RESUMO

In August 2018, symptoms of apical and basal rot resembling those caused by Sclerotinia sclerotiorum infection were observed in a commercial Brussels sprouts field in North Patagonia, Argentina. The incidence of apical and basal rot was 23.30% and 2.30%, respectively. Carpogenic germination of sclerotia was detected in shaded, highly humid soil areas. To our knowledge, this is the first report of carpogenic germination of sclerotia from S. sclerotiorum in North Patagonia.

Assuntos

RESUMO

The association of both cell-surface PRRs (Pattern Recognition Receptors) and intracellular receptor NLRs (Nucleotide-Binding Leucine-Rich Repeat) in engineered plants have the potential to activate strong defenses against a broad range of pathogens. Here, we describe the identification, characterization, and in planta functional analysis of a novel truncated NLR (TNx) gene from the wild species Arachis stenosperma (AsTIR19), with a protein structure lacking the C-terminal LRR (Leucine Rich Repeat) domain involved in pathogen perception. Overexpression of AsTIR19 in tobacco plants led to a significant reduction in infection caused by Sclerotinia sclerotiorum, with a further reduction in pyramid lines containing an expansin-like B gene (AdEXLB8) potentially involved in defense priming. Transcription analysis of tobacco transgenic lines revealed induction of hormone defense pathways (SA; JA-ET) and PRs (Pathogenesis-Related proteins) production. The strong upregulation of the respiratory burst oxidase homolog D (RbohD) gene in the pyramid lines suggests its central role in mediating immune responses in plants co-expressing the two transgenes, with reactive oxygen species (ROS) production enhanced by AdEXLB8 cues leading to stronger defense response. Here, we demonstrate that the association of potential priming elicitors and truncated NLRs can produce a synergistic effect on fungal resistance, constituting a promising strategy for improved, non-specific resistance to plant pathogens.

RESUMO

Microbial crop protection products based on Trichoderma have the ability to display multifunctional roles in plant protection, such as pathogen parasitism, enhance nutrient availability and stimulate plant growth, and these traits can be used to enhance the overall agronomic performance of a variety of crops. In the current study, we explored the multifunctional potential of two indigenous Brazilian strains of Trichoderma (T. asperelloides CMAA 1584 and T. lentiforme CMAA 1585) for their capability of controlling Sclerotinia sclerotiorum, a key plant pathogen of cotton, and for their ability of growth promotion in cotton plants (Gossypium hirsutum). Both strains were able to solubilize mineral phosphorus (CaHPO4), to release volatile organic compounds that impaired the mycelial growth of S. sclerotiorum, and to promote the growth of cotton plants under greenhouse conditions. In dual culture, Trichoderma strains reduced the growth rate and the number of sclerotia formed by S. sclerotiorum. By treating sclerotia with conidial suspensions of these Trichoderma strains, a strong inhibition of the myceliogenic germination was observed, as a result of the marked mycoparasitic activity exerted on the sclerotia. The parasitism over S. sclerotiorum was more effective with T. asperelloides CMAA 1584, whilst the biostimulant effects on cotton growth were more pronounced with T. lentiforme CMAA 1585, which also showed a higher capacity of phosphate solubilization. Thus, T. asperelloides CMAA 1584 displays higher efficiency in controlling S. sclerotiorum, while T. lentiforme CMAA 1585 is more suitable as a biostimulant due to its ability to promote growth in cotton plants. Overall, these Trichoderma strains may be used in mixture to provide both pathogen control and promotion of plant growth, and this strategy will support growers in minimizing the use of synthetic fertilizers and fungicides against white mold in cotton crops.

RESUMO

The common bean (Phaseolus vulgaris L.) is the most important grain legume in the human diet, mainly in Africa and Latin America. Argentina is one of the five major producers of the common bean in the world, and the main cultivation areas are concentrated in the northwestern provinces of this country. Crop production of the common bean is often affected by biotic factors like some endemic fungal diseases, which exert a major economic impact on the region. The most important fungal diseases affecting the common bean in Argentina are white mold caused by Sclerotinia sclerotiorum, angular leaf spot caused by Pseudocercospora griseola, web blight and root rot caused by Rhizoctonia solani, which can cause production losses of up to 100% in the region. At the present, the most effective strategy for controlling these diseases is the use of genetic resistance. In this sense, population study and characterization of fungal pathogens are essential for developing cultivars with durable resistance. In this review we report diversity studies carried out on these three fungal pathogens affecting the common bean in northwestern Argentina, analyzing more than 200 isolates by means of molecular, morphological and pathogenic approaches. Also, the screening of physiological resistance in several common bean commercial lines and wild native germplasm is reviewed. This review contributes to the development of sustainable management strategies and cultural practices in bean production aimed to minimize yield losses due to fungal diseases in the common bean.

