Browsing by Author "Tavares, Rui Manuel"
Now showing 1 - 10 of 32
Results Per Page
Sort Options
- Bacteria could help ectomycorrhizae establishment under climate variationsPublication . Reis, Francisca; Magalhães, Alexandre P.; Tavares, Rui Manuel; Baptista, Paula; Lino-Neto, TeresaRhizosphere microbiome is one of the main sources of plant protection against drought. Beneficial symbiotic microorganisms, such as ectomycorrhizal fungi (ECMF) and mycorrhiza helper bacteria (MHB), interact with each other for increasing or maintaining host plant fitness. This mutual support benefits all three partners and comprises a natural system for drought acclimation in plants. Cork oak (Quercus suber L.) tolerance to drought scenarios is widely known, but adaptation to climate changes has been a challenge for forest sustainability protection. In this work, ECMF and MHB communities from cork oak forests were cross-linked and correlated with climates. Cenococcum, Russula and Tuber were the most abundant ECMF capable of interacting with MHB (ECMF~MHB) genera in cork oak stands, while Bacillus, Burkholderia and Streptomyces were the most conspicuous MHB. Integrating all microbial data, two consortia Lactarius/Bacillaceae and Russula/Burkholderaceae have singled out but revealed a negative interaction with each other. Russula/Burkholderaceae might have an important role for cork oak forest sustainability in arid environments, which will be complemented by the lower drought adaptation of competitive Lactarius/Bacillaceae. These microbial consortia could play an essential role on cork oak forest resilience to upcoming climatic changes.
- Caracterização do sistema antioxidativo no estabelecimento da associação micorrízica Castanea sativa Mill. / Amanita muscariaPublication . Baptista, Paula; Martins, Anabela; Tavares, Rui Manuel; Lino-Neto, TeresaAs micorrizas são associações mutualistas que se estabelecem entre fungos, pertencentes sobretudo às divisões Basidiomycota, Ascomycota e Zigomycota, e raízes de plantas vasculares. Com o estabelecimento da associação micorrízica, ocorrem várias alterações morfológicas, fisiológicas e ecológicas em ambos os intervenientes, que têm sido objecto de estudo por diversos autores. Contudo, os mecanismos que controlam o processo de colonização e como este processo se inicia é completamente desconhecido. Os poucos trabalhos desenvolvidos nesta área, utilizando micorrizas arbusculares, sugerem que, durante as primeiras horas de invasão do fungo, ocorre uma indução de resposta de defesa por parte da planta hospedeira, semelhante à observada na interacção planta-patogénio. O presente trabalho pretende averiguar o efeito da inoculação de plantas de Castanea sativa Mill. com o fungo ectomicorrízico Amanita muscaria, na indução de resposta de defesa da planta hospedeira.O trabalho experimental decorreu num sistema in vitro estabelecido entre plantas de C. sativa e o fungo A. muscaria. Durante as primeiras horas de contacto (0 às 48 horas) procedeu-se à recolha de amostras de raízes, caules e folhas da planta hospedeira e de micélio de fungo que esteve em contacto com a raiz. Nestas amostras analisaram-se os níveis de peróxido de hidrogénio (H2O2), a actividade da catalase (CAT) (EC 1.11.1.6) e da superóxido dismutase (SOD) (EC 1.15.1.1). Os resultados obtidos evidenciam três picos de produção de H2O2, sugerindo o seu possível envolvimento no estabelecimento de micorrizas, nas primeiras horas de contacto planta-fungo. As variações observadas na actividade da SOD e da CAT, indiciam o seu envolvimento no controlo dos níveis de H2O2 em raízes, permitindo que esta molécula possa actuar como molécula sinalizadora, mas evitando que os níveis se tornem nocivos para o sistema. Estes resultados, apesar de preliminares, reflectem uma condição de stresse oxidativo semelhante àquela observada em interacções plantapatogénio, durante as primeiras horas de contacto.
