Averil E. Brown
Bio: Averil E. Brown is an academic researcher from Queen's University Belfast. The author has contributed to research in topics: Ribosomal DNA & Restriction fragment length polymorphism. The author has an hindex of 30, co-authored 75 publications receiving 2654 citations. Previous affiliations of Averil E. Brown include ADAS & Queen's University.
Papers published on a yearly basis
TL;DR: The potential of PCR for detection and differentiation of C. gloeosporioides is discussed and a 450-bp fragment was amplified from as little as 10 fg of fungal DNA.
Abstract: An oligonucleotide primer (CgInt), synthesised from the variable internally transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) of Colletotrichum gloeosporioides was used for PCR with primer ITS4 (from a conserved sequence of the rDNA) to amplify a 450-bp fragment from the 25 C. gloeosporioides isolates tested. This specific fragment was amplified from as little as 10 fg of fungal DNA. A similar sized fragment was amplified from DNA extracted from C. gloeosporioides-infected tomato tissue. RAPD analysis divided 39 C. gloeosporioides isolates into more than 12 groups linked to host source and geographic origin. Based on the results obtained, the potential of PCR for detection and differentiation of C. gloeosporioides is discussed.
TL;DR: The potential use of the ribosomal DNA internal transcribed spacer (ITS) sequences in understanding the phylogeny and systematics of Colletotrichum species has been evaluated as discussed by the authors.
Abstract: The potential use of the ribosomal DNA internal transcribed spacer (ITS) sequences in understanding the phylogeny and systematics of Colletotrichum species has been evaluated. Sequence data from a limited number of isolates revealed that in Colletotrichum species the ITS 1 region (50.3% variable sites) shows a greater degree of intra- and inter-specific divergence than ITS 2 (12.4% variable sites). Nucleotide sequences of the ITS 1 region from 93 isolates representing 18 Colletotrichum species were determined. Data for 71 of these isolates where molecular and morphological identities concurred were used for phylogenetic analysis. The size of the ITS 1 region varied from 159 to 185 base pairs. Maximum intraspecific divergence was recorded with C. acutatum (5.8%), and C. capsici showed the greatest level of interspecific divergence (8.9-23.3%). Parsimony and distance analyses gave similar tree topologies. The bootstrapped consensus parsimony tree divided the 18 Colletotrichum species into six phylogenetic groups, designated 1-6. These groups, however, are not congruent with species clusterings based on spore shape. For example, the straight cylindrical spored species were represented both in groups 1 and 6; group 6 also included the falcate fusiform spored species C. capsici. The molecular evidence suggests refinement of the species concepts of some of the taxa examined. In group 6, divergence between C. gloeosporioides and C. fuscum (0.6-3.0%) or C. kahawae (0.6-3.0%) or C. fragariae (0.6-4.2%) overlap the divergence (3.6%) within C. gloeosporioides. It is suggested that C. fuscum as well as C. kahawae and C. fragariae fall within the group species C. gloeosporioides. ITS 1 data enabled clear distinction (7.1%) of Colletotrichum isolates from maize and sorghum into C. graminicola and C. sublineolum, respectively (group 2). Species such as C. acutatum, C. coccodes, C. dematium, and C. trichellum can be clearly distinguished based on ITS 1 sequence divergence, but C. destructivum cannot be confidently separated (98% homology) from C. linicola. Colletotrichum dematium f. truncatum is distinct (12.9%) from C. dematium and should probably be called C. truncatum.
TL;DR: The species-specific primer (CaInt2) developed in this work could be used for the accurate identification of C. acutatum and its detection on other host plants.
Abstract: An oligonucleotide primer (CaInt 2) was synthesized from the variable internal transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) from Colletotrichum acutatum PCR with primers CaInt2 and ITS4 (from a conserved sequence of the rDNA) amplified a 490 bp fragment from several isolates of C acutatum but not from other members of the genus Colletotrichum Amplification of this fragment was achieved from 100 fg of fungal DNA These primers amplified a fragment of the same size from DNA extracted from strawberry tissues infected by C acutatum Southern hybridization analysis confirmed the 490 bp fragment from C acutatum DNA and infected strawberry to be identical The species-specific primer (CaInt2) developed in this work could be used for the accurate identification of C acutatum and its detection on other host plants
TL;DR: Restriction fragment length polymorphisms (RFLPs) of the ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) of isolates of the strawberry anthracnose pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides were analysed using rDNA from Saccharomyces carlsbergensis and mtDNA extracted from C. Acutatum as probes.
TL;DR: Primers designed from unique regions within the rDNA internal transcribed spacers have been used to develop a rapid PCR-based diagnostic test to provide an accurate identification of the species on rice.