RESUMO

Among the prospective biocontrol agents, the saprophytic filamentous fungus Clonostachys rosea is an excellent necrotrophic mycoparasite of numerous plant pathogenic fungi. However, its commercial development has been hampered by mass production difficulties during solid-state fermentation. Conversely, the submerged liquid fermentation shortens the cultivation time while increasing yields of fungal propagules. However, this method has been overlooked for C. rosea. In this work, we investigated the impact of liquid pre-culture inoculum on the spore production by the two-stage fermentation process using rice grains in comparison to the traditional solid-state fermentation. In parallel, we studied the submerged cultivation of C. rosea by manipulating carbon-to-nitrogen (C:N) ratio and nitrogen source, with the further optimization of spore production in a benchtop bioreactor. Additional bioassays included assessing the bioactivity of water-dispersible microgranules (that contained a submerged conidia) against the whitefly (Bemisia tabaci biotype B) and Sclerotinia sclerotiorum (causal agent of the white mold). Our results showed a maximum concentration of 1.1 × 109 conidia/g-dry-matter after 7 days of cultivation by two-stage fermentation process. The liquid fermentation yielded 1.4 × 109 submerged conidia/ml after 7 days using a medium with a 50:1 C:N ratio, and it also induced the production of microsclerotia (MS) up to 1.35 × 104/ml within 6 days with 10:1 C:N ratio; both media were supplemented with dextrose monohydrate and soybean meal. The fermentation batches carried out in a benchtop bioreactor with medium 50:1 C:N ratio and amended with soybean meal rendered a production peak on the fourth day, corresponding to 1.11 × 109 conidia/ml and 4.35 × 108 colony forming units (CFU)/ml. Following air-drying, the conidia production from air-dried microgranules of C. rosea biomass was estimated at 3.4 × 1010 conidia/g of formulated product upon re-hydration for 7 days. Both submerged conidia and MS of C. rosea inhibited 100% germination of S. sclerotiorum sclerotia by direct parasitism. The air-dried submerged conidia exhibited a suppressive activity on sclerotia (88% mycoparasitism) and early whitefly nymphs (76.2% mortality) that rendered LC50 values of 3.2 × 104 CFU/g soil and 1.5 × 107 CFU/ml, respectively. Therefore, the submerged liquid culture of C. rosea may offer a feasible and cost-effective method for its large-scale production, alleviating critical constraints to their commercial use while providing an additional tool for management of B. tabaci and S. sclerotiorum.

RESUMO

Introdução: a espécie vegetal Curatella americana produz anualmente inflorescências com aroma adocicado rica em óleo essencial. Objetivo: avaliar as características físico-químicas, e atividades antifúngica e antioxidante do óleo essencial da flor de Curatella americana. Metodologia: as flores foram coletadas em quatro áreas de Cerrado no estado de Goiás; o rendimento de óleo essencial foi obtido através de hidrodestilação; as características físicas foram determinadas para densidade e solubilidade, a atividade antioxidante foi determinada pela redução do radical livre DPPH; a atividade antifúngica foi determinada por inibição das cepas de Candida, Sclerotinia sclerotiorum, Colletotrichum gloeosporioides e Aspergillus flavus. Resultados: o rendimento de óleo foi de 0,18%, densidade de 0,907 g mL-1, solubilidade positiva para EtOH 70%, atividade antioxidante de CI50 µL mL-1 1,95. Atividade de inibição fúngica apenas para Candida tropicalis na concentração de 8% com halo de antibiose de 10 mm. Sensibilidade discreta nas maiores concentrações de 25, 50 e 100 µL-1 para Aspergillus flavus e Sclerotinia sclerotiorum e baixa atividade de inibição para Colletotrichum gloeosporioides. Conclusão: o óleo essencial da flor de Curatella americana apresentou baixo rendimento, entretanto, alta eficiência na redução do radical livre DPPH. As atividades antifúngicas apresentaram bons resultados de inibição, entretanto, torna-se necessário a adição de outros óleos essenciais para aumento das taxas de inibição micelial.

