Marin Talbot Brewer

University of Georgia | UGA · Department of Plant Pathology

Azole drugs target fungal sterol biosynthesis and are used to treat millions of human fungal infections each year. Resistance to azole drugs has emerged in multiple fungal pathogens including Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum, and Aspergillus fumigatus. The most well-studied resistance mechanism in A. fumigatus arise...

Numerous plant-pathogenic fungi secrete necrotrophic effectors (syn. host-selective toxins) that are important determinants of pathogenicity and virulence in species that have a necrotrophic lifestyle. Corynespora cassiicola is a necrotrophic fungus causing emerging target spot epidemics in the southeastern United States (US). Previous studies reve...

Azole drugs target fungal sterol biosynthesis and are used to treat millions of human fungal infections each year. Resistance to azole drugs has emerged in multiple fungal pathogens including Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum , and Aspergillus fumigatus . The most well-studied resistance mechanism in A. fumigatus ari...

Grapevine downy mildew, caused by Plasmopara viticola, is among the most damaging diseases of grapes globally and in the viticultural regions of Georgia (U.S.A.). Although management of this disease typically involves fungicide applications, resistance development in P. viticola can render chemical management ineffective. The objective of this stud...

To better understand the evolution of virulence we are interested in identifying the genetic basis of this trait in pathogenic fungi and in developing tools for the rapid characterization of variation in virulence among populations associated with epidemics . Fusarium oxysporum f. sp. vasinfectum (FOV) is a haploid fungus that causes devastating ou...

Resistance to clinical antimicrobials is an urgent problem, reducing our ability to combat deadly pathogens of humans. Azole antimicrobials target ergosterol synthesis and are highly effective against fungal pathogens of both humans and plants leading to their widespread use in clinical and agricultural settings 1,2 . The fungus Aspergillus fumigat...

Uromyces transversalis , the causal agent of Gladiolus rust, is an invasive plant pathogen in the United States and is regulated as a quarantine pathogen in Europe. The aim of this research was to: (i) determine the origin of introductions of U. transversalis to the United States, (ii) track the movement of genotypes, and (iii) understand the world...

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (FON), occurs worldwide and is responsible for substantial yield losses in watermelon-producing areas of the southeastern United States. Management of this disease largely relies on the use of integrated pest management (i.e., fungicides, resistant cultivars, crop rotation, etc...

Previous phylogenetic studies of the grape downy mildew pathogen, Plasmopara viticola, revealed five cryptic species in eastern North America that differed in their host range and geographic distribution. Preliminary comparative studies also documented differences in temperature responses during infection between certain cryptic species, indicating...

Sensitivity monitoring of Venturia effusa, cause of pecan scab, has revealed insensitivity to fentin hydroxide and tebuconazole, but recent research indicates that the insensitivity to fentin hydroxide is not stable. A study was undertaken to determine if a fitness cost may be responsible for this instability. In this study, experiments were conduc...

Orange cane blotch affects commercial blackberry production in the southeastern United States, mainly in the Coastal Plain region. The causal agent is a slow-growing parasitic alga, Cephaleuros virescens, which has a wide host range. Disease development is linked to the biennial growth pattern of blackberry, whereby symptoms appear in the early fal...

BACKGROUND Gummy stem blight (GSB) is a devastating disease of cucurbits that has been effectively managed with fungicide applications. However, the Stagonosporopsis spp. that cause GSB have rapidly evolved resistance to multiple classes of fungicides. To better understand the evolution and persistence of fungicide resistance in field populations,...

The interaction between Fusarium oxysporum f. sp. vasinfectum (Fov) and Meloidogyne incognita (root-knot nematode) resulting in Fusarium wilt (FW) of cotton is well-known. Although Belonolaimus longicaudatus (sting nematode) can also interact with Fov and cause FW, it has long been believed that virtually all of the FW in Georgia is caused by the i...

Corynespora cassiicola is a destructive plant-pathogenic fungus causing widespread target spot epidemics, including outbreaks on cotton, soybean, and tomato in the southeastern United States. Previous studies revealed that populations from the three hosts are genetically distinct and host specialized. Although variation in aggressiveness to cotton...

