Academic literature on the topic 'Biscogniauxia'

Dead wood is an important habitat for both fungi and insects, two enormously diverse groups that contribute to forest biodiversity. Unlike the myriad of studies on fungus–insect relationships, insect communities on ascomycete sporocarps are less explored, particularly for those in hidden habitats such as underneath bark. Here, I present my observations of insect community dynamics on Biscogniauxia spp. on oak dead wood from the early anamorphic stage to matured teleomorph stage, aided by the debarking behaviour of squirrels probably targeting on these fungi. In total, 38 insect taxa were observed on Biscogniauxia spp. from March to November. The community composition was significantly correlated with the presence/absence of Biscogniauxia spp. Additionally, Librodor (Glischrochilus) ipsoides, Laemophloeus submonilis, and Neuroctenus castaneus were frequently recorded and closely associated with Biscogniauxia spp. along its change from anamorph to teleomorph. L. submonilis was positively associated with both the anamorph and teleomorph stages. L. ipsoides and N. castaneus were positively associated with only the teleomorph but not with the anamorph stage. N. castaneus reproduced and was found on Biscogniauxia spp. from June to November. These results suggest that sporocarps of Biscogniauxia spp. are important to these insect taxa, depending on their developmental stage.

The genus Biscogniauxia is paraphyletic to members of the family Xylariaceae and includes at least 52 species to date that are mainly pathogens of dicotyledonous angiosperm trees. Most of these are forest trees, such as those in the genera Acacia, Acer, Alnus, Eucalyptus, Fraxinus, Populus, and Quercus, and other species of minor importance. Biscogniauxia spp. have been reported as endophytes or secondary invaders that attack only stressed plants. During a survey in rosaceous orchards in southern Italy, several charcoal cankers were observed and stroma samples were collected. A collection of 31 Biscogniauxia isolates was analyzed. Their phylogenetic relationships were determined through study of the internal transcribed spacer, β-tubulin, and actin gene sequences. Combining morphological, cultural, and molecular data, a new species of Biscogniauxia is described here as Biscogniauxia rosacearum. This new species was isolated for the first time from rosaceous hosts in Apulia. Pathogenicity tests showed that it causes symptoms on stems when artificially inoculated and produces stromata on the bark surface.

Mycoparasites are a collection of fungicolous eukaryotic organisms that occur on and are antagonistic to a wide range of plant pathogenic fungi. To date, this fungal group has largely been neglected by biodiversity studies. However, this fungal group is of interest, as it may contain potential biocontrol agents of pathogenic fungi that cause beech Tarcrust disease (BTC), which has contributed to the devastation of European beech (Fagus sylvatica) forests. Biscogniauxia nummularia has been demonstrated to cause BTC. However, a trophic association between mycoparasites and pathogenic Biscogniauxia spp., has not been established. This study aimed to taxonomically identify and characterize Biscogniauxia, a fungus causing destructive BTC disease in European beech at Lovćen national park, Montenegro and to uncover the diversity of mycopathogens that are natural regulators of xylariaceous Biscogniauxia stroma formation, associated with beech decline. This finding is supported by distinctive phylogenetic and evolutionary characteristics, as well as unique morphological-microscopic fungal features indicating that Biscogniauxia from Montenegro, which is a major cause of BTC occurring in ancient beech forests at the edge of southern Fagus sylvatica distribution, may be described as a novel fungus specific to Fagus. Its evolutionary nuSSU–complete ITS–partial nuLSU rDNA phylogeny indicates its likely emergence by asexual fusion or introgressive hybridization between diverged B. nummularia and B. anceps species. The name Biscogniauxia destructiva is proposed for the novel fungus, as it is aggressive and highly destructive BTC disease.

Biscogniauxia nummularia (Bull.) Kuntze is a fungus which induces strip-cankers on beech, commonly referred to as charcoal canker. The symptoms of infection are visible on the host tree’s bark as elongated, blackish bark lesions on the trunk and branches. Recent years have shown that, due to climate change causing local epidemics, the species is increasing its economic impact in Mediterranean regions. Until recently, B. nummularia was considered rare and uncommon in central Europe. However, in the last few years it has been noticed more often, mostly in coniferous trees, which are out of B. nummularia’s host range. A similar situation has been observed with the closely related species Biscogniauxia mediterranea (De Not.) Kuntze, which prior to 2017 had not been observed in central Europe at all. This study shows the genetic diversity of mid-European strains of Biscogniauxia spp. (based on the ITS, TEF1, TUB2 and ACT regions) and, as the first in Europe, presents a molecular investigation of this species isolated from coniferous trees. It is also the first attempt at estimating the potential impact of this pathogenic fungus on European forestry management in the close future.

Cultural data and anamorphs of Biscogniauxia marginata, B. dennisii, and B. repanda are presented. Each species produces a characteristic anamorph which can be accommodated in the hyphomycetous genus Nodulisporium. They are separable from one another on gross colony morphology and conidiophore morphology.