Introduction: the plant species Curatella americana produces annual inflorescences with a sweet flavour rich in essential oil. Objective: to evaluate the physicochemical characteristics, antifungal and antioxidant activities of the essential oil of the Curatella americana flower. Methodology: the flowers were collected in four areas of Cerrado in the state of Goiás; the essential oil yield was obtained through hydrodistillation; the physical characteristics were determined for density and solubility, the antioxidant activity was determined by the reduction of the free radical DPPH; antifungal activity was determined by inhibiting the strains of Candida, Sclerotinia sclerotiorum, Colletotrichum gloeosporioides and Aspergillus flavus. Results: the oil yield was 0.18%, density 0.907 g mL-1, positive solubility for EtOH 70%, antioxidant activity of IC50 µL mL-1 1.95. Fungal inhibition activity only for Candida tropicalis at a concentration of 8% with a 10 mm antibiosis halo. Discrete sensitivity in the highest concentrations of 25, 50 and 100 µL-1 for Aspergillus flavus and Sclerotinia sclerotiorum and low inhibition activity for Colletotrichum gloeosporioides. Conclusion: The essential oil of the Curatella americana flower showed low yield, however, high efficiency in reducing DPPH free radical. Antifungal activities showed good inhibition results, however, it is necessary to add other essential oils to increase mycelial inhibition rates.

Assuntos

RESUMO

The genetic structure of the population of Sclerotinia sclerotiorum was analyzed using 238 individuals collected from different hosts. Individuals were characterized for microsatellite genotypes and mycelial compatibility groups (MCGs). A total of 22 MCGs and 64 multilocus lineages (MLLs) were identified. There was a close relationship between the MCGs and MLLs, but there was no association between MLLs and hosts or regions. At least 39 MCGs are present in Brazil, and 68.5% of the isolates were assigned to either MCG 1 or MCG 2. Eight new MCGs were found. Seven genetic groups were identified and associated with MCGs. Most genetic variation (70.0%) was because of differences among MCGs. High values of estimates of linkage disequilibrium among loci were more frequent in the total population (all MCGs). By contrast, there was evidence of random mating in subpopulations defined by MCGs 1 and 2. Additionally, there was evidence of outcrossing in the population of S. sclerotiorum in Brazil. The population was structured by MCGs; lineages originating from asexual reproduction or selfing prevail and are widely distributed in space, are persistent in time, and affect many hosts, but there is evidence of some degree of outcrossing, which may lead to a more genetically variable population in the future.

Assuntos

RESUMO

Endophytic bacteria show important abilities in promoting plant growth and suppressing phytopathogens, being largely explored in agriculture as biofertilizers or biocontrol agents. Bacteria from canola roots were isolated and screened for different plant growth promotion (PGP) traits and biocontrol of Sclerotinia sclerotiorum. Thirty isolates belonging to Bacillus, Paenibacillus, Lysinibacillus, and Microbacterium genera were obtained. Several isolates produced auxin, siderophores, hydrolytic enzymes, fixed nitrogen and solubilized phosphate. Five isolates presented antifungal activity against S. sclerotiorum by the dual culture assay and four of them also inhibited fungal growth by volatile organic compounds production. All antagonistic isolates belonged to the Bacillus genus, and had their genomes sequenced for the search of biosynthetic gene clusters (BGC) related to antimicrobial metabolites. These isolates were identified as Bacillus safensis (3), Bacillus pumilus (1), and Bacillus megaterium (1), using the genomic metrics ANI and dDDH. Most strains showed several common BGCs, including bacteriocin, polyketide synthase (PKS), and non-ribosomal peptide synthetase (NRPS), related to pumilacidin, bacillibactin, bacilysin, and other antimicrobial compounds. Pumilacidin-related mass peaks were detected in acid precipitation extracts through MALDI-TOF analysis. The genomic features demonstrated the potential of these isolates in the suppression of plant pathogens; however, some aspects of plant-bacterial interactions remain to be elucidated.

Assuntos

RESUMO

AIMS: Sclerotinia sclerotiorum, the causal agent of white mold, can infect several host species, including economically important crops. In this study, we propose and validate a new in vitro system able to mimic the conditions of interaction with the host and promote the induction of S. sclerotiorum effectors. METHODS AND RESULTS: For culture media production, we selected three plant species, common bean (Phaseolus vulgaris L, cv. Requinte.), maize (Zea mays, cv. BRS1030) and beggarticks (Bidens pilosa). To validate this system as an in vitro inducer of effectors, the qRT-PCR technique was used to investigate the expression profile of some S. sclerotiorum effector genes in each growth medium at different times after inoculation. CONCLUSION: The results obtained in this study provide a validation of a new method to study S. sclerotiorum during mimetic interaction with different hosts. Although leaf extract does not fully represent the plant environment, the presence of plant components in the culture medium seems to induce effector genes, mimicking in planta conditions. The use of MEVM is simpler than in planta growth, bypasses problems such as the amount of mycelium produced, as well as contamination of host cells during transcriptomic and proteomic analyses. SIGNIFICANCE AND IMPACT OF THE STUDY: We have devised MEVM media as a model mimicking the interaction of S. sclerotiorum and its hosts and used it to evaluate in vitro expression of effectors normally expressed only in planta.

