Caracterização morfomolecular de isolados de Pleurotus ostreatus (Jacq. Fr.) kummer em relação à luminosidade e temperatura de frutificação

A temperatura é um dos principais fatores que influenciam o desenvolvimento e a introdução de cogumelos em nova áreas. O efeito da temperatura (15ºC e 28ºC) e a luminosidade (120 e 900 lux) foram avaliados em oito isolados de P. ostreatus quanto à precocidade, eficiência biológica, área do pileus, padrão de formação das pencas, coloração e resistência ao manuseio. A variabilidade genética dos isolados foi analisada pelo método "Random Amplified Polymorphic DNA" ou DNA polimórfico amplificado ao acaso (RAPD). O isolado Pos 98/37 foi o único a produzir a 28ºC e 900 lux, apresentando píleo branco nessa temperatura e cinza a 15ºC e 120 lux. O isolado Pos 96/05, o mais tardio, apresentou píleo chumbo a 15ºC a 120 lux, assim como os demais isolados nesta temperatura. Os isolados cultivados a 15ºC não diferiram quanto à maior resistência ao manuseio, enquanto a 28ºC, os cogumelos obtidos foram mais frágeis. Quanto à eficiência biológica, o isolado Pos 98/38 foi mais eficiente. O isolado 98/37 a 28ºC, comparado com o mesmo isolado a 15ºC, foi mais eficiente e apresentou padrão de formação de pencas assimétrico. Entre os isolados cultivados a 15ºC, o padrão de formação de pencas foi similar exceto nos isolados Pos 97/15 e Pos 97/17. Na caracterização molecular, o isolado Pos 98/37 apresentou 30% de similaridade com os demais. A temperatura de frutificação e a intensidade luminosa influenciaram a indução e o desenvolvimento dos isolados.Temperature is one of the main factors affecting mushrooms development and introduction in new areas. Effects of temperature (15ºC and 28ºC) and luminosity (120 and 900 lux) were evaluated for eight P. ostreatus strains in relation to precocity, yield, pileus area, stalk formation pattern, coloration and handling resistance. Genetic variability of strains was analysed by the Random Amplified Polymorphic DNA (RAPD) method. The Pos 98/37 strain was the only to yield white pileus at 28ºC - 900 lux, and grey ones at 15ºC and 120 lux. The Pos 96/05 strain, the latest, produced lead-coloured pileus at 15ºC, as did the remaining strains at this temperature. Strains cultivated at 15ºC did not differ in relation to handling resistance. At 28ºC mushrooms were less resistant. In relation to yield, the Pos 98/38 strain was significantly more efficient. The Pos 98/37 strain, at 28ºC, as compared to the same strain at 15ºC, was more efficient and had an asymmetric stalk formation pattern. Among strains cultivated at 15ºC, the stalk formation pattern was symmetric, except for the Pos 97/15 and Pos 97/17 strains. Molecular characterization of the Pos 98/37 strain was 30% similar to the remaining strains. The temperature of fructification and luminosity influence the induction and development of the isolates

Stability of ammonia oxidizer communities upon nitrogen fertilizer pulse disturbances is dependent on diversity

Diversity of the soil microbial community is an important factor affecting its stability against disturbance. However, the impact of the decline in soil microbial diversity on the stability of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) is not known, particularly considering the repeated soil nutrient disturbances occurring in modern agricultural systems. Here, we conducted a microcosm experiment and modified the soil microbial diversity using the dilution-to-extinction approach to determine the stability and population dynamics of AOB and AOA communities with repeated nitrogen (N) fertilizer application. Our results demonstrated that the AOB community became more abundant and stable against repeated disturbances by N in the treatments with the highest microbial diversity. In contrast, the abundance of AOA decreased following repeated N fertilizer application, regardless of the microbial diversity. Notably, during the initial application phase, AOA displayed a potential for increased abundance in treatments with high soil microbial diversity. These findings highlight that the soil microbial diversity controls the stability of ammonia oxidizers during short- interval repeated N disturbances

Ammonia-oxidizing bacteria and fungal denitrifier diversity are associated with N2O production in tropical soils

