collected across the leafcutter range. Fungal cultivars belong to two clades (Clade-A, Clade-B). The dominant and widespread Clade-A cultivars form three genotype-clusters, with their relative prevalence corresponding to southern South America, northern South America, and Central & North America. Admixture between Clade-A populations support genetic exchange within a single species, Leucocoprinus gongylophorus. Some leafcutter species that cut grass as fungicultural substrate are specialized to cultivate Clade-B fungi, whereas leafcutters preferring dicot plants appear specialized on Clade-A fungi. Cultivar sharing between sympatric leafcu...
Science, 1998
Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 mil... more Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 million years ago. The subsequent evolutionary history of this agricultural symbiosis was inferred from phylogenetic and population-genetic patterns of 553 cultivars isolated from gardens of “primitive” fungus-growing ants. These patterns indicate that fungus-growing ants succeeded at domesticating multiple cultivars, that the ants are capable of switching to novel cultivars, that single ant species farm a diversity of cultivars, and that cultivars are shared occasionally between distantly related ant species, probably by lateral transfer between ant colonies.
Trends in Ecology & Evolution, 1999
Mycologia, Jan 12, 2016
In fungi, stable diploid genome arrangements are rare. Here we present evidence from nuclear inte... more In fungi, stable diploid genome arrangements are rare. Here we present evidence from nuclear intergenic DNA sequencing, microsatellite genotyping, and configuration of the mating-type locus to demonstrate two independent origins of persistent diploid genome organization in the Metarhizium majus species complex. Most taxa in the complex are genotypically haploid, with individual isolates consistently displaying a single allele across all nuclear loci, as well as having a single mating-type locus. In contrast, individuals of M. majus and the clade designated here MGT1 are shown to be diploid, based on a consistent finding of heterozygosity and the presence of both MAT1 and MAT2 mating-type loci. In single locus phylogenies, nuclear intergenic alleles of M. majus and MGT1 each form monophyletic groups, indicating that diploidy in both taxa likely originated by the union of conspecific individuals. Sequence divergence in the APN2/MAT1-1-3 and APN2/MAT2-1 intergenic spacers indicate the ...
Molecular Ecology Notes, Sep 1, 2003
Journal of invertebrate pathology, Jan 22, 2015
Cross-species transferability of 41 previously published simple sequence repeat (SSR) markers was... more Cross-species transferability of 41 previously published simple sequence repeat (SSR) markers was assessed for 11 species of the entomopathogenic fungus Metarhizium. A collection of 65 Metarhizium isolates including all 54 used in a recent phylogenetic revision of the genus were characterized. Between 15 and 34 polymorphic SSR markers produced scorable PCR amplicons in seven species, including M. anisopliae, M. brunneum, M. guizhouense, M. lepidiotae, M. majus, M. pingshaense, and M. robertsii. To provide genotyping tools for concurrent analysis of these seven species fifteen markers grouped in five multiplex pools were selected based on high allelic diversity and easy scorability of SSR chromatograms.
Mycologia
The genus Metarhizium historically refers to green-spored asexual insect pathogenic fungi. Throug... more The genus Metarhizium historically refers to green-spored asexual insect pathogenic fungi. Through culturing and molecular methods, Metarhizium has been linked to Metacordyceps sexual states. Historically fungal nomenclature has allowed separate names for the different life stages of pleomorphic fungi. However, with the move to one name for one fungus regardless of life stage, there is a need to determine which name is correct. For Metarhizium the situation is complicated by the fact that Metacordyceps sexual states are interspersed among additional asexual genera, including Pochonia, Nomuraea and Paecilomyces. Metarhizium has priority as the earliest available name, but delimiting the boundaries of this genus remains problematic. To clarify relationships among these taxa we have obtained representative material for each genus and established a molecular dataset of the protein-coding genes BTUB, RPB1, RPB2 and TEF. The resulting phylogeny supports Metarhizium combining the majority ...
Journal of Insect Science, 2004
Environmental Microbiology, 2015
Fungi in the genus Metarhizium are insect pathogens able to function in other niches, including s... more Fungi in the genus Metarhizium are insect pathogens able to function in other niches, including soil and plant rhizosphere habitats. In agroecosystems, cropping and tillage practices influence soil fungal communities with unknown effects on the distribution of Metarhizium, whose presence can reduce populations of crop pests. We report results from a selective media survey of Metarhizium in soils sampled from a long-term experimental farming project in the mid-Atlantic region. Field plots under soybean cultivation produced higher numbers of Metarhizium colony-forming units (cfu) than corn or alfalfa. Plots managed organically and via chisel-till harboured higher numbers of Metarhizium cfu than no-till plots. Sequence typing of Metarhizium isolates revealed four species, with M. robertsii and M. brunneum predominating. The M. brunneum population was essentially fixed for a single clone as determined by multilocus microsatellite genotyping. In contrast, M. robertsii was found to contain significant diversity, with the majority of isolates distributed between two principal clades. Evidence for recombination was observed only in the most abundant clade. These findings illuminate multiple levels of Metarhizium diversity that can be used to inform strategies by which soil Metarhizium populations may be manipulated to exert downward pressure on pest insects and promote plant health.