Abstract: Identification of Rhizoctonia solani, R. oryzae and R. oryzae-sativae, components of the rice sheath disease complex, is extremely difficult and often inaccurate and as a result may hinder the success of extensive breeding programmes throughout Asia. In this study, primers designed from unique regions within the rDNA internal transcribed spacers have been used to develop a rapid PCR-based diagnostic test to provide an accurate identification of the species on rice. Tests on the specificity of the primers concerned showed that they provide the means for accurate identification of the Rhizoctonia species responsible for sheath diseases in rice.
TL;DR: It is suggested that bacterial IAA plays a major role in the development of the host plant root system.
Abstract: Many plant-associated bacteria synthesize the phytohormone indoleacetic acid (IAA). While IAA produced by phytopathogenic bacteria, mainly by the indoleacetamide pathway, has been implicated in the induction of plant tumors, it is not clear whether IAA synthesized by beneficial bacteria, usually via the indolepyruvic acid pathway, is involved in plant growth promotion. To determine whether bacterial IAA enhances root development in host plants, the ipdc gene that encodes indolepyruvate decarboxylase, a key enzyme in the indolepyruvic acid pathway, was isolated from the plant growth-promoting bacterium Pseudomonas putida GR12-2 and an IAA-deficient mutant constructed by insertional mutagenesis. The canola seedling primary roots from seeds treated with wild-type P. putida GR12-2 were on average 35 to 50% longer than the roots from seeds treated with the IAA-deficient mutant and the roots from uninoculated seeds. In addition, exposing mung bean cuttings to high levels of IAA by soaking them in a suspension of the wild-type strain stimulated the formation of many, very small, adventitious roots. Formation of fewer roots was stimulated by treatment with the IAA-deficient mutant. These results suggest that bacterial IAA plays a major role in the development of the host plant root system.
TL;DR: The limit of the Colletotrichum gloeosporioides species complex is defined genetically, based on a strongly supported clade within the Col letteredum ITS gene tree, as well as all taxa accepted within this clade, as it has been applied in the literature for the past 50 years.
TL;DR: It is demonstrated that fragments released from the cell wall by pectic enzymes can elicit plant defense reactions and that the highly pectolytic bacteria, Erwinia chrysanthemi and E. carotovora, are amenable to a powerful array of molecular genetic manipulations.
Abstract: cell components. A convincing role in pathogenesis, however, has been es tablished only for those enzymes that attack the pectic fraction of the plant cell wall. Several fundamental advances in our understanding of these enzymes have been made since the role of pectic enzymes in tissue degradation was reviewed in this series by Bateman & Millar (17) twenty years ago. In the past decade it was demonstrated that highly purified pectic enzymes could macer ate and kill plant tissues in a manner similar to that occurring in soft-rot diseases; that the same enzymes could be used to disassemble the dicot primary cell wall, thus revealing the structural importance of pectic polymers in cell-wall architecture; and that a relationship exists between the enzymatic vulnerability of pectic polymers in the cell wall and the regulation of pectic enzyme synthesis in pathogenic fungi. In the present decade it has been demonstrated that fragments released from the cell wall by pectic enzymes can elicit plant defense reactions and that the highly pectolytic bacteria, Erwinia chrysanthemi and E. carotovora, are amenable to a powerful array of molecular genetic manipulations. This paper considers these most recent advances and attempts to project future progress. The following steps occur during the interaction of a pectolytic pathogen and a potential host: (a) The entering pathogen possesses structural genes encoding pectic enzymes with particular physical and catalytic properties. (b)
TL;DR: A review is provided of the current state of understanding of Colletotrichum systematics, focusing on species-level data and the major clades, and the taxonomic placement of the genus is discussed.
TL;DR: This review aims to give a broad overview on the qualities and versatility of the best studied Trichoderma species and to highlight intriguing findings as well as promising applications.
Abstract: Fungi of the genus Trichoderma are soilborne, green-spored ascomycetes that can be found all over the world. They have been studied with respect to various characteristics and applications and are known as successful colonizers of their habitats, efficiently fighting their competitors. Once established, they launch their potent degradative machinery for decomposition of the often heterogeneous substrate at hand. Therefore, distribution and phylogeny, defense mechanisms, beneficial as well as deleterious interaction with hosts, enzyme production and secretion, sexual development, and response to environmental conditions such as nutrients and light have been studied in great detail with many species of this genus, thus rendering Trichoderma one of the best studied fungi with the genome of three species currently available. Efficient biocontrol strains of the genus are being developed as promising biological fungicides, and their weaponry for this function also includes secondary metabolites with potential applications as novel antibiotics. The cellulases produced by Trichoderma reesei, the biotechnological workhorse of the genus, are important industrial products, especially with respect to production of second generation biofuels from cellulosic waste. Genetic engineering not only led to significant improvements in industrial processes but also to intriguing insights into the biology of these fungi and is now complemented by the availability of a sexual cycle in T. reesei/Hypocrea jecorina, which significantly facilitates both industrial and basic research. This review aims to give a broad overview on the qualities and versatility of the best studied Trichoderma species and to highlight intriguing findings as well as promising applications.