Nitrous oxide (N2O) production in tropical soils cultivated with sugarcane is associated with ammonia-oxidizing bacteria (AOB) and fungal denitrifiers. However, the taxonomic identities and the community diversities, compositions, and structures of AOB and fungal denitrifiers in these soils are not known. Here, we examined the effects of applying different concentrations of an organic recycled residue (vinasse: regular non-concentrated or 5.8-fold concentrated) on the dynamics of AOB and fungal denitrifier community diversity and composition and greenhouse gas emissions during the sugarcane cycle in two different seasons, rainy and dry. DNA was extracted from soil samples collected at six timepoints to determine the dynamics of amoA-AOB and nirK-fungal community diversity and composition by amplicon sequencing with gene-specific primers. Bacterial and archaeal amoA, fungal and bacterial nirK, bacterial nirS and nosZ, total bacteria (16S rRNA) and total fungi (18S rRNA) were quantified by real-time PCR, and N2O and CO2 emissions were measured. The genes amoA-AOB and bacterial nirK clade II correlated with N2O emissions, followed by fungal nirK. The application of inorganic nitrogen fertilizer combined with organic residue, regardless of concentration, did not affect the diversity and structure of the AOB and fungal denitrifier communities but increased their abundances and N2O emissions. Nitrosospira sp. was the dominant AOB, while unclassified fungi were the dominant fungal denitrifiers. Furthermore, the community structures of AOB and fungal denitrifiers were affected by season, with dominance of uncultured Nitrosospira and unclassified fungi in the rainy season and the genera Nitrosospira and Chaetomium in the dry season. Nitrosospira, Chaetomium, Talaromyces purpureogenus, and Fusarium seemed to be the main genera governing N2O production in the studied tropical soils. These results highlight the importance of deciphering the main players in N2O production and demonstrate the impact of fertilization on soil microbial N functions

Caracterização de isolados de Xanthomonas axonopodis pv. phaseoli

A simple, quick and easy protocol was standardized for extraction of total DNA of the bacteria Xanthomonas axonopodis pv. phaseoli. The DNA obtained by this method had high quality and the quantity was enough for the Random Amplified Polymorphic DNA (RAPD) reactions with random primers, and Polymerase Chain Reaction (PCR) with primers of the hypersensitivity and pathogenicity gene (hrp). The DNA obtained was free of contamination by proteins or carbohydrates. The ratio 260nm/380nm of the DNA extracted ranged from 1.7 to 1.8. The hrp gene cluster is required by bacterial plant pathogen to produce symptoms on susceptible hosts and hypersensitive reaction on resistant hosts. This gene has been found in different bacteria as well as in Xanthomonas campestris pv. vesicatoria (9). The primers RST21 and RST22 (9) were used to amplify the hrp gene of nine different isolates of Xanthomonas axonopodis pv. phaseoli from Botucatu, São Paulo State, Brazil, and one isolate, "Davis". PCR amplified products were obtained in all isolates pathogenic to beans.Um protocolo simples, rápido e fácil foi padronizado para extração de DNA total da bactéria Xanthomonas axonopodis pv. phaseoli. O DNA obtido por esse método foi de ótima qualidade e quantidades suficientes para reações de RAPD (Random Amplified Polymorphic DNA) com "primers" randômicos e PCR (Polymerase Chain Reaction) com "primers" do gene de hipersensibilidade e patogenicidade (hrp). O DNA obtido não apresentou nenhuma contaminação por proteínas ou carboidratos, sendo a razão 260 nm/ 380nm entre 1,7 a 1,8. O agrupamento do gene hrp (reação de hipersensibilidade e patogenicidade) é requerido através do patogeno bacteriano de planta para produzir sintomas nos hospedeiros suscetíveis e reação hipersensível em hospedeiros resistentes é encontrado em diferentes bactérias e também em Xanthomonas campestris pv. vesicatoria (9). Os primers RST21 e RST22 (9) foram usados para ampliar o gene de hrp de nove diferentes isolados de Xanthomonas axonopodis pv. phaseoli, sendo oito de Botucatu, São Paulo, Brasil, e um de "Davis" (EUA). Foi encontrado o produto de PCR amplificado em todos os isolados testados e todos eram patogênicos ao feijão. A presença do gene em isolados patogênicos de Xanthomonas axonopodis pv. phaseoli foi discutido geneticamente

Microbiome resilience of Amazonian forests: agroforest divergence to bacteria and secondary forest succession convergence to fungi

