Draft genome sequence data of Nothopassalora personata, peanut foliar pathogen from Argentina.

Late leaf spot (LLS) caused by the Ascomycete Nothopassalora personata (N.p.) (Syn. Cercosporidium personatum) is the main foliar disease of peanuts in Argentina and in peanut producing areas of the world, causing up to 70% yield losses. The extremely slow growth of this fungus in culture, that takes around one month to form a 1 cm colony (0.45 mm/day), and the lack of adequate young tissues from where to extract nucleic acids, have hindered genetic studies of this pathogen. Here, we report the first genome sequence of a N. personata isolate from South America, as well as genetic variants on its conserved genes, and the complete sequence of its mating-type locus MAT1-2 idiomorph. The N. personata isolate IPAVE 0302 was obtained from peanut leaves in Córdoba, Argentina. The whole genome sequencing of IPAVE 0302 was performed as paired end 150 bp NovaSeq 6000 and de novo assembled. Clean reads were mapped to the reference genome for this species NRRL 64463 and the genetic variants on highly conserved genes and throughout the genome were analyzed. Sequencing data were submitted to NCBI GenBank Bioproject PRJNA948451, accession number SRR23957761. Additional Fasta files are available from Harvard Dataverse (https://doi.org/10.7910/DVN/9AGPMG and https://doi.org/10.7910/DVN/YDO3V6). The data reported here will be the basis for the analysis of genetic diversity of the LLS pathogen of peanut in Argentina, information that is critical to make decisions on management strategies.

Evolution of the Toxb Gene in Pyrenophora tritici-repentis and Related Species.

Pyrenophora tritici-repentis (tan spot) is a destructive foliar pathogen of wheat with global impact. This ascomycete fungus possesses a highly plastic open pangenome shaped by the gain and loss of effector genes. This study investigated the allelic variations in the chlorosis-encoding gene ToxB across 422 isolates representing all identified pathotypes and worldwide origins. To gain better insights into ToxB evolution, we examined its presence and variability in other Pyrenophora spp. A ToxB haplotype network was constructed, revealing the evolutionary relationships of this gene (20 haplotypes) across four Pyrenophora species. Notably, toxb, the homolog of ToxB, was detected for the first time in the barley pathogen Pyrenophora teres. The ToxB/toxb genes display evidence of selection that is characterized by loss of function, duplication, and diverse mutations. Within the ToxB/toxb open reading frame, 72 mutations were identified, including 14 synonymous, 55 nonsynonymous, and 3 indel mutations. Remarkably, a, ∼5.6-kb Copia-like retrotransposon, named Copia-1_Ptr, was found inserted in the toxb gene of a race 3 isolate. This insert disrupted the ToxB gene's function, a first case of effector gene disruption by a transposable element in P. tritici-repentis. Additionally, a microsatellite with 25 nucleotide repeats (0 to 10) in the upstream region of ToxB suggested a potential mechanism influencing ToxB expression and regulation. Exploring ToxB-like protein distribution in other ascomycetes revealed the presence of ToxB-like proteins in 19 additional species, including the Leotiomycetes class for the first time. The presence/absence pattern of ToxB-like proteins defied species relatedness compared with a phylogenetic tree, suggesting a past horizontal gene transfer event during the evolution of the ToxB gene. [Formula: see text] Copyright © 2024 His Majesty the King in Right of Canada, as represented by the Minister of Agriculture and Agri-Food. This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Cellular Automata Modeling as a Tool in Corrosion Management.

Cellular automata models have emerged as a valuable tool in corrosion management. This manuscript provides an overview of the application of cellular automata models in corrosion research, highlighting their benefits and contributions to understanding the complex nature of corrosion processes. Cellular automata models offer a computational approach to simulating corrosion behavior at the microscale, capturing the intricate interactions between electrochemical reactions, material properties, and environmental factors and generating a new vision of predictive maintenance. It reviews the key features of cellular automata, such as the grid-based representation of the material surface, the definition of state variables, and the rules governing cell-state transitions. The ability to model local interactions and emergent global behavior makes cellular automata particularly suitable for simulating corrosion processes. Finally, cellular automata models offer a powerful and versatile approach to studying corrosion processes, expanding models that can continue to enhance our understanding of corrosion and contribute to the development of effective corrosion prevention and control strategies.