Assuntos

RESUMO

Precise diagnosis of plant diseases is one of the most effective tools to minimize yield losses. Colletotrichum truncatum, Corynespora cassiicola, and Sclerotinia sclerotiorum are common soilborne pathogens that affect soybeans all over the world. We developed a multiplex quantitative real-time polymerase chain reaction (qPCR) assay to simultaneously detect and quantify the three pathogens in soybean seeds and to survey their occurrence in the main soybean production areas in Brazil. Species-specific primers and probes for C. truncatum and C. cassiicola were designed based on GAPDH and TEF1 genes, respectively, to be combined with qPCR detection of S. sclerotiorum previously reported. The multiplex qPCR assay was successful in the simultaneous detection of C. truncatum, C. cassiicola, and S. sclerotiorum, along with a host internal control. The four pathogens were detected and quantified in artificially and naturally infested soybean seeds, even in the lowest incidence level tested of 0.0625% or 1 infected seed out of 1,599 healthy ones. From 81 seed samples tested, C. truncatum was the most frequently detected pathogen and with higher incidence levels (0.25 to 0.125%), followed by S. sclerotiorum and C. cassiicola, both with lower incidence levels (0.125 to 0.0625%). Together, the results evidenced the high sensitivity of the multiplex qPCR assay, indicating its usefulness for a quick and reliable diagnosis of soybean diseases in seeds.

Assuntos

RESUMO

Schinus molle é popularmente conhecida por aroeira-salsa, apresentando aroma nas folhas e galhos. O presente estudo objetivou avaliar a composição química dos óleos essenciais dos galhos e folhas e a atividade antifúngica frente à Sclerotinia sclerotiorum (mofo-branco). Os galhos e folhas foram coletados e processados para extração dos óleos essenciais por hidrodestilação em aparelho de Clevenger. Os rendimentos de extrações dos óleos essenciais, e seus perfis químicos foram avaliados por CG-MS. A atividade antifúngica foi determinada utilizando diferentes concentrações de ambos os óleos essenciais. Como resultados, os rendimentos foram de 0,21 e 0,37%, com cerca de 16 e 21 compostos identificados para os óleos essenciais dos galhos e folhas respectivamente. Os compostos majoritários foram -cadieno 21,77%, Viridifloral 21,74, copaeno 12,9% e cariofileno 9,99% para o óleo essencial dos galhos, e para o óleo essencial das folhas, destacaram-se os compostos -pineno 14,77%, germacreno D 9,00% e germacreno B 6,25%. A atividade antifúngica apresentou inibição micelial em S. sclerotiorum em todas as concentrações avaliadas, em especial para 100 µL-1 onde apresentaram inibição de 86,4 e 81,3% e para a concentração de 50 µL-1 de 41,2 e 50,3% para galhos e folhas respectivamente. Os óleos essenciais de S. molle apresentaram bons rendimentos de extração, bem como ricos em compostos...

Schinus molle is popularly known as aroeira-salsa, presenting aroma in the leaves and branches. The present study aimed to evaluate the chemical composition of the essential oils of the branches and leaves and the antifungal activity against Sclerotinia sclerotiorum (mofo branco). The branches and leaves were collected and processed for extraction of the essential oils by hydrodistillation in a Clevenger apparatus. The yields of extractions of the essential oils, and their chemical profiles were evaluated by GC-MS. The antifungal activity was determined using different concentrations of both essential oils. As results, yields were 0.21 and 0.37%, with about 16 and 21 compounds identified for the essential oils of the branches and leaves respectively. The major compounds were -cadiene 21.77%, Viridiflorol 21.74, copaene 12.9% and caryophyllene 9.99% for the essential oil of the branches, and the essential oil of the leaves, the -pinene 14.77%, germacrene D 9.00% and germacrene B 6.25%. The antifungal activity showed mycelial inhibition in S. sclerotiorum at all concentrations evaluated, especially for 100 L-1 where they showed inhibition of 86.4 and 81.3% and for the 50 L-1 concentration of 41.2 and 50.3% for branches and leaves respectively. The essential oils of S. molle presented good extraction yields, as well as rich in monoterpenes and sesquiterpenes compounds, and...