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia
Charcoal canker is a disease caused by Biscogniauxia mediterranea that affects Quercus suber and other hardwood species. The fungus develops endophytically in the hosts becoming pathogenic under stress conditions. However, it has become more frequent, particularly in young trees expressing atypical symptoms. This work intends to clarify the agent involved in these disease outbreaks and its variability in different situations, as well as dispersion in natural conditions. The fungal anamorph was identified as Nodulisporium sp. in young hosts. In the stands, ascospores airborne dispersal is predominant, occurring after precipitation periods, and vertical contamination of plants doesn’t happen. A collection of isolates obtained from cork oak in Portugal and other Mediterranean countries, from other hosts and from trees with different ages and disease expression were analyzed by microsatellite-primed PCR, multigene sequencing, morpho-cultural characteristics and growth rates at different temperatures. All the approaches revealed high level of intraspecific polymorphism among isolates, not allowing relating the disease development with any considered feature. The results highlighted the variability and adaptation ability of this fungus in special in the Mediterranea region, in the present worrying scenario of climatic change. All the conditions are gathered to favor the aggravation of the disease in cork oak stands

As florestas são um dos ecossistemas mais importantes no nosso planeta, tendo alto valor ambiental e económico. Por isso, a preservação destes ecossistemas é de extrema importância. No entanto, a floresta é cada vez mais afetada por problemas abióticos, como a seca, e bióticos, como é o caso dos fungos patogénicos, a principal causa de doenças florestais. Biscogniauxia mediterranea é um fungo que ataca preferencialmente plantas em stress hídrico e que tem vindo a causar maior preocupação por estar associado ao declínio do montado. Neste estudo foi caracterizado um conjunto de isolados com características morfológicas semelhantes a B. mediterranea, obtidos de diferentes espécies florestais distribuídas por Portugal Continental. Para uma primeira avaliação da diversidade genética geral, um conjunto de 91 isolados foi submetido a tipagem por MSP-PCR. A partir dos perfis genéticos foram selecionados 37 isolados para identificação molecular através da sequenciação e análise da região ITS, permitindo confirmar a maioria dos isolados como pertencentes ao género Biscogniauxia. Para determinar a identidade ao nível da espécie recorreu-se a uma análise multi-locus combinando a região ITS, o fator de alongamento da transcrição 1-alfa (tef1-α) e beta-tubulina 2 (tub2). A análise filogenética demonstrou que na verdade os isolados estudados são mais próximos de B. rosacearum. Desta forma, três isolados (236alfa, 292alfa e 358beta) foram selecionados e caracterizados em termos morfológicos e de capacidade de crescimento a diferentes temperaturas de incubação. Testes de patogenicidade com dois isolados selecionados foram realizados em Eucalyptus globulus, Quercus suber e Pinus pinaster em condições bem regadas e de défice hídrico, e monitorizados os parâmetros como potencial hídrico, necrose relativa e biomassa seca das folhas. O potencial hídrico demonstrou diminuição significativa para as plantas de E. globulus e Q. suber que foram inoculadas sob efeito de défice hídrico. No entanto, não foi possível reisolar o fungo da plantas inoculadas, não permitindo confirmar a patogenicidade de B. rosacearum. Este estudo representa a primeira caracterização de isolados de B. rosacearum em Portugal. No futuro seria importante analisar a disseminação deste fungo a nível nacional e realizar novos testes de patogenicidade.
Forests are one of the most important ecosystems on our planet, having high environmental and economic value. Therefore, the preservation of these ecosystems is extremely important. However, the forest is increasingly affected by abiotic problems, such as drought, and biotic problems, such as pathogenic fungi, the main cause of forest diseases. Biscogniauxia mediterranea is a fungus that preferentially attacks plants under water stress and has been causing some concern as it is associated with the decline of cork oak forests. This study characterized a set of isolates with morphological characteristics similar to B. mediterranea, obtained from different forest species distributed throughout mainland Portugal. For a first evaluation of the general genetic diversity, a set of 91 isolates was submitted to MSP-PCR fingerprinting. From the genetic profiles it was possible to select 37 isolates were selected for molecular identification through sequencing and analysis of the ITS region, allowing to confirm most of the isolates as belonging to the genus Biscogniauxia. To determine identity at the species level, a multi-locus analysis was used combining the ITS region whit the transcription elongation factor 1-alpha (tef1-α) and beta-tubulin 2 (tub2) genes. Phylogenetic analyses showed that the isolates studied are related to B. rosacearum. Thus, three isolates (236alpha, 292alpha e 358beta) were selected and characterized in terms of morphology and growth capacity at different incubation temperatures. Pathogenicity tests with two selected isolates were carried out on Eucalyptus globulus, Quercus suber and Pinus pinaster under well-watered and water deficit conditions, and parameters such as water potential, relative necrosis and leaf dry biomass were monitored. The water potential showed a significant decrease for E. globulus and Q. suber plants that were inoculated under the effect of water deficit. However, it was not possible to re-isolate the fungus from the inoculated plants, not allowing to confirm the pathogenicity of B. rosacearum. This study is the first to characterize B. rosacearum isolates from Portugal. For future work, it would be important to analyze the dissemination of this fungus at the national level and perform new pathogenicity tests.
Mestrado em Microbiologia