Correction: Masi et al. Araufuranone: A New Phytotoxic Tetrasubstituted Dihydrofuro[3,2-b]furan-2(5H)-One Isolated from Ascochyta araujiae. Biomolecules 2022, 12, 1274.

In the original article [...].

SDHI resistance in Pyrenophora teres f teres and molecular detection of novel double mutations in sdh genes conferring high resistance.

BACKGROUND: Net blotch (NB), caused by Pyrenophora teres f. teres (Ptt), is an important disease of barley worldwide. NB control is commonly achieved through the use of fungicide mixtures including strobilurins, triazoles and carboxamides. Succinate dehydrogenase inhibitors (SDHI) are important components of fungicide management programs of barley diseases. However, during the last growing seasons in Argentina, barley fields sprayed with mixtures containing SDHI fungicides have shown failures in NB control. Here, we report the isolation and characterization of Argentine Ptt strains resistant to SDHI fungicides. RESULTS: Compared against a sensitive (wild-type) reference strain collected in 2008, all 21 Ptt isolates collected in 2021 exhibited resistance to pydiflumetofen and fluxapyroxad both in vitro and in vivo. Concordantly, all of them presented target-site mutations in any of the sdhB, sdhC and sdhD genes. Although the mutations detected have been previously reported in other parts of the world, this study documents for the first time the occurrence of double mutations in the same Ptt isolate. Specifically, the double mutation sdhC-N75S + sdhD-D145G confers high resistance to SDHI fungicides, while the double mutations sdhB-H277Y + sdhC-N75S and sdhB-H277Y + sdhC-H134R confer moderate levels of resistance in Ptt. CONCLUSIONS: SDHI-resistance in Argentine Ptt populations is expected to increase. These findings emphasize the urgent need to perform a wider survey and a more frequent monitoring of SDHI sensitivity of Ptt populations and to develop and implement effective antiresistance tactics. © 2023 Society of Chemical Industry.

Araufuranone: A New Phytotoxic Tetrasubstituted Dihydrofuro[3,2-b]furan-2(5H)-One Isolated from Ascochyta araujiae.

Araujia hortorum is a perennial vining plant species native to South America. It was introduced into many countries for ornamental and medicinal purposes as well as for its edible fruits, but it has become highly invasive, generating severe environmental problems. Biological control using bioherbicides and natural compounds is an interesting control option. The pathogenic fungus Ascochyta araujiae, isolated from infected leaves of A. hortorum, could be considered as a potential biocontrol agent. Its ability to produce bioactive metabolites was studied. The organic extract of the fungal culture filtrates showed interesting phytotoxic activities consisting of clearly visible necrotic symptoms (0.5-1 cm in diameter) in the punctured leaves. Thus, it was purified; this afforded three main metabolites. These were chemically and biologically characterised: one proved to be a new pentasubstituted dihydrofuro[3,2-b]furan-2(5H)-one, named araufuranone (1). The others were the already known fungal metabolites neovasinin and 2,4-dihydroxy-6-hydoxymethylbenzaldehyde (2 and 3). The structure of araufuranone was determined using spectroscopic methods (essentially 1D and 2D 1H and 13C NMR and HR ESIMS spectra); its relative configuration was assigned by a NOESY spectrum. To the best of our knowledge, araufuranone is the first example of a naturally occurring compound showing that carbon skeleton. Assayed by a puncture, araufuranone proved to be weakly active on the leaves of Diplotaxis sp. and Sonchus sp.; the other two metabolites were even less toxic. Tested on cress, compounds 2 and 3 were able to partially inhibit rootlet elongation whereas araufuranone was almost inactive.