Assuntos

RESUMO

Schinus molle é popularmente conhecida por aroeira-salsa, apresentando aroma nas folhas e galhos. O presente estudo objetivou avaliar a composição química dos óleos essenciais dos galhos e folhas e a atividade antifúngica frente à Sclerotinia sclerotiorum (mofo-branco). Os galhos e folhas foram coletados e processados para extração dos óleos essenciais por hidrodestilação em aparelho de Clevenger. Os rendimentos de extrações dos óleos essenciais, e seus perfis químicos foram avaliados por CG-MS. A atividade antifúngica foi determinada utilizando diferentes concentrações de ambos os óleos essenciais. Como resultados, os rendimentos foram de 0,21 e 0,37%, com cerca de 16 e 21 compostos identificados para os óleos essenciais dos galhos e folhas respectivamente. Os compostos majoritários foram -cadieno 21,77%, Viridifloral 21,74, copaeno 12,9% e cariofileno 9,99% para o óleo essencial dos galhos, e para o óleo essencial das folhas, destacaram-se os compostos -pineno 14,77%, germacreno D 9,00% e germacreno B 6,25%. A atividade antifúngica apresentou inibição micelial em S. sclerotiorum em todas as concentrações avaliadas, em especial para 100 µL-1 onde apresentaram inibição de 86,4 e 81,3% e para a concentração de 50 µL-1 de 41,2 e 50,3% para galhos e folhas respectivamente. Os óleos essenciais de S. molle apresentaram bons rendimentos de extração, bem como ricos em compostos...(AU)

Schinus molle is popularly known as aroeira-salsa, presenting aroma in the leaves and branches. The present study aimed to evaluate the chemical composition of the essential oils of the branches and leaves and the antifungal activity against Sclerotinia sclerotiorum (mofo branco). The branches and leaves were collected and processed for extraction of the essential oils by hydrodistillation in a Clevenger apparatus. The yields of extractions of the essential oils, and their chemical profiles were evaluated by GC-MS. The antifungal activity was determined using different concentrations of both essential oils. As results, yields were 0.21 and 0.37%, with about 16 and 21 compounds identified for the essential oils of the branches and leaves respectively. The major compounds were -cadiene 21.77%, Viridiflorol 21.74, copaene 12.9% and caryophyllene 9.99% for the essential oil of the branches, and the essential oil of the leaves, the -pinene 14.77%, germacrene D 9.00% and germacrene B 6.25%. The antifungal activity showed mycelial inhibition in S. sclerotiorum at all concentrations evaluated, especially for 100 L-1 where they showed inhibition of 86.4 and 81.3% and for the 50 L-1 concentration of 41.2 and 50.3% for branches and leaves respectively. The essential oils of S. molle presented good extraction yields, as well as rich in monoterpenes and sesquiterpenes compounds, and...(AU)

Assuntos

RESUMO

Abstract Essential oils (EO) from aromatic and medicinal plants generally perform a diverse range of biological activities because they have several active constituents that work in different mechanisms of action. EO from Citrus peel have an impressive range of food and medicinal uses, besides other applications. EO from Citrus reticulata, C. sinensis and C. deliciosa were extracted from fruit peel and analyzed by GC-MS. The major constituent of EO under evaluation was limonene, whose concentrations were 98.54%, 91.65% and 91.27% for C. sinensis, C. reticulata and C. deliciosa, respectively. The highest potential of inhibition of mycelial growth was observed when the oil dose was 300 μL. Citrus oils inhibited fungus growth in 82.91% (C. deliciosa), 65.82% (C. sinensis) and 63.46% (C. reticulata). Anti-Sclerotinia sclerotiorum activity of 90% pure limonene and at different doses (20, 50, 100, 200 and 300 μL) was also investigated. This monoterpene showed to be highly active by inhibiting 100% fungus growth even at 200 and 300 μL doses. This is the first report of the in vitro inhibitory effect of natural products from these three Citrus species and its results show that there is good prospect of using them experimentally to control S. sclerotiorum, in both greenhouse and field conditions.