Multilocus genotype (MLG) data for all isolates in this study. Isolate name, host, MLG, collection location, and allele size for 13 loci. (XLSX)

Corynespora cassiicola is a ubiquitous fungus causing emerging plant diseases worldwide, including target spot of cotton, soybean, and tomato, which have rapidly increased in incidence and severity throughout the southeastern United States. The objectives of this study were to understand the causes for the emerging target spot epidemics in the U.S....

The state of Georgia (U.S.A.), with its hot and humid climate, comprises an extreme and diverse environment for growing wine grapes. Vitis vinifera, V. aestivalis and French-American hybrids are produced in the foothills of the Appalachian Mountains in the north, whereas V. aestivalis, hybrids, and muscadine grapes (V. rotundifolia) are grown in th...

Population divergence and speciation of closely related lineages can result from reproductive differences leading to genetic isolation. An increasing number of fungal diseases of plants and animals have been determined to be caused by morphologically indistinguishable species that are genetically distinct, thereby representing cryptic species. We w...

Since 2008, severe disease epidemics with symptoms resembling gummy stem blight have occurred on gherkin cucumbers (Cucumis sativus) in Karnataka, India. Three morphologically identical, but genetically distinct, Stagonosporopsis species, namely: Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), Stagonosporopsis citrulli, and Stagonosporo...

Gummy stem blight (GSB) is a destructive disease of cucurbits caused by three closely related Stagonosporopsis species. In the southeastern United States, GSB management relies heavily on triazole fungicides. Our objectives were to determine if resistance to triazoles has developed in populations of GSB fungi in the southeastern United States, and...

The epidemiology of gummy stem blight of cucurbits, particularly the sources of inoculum for epidemics, and the regional population genetic structure of the causal fungi: Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), S. citrulli, and S. caricae, are not well understood. Our goal was to better understand the population structure and fi...

Since 2008, severe disease epidemics with symptoms resembling gummy stem blight have occurred on gherkin cucumbers (Cucumis sativus) in Karnataka, India. Three morphologically identical, but genetically distinct, Stagonosporopsis species, namely: Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), Stagonosporopsis citrulli, and Stagonosporo...

Gummy stem blight (GSB), caused by Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), S. citrulli, and S. caricae, is a destructive disease that is a major threat to cucurbit production worldwide. In India, a variety of cucurbits are cultivated, which contribute to approximately 5.6% of the total vegetable production. Gherkin (Cucumis sati...

Emerging diseases caused by fungi are increasing at an alarming rate. Exobasidium leaf and fruit spot of blueberry, caused by the fungus Exobasidium maculosum, is an emerging disease that has rapidly increased in prevalence throughout the southeastern USA, severely reducing fruit quality in some plantings. The objectives of this study were to deter...

Combining population genetics with epidemiology provides insight into the population biology of pathogens, which could lead to improved management of plant diseases. Gummy stem blight, caused by three closely related species of Stagonosporopsis - S. cucurbitacearum (syn. Didymella bryoniae), S. citrulli, and S. caricae - is a devastating disease of...

Recently diverged species may form complexes of morphologically similar, yet genetically distinct lineages that occur in overlapping geographic ranges and niches. Using a multilocus sequencing approach we discovered that gummy stem blight of cucurbits is caused by three genetically distinct species: Stagonosporopsis cucurbitacearum (syn. Didymella...

Peach and almond scab caused by Venturia carpophila and pecan scab caused by Fusicladium effusum result in yield loss, downgrading of fruit, defoliation and subsequent decline of an orchard. To understand the levels of genetic diversity and divergence of pathogens from different hosts and locations 51 isolates were genotyped and analyzed using 10 R...

Peach and almond scab, caused by Fusicladium carpophilum, and pecan scab, caused by F. effusum are serious diseases of their host crops, causing yield loss and downgrading of fruit. Genetic diversity of these pathogens has not previously been compared, but helps characterize pathogen variability and can aid with resistance breeding. The aim of this...

Exobasidium leaf and fruit spot of blueberry (Vaccinium section Cyanococcus) is an emerging disease that has rapidly increased in prevalence throughout the southeastern USA. To determine whether this disease is caused by a new species of Exobasidium, we studied the morphology and phylogenetic relationship of the causal fungus compared with other me...

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The formation of chasmothecia by the strawberry powdery mildew pathogen (Podosphaera aphanis) is widespread, but often sporadic throughout the range of strawberry cultivation. In some production regions, notably in warmer climates, they are reportedly rare. We confirmed that the pathogen is heterothallic, and that initiation of chasmothecia is not...