Truncatenolide, a Bioactive Disubstituted Nonenolide Produced by Colletotrichum truncatum, the Causal Agent of Anthracnose of Soybean in Argentina: Fungal Antagonism and SAR Studies.

A bioactive disubstituted nonenolide, named truncatenolide, was produced by Colletotrichum truncatum, which was collected from infected tissues of soybean showing anthracnose symptoms in Argentina. This is a devastating disease that drastically reduces the yield of soybean production in the world. The fungus also produced a new trisubstituted oct-2-en-4-one, named truncatenone, and the well-known tyrosol and N-acetyltyramine. Truncatenolide and truncatenone were characterized by spectroscopic (essentially one-dimensional (1D) and two-dimensional (2D) 1H and 13C NMR and HR ESIMS) and chemical methods as (5E,7R,10R)-7-hydroxy-10-methyl-3,4,7,8,9,10-hexahydro-2H-oxecin-2-one and (Z)-6-hydroxy-3,5-dimethyloct-2-en-4-one, respectively. The geometry of the double bond of truncatenolide was assigned by the value of olefinic proton coupling constant and that of truncatenone by the correlation observed in the corresponding NOESY spectrum. The relative configuration of each stereogenic center was assigned with the help of 13C chemical shift and 1H-1H scalar coupling DFT calculations, while the absolute configuration assignment of truncatenolide was performed by electronic circular dichroism (ECD). When tested on soybean seeds, truncatenolide showed the strongest phytotoxic activity. Tyrosol and N-acetyltyramine also showed phytotoxicity to a lesser extent, while truncatenone weakly stimulated the growth of the seed root in comparison to the control. When assayed against Macrophomina phaseolina and Cercospora nicotianae, other severe pathogens of soybean, truncatenolide showed significant activity against M. phaseolina and total inhibition of C. nicotianae. Thus, some other fungal nonenolides and their derivatives were assayed for their antifungal activity against both fungi in comparison with truncatenolide. Pinolidoxin showed to a less extent antifungal activity against both fungi, while modiolide A selectively and totally inhibited only the growth of C. nicotianae. The SAR results and the potential of truncatenolide, modiolide A, and pinolidoxin as biofungicides were also discussed.

Pseudomonas fluorescens Showing Antifungal Activity against Macrophomina phaseolina, a Severe Pathogenic Fungus of Soybean, Produces Phenazine as the Main Active Metabolite.

Pseudomonas fluorescens 9 and Bacillus subtilis 54, proposed as biofungicides to control Macrophomina phaseolina, a dangerous pathogen of soybean and other crops, were grown in vitro to evaluate their ability to produce metabolites with antifungal activity. The aim of the manuscript was to identify the natural compounds responsible for their antifungal activity. Only the culture filtrates of P. fluorescens 9 showed strong antifungal activity against M. phaseolina. Its organic extract contained phenazine and mesaconic acid (1 and 2), whose antifungal activity was tested against M. phaseolina, as well as Cercospora nicotianae and Colletotrichum truncatum, other pathogens of soybean; however, only compound 1 exhibited activity. The antifungal activity of compound 1 was compared to phenazine-1-carboxylic acid (PCA, 3), 2-hydroxyphenazine (2-OH P, 4), and various semisynthetic phenazine nitro derivatives in order to perform a structure-activity relationship (SAR) study. PCA and phenazine exhibited the same percentage of growth inhibition in M. phaseolina and C. truncatum, whereas PCA (3) showed lower activity against C. nicotianae than phenazine. 2-Hydroxyphenazine (4) showed no antifungal activity against M. phaseolina. The results of the SAR study showed that electron attractor (COOH and NO2) or repulsor (OH) groups significantly affect the antifungal growth, as well as their α- or ß-location on the phenazine ring. Both PCA and phenazine could be proposed as biopesticides to control the soybean pathogens M. phaseolina, C. nicotianae, and C. truncatum, and these results should prompt an investigation of their large-scale production and their suitable formulation for greenhouse and field applications.

