The indiscriminate use of chemical pesticides increasingly harms the health of living beings and the environment. Thus, biological control carried out by microorganisms has gained prominence, since ...it consists of an environmentally friendly alternative to the use of pesticides for controlling plant diseases. Herein, we evaluated the potential role of endophytic Trichoderma strains isolated from forest species of the Cerrado-Caatinga ecotone as biological control agents of crop pathogenic fungi. Nineteen Trichoderma strains were used to assess the antagonistic activity by in vitro bioassays against the plant pathogens Colletotrichum truncatum, Lasiodiplodia theobromae, Macrophomina phaseolina, and Sclerotium delphinii isolated from soybean, cacao, fava bean, and black pepper crops, respectively. All Trichoderma strains demonstrated inhibitory activity on pathogen mycelial growth, with maximum percent inhibition of 70% against C. truncatum, 78% against L. theobromae, 78% against M. phaseolina, and 69% against S. delphinii. Crude methanol extracts (0.5 to 2.0 mg mL-1) of Trichoderma strains were able to inhibit the growth of C. truncatum, except Trichoderma sp. T3 (UFPIT06) and T. orientale (UFPIT09 and UFPIT17) at 0.5 mg mL-1, indicating that the endophytes employ a biocontrol mechanism related to antibiosis, together with multiple mechanisms. Discriminant metabolites of Trichoderma extracts were unveiled by liquid chromatography-tandem mass spectrometry-based metabolomics combined with principal component analysis (PCA), which included antifungal metabolites and molecules with other bioactivities. These results highlight the biocontrol potential of Trichoderma strains isolated from the Cerrado-Caatinga ecotone against crop pathogenic fungi, providing support for ongoing research on disease control in agriculture.
Plant pathogenic fungi are the main causative agents of diseases associated with significant productivity and economic losses in agriculture. Thus, the rapid and early identification of plant ...pathogens is essential for directing effective management and control strategies for diseases to prevent or reduce their severity. The objective of this study was to characterize and discriminate different species of plant pathogenic fungi using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and chemometric analysis. Five fungal species of the genera
Colletotrichum
,
Fusarium
,
Macrophomina
,
Neoscytalidium
, and
Pseudofusicoccum
, isolated from agricultural crops, fruit trees, and ornamental plants, were used. Discrimination of the fungal samples was conducted using different fingerprint regions of ATR-FTIR spectra and partial least squares-discriminant analysis (PLS-DA). The results showed that regions I (800–1800 cm
−1
) and III (800–1800 and 2800–2990 cm
−1
) can be used as spectroscopic biomarkers for the differentiation and classification of fungi by ATR-FTIR, as PLS-DA revealed adjustment quality and satisfactory prediction, generating values of R
2
= 0.96 and Q
2
= 0.60 in cross-validation. The most relevant infrared absorption bands in the separation of classes were the C–O stretching vibrations, bending of C-H bonds, amide III bands, and C–C stretching. This method can be an important diagnostic tool in the agricultural sector for disease management, considering that it can provide biological differentiation and/or similarity between fungal species.
In 2022, virus‐like symptoms were observed in Adenium obesum plants in Brazil. High‐throughput sequencing analysis found three contig sequences of cucumber mosaic virus (CMV) genome segments, which ...were of 3352, 3006 and 2221 nucleotides, and shared 98.59%, 95.02% and 98.05% nucleotide identities with the nucleotide sequences of CMV RNAs 1, 2 and 3, respectively. Phylogenetic analysis of the coat protein gene indicated that the CMV isolate belongs to the subgroup IB. Symptoms of mottle like those observed in the field samples were reproduced on mechanically inoculated plants of A. obesum, and RT‐PCR confirmed the CMV infection. CMV was transmitted by Aphis gossypii to A. obesum plants. This is the first report of CMV infecting A. obesum plants in Brazil.
Adenium obesum
plants showing virus-like symptoms were collected in several regions of Brazil. Mottling symptoms like those observed in symptomatic plants in the field were reproduced in mechanically ...inoculated
A. obesum
plants. This potexvirus was named “desert rose mottle virus” (DRMoV), and its genome sequence was first determined by high-throughput sequencing and then confirmed by Sanger sequencing. The complete genome of DRMoV is 6,781 nt in length, excluding the poly(A) tail, and five ORFs were predicted in order from 5’ to 3’: Rep-TGB1-TGB2-TGB3-CP. Phylogenetic analysis based on Rep amino acid sequences showed different clustering among potexviruses. These data suggest that RDMoV is a new member of the genus
Potexvirus
, and the binomial name “
Potexvirus adenii
” is proposed for its species.