Resumo Óleos essenciais de plantas aromáticas e medicinais geralmente exibem uma gama diversificada de atividades biológicas, pois possuem vários constituintes ativos que atuam por meio de vários mecanismos de ação. Os óleos essenciais das cascas de Citrus têm uma variedade impressionante de usos em alimentos, medicamentos entre várias outras aplicações. Os óleos essenciais (OE) de Citrus reticulata, C. sinenses e C. deliciosa foram extraídos das cascas dos frutos e analisados por CG-EM. O limoneno foi o constituinte majoritário encontrado nos óleos essenciais avaliados, nas concentrações de 98,54%, 91,65% e 91,27% para C. sinensis, C. reticulata e C. deliciosa, respectivamente. Os maiores potenciais de inibição do crescimento micelial foi observado na dose de 300 µL dos óleos. Os óleos de Citrus inibiram em 82,91% (C. deliciosa), 65,82% (C. sinensis) e 63,46% (C. reticulata) o crescimento do fungo. A atividade anti-Sclerotinia sclerotiorum do limoneno 90% puro e em diferentes doses (20, 50, 100, 200 e 300 µL) foi também investigada e este monoterpeno demonstrou-se altamente ativo inibindo 100% o crescimento do fungo inclusive nas doses de 200 e 300 µL. Este é o primeiro relato sobre o efeito inibitório in vitro dos óleos essenciais destas três espécies de Citrus e os resultados deste estudo mostram que existe uma boa perspectiva de uso destes produtos naturais experimentalmente para controlar o S. sclerotiorum tanto em condições de estufa como em condições de campo.

Assuntos

RESUMO

Sclerotinia sclerotiorum is one of the most devastating and cosmopolitan plant pathogens. Rapid detection of S. sclerotiorum can provide growers an advantage in knowing what control measures should be taken to minimize crop damage and financial losses caused by it. Loop-mediated isothermal amplification (LAMP) is a fast, sensitive, and specific nucleic acid amplification method that does not require a thermal cycler. This study aimed to develop a LAMP-based assay for the specific detection of S. sclerotiorum (Ss-LAMP). A real-time quantitative LAMP reaction (Ss-qLAMP) and a calcein ion indicator-based LAMP reaction (Ss-cLAMP) were designed, optimized, and tested on fungi, plant, and soil samples. The Ss-LAMP reactions were very specific and sensitive. Applying the artificially inoculated soil samples with DNA purified by five protocols in the Ss-qLAMP reaction, it was possible to detect and quantify the pathogen DNA, regardless of the extraction protocol. Naturally infected soybean tissues had the pathogen detected by Ss-cLAMP directly in the reaction tube with no DNA extraction requirement. The assays should be applicable for many types of samples, such as soil, spore traps, and plant tissues from several crops, with no requirement for DNA extraction. The Ss-LAMP reactions took less than 1 h to complete, and they can be made directly in the field with real-time quantitative results (Ss-qLAMP) or qualitative naked-eye visual results (Ss-cLAMP). Results were obtained with 10 pg of DNA or 10 ng of crude mycelium, suggesting a detection limit close to a single DNA copy. Ss-LAMP reactions will allow rapid and accurate diagnosis of S. sclerotiorum and assist in pathogen management and control.

Assuntos

RESUMO

Fungal endophytes of Brachiaria, a nonhost of Sclerotinia sclerotiorum, may harbor species with antagonistic effects against this plant pathogen. The objective of this work was to investigate the diversity of endophytic fungi associated with different Brachiaria species and hybrids and evaluate their potential to inhibit the plant pathogen S. sclerotiorum. Stem samples from 39 Brachiaria spp. plants were collected in pasture fields and experimental areas of three states of Brazil resulting in 74 endophytes isolated. Twenty-eight species were identified by sequences of the Internal Transcribed Spacer (ITS) and 18S rDNA regions. Paraconiothyrium sp. was the most abundant endophyte, accounting for 24 % (14 isolates) of total, and it was isolated from B. ruziziensis, B. decumbens, B. humidicola, and B. brizantha. Phoma sorghina was the second most abundant taxon, followed by Sarocladium strictum, and Plenodomus sp. In vitro analyses showed that Paraconiothyrium sp., Sarocladium kiliense, Acremonium curvulum, Setophoma terrestris, Dissoconium sp., and Cladosporium flabelliforme exhibited antagonistic activity against S. sclerotiorum, with percentages of growth inhibition ranging from 25 to 60 (p < 0.05). Paraconiothyrium sp. BBXE1 (60 %), BBPB4.1 (60 %), BCMT4.1 (54 %), and S. kiliense (54 %) showed the highest values of Antagonism Percentages (AP). Therefore, fungi with inhibitory activity against S. sclerotiorum such as Paraconiothyrium sp. are naturally endophytic in Brachiaria grasses.