- Characterization of the oxidative system on Castanea sativa Mill. in association with the ectomycorrhizal fungi Pisolithus tinctorius and Amanita muscaria during the early stages of contactPublication . Baptista, Paula; Martins, Anabela; Tavares, Rui Manuel; Lino-Neto, TeresaMycorrhizae are symbiotic associations between soil borne fungi and the root system of higher plants having a beneficial role on plant growth. The fungus receives carbon from plant, while the plant increased nutrient uptake mediated via the fungus. In agroforestry systems, most of the mycorrhizae belong to ectomycorrhizal (ECM) group being the mechanisms controlling its development poorly defined. During arbuscular mycorrhizal (AM) establishment, some evidences suggest that a temporal and spatial activation of different defence mechanisms by plants are activated. The present work pretends to assess the influence of ECM inoculation on the activity of antioxidant enzymes from roots of Castanea sativa Mill., during the early stages of contact. The experimental work was carried out in an “in vitro” system, established between two symbiotic associations: Castanea sativa Mill. / Pisolithus tinctorius and Castanea sativa Mill. / Amanita muscaria. In these systems, plants were harvested at different times of fungi contact. The levels of H2O2 and the activity of oxidative stress enzymes, namely catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and ascorbate peroxidase (EC 1.11.1.11), were determined in roots. The results suggest that in the early stages of plant-ECM fungi interaction the oxidative metabolism could be involved, in a similar way as described for plant-AM interactions, where the plants produce enzymatic as well as non-enzymatic defence responses. Preliminary results will be presented and discussed in order to understand the effect of ectomycorrhizal fungi contact on oxidative stress enzyme activities of the host.
- Climatic impacts on the bacterial community profiles of cork oak soilsPublication . Reis, Francisca; Soares-Castro, Pedro; Costa, Daniela; Tavares, Rui Manuel; Baptista, Paula; Santos, Pedro M.; Lino-Neto, TeresaClimate changes comprise increasing global temperature and water cycle deregulation (precipitation storms and long dry seasons). Many affected ecosystems are located within the Mediterranean basin, where cork oak (Quercus suber L.) is one of the most important forest ecosystems. Despite cork oak tolerance to drought, the decrease of water availability and increase of temperature is causing a serious decline of cork oak populations. In the present work, the bacterial community of cork oak soils was assessed by metabarcoding using Illumina Miseq. Soils from seven independent cork oak forests were collected along a climate gradient. In all forest soils, Proteobacteria and Actinobacteria were the richest and more abundant bacteria. Acidobacteria also presented a high relative abundance, and Chloroflexi was a rich phylum. The soil bacterial community diversity and composition was strongly affected by the climatic region where cork oak resides and specific bacterial taxa were differently affected by precipitation and temperature. Accordingly, cork oak bacterial communities clustered into three distinct groups, related with humid, sub-humid and arid/semi-arid climates. Driest and warmer forests presented more diverse bacterial communities than humid and coolest forests. However, driest climates presented more homogenous bacterial communities among forests than humid climates. Climate (mainly precipitation) revealed to be the strongest driver leading to significant variations of bacterial community profiles. The most impacted bacterial taxa by climatic variables were Proteobacteria, in particular Gammaproteobacteria and Deltaproteobacteria, Chloroflexi, and Firmicutes. Humid forests presented mainly Acidobacteria as good indicators of climate, whereas Actinobacteria members were better indicators for arid forests (mainly Gaiellales and Frankiales). Some indicator species for different climate conditions were members of the bacterial core of cork oak stands (7% of the total bacterial community). Taken together, different microbiomes were selected by the climate conditions in cork oak stands along a climate gradient and might provide the key to forest sustainability in times of global warming.