A high frequency of plants showing symptoms of wilting and root rot has been observed in tomato‐producing areas in Santarém and Belterra, Pará, Brazil. These plants showed symptoms ranging from ...yellowing to wilting, with roots displaying reduced development and darkening of the xylem. Four fungal isolates, derived from a collection of 12 obtained from symptomatic plants, were chosen for identification using both morphological and phylogenetic species concepts. To determine the identity of the fungi, DNA was extracted and used in PCR reactions. PCR products were sequenced from the TEF‐1α and RBP2 regions and compared with sequences in GenBank using BLASTn. Based on the phylogenetic analyses, the isolates were identified as Fusarium falciforme and Fusarium suttonianum, belonging to the species complex Fusarium solani – (FSSC), and Fusarium triseptatum, belonging to the species complex Fusarium oxysporum – (FOSC). The fourth isolate, COUFPI 295, grouped within a clade of F. kalimantanense and F. sangayamense from FOSC. The fulfilment of Koch's postulates confirmed that all isolates induced symptoms of root rot and concomitant reduction in root mass, leading to observable wilting symptoms. This is the first report of F. suttonianum, F. falciforme and F. triseptatum causing root rot and wilt in tomato plants in Brazil.
Biodiversity underlies ecosystem functioning. While aboveground biodiversity is often well studied, the belowground microbiome, in particular protists, remains largely unknown. Indeed, holistic ...insights into soil microbiome structures in natural soils, especially in hyperdiverse biomes such as the Brazilian Cerrado, remain unexplored. Here, we study the soil microbiome across four major vegetation zones of the Cerrado, ranging from grass-dominated to tree-dominated vegetation with a focus on protists. We show that protist taxon richness increases towards the tree-dominated climax vegetation. Early successional habitats consisting of primary grass vegetation host most potential plant pathogens and least animal parasites. Using network analyses combining protist with prokaryotic and fungal sequences, we show that microbiome complexity increases towards climax vegetation. Together, this suggests that protists are key microbiome components and that vegetation succession towards climax vegetation is stimulated by higher loads of animal and plant pathogens. At the same time, an increase in microbiome complexity towards climax vegetation might enhance system stability.
Plants of the genus Hibiscus are commonly cultivated in Brazil as ornamentals. Symptoms of leaf spot in Hibiscus tiliaceus trees are frequently observed. The objective of this study was to identify ...and characterize the etiological agent of the H. tiliaceus leaf spot. Leaves with symptoms were collected in Teresina, state of Piauí, Brazil and a Colletotrichum species was consistently isolated from them. Morphological identification, phylogeny of ITS region, GAPDH and ACT genes, a pathogenicity test and re‐isolation of the fungus from symptomatic artificially inoculated plants confirmed Colletotrichum siamense as the causative agent of the disease. This is the first record of C. siamense causing anthracnose in H. tiliaceus in Brazil.
Isolates from the Fusarium fujikuroi species complex, mainly F. sacchari, have been reported to be the causal agents of pokkah boeng in sugarcane in Brazil. However, inadequate information was ...available on the occurrence and genetic diversity of F. sacchari in Northeast Brazil, which is a limiting factor on management. Thus, isolates of F. subglutinans sensu lato from sugarcane plants with symptoms of pokkah boeng were evaluated using the sexual cross‐fertility to determine species. All the isolates produced black perithecia when they were crossed with the test isolates of F. sacchari. Three weeks after the crossing, the formation of fertile ascospores cirri was observed. Thirty‐four isolates were self‐sterile hermaphrodites, while 21 were fertile only as males. Five isolates were homothallic. The effective size Ne(f) of the population as a function of the frequency of hermaphrodites and female sterile strains was 95.5%. The F. sacchari isolates were separated into four genetic groups independent of geographic location. The mean of polymorphism among all populations was 79%, and the average unbiased genetic diversity (uh) was considered moderate (0.31). This study in addition to confirming that F. sacchari as the main species associated with pokkah boeng in sugarcane in Northeast Brazil, reveals the relationship of mating type and genetic diversity of F. sacchari. The unrestricted gene flow between regions is probably the best explanation for the low geographic correlation. This knowledge will help in the adoption of management measures with fungicides or resistant cultivars.