Current recommendations and novel strategies for sustainable management of soybean sudden death syndrome.

The increase in food production requires reduction of the damage caused by plant pathogens, minimizing the environmental impact of management practices. Soil-borne pathogens are among the most relevant pathogens that affect soybean crop yield. Soybean sudden death syndrome (SDS), caused by several distinct species of Fusarium, produces significant yield losses in the leading soybean-producing countries in North and South America. Current management strategies for SDS are scarce since there are no highly resistant cultivars and only a few fungicide seed treatments are available. Because of this, innovative approaches for SDS management need to be developed. Here, we summarize recently explored strategies based on plant nutrition, biological control, priming of plant defenses, host-induced gene silencing, and the development of new SDS-resistance cultivars using precision breeding techniques. Finally, sustainable management of SDS should also consider cultural control practices with minimal environmental impact. © 2021 Society of Chemical Industry.

Phaseocyclopentenones A and B, Phytotoxic Penta- and Tetrasubstituted Cyclopentenones Produced by Macrophomina phaseolina, the Causal Agent of Charcoal Rot of Soybean in Argentina.

Two new penta- and tetrasubstituted cyclopentenones, named phaseocyclopentenones A and B (1 and 2), together with guignardone A (3), were isolated from Macrophomina phaseolina cultures. The phytopathogenic fungus was isolated from infected soybean tissues showing charcoal rot symptoms in Argentina. Charcoal rot is a devastating disease considering that soybean is one of the main legumes cultivated in the world. Phaseocyclopentenones A and B were characterized by 1D and 2D 1H and 13C NMR spectroscopic and HRESIMS spectrometric data and chemical methods as 4-benzoyl-3,4,5-trihydroxy-2-phenylcyclopent-2-enone and 3,5-dihydroxy-2,4-diphenylcyclopent-2-enone, respectively. The relative configuration of phaseocyclopentenones A and B was assigned by 1H and NOESY NMR methods, while their absolute configurations were assigned by electronic circular dichroism methods. When assayed on a nonhost plant (Solanum lycopersicum L.) by the leaf puncture assay, phaseocyclopentenones A and B and guignardone A showed phytotoxic activity, while only 1 and 2 were toxic when tested on cuttings of the same plant. No phytotoxicity or antifungal activity was detected for the three compounds on the host plant soybean (Glycine max L.) and against some of its fungal pathogens, namely, Cercospora nicotianae and Colletotrichum truncatum, also isolated from infected soybean plants in Argentina.

Antifungal susceptibility profile and molecular identification of Cyp51C mutations in clinical and environmental isolates of Aspergillus flavus from Argentina.

BACKGROUND: The emergence of azole resistance in non-fumigatus Aspergillus strains is on the raise. OBJECTIVES: To study the susceptibility profiles and the molecular mechanisms of azole resistance of environmental and clinical strains of Aspergillus flavus from Argentina. METHODS: Thirty-five A flavus isolates (18 from soybean seeds and chickpea seeds and 17 from the clinic) were analysed for amphotericin B and azole resistance using the standard microbroth dilution method according to CLSI M38-A2 guidelines. Sequencing analysis of the cyp51 genes was conducted in those isolates displaying high MICs values to itraconazole, voriconazole and/or posaconazole. RESULTS: Among the environmental isolates, 33.3% of them showed high MIC values for at least one triazole whereas 23.5% of the clinical isolates displayed high MIC values for amphotericin B. Point mutations in the Cyp51C gene were recorded in most environmental isolates with non-wild-type MIC values. CONCLUSIONS: Susceptibility differences among environmental A flavus isolates might suggest the possibility of native resistance to certain triazole antifungals used in the clinic. To the best of our knowledge, this is the first report of antifungal screening of environmental strains of A flavus in soybean seeds and chickpea seeds from Argentina that showed increased resistance to voriconazole and itraconazole in comparison to clinical strains.

