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Phytopathogenic fungi significantly threaten global food security, causing substantial yield and quality losses. Sustainable solutions are urgently needed to combat these agricultural pathogens. This study explored the potential of silver (Ag), copper (Cu), and combined Ag/Cu nanoparticles capped with aminolevulinic acid (ALA) as antifungal agents. The nanoparticles (ALAAg, ALACu, and ALAAgCu) were synthesized via photoreduction and characterized using various techniques (UV-Vis, TEM, XRD, Zeta potential). Their antifungal activity against four key plant pathogens (Alternaria grandis, Colletotrichum truncatum, Corynespora cassiicola, and Fusarium oxysporum) was evaluated using poisoned food techniques. Notably, ALAAgCuNPs demonstrated superior antifungal activity compared to a conventional fungicide against two fungal strains. Even at lower concentrations, ALAAgCuNPs exhibited fungistatic effects comparable to those of the control. These promising results suggest the potential of ALAAgCu NPs as a broad-spectrum, potentially eco-friendly alternative for fungal control in plants and seeds. This approach is crucial for ensuring crop health, harvest quality, and food safety.

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Genetic variability in phytopathogens is one of the main problems encountered for effective plant disease control. This fact may be related to the presence of transposable elements (TEs), but little is known about their role in host genomes. Here, we performed the most comprehensive analysis of insertion sequences (ISs) and transposons (Tns) in the genomes of the most important bacterial plant pathogens. A total of 35 692 ISs and 71 transposons were identified in 270 complete genomes. The level of pathogen-host specialization was found to be a significant determinant of the element distribution among the species. Some Tns were identified as carrying virulence factors, such as genes encoding effector proteins of the type III secretion system and resistance genes for the antimicrobial streptomycin. Evidence for IS-mediated ectopic recombination was identified in Xanthomonas genomes. Moreover, we found that IS elements tend to be inserted in regions near virulence and fitness genes, such ISs disrupting avirulence genes in X. oryzae genomes. In addition, transcriptome analysis under different stress conditions revealed differences in the expression of genes encoding transposases in the Ralstonia solanacearum, X. oryzae, and P. syringae species. Lastly, we also investigated the role of Tns in regulation via small noncoding regulatory RNAs and found these elements may target plant-cell transcriptional activators. Taken together, the results indicate that TEs may have a fundamental role in variability and virulence in plant pathogenic bacteria.

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Corn head smut is a disease caused by the fungus Sporisorium reilianum. This phytosanitary problem has existed for several decades in the Mezquital Valley, an important corn-producing area in central Mexico. To combat the problem, a strain identified as Bacillus subtilis 160 was applied in the field, where it decreased disease incidence and increased crop productivity. In this study, the sequencing and analysis of the whole genome sequence of this strain were carried out to identify its genetic determinants for the production of antimicrobials. The B. subtilis 160 strain was found to be Bacillus velezensis. Its genome has a size of 4,297,348 bp, a GC content of 45.8%, and 4,174 coding sequences. Comparative analysis with the genomes of four other B. velezensis strains showed that they share 2,804 genes and clusters for the production of difficidin, bacillibactin, bacilysin, macrolantin, bacillaene, fengycin, butirosin A, locillomycin, and surfactin. For the latter metabolite, unlike the other strains that have only one cluster, B. velezensis 160 has three. A cluster for synthesizing laterocidine, an antimicrobial reported only in Brevibacillus laterosporus, was also identified. IMPORTANCE: In this study, we performed sequencing and analysis of the complete genome of the strain initially identified as Bacillus subtilis 160 as part of its characterization. This bacterium has shown its ability to control corn head smut in the field, a disease caused by the basidiomycete fungus Sporisorium reilianum. Analyzing the complete genome sequence not only provides a more precise taxonomic identification but also sheds light on the genetic potential of this bacterium, especially regarding mechanisms that allow it to exert biological control. Employing molecular and bioinformatics tools in studying the genomes of agriculturally significant microorganisms offers insights into the development of biofungicides and bioinoculants. These innovations aim to enhance plant growth and pave the way for strategies that boost crop productivity.

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Bacteria from RSSC hold agricultural significance as they are the causal agents of bacterial wilt. Here, we report the draft genomes of two bacteria extracted from vascular tissues of infected tomato plants. Isolate RALF-MA was classified as Ralstonia pseudosolanacearum (phylotype I) and RALSA-MA as Ralstonia solanacearum (phylotype II).