- Comunidade macrofúngica associada a Castanea sativa Mill. no Nordeste TransmontanoPublication . Baptista, Paula; Martins, Anabela; Tavares, Rui Manuel; Lino-Neto, TeresaNo Nordeste Transmontano, a cultura do castanheiro, Castanea sativa Mill., tem uma grande importância, económica, social, cultural e paisagística. Esta espécie caracteriza-se por estabelecer associações simbióticas com fungos do solo, resultando na formação de ectomicorrizas que, na sua maioria, são produtoras de estruturas reprodutoras macroscópicas, os macrofungos. Com o presente trabalho pretendeu-se por um lado conhecer a flora micológica associada ao castanheiro no Nordeste Transmontano, e por outro analisar a sua ocorrência ao longo das diferentes estações do ano. A parte experimental do trabalho decorreu de Outubro de 2002 a Dezembro de 2004, num souto localizado na região de Bragança (UTM PG8937). Trata-se de uma parcela não mobilizada, onde foram marcados cinco talhões de 100m2. Com uma periodicidade semanal, nos períodos de Outono e Primavera, e quinzenal, nos restantes períodos, procedeu-se à colheita de todos os macrofungos que ocorreram nos talhões. Os exemplares recolhidos foram observados em laboratório e identificados até à espécie ou ao género, quer através da observação e registo das características macroscópicas e microscópicas, quer através de testes macro-microquímicos. No decurso do trabalho foram identificadas 87 espécies de macrofungos pertencentes a 23 géneros, sendo os géneros Russula spp. e Inocybe spp. os mais representados. Neste estudo, observou-se uma clara dominância de espécies micorrízicas representando 85% do total de espécies encontradas. O maior número de espécies, isto é 68 pertencentes a 20 géneros, ocorreu durante o primeiro ano de amostragem (Outono de 2002). Neste período, os géneros mais representativos foram Russula spp. e Inocybe spp., com 13 espécies cada, seguindo-se-lhes Amanita spp. e Lactarius spp., com seis cada, Tricholoma spp. com cinco, e Boletus spp. e Cortinarius spp. com quatro espécies cada. A época de frutificação descreve claramente uma curva gaussiana entre o final de Setembro e meados de Novembro, com o número máximo de espécies (36), recolhido na segunda quinzena de Outubro. Neste ano, observou-se uma clara dominância de espécies micorrízicas que perfizeram 91% do total encontrado. Em 2003 registou-se um menor número de espécies (50), que se distribuíram por 18 géneros, sendo os mais representados Russula spp., com 11 espécies, Inocybe spp., com nove, e Cortinarius spp. com cinco espécies. A frutificação Outonal ajusta-se a uma curva de Gauss, apresentado um número máximo de espécies (27) na primeira quinzena de Novembro. Na época de Primavera, apenas se registou a ocorrência de espécies macrofúngicas na primeira quinzena de Junho. Cerca de 84% do total das espécies colhidas neste ano eram micorrízicas. Em 2004, devido provavelmente às condições climáticas, foi encontrado um reduzido número de espécies macrofúngicas (18), distribuídas por 10 géneros, sendo os mais representados Russula spp., com cinco espécies, e Inocybe spp., com três. Contrariamente aos anos anteriores, a ocorrência de espécies no período outonal não se ajustou à curva normal, ocorrendo praticamente o mesmo número de espécies em todas as saídas efectuadas durante esta estação (em média 2 espécies). Na Primavera a frutificação deu-se essencialmente durante o mês de Junho. A distribuição das espécies pelos grupos funcionais revela uma dominância dos macrofungos micorrízicos, perfazendo 94% do total. Numa análise conjunta do período observado, verificou-se que os géneros Clitocybe spp., Entoloma spp. e Gyroporus spp. ocorreram apenas em 2002 e Calocybe spp. e Leotia spp. registaram-se somente em 2003. Pelo contrário, os géneros Boletus spp., Cantharellus spp., Cortinarius spp., Hebeloma spp., Inocybe spp., Lactarius spp., Russula spp. e Tricholoma spp. surgiram ao longo dos três anos de estudo.