Role of Fungicide Applications on the Integrated Management of Wheat Stripe Rust.

First described in Europe in 1777, stripe rust (SR) caused by Puccinia striiformis Westend. f. sp. tritici Erikss (Pst) is one of the most important and destructive diseases of wheat worldwide. Until 2000, SR was mainly endemic to cooler regions, but since then, new aggressive strains have emerged, spread intercontinentally, and caused severe epidemics in warmer regions across the world. This has put SR as a disease that poses a threat to the world food security. At present, the preferred strategy for control of SR is the access to wheat cultivars with adequate levels of SR resistance. However, wheat breeding programs are not sufficiently advanced to cope with the recently emerged Pst strains. Under this scenario, foliar fungicide applications have become an important component of SR management, but information on the effects of fungicide applications on SR control and wheat cultivar yield response is scarce. This review seeks to provide an overview of the impact and role of fungicides on SR management. With focus on wheat management in the major wheat-growing regions of the world, the review addresses: (a) the efficacy of different fungicide active ingredients, optimal fungicide timing and number of applications in controlling SR, and (b) the impact of fungicide on wheat grain yield response. Inclusion of fungicides in an integrated crop management approach is discussed.

Draft genome sequence data of Cercospora kikuchii, a causal agent of Cercospora leaf blight and purple seed stain of soybeans.

Cercospora kikuchii (Tak. Matsumoto & Tomoy.) M.W. Gardner 1927 is an ascomycete fungal pathogen that causes Cercospora leaf blight and purple seed stain on soybean. Here, we report the first draft genome sequence and assembly of this pathogen. The C. kikuchii strain ARG_18_001 was isolated from soybean purple seed collected from San Pedro, Buenos Aires, Argentina, during the 2018 harvest. The genome was sequenced using a 2 × 150 bp paired-end method by Illumina NovaSeq 6000. The C. kikuchii protein-coding genes were predicted using FunGAP (Fungal Genome Annotation Pipeline). The draft genome assembly was 33.1 Mb in size with a GC-content of 53%. The gene prediction resulted in 14,856 gene models/14,721 protein coding genes. Genomic data of C. kikuchii presented here will be a useful resource for future studies of this pathosystem. The data can be accessed at GenBank under the accession number VTAY00000000 https://www.ncbi.nlm.nih.gov/nuccore/VTAY00000000.

Effect of potassium and manganese phosphites in the control of Pythium damping-off in soybean: a feasible alternative to fungicide seed treatments.

BACKGROUND: Use of fungicide seed treatments for control of soybean soilborne diseases such as Pythium damping-off has increased worldwide. However, emergence of Pythium strains resistant to metalaxyl-M has prompted the need for alternative technologies to fungicides for damping-off control. The use of phosphites (Phis) has been proposed as a method to control oomycetes, but their use as seed treatments in soybean is limited by the lack of information on their efficacy. The effect of potassium (K) and manganese (Mn) Phis (as seed treatments) in the control of Pythium damping-off in soybean was evaluated in vitro and in vivo. In vitro, treated seeds and a control were placed on potato dextrose agar and the damping-off severity caused by Pythium aphanidermatum (Edson) Fitzpatrick, Pythium irregulare Buisman, and Pythium ultimum Trow was assessed 5 days after incubation using an ordinal scale. In vivo, treated seeds and a control were planted in polystyrene pots and emergence was evaluated 21 days after planting. RESULTS: Analysis of the in vitro data using a multinomial generalized linear model showed that the probabilities of non-germinated, dead seeds ranged from 0.64 to 1.00 in the control and from 0 to 0.13 in the Phi treatments in each of the Pythium species. Probabilities of seed germination without or with damping-off symptoms were significantly higher for seeds treated with the Phi products than for the control. In the in vivo experiment, the Phi-based products increased seedling emergence by up to 29% on average compared with the untreated control. CONCLUSION: Mn and K Phis are feasible alternatives as seed treatments to control Pythium damping-off in soybean. This study is the first, worldwide, to document the efficacy of K and Mn Phis in the control of soybean Pythium damping-off. © 2017 Society of Chemical Industry.