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With global climate changes and the increased demand for food due to expected world population growth, genetic improvement programs have aimed at producing crops with increased yield and tolerance to environmental stresses, such as drought, salinity, and pathogens. On the other hand, genetic improvement programs via biotechnology require candidate genes that confer traits of interest to be incorporated into improved crops. In this regard, genes encoding transcription factors (TFs) can be promising since they are proteins that transcriptionally regulate the expression of target genes related to the most diverse roles in the plant, including defense against stresses. Among TFs, bZIP (basic leucine zipper) proteins regulate many developmental and physiological processes in the plant, such as seed formation, fruit ripening, nutrient assimilation, and defense response to abiotic and biotic stresses. In this review, we aim to highlight the main advances in the potential use of bZIP TFs in the genetic improvement of crops. We address this potential mainly regarding crop tolerance to stresses and other agricultural traits, such as increased yield and fruit features.

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Tomato is one of the most produced and consumed fruits in the world. However, it is a crop that faces several phytosanitary problems, such as fusarium wilt, caused by Fusarium oxysporum. Thus, this study aimed to evaluate citronella and melaleuca essential oils in vitro potential in the fungus F. oxysporum management. The chemical identification of the components in the essential oils was performed by gas chromatography with flame ionization and mass spectrometer detectors. The IC50 and IC90 were determined by linear regression and the percentage of inhibition of the fungus by analysis of variance. The major compounds in citronella essential oil were citronellal, Geraniol, and citronellol; in melaleuca (tea tree) oil were terpinen-4-ol and α-terpinene. Both oils promoted more significant inhibition at concentrations of 1.5 and 2.5 µL/mL, besides not presenting significant differences with commercial fungicides, confirming the high potential for using this control method in agriculture.

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The use of natural products obtained from plants, for example, invasive plants, offers a variety of allelochemicals with fungicidal potential. With this in perspective, the objective was to evaluate the fungicidal potential of ethanolic extracts of Cerrado plants on Rhizoctonia solani and Macrophomina phaseolina. The ethanolic hydroalcoholic extract of the 12 plants identified as invaders in the Brazilian Cerrado was prepared (Anacardium humile Saint Hill; Baccharis dracunculifolia DC.; Cenchrus echinatus L; Commelina erecta L.; Erigeron bonariensis L.; Digitaria horizontalis Willd.; Digitaria insularis L.; Porophyllum ruderale Jacq. Cass; Richardia brasiliensis Gomes; Sida rhombifolia L.; Turnera ulmifolia L.; Smilax fluminensis Steud)) and phytochemical screening and determination of total phenols and flavonoids were performed. To evaluate the in vitro antifungal activity, the hydroalcoholic solutions at concentrations of 800, 1200, 1600, 2000, and 2400 µL 100 mL-1 were separately incorporated into BDA agar and poured into Petri dishes, followed by the mycelium disk of the fungus. As a control, two solutions were prepared, one ethanolic solution added to the BDA medium (2400 µg 100 mL-1) and the other with BDA medium only. They were poured into Petri dishes, followed by a 0.5 cm diameter disk of mycelium of the fungus, incubated (23±2 ºC), with a 24-hour photoperiod. Among the constituents found in the plants, 75% are phenolic compounds, 58.3% are cardiotonic heterosides, 50% are steroids, 33.3% are flavonoids, 16.7% are anthraquinones, and 8.3% are alkaloids, saponins, and reducing sugars. Out of the 12 species, only the extracts of C. erecta and R. brasiliensis were active for M. phaseolina and R. solani. Thus, it is concluded that the ethanolic extract of C. erecta has the fungicidal potential to control diseases caused by fungi that are soil inhabitants. Of the other species, A. humille, B. dracuncufolia, D. insulares, C. erecta, D. insulares, P. ruderale, and R. brasiliensis have natural fungitoxic potential because they stand out in the content of polyphenols efficient in reducing the mycelial growth of M. phaseolina and R. solani.