Macrocybe titans is the largest gilled mushroom of any species in the Western Hemisphere, with caps in excess of 100 cm (3 ft). These giant mushrooms often occur in clusters within the tropics and subtropics of the New World, with previous sightings reported in the Caribbean, Central America, Mexico, South America, and only in Florida within the US...

Random mating and recombination in heterothallic ascomycetes should result in high genotypic diversity, 1:1 mating-type ratios, and random associations of alleles, or linkage equilibrium, at different loci. To test for random mating in populations of the grape powdery mildew fungus Erysiphe necator, we sampled isolates from vineyards of Vitis vinif...

Tomato (Solanum lycopersicum) is an important crop in the Solanaceae family. One of the key traits selected during domestication is fruit mass which is controlled by many quantitative trait loci. The fruit weight locus fw3.2 is one of the major loci responsible for fruit mass in tomato. Identification of the underlying gene will improve our underst...

Transcriptome sequences of the grape powdery mildew fungus Erysiphe necator were used to develop microsatellite markers (EST-SSRs) to study its relatively unexplored population structure in its centre of diversity in eastern North America. Screening the transcriptome sequences revealed 116 contigs with candidate microsatellites, from which 11 polym...

From Blight to Powdery Mildew Pathogenic effects of microbes on plants have widespread consequences. Witness, for example, the cultural upheavals driven by potato blight in the 1800s. A variety of microbial pathogens continue to afflict crop plants today, driving both loss of yield and incurring the increased costs of control mechanisms. Now, four...

Eastern North America is considered the center of diversity for many Vitis spp. and for the grape powdery mildew pathogen, Erysiphe necator. However, little is known about populations of E. necator from wild Vitis spp. We determined the phenotypic variation in pathogenicity and aggressiveness of E. necator among isolates from wild and domesticated...

The grape powdery mildew fungus, Erysiphe necator, was introduced into Europe more than 160 years ago and is now distributed everywhere that grapes are grown. To understand the invasion history of this pathogen we investigated the evolutionary relationships between introduced populations of Europe, Australia and the western United States (US) and p...

Table S1. Origin, collection date, and multilocus haplotypes of Erysiphe necator isolates.

Evidence for parasexuality in natural populations of haploid fungi requires the demonstration of diploids or heterokaryons and recombinant genotypes in the absence of sex. We studied clonal populations of the chestnut blight fungus, Cryphonectria parasitica, in southeastern Europe and found evidence of parasexuality in two locations. In Osoj, Maced...

The definitive publisher version is available at: http://journal.ashspublications.org/ Reliable analysis of plant traits depends on the accuracy of scoring the phenotype. We report here on the efficacy of two methods in the detection of quantitative trait loci (QTL) controlling fruit morphology in three segregating tomato (Solanum spp.) F2 populati...

Expanding populations are often less genetically diverse at their margins than at the centre of a species' range. Established, older populations of the chestnut blight fungus, Cryphonectria parasitica, are more variable for vegetative compatibility (vc) types than in expanding populations in southeastern Europe where C. parasitica has colonized rel...

Variation in fruit morphology is a prevalent characteristic among cultivated tomato. The genetic and developmental mechanisms underlying similarities and differences in shape between the fruit of two elongated tomato varieties were investigated. Fruit from two F2 populations constructed from either Solanum lycopersicum cv. Howard German or cv. Bana...

The domestication and improvement of fruit-bearing crops resulted in a large diversity of fruit form. To facilitate consistent terminology pertaining to shape, a controlled vocabulary focusing specifically on fruit shape traits was developed. Mathematical equations were established for the attributes so that objective, quantitative measurements of...

Twenty-eight potential biocontrol organisms were tested for efficacy against Rhizoctonia solani on potato in a series of greenhouse trials. Organisms tested consisted of field isolates of Paenibacillus polymyxa, Pseudomonas fluorescens, Penicillium sp., Trichoderma sp., and Rhizoctonia zeae; known biocontrol isolates including Laetisaria arvalis, V...

Rhizoctonia solani is an important pathogen of potato capable of reducing tuber yield and quality. Integrated, sustainable methods including biocontrol and effective crop rotations are necessary for control of this pathogen. Twenty-eight potential biocontrol organisms were tested for efficacy against R. solani on potato in a series of greenhouse tr...