Dissertação de mestrado em Biologia Molecular, Biotecnologia e Bioempreendedorismo em Plantas
Cork oak (Quercus suber) is a species of high importance in the Mediterranean. Besides its ecological importance, the cork oak also has a high relevance for the Portuguese economy. This importance is due to the production and processing of cork. However, the sustainability of the cork oak is being threatened due to climate change, which will reduce the availability of water in the Mediterranean, and the occurrence of diseases that increasingly affect their normal development. The charcoal disease, caused by the fungus Biscogniauxia mediterranea, leads to decline, and eventually, death of the tree. Diplodia corticola is another pathogen of the cork oak and is involved in various diseases considered responsible for the decline of the cork oak in the Mediterranean Basin. Currently, the use of fungicides is the main technique used to combat these problems. However the environmental hazard and toxicity of this process leads to the necessity of finding a more effective method. Biological control is an appropriate strategy as an alternative to this problem. Endophytes have the potential to be used as biological agents to control diseases. In addition to being described as potentiators of plant responses to stressful situations, endophytes have the potential for use as biological control agents. To identify endophytic fungi in cork oak, four sites of continental Portugal (Bragança, Gerês, Alcobaça and Grândola), which had differences in water availability, were selected to carry out the collection of biological material. Subsequently, the community of fungal endophytes of three organs (leaves, stems, roots) was evaluated. The trees analysed were largely colonized by fungi of the phylum Ascomycota. In general, Grândola had the highest colonization frequency and diversity of endophytes, while Alcobaça had the lowest. Of all study sites, the cork oaks from Gerês showed a more distinct community, differentiating from all other locations. The roots have a more diverse fungal community than the leaves and stems. It was found that the pathogenic fungi tested (B. mediterranea and D. corticola), essentially affect the aboveground organs of the tree, however no disease symptoms were detected. Furthermore, Gerês was the only study site that did not show any signs of infection by these pathogenic fungi. D. corticola only infected the southern regions (Alcobaça and Grândola), where as B. mediterranea also infected the trees in Bragança. Taking this into account, many fungi were selected for antagonism assays of biological control. Three species (belonging to two genera) may potentially act as biocontrol agents against diseases in Q. suber.
O sobreiro (Quercus suber) é uma espécie de elevada importância na região do Mediterrâneo. Para além da sua importância ecológica, o sobreiro também apresenta uma elevada relevância para a economia Portuguesa. Esta relevância provém da indústria de produção e transformação da cortiça. No entanto, a sustentabilidade do sobreiro poderá estar ameaçada devido às previstas alterações climáticas, que diminuirão a disponibilidade de água na região do Mediterrâneo, e à ocorrência de doenças que afetam cada vez mais o seu normal desenvolvimento. A doença do carvão do entrecasco, causada pelo fungo Biscogniauxia mediterranea, origina um acentuado declínio na árvore, podendo levar à sua morte. Diplodia corticola é um outro fungo patogénico do sobreiro, que está envolvido em várias doenças consideradas responsáveis pelo declínio do sobreiro na Bacia do Mediterrâneo. Atualmente, a utilização de fungicidas é a técnica mais usada para o combate destes problemas. Contudo, o risco ambiental e a toxicidade deste processo levam à necessidade da utilização de outros métodos eficazes. A luta biológica é uma estratégia adequada como alternativa a este problema. Além de se encontrarem descritos como potenciadores das respostas das plantas a situações de stresse, os organismos endófitos têm potencial para serem utilizados como agentes na luta biológica. Para identificar fungos endófitos em sobreiro, quatro locais de Portugal continental (Bragança, Gerês, Alcobaça e Grândola), que apresentavam diferenças na disponibilidade de água, foram selecionados para realizar a recolha de material biológico. A comunidade de fungos endófiticos foi avaliada em três órgãos (folhas, caules, raiz). Os sobreiros testados encontram-se maioritariamente colonizados por fungos do filo Ascomycota. Os sobreiros de Grândola apresentaram uma maior frequência de colonização e diversidade de endófitos, enquanto que os de Alcobaça apresentaram a menor. De todos os locais, os sobreiros do Gerês foram os que apresentaram uma comunidade mais distinta, diferenciando-se de todos os outros locais. As raízes apresentaram uma comunidade de fungos mais diversa do que as folhas e caules. Verificou-se ainda que os fungos patogénicos testados (B. mediterranea e D. corticola), infetaram essencialmente a parte aérea da árvore, apesar de não terem sido verificados sintomas nas mesmas. O Gerês foi o único local de estudo que não apresentou nenhum sinal de infeção por parte destes fungos. O fungo D. corticola infetou exclusivamente as regiões mais a sul (Alcobaça e Grândola), enquanto o fungo B. mediterranea foi também encontrado na região de Bragança. Tendo isto em consideração, diversos fungos foram selecionados para estudos de antagonismo e luta biológica, tendo sido encontradas três espécies (pertencentes a dois géneros) que poderão potencialmente atuar como agentes de biocontrolo contra as doenças de Q. suber.