Biological Control, 2021
Abstract The coffee berry borer Hypothenemus hampei (CBB) is a major pest of coffee, and the ento... more Abstract The coffee berry borer Hypothenemus hampei (CBB) is a major pest of coffee, and the entomopathogenic fungus Beauveria bassiana (Bb) is used worldwide for its biological control. Commercial formulations of Bb are sprayed on coffee, but local isolates of Bb may also provide some level of natural control. We compared selected local Bb isolates from CBB-infested coffee fruits in Puerto Rico against the commercial strain, GHA, derived from Mycotrol®. Isolates were tested for their virulence toward CBB in vitro. Two local isolates and the commercial isolate were sprayed on coffee plants in the field, and percent CBB infected, percent fruits with CBB damage, and number of CBB per fruit were surveyed over eight weeks in three consecutive years. Genotypes of Bb isolates in the field were discriminated with microsatellites to determine if isolates persisted after application. Several local isolates and mixtures of isolates were as virulent in vitro as the commercial isolate. In the field, all isolates significantly reduced CBB damage; one local isolate was more successful than the others. Genetic structure of local Bb populations varied from field to field and from year to year. Local isolates persisted; the commercial isolate did not, except in one plot. The commercial isolate may not be adapted to the warm, humid environment of coffee farms. Local isolates and perhaps combinations of isolates can provide more effective control, although current regulations preclude their use.
Applied and Environmental Microbiology, 2020
Genomic sequence data indicate certain fungi in the genus Metarhizium have the capacity to produc... more Genomic sequence data indicate certain fungi in the genus Metarhizium have the capacity to produce lysergic acid-derived ergot alkaloids, but accumulation of ergot alkaloids in these fungi has not been demonstrated previously. We assayed several Metarhizium species grown under different conditions for accumulation of ergot alkaloids. Isolates of M. brunneum and M. anisopliae accumulated the lysergic acid amides lysergic acid α-hydroxyethyl amide, ergine, and ergonovine on sucrose-yeast extract agar but not on two other tested media. Isolates of six other Metarhizium species did not accumulate ergot alkaloids on sucrose-yeast extract agar. Conidia of M. brunneum lacked detectable ergot alkaloids, and mycelia of this fungus secreted over 80% of their ergot alkaloid yield into the culture medium. Isolates of M. brunneum, M. flavoviride, M. robertsii, M. acridum, and M. anisopliae produced high concentrations of ergot alkaloids in infected larvae of the model insect Galleria mellonella,...
IMA fungus, 2017
The ending of dual nomenclatural systems for pleomorphic fungi in 2011 requires the reconciliatio... more The ending of dual nomenclatural systems for pleomorphic fungi in 2011 requires the reconciliation of competing names, ideally linked through culture based or molecular methods. The phylogenetic systematics of and its many genera have received extensive study in the last two decades, however resolution of competing names in has not yet been addressed. Here we present a molecular phylogenetic investigation of that enables identification of competing names in this family, and provides the basis upon which these names can be maintained or suppressed. The taxonomy presented here seeks to harmonize competing names by principles of priority, recognition of monophyletic groups, and the practical usage of affected taxa. In total, we propose maintaining nine generic names, and and the rejection of eight generic names, , , , and . Two new generic names, and , and a new species, , are described. New combinations are also proposed in the genera and
Molecular ecology, Jan 13, 2017
Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (A... more Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (Atta, Acromyrmex) range from Argentina to the USA, with the greatest species diversity in southern South America. We elucidate the biogeography of fungi cultivated by leafcutter ants using DNA-sequence and microsatellite-marker analyses of 474 cultivars collected across the leafcutter range. Fungal cultivars belong to two clades (Clade-A, Clade-B). The dominant and widespread Clade-A cultivars form three genotype-clusters, with their relative prevalence corresponding to southern South America, northern South America, and Central & North America. Admixture between Clade-A populations support genetic exchange within a single species, Leucocoprinus gongylophorus. Some leafcutter species that cut grass as fungicultural substrate are specialized to cultivate Clade-B fungi, whereas leafcutters preferring dicot plants appear specialized on Clade-A fungi. Cultivar sharing between sympatric leafcu...