Assuntos

RESUMO

Fungal endophytes of Brachiaria, a nonhost of Sclerotinia sclerotiorum, may harbor species with antagonistic effects against this plant pathogen. The objective of this work was to investigate the diversity of endophytic fungi associated with different Brachiaria species and hybrids and evaluate their potential to inhibit the plant pathogen S. sclerotiorum. Stem samples from 39 Brachiaria spp. plants were collected in pasture fields and experimental areas of three states of Brazil resulting in 74 endophytes isolated. Twenty-eight species were identified by sequences of the Internal Transcribed Spacer (ITS) and 18S rDNA regions. Paraconiothyrium sp. was the most abundant endophyte, accounting for 24 % (14 isolates) of total, and it was isolated from B. ruziziensis, B. decumbens, B. humidicola, and B. brizantha. Phoma sorghina was the second most abundant taxon, followed by Sarocladium strictum, and Plenodomus sp. In vitro analyses showed that Paraconiothyrium sp., Sarocladium kiliense, Acremonium curvulum, Setophoma terrestris, Dissoconium sp., and Cladosporium flabelliforme exhibited antagonistic activity against S. sclerotiorum, with percentages of growth inhibition ranging from 25 to 60 (p < 0.05). Paraconiothyrium sp. BBXE1 (60 %), BBPB4.1 (60 %), BCMT4.1 (54 %), and S. kiliense (54 %) showed the highest values of Antagonism Percentages (AP). Therefore, fungi with inhibitory activity against S. sclerotiorum such as Paraconiothyrium sp. are naturally endophytic in Brachiaria grasses.(AU)

Assuntos

RESUMO

Essential oils (EO) from aromatic and medicinal plants generally perform a diverse range of biological activities because they have several active constituents that work in different mechanisms of action. EO from Citrus peel have an impressive range of food and medicinal uses, besides other applications. EO from Citrus reticulata, C. sinensis and C. deliciosa were extracted from fruit peel and analyzed by GC-MS. The major constituent of EO under evaluation was limonene, whose concentrations were 98.54%, 91.65% and 91.27% for C. sinensis, C. reticulata and C. deliciosa, respectively. The highest potential of inhibition of mycelial growth was observed when the oil dose was 300 L. Citrus oils inhibited fungus growth in 82.91% (C. deliciosa), 65.82% (C. sinensis) and 63.46% (C. reticulata). Anti-Sclerotinia sclerotiorum activity of 90% pure limonene and at different doses (20, 50, 100, 200 and 300 L) was also investigated. This monoterpene showed to be highly active by inhibiting 100% fungus growth even at 200 and 300 L doses. This is the first report of the in vitro inhibitory effect of natural products from these three Citrus species and its results show that there is good prospect of using them experimentally to control S. sclerotiorum, in both greenhouse and field conditions.(AU)

Óleos essenciais de plantas aromáticas e medicinais geralmente exibem uma gama diversificada de atividades biológicas, pois possuem vários constituintes ativos que atuam por meio de vários mecanismos de ação. Os óleos essenciais das cascas de Citrus têm uma variedade impressionante de usos em alimentos, medicamentos entre várias outras aplicações. Os óleos essenciais (OE) de Citrus reticulata, C. sinenses e C. deliciosa foram extraídos das cascas dos frutos e analisados por CG-EM. O limoneno foi o constituinte majoritário encontrado nos óleos essenciais avaliados, nas concentrações de 98,54%, 91,65% e 91,27% para C. sinensis, C. reticulata e C. deliciosa, respectivamente. Os maiores potenciais de inibição do crescimento micelial foi observado na dose de 300 µL dos óleos. Os óleos de Citrus inibiram em 82,91% (C. deliciosa), 65,82% (C. sinensis) e 63,46% (C. reticulata) o crescimento do fungo. A atividade anti-Sclerotinia sclerotiorum do limoneno 90% puro e em diferentes doses (20, 50, 100, 200 e 300 µL) foi também investigada e este monoterpeno demonstrou-se altamente ativo inibindo 100% o crescimento do fungo inclusive nas doses de 200 e 300 µL. Este é o primeiro relato sobre o efeito inibitório in vitro dos óleos essenciais destas três espécies de Citrus e os resultados deste estudo mostram que existe uma boa perspectiva de uso destes produtos naturais experimentalmente para controlar o S. sclerotiorum tanto em condições de estufa como em condições de campo.(AU)

Assuntos

RESUMO

White mold is a disease caused by the fungus Sclerotinia sclerotiorum, a highly destructive necrotrophic pathogen that infects soybean crops, among others. Usually, the infection triggers the plant defense system to minimize the damages. However, the effects of the infection on soybean plant metabolism are still unclear. In this work, the metabolic profiles of soybean stems and leaves were accessed using 1H HR-MAS NMR spectroscopy to identify metabolic changes as a response to S. sclerotiorum infection. This fungus widely affects the central metabolism of soybean plants, and most of the altered metabolites are involved in carbon metabolism, as suggested by the results. Furthermore, the metabolites of central metabolism can be associated with the production of several polyphenolic metabolites. Changes in metabolic profile of leaves indicate systemic effects.