Detección de Porphyromonas gingivalis en pacientes adultos con periodontitis crónica / Porphyromonas gingivalis detection in adult patient with chronic periodontitis

Se realizó la detección de Porphyromonas gingivalis (P. gingivalis) en pacientes adultos con periodontitis crónica que se atendieron en la Clínica de Periodoncia de la Universidad de Antofagasta, a través de técnicas de microbiología convencional y técnica de biología molecular. fueron obtenidas muestras de fluido gingival crevicular de 37 pacientes con periodontitis crónica, con conos de papel (N 30) por 20 segundos del sitio periodontal más severo de cada cuadrante, posteriormente se realizó cultivo microbiológico en agar sangre y se detectó la presencia de P. gingivalis a través de técnicas de microbiología convencional (lupa estereoscópica y fluorescencia) y técnica de biología molecular (reacción en cadena de la polimerasa). se detectó con lupa estereoscópica colonias pigmentadas de negro en el 75,7 % de las muestras (n=28), de ellas el 67,9 % fueron positivas para P. gingivalis con la técnica de fluorescencia (n=19). A través de la reacción en cadena de la polimerasa se pudo confirmar que el 84,2 % de las colonias positivas por fluorescencia correspondían a P. gingivalis (n=16). En la población de estudio analizada es posible concluir que existe una alta prevalencia de P. gingivalis en la microbiota subgingival de los pacientes con periodontitis crónica lo que ha sido detectado a través de técnicas de microbiología convencional y mediante la reacción en cadena de la Polimerasa. Los pacientes fumadores presentaron mayor presencia de P. gingivalis que los no fumadores.

The detection of Porphyromonas gingivalis (P. gingivalis) was performed in adult patients with chronic periodontitis treated at the Clinic of Periodontology in the University of Antofagasta, through of microbiology techniques conventional and molecular biology. Were obtained samples of gingival crevicular fluid with paper cones (N 30) for 20 seconds of the more severe periodontal site in each quadrant, 37 patients were studied with chronic periodontitis, subsequent microbiological culture was performed on blood agar and the presence of P. gingivalis was detected through conventional microbiology techniques (fluorescence and stereomicroscope) and molecular biology technique (polymerase chain reaction). There was detected with stereomicroscope pigmented black in 75.7 % of the samples, of which 67.9 % were positive for P. gingivalis with the fluorescence technique. Through the polymerase chain reaction it was confirmed that 84.2 % of fluorescence positive colonies corresponded to P. gingivalis. In the population analyzed can conclude that there is a high prevalence of P. gingivalis in the subgingival microbiota of patients with chronic periodontitis which has been detected through techniques of conventional microbiology and by polymerase chain reaction. The smokers had a higher presence of P. gingivalis than nonsmokers.

[In vitro susceptibility of Trichoconiella padwickii to various active ingredients used as fungicides in the cultivation of rice]. / Sensibilidad in vitro de Trichoconiella padwickii a diversos principios activos usados como fungicidas en el cultivo del arroz.

The aim of this study was to evaluate in vitro the mycelial susceptibility of Trichoconiella padwickii to different active ingredients through average median concentration IC50 calculation. Inoculum disks were seeded on bean agar at different concentrations (0.1; 1; 10; 30, 50; 100 and 1000mg/l) of various fungicides. After seven days the colony diameter was measured. The data obtained were fitted to nonlinear regression models. Susceptibility was classified using the scale proposed by Edgington. The results show that the pathogen is very sensitive to products that act on the respiratory chain (quinone outside inhibitors [QoI] and succinate dehydrogenase inhibitors [SDHI]) and cell membrane (multi-site contact activity), and moderately sensitive to those products interfering with cell division (methyl benzimidazole carbamates [MBC]), synthesis of nucleic acids (phenylamides [PA]) and osmotic signal transduction (multi-site contact activity). This work is the first record on the sensitivity of T. padwickii.