An alarming and increasing deforestation rate threatens Amazon tropical ecosystems and subsequent degradation due to frequent fires. Agroforestry systems (AFS) may offer a sustainable alternative, reportedly mimicking the plant-soil interactions of the natural mature forest (MF). However, the role of microbial community in tropical AFS remains largely unknown. This knowledge is crucial for evaluating the sustainability of AFS and practices given the key role of microbes in the aboveground-belowground interactions. The current study, by comparing different AFS and successions of secondary and MFs, showed that AFS fostered distinct groups of bacterial community, diverging from the MFs, likely a result of management practices while secondary forests converged to the same soil microbiome found in the MF, by favoring the same groups of fungi. Model simulations reveal that AFS would require profound changes in aboveground biomass and in soil factors to reach the same microbiome found in MFs. In summary, AFS practices did not result in ecosystems mimicking natural forest plant-soil interactions but rather reshaped the ecosystem to a completely different relation between aboveground biomass, soil abiotic properties, and the soil microbiome

Fusarium: more than a node or a foot-shaped basal cell

Recent publications have argued that there are potentially serious consequences for researchers in recognising distinct genera in the terminal fusarioid clade of the family Nectriaceae. Thus, an alternate hypothesis, namely a very broad concept of the genus Fusarium was proposed. In doing so, however, a significant body of data that supports distinct genera in Nectriaceae based on morphology, biology, and phylogeny is disregarded. A DNA phylogeny based on 19 orthologous protein-coding genes was presented to support a very broad concept of Fusarium at the F1 node in Nectriaceae. Here, we demonstrate that re-analyses of this dataset show that all 19 genes support the F3 node that represents Fusarium sensu stricto as defined by F. sambucinum (sexual morph synonym Gibberella pulicaris). The backbone of the phylogeny is resolved by the concatenated alignment, but only six of the 19 genes fully support the F1 node, representing the broad circumscription of Fusarium. Furthermore, a re-analysis of the concatenated dataset revealed alternate topologies in different phylogenetic algorithms, highlighting the deep divergence and unresolved placement of various Nectriaceae lineages proposed as members of Fusarium. Species of Fusarium s. str. are characterised by Gibberella sexual morphs, asexual morphs with thin- or thick-walled macroconidia that have variously shaped apical and basal cells, and trichothecene mycotoxin production, which separates them from other fusarioid genera. Here we show that the Wollenweber concept of Fusarium presently accounts for 20 segregate genera with clear-cut synapomorphic traits, and that fusarioid macroconidia represent a character that has been gained or lost multiple times throughout Nectriaceae. Thus, the very broad circumscription of Fusarium is blurry and without apparent synapomorphies, and does not include all genera with fusarium-like macroconidia, which are spread throughout Nectriaceae (e.g., Cosmosporella, Macroconia, Microcera). In this study four new genera are introduced, along with 18 new species and 16 new combinations. These names convey information about relationships, morphology, and ecological preference that would otherwise be lost in a broader definition of Fusarium. To assist users to correctly identify fusarioid genera and species, we introduce a new online identification database, Fusarioid-ID, accessible at www.fusarium.org. The database comprises partial sequences from multiple genes commonly used to identify fusarioid taxa (act1, CaM, his3, rpb1, rpb2, tef1, tub2, ITS, and LSU). In this paper, we also present a nomenclator of names that have been introduced in Fusarium up to January 2021 as well as their current status, types, and diagnostic DNA barcode data. In this study, researchers from 46 countries, representing taxonomists, plant pathologists, medical mycologists, quarantine officials, regulatory agencies, and students, strongly support the application and use of a more precisely delimited Fusarium (= Gibberella) concept to accommodate taxa from the robust monophyletic node F3 on the basis of a well-defined and unique combination of morphological and biochemical features. This F3 node includes, among others, species of the F. fujikuroi, F. incarnatum-equiseti, F. oxysporum, and F. sambucinum species complexes, but not species of Bisifusarium [F. dimerum species complex (SC)], Cyanonectria (F. buxicola SC), Geejayessia (F. staphyleae SC), Neocosmospora (F. solani SC) or Rectifusarium (F. ventricosum SC). The present study represents the first step to generating a new online monograph of Fusarium and allied fusarioid genera (www.fusarium.org)