Assuntos

RESUMO

Abstract Essential oils (EO) from aromatic and medicinal plants generally perform a diverse range of biological activities because they have several active constituents that work in different mechanisms of action. EO from Citrus peel have an impressive range of food and medicinal uses, besides other applications. EO from Citrus reticulata, C. sinensis and C. deliciosa were extracted from fruit peel and analyzed by GC-MS. The major constituent of EO under evaluation was limonene, whose concentrations were 98.54%, 91.65% and 91.27% for C. sinensis, C. reticulata and C. deliciosa, respectively. The highest potential of inhibition of mycelial growth was observed when the oil dose was 300 L. Citrus oils inhibited fungus growth in 82.91% (C. deliciosa), 65.82% (C. sinensis) and 63.46% (C. reticulata). Anti-Sclerotinia sclerotiorum activity of 90% pure limonene and at different doses (20, 50, 100, 200 and 300 L) was also investigated. This monoterpene showed to be highly active by inhibiting 100% fungus growth even at 200 and 300 L doses. This is the first report of the in vitro inhibitory effect of natural products from these three Citrus species and its results show that there is good prospect of using them experimentally to control S. sclerotiorum, in both greenhouse and field conditions.

Resumo Óleos essenciais de plantas aromáticas e medicinais geralmente exibem uma gama diversificada de atividades biológicas, pois possuem vários constituintes ativos que atuam por meio de vários mecanismos de ação. Os óleos essenciais das cascas de Citrus têm uma variedade impressionante de usos em alimentos, medicamentos entre várias outras aplicações. Os óleos essenciais (OE) de Citrus reticulata, C. sinenses e C. deliciosa foram extraídos das cascas dos frutos e analisados por CG-EM. O limoneno foi o constituinte majoritário encontrado nos óleos essenciais avaliados, nas concentrações de 98,54%, 91,65% e 91,27% para C. sinensis, C. reticulata e C. deliciosa, respectivamente. Os maiores potenciais de inibição do crescimento micelial foi observado na dose de 300 µL dos óleos. Os óleos de Citrus inibiram em 82,91% (C. deliciosa), 65,82% (C. sinensis) e 63,46% (C. reticulata) o crescimento do fungo. A atividade anti-Sclerotinia sclerotiorum do limoneno 90% puro e em diferentes doses (20, 50, 100, 200 e 300 µL) foi também investigada e este monoterpeno demonstrou-se altamente ativo inibindo 100% o crescimento do fungo inclusive nas doses de 200 e 300 µL. Este é o primeiro relato sobre o efeito inibitório in vitro dos óleos essenciais destas três espécies de Citrus e os resultados deste estudo mostram que existe uma boa perspectiva de uso destes produtos naturais experimentalmente para controlar o S. sclerotiorum tanto em condições de estufa como em condições de campo.

RESUMO

The success of Sclerotinia sclerotiorum infection relies mainly on the production of the non-host selective toxin named oxalic acid (OA). This toxin is known to play multiple roles in a host infected by the fungus, but its effect on photosynthesis and the antioxidant system of common bean plants remain elusive. Therefore, we performed detailed analysis of leaf gas exchange, chlorophyll a fluorescence, activities of antioxidant enzymes, concentrations of reactive oxygen species and photosynthetic pigments to investigate the OA's role during the S. sclerotiorum pathogenesis. To achieve this goal, common bean plants were sprayed with water or with oxalic acid (referred to as -OA and +OA plants, respectively) and either non-challenged or challenged with a wild-type (WT) or an OA-defective mutant (A4) of S. sclerotiorum. Irrespective of OA spray, the WT isolate was more aggressive than the A4 isolate and spraying OA increased OA concentration in the leaflets as well as the aggressiveness of both isolates. Biochemical limitations were behind S. sclerotiorum-induced photosynthetic impairments notably for the +OA plants inoculated with the WT isolate. Inoculated plants were not able to fully capture and exploit the collected energy due to the degradation of photosynthetic pigments. Photoinhibition of photosynthesis and photochemical dysfunctions were potentiated by OA. Higher activities of superoxide dismutase, peroxidase and ascorbate peroxidase besides reductions on catalase activity were noticed for plants inoculated with the WT isolate. OA was able to counteract most of the increases in the activities of antioxidant enzymes thereby increasing the generation of superoxide and hydrogen peroxide and the concurrent damage to the membranes of host cells as evidenced by the high malondialdehyde concentration. In conclusion, OA was found to enhance biochemical limitations to photosynthesis, photochemical dysfunctions and oxidative stress in the leaflets of common bean plants infected by S. sclerotiorum.

Assuntos