Pepper stem rot is a disease caused by Sclerotium delphinii, a necrotrophic pathogen and a natural soil inhabitant. Identifying genotypes of Capsicum resistant to the pathogen and applying silicon ...(Si) can be effective management measures. The objective of the study was to identify sources of resistance in 24 accessions of Capsicum spp. against S. delphinii, and to evaluate the potential of sodium silicate (Si) to induce resistance. Two experiments were conducted: In Experiment I, the resistance reaction of Capsicum in a greenhouse was evaluated. The experiment was conducted in two periods of the year (July and November 2019). In Experiment II, the effect of Si on Capsicum resistance was evaluated. The experimental design used in Experiment I employed randomized blocks in a factorial design of 2 (isolates) x 24 (accessions), with five replications. For Experiment II, six accessions were selected with contrasting resistance responses observed in Experiment I, in a factorial design of 1 (isolate) x 6 (accessions) x 4 (doses: 0.0, 0.025, 0.05, and 0.1 mL per vase). Accessions BGH 71 and BAGC 134 showed greater resistance to the pathogen. Accession BAGC 134 demonstrated high resistance stability in both periods and against the two isolates tested. Si doses had no significant effect on the resistance reaction. Therefore, the genotypes BGH 71 and BAGC 134 have the potential to be used in breeding programs for Capsicum for resistance to S. delphinii for control of stem rot.
ABSTRACT The search for vegetable extracts for phytosanitary control has been expanded to find new active ingredients to control plant diseases. This study aimed to evaluate the in vitro effect of ...the fixed constituents of Copaifera luetzelburgii, Croton zehntneri and Lippia lasiocalycina, at the concentrations of 2, 20, 200 and 2,000 μg mL-1, on the percentage of mycelial growth inhibition of Colletotrichum siamense, C. truncatum, Fusarium sacchari, F. udum, Lasiodiplodia theobromae and Thielaviopsis ethacetica, as well as the conidium concentration of C. siamense, F. sacchari and F. udum produced in culture medium with all the extracts. The tested ethanolic extract, especially at the highest concentration, inhibited the percentage of mycelial growth and/or conidium concentration of the evaluated fungi. The other concentrations showed low inhibitory effects or no activity against the fungi. The average values for percentage of mycelial growth inhibition of the ethanolic extract from L. lasiocalycina, C. zehntneri and C. luetzelburgii against the six fungi were 62.5, 53.4 and 51.0 %, respectively. The ethanolic extract of L. lasiocalycina showed the most significant effect on the percentage of mycelial growth inhibition and conidia concentration. The fixed constituents of C. luetzelburgii, C. zehntneri and L. lasiocalycina at 2,000 μg mL-1 showed to be efficient in inhibiting the mycelial growth of C. siamense, C. truncatum, F. sacchari, F. udum, L. theobromae and T. ethacetica, and inhibit the conidia production of C. siamense, F. sacchari and F. udum.
RESUMO A busca por extratos vegetais para serem utilizados no controle fitossanitário tem sido ampliada, visando encontrar novos ingredientes ativos para o controle de doenças de plantas. Objetivou-se avaliar o efeito in vitro dos constituintes fixos de Copaifera luetzelburgii, Croton zehntneri e Lippia lasiocalycina, nas concentrações de 2; 20; 200; e 2.000 μg mL-1, sobre o percentual de inibição de crescimento micelial de Colletotrichum siamense, C. truncatum, Fusarium sacchari, F. udum, Lasiodiplodia theobromae e Thielaviopsis ethacetica, bem como a concentração de conídios de C. siamense, F. sacchari e F. udum produzidos em meio de cultura com todos os extratos. O extrato etanólico testado, principalmente na maior concentração, inibiu o percentual de crescimento micelial e/ou concentração de conídios dos fungos avaliados. As demais concentrações apresentaram baixos efeitos inibitórios ou nenhuma atividade contra os fungos. Os valores médios para percentual de inibição de crescimento micelial do extrato etanólico de L. lasiocalycina, C. zehntneri e C. luetzelburgii contra os seis fungos foram de 62,5; 53,4; e 51,0 %, respectivamente. O extrato etanólico de L. lasiocalycina apresentou o efeito mais significativo sobre o percentual de inibição de crescimento micelial e concentração de conídios. Os constituintes fixos de C. luetzelburgii, C. zehntneri e L. lasiocalycina a 2.000 μg mL-1 mostraram-se eficientes na inibição do crescimento micelial de C. siamense, C. truncatum, F. sacchari, F. udum, L. theobromae e T. ethacetica, e inibem a produção de conídios de C. siamense, F. sacchari e F. udum.
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