Sensibilidad in vitro de Trichoconiella padwickii a diversos principios activos usados como fungicidas en el cultivo del arroz / In vitro susceptibility of Trichoconiella padwickii to various active ingredients used as fungicides in the cultivation of rice

El objetivo de este trabajo fue evaluar in vitro la sensibilidad micelial de Trichoconiella padwickii a diferentes principios activos por medio del cálculo de la concentración inhibitoria media (CI50). Para ello se realizaron siembras de discos de inóculo en agar poroto con distintas concentraciones (0,1; 1; 10; 30, 50; 100 y 1.000 mg/l) de diversos fungicidas. A los 7 días se midió el diámetro de crecimiento de la colonia (cm). Los datos obtenidos se ajustaron a modelos de regresión no lineal. La sensibilidad se clasificó utilizando la escala de Edgington. Los resultados obtenidos demuestran que el patógeno es muy sensible a los productos que actúan sobre la cadena respiratoria (quinone outside inhibitors QoI y succinate dehydrogenase inhibitors SDHI) y la membrana celular (multisitio), y moderadamente sensible a los que interfieren en la división celular (metil benzimidazol carbamatos MBC), en la síntesis de ácidos nucleicos (fenilamidas PA) y en la transducción de la señal osmótica (actividad multisitio). Este trabajo es el primer antecedente sobre la sensibilidad in vitro de T. padwickii a principios activos fungicidas.

The aim of this study was to evaluate in vitro the mycelial susceptibility of Trichoconiella padwickii to different active ingredients through average median concentration IC50 calculation. Inoculum disks were seeded on bean agar at different concentrations (0.1; 1; 10; 30, 50; 100 and 1000 mg/l) of various fungicides. After seven days the colony diameter was measured. The data obtained were fitted to nonlinear regression models. Susceptibility was classified using the scale proposed by Edgington. The results show that the pathogen is very sensitive to products that act on the respiratory chain (quinone outside inhibitors QoI and succinate dehydrogenase inhibitors SDHI) and cell membrane (multi-site contact activity), and moderately sensitive to those products interfering with cell division (methyl benzimidazole carbamates MBC), synthesis of nucleic acids (phenylamides PA) and osmotic signal transduction (multi-site contact activity). This work is the first record on the sensitivity of T. padwickii.

Evaluation of native bacteria and manganese phosphite for alternative control of charcoal root rot of soybean.

Plant growth promoting rhizobacteria (PGPR) are potential agents to control plant pathogens and their combined use with biopesticides such as phosphites may constitute a novel strategy to incorporate in disease management programs. In the present study, 11 bacterial isolates were selected on the basis of their antagonistic activity against Macrophomina phaseolina in dual-culture tests, and their plant growth promoting traits. Selected isolates were characterised on the basis of auxin and siderophore production, phosphate solubilisation and rep-PCR genomic fingerprinting. Two of these isolates, identified as Pseudomonas fluorescens 9 and Bacillus subtilis 54, were further evaluated for their inhibitory capacity against M. phaseolina using in vitro (on soybean seeds) and in vivo (greenhouse assay) tests. Both bacteria were applied individually as well as in combined treatment with manganese phosphite as seed treatments. Damage severity on soybean seeds was significantly reduced, compared with the untreated control, by both bacterial strains; however, the individual application of phosphite showed to be least effective in controlling M. phaseolina. Interestingly, the phosphite treatment improved its performance under greenhouse conditions compared to the results from the in vitro assays. In the greenhouse trials, the greatest reductions in disease severity were achieved when strain P. fluorescens 9 was applied singly or when strain B. subtilis 54 was combined with manganese phosphite, achieving 82% of control in both cases. This work is the first to report the control of M. phaseolina using combined treatment with PGPR and phosphite under greenhouse conditions.