- Cork oak endophytic fungi as potential biocontrol agents against biscogniauxia mediterranea and diplodia corticolaPublication . Costa, Daniela; Tavares, Rui Manuel; Baptista, Paula; Lino-Neto, TeresaAn increase in cork oak diseases caused by Biscogniauxia mediterranea and Diplodia corticola has been reported in the last decade. Due to the high socio-economic and ecologic importance of this plant species in the Mediterranean Basin, the search for preventive or treatment measures to control these diseases is an urgent need. Fungal endophytes were recovered from cork oak trees with different disease severity levels, using culture-dependent methods. The results showed a higher number of potential pathogens than beneficial fungi such as cork oak endophytes, even in healthy plants. The antagonist potential of a selection of eight cork oak fungal endophytes was tested against B. mediterranea and D. corticola by dual-plate assays. The tested endophytes were more efficient in inhibiting D. corticola than B. mediterranea growth, but Simplicillium aogashimaense, Fimetariella rabenhorstii, Chaetomium sp. and Alternaria alternata revealed a high potential to inhibit the growth of both. Simplicillium aogashimaense caused macroscopic and microscopic mycelial/hyphal deformations and presented promising results in controlling both phytopathogens’ growth in vitro. The evaluation of the antagonistic potential of non-volatile and volatile compounds also revealed that A. alternata compounds could be further explored for inhibiting both pathogens. These findings provide valuable knowledge that can be further explored in in vivo assays to find a suitable biocontrol agent for these cork oak diseases.
- Cork oak forests soil bacteria: Potential for sustainable agroforest productionPublication . Reis, Francisca; Pereira, Ana João; Tavares, Rui Manuel; Baptista, Paula; Lino-Neto, TeresaPlant growth promoting rhizobacteria (PGPR) are in increasing demand due to their role in promoting sustainable practices, not only in agriculture but also in forestry. Keeping in mind the future application of PGPR for increasing cork oak sustainability, the aim of this study was to find cork oak PGPR isolates with increased nutrient solubilisation traits, able to promote root morphological changes and/or antagonize cork oak bark phytopathogens. Soils from three cork oak forests with distinct bioclimates (humid, semi†humid and semi†arid) were used for isolating bacteria. From the 7634 colony†forming units, 323 bacterial isolates were biochemically assayed for PGPR traits (siderophores production, phosphate solubilizing and organic acids production), and 51 were found to display all these traits. These PGPR were able to induce root morphological changes on Arabidopsis thaliana, like suppression of primary root growth, increase of lateral roots or root hairs formation. However, the most proficient PGPR displayed specific ability in changing a single root morphological trait. This ability was related not only to bacterial genotype, but also with the environment where bacteria thrived and isolation temperature. Bacteria from semi†arid environments (mainly Bacillus megaterium isolates) could hold a promising tool to enhance plant development. Other isolates (Serratia quinivorens or B. cereus) could be further explored for biocontrol purposes.
- Diversity and fruiting pattern of macrofungi associated with chestnut tree (Castanea sativa Mill.) in the Trás-os-Montes region (Northeast Portugal)Publication . Baptista, Paula; Martins, Anabela; Tavares, Rui Manuel; Lino-Neto, TeresaThe chestnut (Castanea sativa) agro-ecosystem is of great social, economic and landscape importance in NE Portugal. There are multiple resources associated with this crop, among them fruit and wood production and mushroom harvesting. However, information about the diversity and ecology of macrofungi is very scarce. In this context, the aim of this study was to assess the macrofungal diversity associated with chestnut trees over 4 y. Carpophore surveys were conducted in a non-tilled C. sativa orchard located in Braganc¸a, Portugal, from Sep. 2002 to Dec. 2005. A total of 2677 carpophores belonging to 73 species across 16 families and 23 genera were recorded. Of the total number of macrofungal species listed, 82 % were ectomycorrhizal (EM) species. The genera with the greatest species richness were Russula, Inocybe and Lactarius, which accounted for 38.4 % of all species collected. The most abundant species were Laccaria laccata, Hebeloma crustuliniforme and Inocybe geophylla, which produced around 35 % of all carpophores. The cumulative number of species over the four successive years revealed that 80.5 % of macrofungal species that potentially exist in the study area were surveyed. Species richness and carpophore abundance fluctuated across years, which could have been related to weather conditions, especially to rainfall. Fructification occurred in two distinct seasons a year, autumn and spring, the first one being the most important in terms of number of species and carpophores. These data could be an important contribution toward the development of sustainable management practices for chestnut agro-ecosystem conservation.