O uso de produtos naturais obtidos de plantas, por exemplo, as plantas invasoras, oferece uma variedade de aleloquímicos com potencial fungicida. Tendo isso em vista, objetivou-se avaliar o potencial fungicida de extratos etanólicos de plantas do Cerrado sobre Rhizoctonia solani e Macrophomina phaseolina. Foi preparado o extrato hidroalcoólicos etanólico das 12 plantas apontadas como invasoras no Cerrado brasileiro (Anacardium humile Saint Hill; Baccharis dracunculifolia DC.; Cenchrus echinatus L; Commelina erecta L.; Erigeron bonariensis L.; Digitaria horizontalis Willd.; Digitaria insularis L.; Porophyllum ruderale Jacq. Cass; Richardia brasiliensis Gomes; Sida rhombifolia L.; Turnera ulmifolia L.; Smilax fluminensis Steud) e foi realizado o screening fitoquímico e a determinação de fenóis e flavonoides totais. Para avaliar a atividade antifúngica in vitro, as soluções hidroalcóolicas nas concentrações de 800, 1200, 1600, 2000 e 2400 µL 100 mL-1 foram incorporadas, separadamente, em ágar BDA, e vertidas em placa de Petri, seguido do disco de micélio do fungo. Como controle, foram preparadas duas soluções, uma solução etanólica adicionada ao meio BDA (2400 µg 100 mL-1), e outra somente com meio BDA, a testemunha. Foram vertidas em placas de Petri, seguido um disco de 0,5 cm de diâmetro de micélio do fungo, incubados (23±2 ºC), com fotoperíodo de 24 horas. Dentre os constituintes encontrados nas plantas, 75% estão os compostos fenólicos, 58,3% estão os heterosídeos cardiotônicos, 50% estão os esteroides, 33,3% estão os flavonoides, 16,7% estão as antraquinonas e 8,3% estão os alcaloides, saponinas e açúcares redutores. Das 12 espécies, apenas os extratos de C. erecta e R. brasiliensis foram ativos para M. phaseolina e R. solani. Desse modo, conclui-se que o extrato etanólico de C. erecta apresenta potencial fungicida para controle de doenças causadas por fungos habitantes do solo. Das demais espécies, a A. humille, B. dracuncufolia, D. insulares, C. erecta, D. insulares, P. ruderale e R. brasiliensis possuem potencial fungitóxicos naturais por destacarem nos teores de polifenóis eficientes na redução do crescimento micelial de M. phaseolina e R. solani.

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IMPORTANCE: Pathogenic Xanthomonas bacteria can affect a variety of economically relevant crops causing losses in productivity, limiting commercialization and requiring phytosanitary measures. These plant pathogens exhibit high level of host and tissue specificity through multiple molecular strategies including several secretion systems, effector proteins, and a broad repertoire of carbohydrate-active enzymes (CAZymes). Many of these CAZymes act on the plant cell wall and storage carbohydrates, such as cellulose and starch, releasing products used as nutrients and modulators of transcriptional responses to support host colonization by mechanisms yet poorly understood. Here, we reveal that structural and storage ß-glucans from the plant cell function as spatial markers, providing distinct chemical stimuli that modulate the transition between higher and lower motility states in Xanthomonas citri, a key virulence trait for many bacterial pathogens.

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Larrea nitida Cav. (Zygophyllaceae) is a plant endemic to Argentina and Chile, and its extract has been studied over the last years due to the presence of antimicrobial agents that can be used to control the growth of some pathogens in agriculture. However, the extract is highly hydrophobic, which strongly affects its fungicidal activity in aqueous media. In this sense, the solid dispersion technique was used to produce L. nitida extract nanodispersions with polyethylene glycol (PLE) and with polyethylene glycol and zinc acetate (PZLE). In order to further evaluate the activity of the extract in PLE and PZLE, blank nanodispersions containing only polyethylene glycol (PEG) and zinc acetate (PZ) without the addition of the extract were also produced. The fungicidal activity of the water-soluble nanoparticles was evaluated at different concentrations (0.037-0.110 g.mL-1). In general, the nanoparticles were successfully produced on a nanometric size and presented a significant inhibitory activity on the growth of the pathogens Fusarium oxysporum and Fusarium verticillioides in aqueous media. Compared to PLE, PZLE presented increased fungistatic activity, possibly due to their increased solubility in water. Even though their application in agriculture should be further investigated, the nanodispersions present great potential to be applied as a green biotechnological tool.