Science, 1998
Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 mil... more Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 million years ago. The subsequent evolutionary history of this agricultural symbiosis was inferred from phylogenetic and population-genetic patterns of 553 cultivars isolated from gardens of “primitive” fungus-growing ants. These patterns indicate that fungus-growing ants succeeded at domesticating multiple cultivars, that the ants are capable of switching to novel cultivars, that single ant species farm a diversity of cultivars, and that cultivars are shared occasionally between distantly related ant species, probably by lateral transfer between ant colonies.
Trends in Ecology & Evolution, 1999
Mycologia, Jan 12, 2016
In fungi, stable diploid genome arrangements are rare. Here we present evidence from nuclear inte... more In fungi, stable diploid genome arrangements are rare. Here we present evidence from nuclear intergenic DNA sequencing, microsatellite genotyping, and configuration of the mating-type locus to demonstrate two independent origins of persistent diploid genome organization in the Metarhizium majus species complex. Most taxa in the complex are genotypically haploid, with individual isolates consistently displaying a single allele across all nuclear loci, as well as having a single mating-type locus. In contrast, individuals of M. majus and the clade designated here MGT1 are shown to be diploid, based on a consistent finding of heterozygosity and the presence of both MAT1 and MAT2 mating-type loci. In single locus phylogenies, nuclear intergenic alleles of M. majus and MGT1 each form monophyletic groups, indicating that diploidy in both taxa likely originated by the union of conspecific individuals. Sequence divergence in the APN2/MAT1-1-3 and APN2/MAT2-1 intergenic spacers indicate the ...
Molecular Ecology Notes, Sep 1, 2003
Journal of invertebrate pathology, Jan 22, 2015
Cross-species transferability of 41 previously published simple sequence repeat (SSR) markers was... more Cross-species transferability of 41 previously published simple sequence repeat (SSR) markers was assessed for 11 species of the entomopathogenic fungus Metarhizium. A collection of 65 Metarhizium isolates including all 54 used in a recent phylogenetic revision of the genus were characterized. Between 15 and 34 polymorphic SSR markers produced scorable PCR amplicons in seven species, including M. anisopliae, M. brunneum, M. guizhouense, M. lepidiotae, M. majus, M. pingshaense, and M. robertsii. To provide genotyping tools for concurrent analysis of these seven species fifteen markers grouped in five multiplex pools were selected based on high allelic diversity and easy scorability of SSR chromatograms.
Mycologia
The genus Metarhizium historically refers to green-spored asexual insect pathogenic fungi. Throug... more The genus Metarhizium historically refers to green-spored asexual insect pathogenic fungi. Through culturing and molecular methods, Metarhizium has been linked to Metacordyceps sexual states. Historically fungal nomenclature has allowed separate names for the different life stages of pleomorphic fungi. However, with the move to one name for one fungus regardless of life stage, there is a need to determine which name is correct. For Metarhizium the situation is complicated by the fact that Metacordyceps sexual states are interspersed among additional asexual genera, including Pochonia, Nomuraea and Paecilomyces. Metarhizium has priority as the earliest available name, but delimiting the boundaries of this genus remains problematic. To clarify relationships among these taxa we have obtained representative material for each genus and established a molecular dataset of the protein-coding genes BTUB, RPB1, RPB2 and TEF. The resulting phylogeny supports Metarhizium combining the majority ...
Journal of Insect Science, 2004
Environmental Microbiology, 2015
Fungi in the genus Metarhizium are insect pathogens able to function in other niches, including s... more Fungi in the genus Metarhizium are insect pathogens able to function in other niches, including soil and plant rhizosphere habitats. In agroecosystems, cropping and tillage practices influence soil fungal communities with unknown effects on the distribution of Metarhizium, whose presence can reduce populations of crop pests. We report results from a selective media survey of Metarhizium in soils sampled from a long-term experimental farming project in the mid-Atlantic region. Field plots under soybean cultivation produced higher numbers of Metarhizium colony-forming units (cfu) than corn or alfalfa. Plots managed organically and via chisel-till harboured higher numbers of Metarhizium cfu than no-till plots. Sequence typing of Metarhizium isolates revealed four species, with M. robertsii and M. brunneum predominating. The M. brunneum population was essentially fixed for a single clone as determined by multilocus microsatellite genotyping. In contrast, M. robertsii was found to contain significant diversity, with the majority of isolates distributed between two principal clades. Evidence for recombination was observed only in the most abundant clade. These findings illuminate multiple levels of Metarhizium diversity that can be used to inform strategies by which soil Metarhizium populations may be manipulated to exert downward pressure on pest insects and promote plant health.