- Diversity of fungal endophytic community in Quercus suber L. and detection of opportunistic phytopathogenic fungiPublication . Costa, Daniela; Cunha, Joana; Tavares, Rui Manuel; Baptista, Paula; Lino-Neto, TeresaCork oak (Quercus suber L.) is a species of high ecological importance in Mediterranean Basin and has high relevance for Portuguese economy due to cork production and processing. The sustainability of cork oak is currently being threatened by reduction of water availability that would increase the occurrence of diseases. Charcoal disease, caused by the fungus Biscogniauxia mediterrânea, leads to death of the tree. Diplodia corticola is involved in various diseases considered responsible for the decline of cork oak in Mediterranean Basin. To identify endophytic fungi in cork oak, including these opportunistic pathogens, four sites of continental Portugal (Bragança, Geres, Alcobaça and Grândola) with differences in water availability were selected to carry out the collection of biological material. The community of fungal endophytes of leaves, st^ms and roots was evaluated. The roots displayed a more diverse fungal community than the aboveground organs. Although no disease symptoms were detected in studied cork oaks, the referred pathogenic fungi were essentially affecting stems and leaves. In general, Grândola presented the highest colonization frequency and diversity of endophytes, while Alcobaça had the lowest. From ali studied sites, cork oaks from Geres showed the most distinct community and did not presentthose pathogens. D. corticola only infected southern regions, while S. mediterrânea also infected trees in Bragança. The exclusive presence of both pathogens in aboveground organs and the absence of visible disease symptoms in ali studied cork oaks encourage the searching of adequate biocontrol agents from the endophytic community for restricting these diseases in cork oak.
- Ectomycorrhizal fungal diversity and community structure associated with cork oak in different landscapesPublication . Reis, Francisca; Valdiviesso, Teresa; Varela, Carolina; Tavares, Rui Manuel; Baptista, Paula; Lino-Neto, TeresaCork oak (Quercus suber L.) forests play an important ecological and economic role. Ectomycorrhizal fungi (ECMF) are key components for the sustainability and functioning of these ecosystems. The community structure and composition of ECMF associated with Q. suber in different landscapes of distinct Mediterranean bioclimate regions have not previously been compared. In this work, soil samples from cork oak forests residing in different bioclimates (arid, semi-arid, sub-humid, and humid) were collected and surveyed for ectomycorrhizal (ECM) root tips. A global analysis performed on 3565 ECM root tips revealed that the ECMF community is highly enriched in Russula, Tomentella, and Cenoccocum, which correspond to the ECMF genera that mainly contribute to community differences. The ECMF communities from the rainiest and the driest cork oak forests were distinct, with soils from the rainiest climates being more heterogeneous than those from the driest climates. The analyses of several abiotic factors on the ECMF communities revealed that bioclimate, precipitation, soil texture, and forest management strongly influenced ECMF structure. Shifts in ECMF with different hyphal exploration types were also detected among forests, with precipitation, forest system, and soil texture being the main drivers controlling their composition. Understanding the effects of environmental factors on the structuring of ECM communities could be the first step for promoting the sustainability of this threatened ecosystem.