Plant Pathogenic Species Research Articles

Effect of Organic and Conventional Cereal Production Methods on Fusarium Head Blight and Mycotoxin Contamination Levels

Fusarium mycotoxins in cereals constitute major problems for animal and human health worldwide. A range of plant pathogenic Fusarium species that can infect cereal plants in the field are considered the most important source of mycotoxins, such as deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin, and HT-2 toxin, in small-grain cereal crops in temperate climates. In this article, we (i) critically review the available knowledge on the impact of contrasting production systems (organic versus conventional) and specific agronomic parameters on the occurrence and concentrations of DON, ZEA, and T-2/HT-2 in small-grain cereals (wheat, oats, barley, and rye), and (ii) discuss Fusarium mycotoxin risks in the context of the need to develop more sustainable cereal production systems. Overall, the available evidence from studies of acceptable scientific quality suggests that the incidence and concentrations of Fusarium mycotoxin are lower in organic compared with conventional cereals. Specifically, 24 comparisons showed lower mycotoxin levels in organic production, 16 detected no significant difference, and only 2 showed higher levels in organic production. When the mean concentrations from all studies were compared, conventionally produced cereals had 62%, 110%, and 180% higher concentrations of DON, ZEA, and T-2/HT-2, respectively, than organic cereals. Overall, published studies on the effects of specific agronomic practices on mycotoxin levels suggest that diverse crop rotations and high soil organic matter content/biological activity are associated with a lower risk of Fusarium mycotoxin contamination, whereas (i) high mineral nitrogen fertiliser inputs, (ii) some fungicides and herbicides, and (iii) minimum or no tillage may increase the risks of Fusarium mycotoxin contamination in cereals. The management of Fusarium head blight and mycotoxins, therefore, requires a preventative, integrated, holistic agronomic approach.

Fungal Pathogenesis-Related Cell Wall Biogenesis, with Emphasis on the Maize Anthracnose Fungus Colletotrichum graminicola.

The genus Colletotrichum harbors many plant pathogenic species, several of which cause significant yield losses in the field and post harvest. Typically, in order to infect their host plants, spores germinate, differentiate a pressurized infection cell, and display a hemibiotrophic lifestyle after plant invasion. Several factors required for virulence or pathogenicity have been identified in different Colletotrichum species, and adaptation of cell wall biogenesis to distinct stages of pathogenesis has been identified as a major pre-requisite for the establishment of a compatible parasitic fungus–plant interaction. Here, we highlight aspects of fungal cell wall biogenesis during plant infection, with emphasis on the maize leaf anthracnose and stalk rot fungus, Colletotrichum graminicola.

Basidiomycota Fungi and ROS: Genomic Perspective on Key Enzymes Involved in Generation and Mitigation of Reactive Oxygen Species.

Our review includes a genomic survey of a multitude of reactive oxygen species (ROS) related intra- and extracellular enzymes and proteins among fungi of Basidiomycota, following their taxonomic classification within the systematic classes and orders, and focusing on different fungal lifestyles (saprobic, symbiotic, pathogenic). Intra- and extracellular ROS metabolism-involved enzymes (49 different protein families, summing 4170 protein models) were searched as protein encoding genes among 63 genomes selected according to current taxonomy. Extracellular and intracellular ROS metabolism and mechanisms in Basidiomycota are illustrated in detail. In brief, it may be concluded that differences between the set of extracellular enzymes activated by ROS, especially by H2O2, and involved in generation of H2O2, follow the differences in fungal lifestyles. The wood and plant biomass degrading white-rot fungi and the litter-decomposing species of Agaricomycetes contain the highest counts for genes encoding various extracellular peroxidases, mono- and peroxygenases, and oxidases. These findings further confirm the necessity of the multigene families of various extracellular oxidoreductases for efficient and complete degradation of wood lignocelluloses by fungi. High variations in the sizes of the extracellular ROS-involved gene families were found, however, among species with mycorrhizal symbiotic lifestyle. In addition, there are some differences among the sets of intracellular thiol-mediation involving proteins, and existence of enzyme mechanisms for quenching of intracellular H2O2 and ROS. In animal- and plant-pathogenic species, extracellular ROS enzymes are absent or rare. In these fungi, intracellular peroxidases are seemingly in minor role than in the independent saprobic, filamentous species of Basidiomycota. Noteworthy is that our genomic survey and review of the literature point to that there are differences both in generation of extracellular ROS as well as in mechanisms of response to oxidative stress and mitigation of ROS between fungi of Basidiomycota and Ascomycota.

ANTAGONIST ACTIVITY OF Streptomyces sp. Y20 AGAINST FUNGI CAUSING DISEASES IN PLANTS AND FRUITS

<p><strong>Background</strong>: Crop microbial pathogens reduce the production and quality of agricultural products. They cause substantial increase costs for producers of fruits, vegetables, and ornamental plants with negative consequences on economy and food security at household, national and global levels. Annually, the losses represent around 40% to 50% for root crops, vegetables, and fruits. Chemical control with fungicides can prevent, kill, mitigate, or inhibit the growth of plant pathogenic fungi. Nevertheless, biological control with microorganisms and natural molecules is an increasingly popular alternative to protect crops. <strong>Objective:</strong> Here, the antagonist activity of soil <em>Streptomyces</em> sp. Y20 against the pathogenic fungi causing diseases in plants and fruits was evaluated. <strong>Methodology</strong>: Streptomycetes bacteria was isolated from soils collected at open field cultures of local farms with tomato. The antagonism was evaluated <em>in vitro</em> via a dual confrontation experiment against fungal species of <em>Fusarium</em>, <em>Lasiodiplodia</em>, <em>Colletotrichum</em>, <em>Aspergillus</em>, <em>Botrytis, </em>and <em>Sclerotium</em>. <em>Streptomyces </em>sp. Y20 was characterized phenotypically and molecularly identified by the 16S rDNA gene. The biosynthetic gene clusters for polyketide synthases (PKS Type I) and non-ribosomal peptide synthase (NSPS) were detected. <strong>Results</strong>: Preliminary, the isolate Y20 was selected by the higher antagonism against <em>F. oxysporum</em> f sp. <em>lycopersici</em>. Taxonomic characterization of the isolate Y20 by the analysis of the 16S rDNA sequence led to its identification as member of <em>Streptomyces</em> genus. Spore surface morphology by Scanning Electronic Microscopy (SEM) showed barrel-like spores. Antagonistic activity of <em>Streptomyces</em> sp Y20 was comparable to the commercial strain <em>S. lydicus</em> WYEC108 (P > 0.5). However, there was a superior antagonism of Y20 strain versus the commercial strain WYEC108 against <em>F. oxysporum</em> f sp. <em>lycopersici</em>, <em>Fusarium</em> sp. CDBB1172, <em>F. oxysporum</em>, <em>Lasiodiplodia</em> sp., and <em>Aspergillus</em> sp. (P < 0.05). <strong>Implications: </strong>Soil streptomycetes with <em>in vitro</em> antagonistic activity on plant pathogenic fungi could be a natural alternative to the use of chemical fungicides to control plant diseases. <strong>Conclusion</strong>: This study presented a novel soil <em>Streptomyces</em> specie which showed <em>in vitro</em> antagonism against a diversity of plant pathogenic fungal species. <em>Streptomyces</em> strain Y20 could be used as a biocontrol agent.</p>

Comparative genomics of plant pathogenic Diaporthe species and transcriptomics of Diaporthe caulivora during host infection reveal insights into pathogenic strategies of the genus

BackgroundDiaporthe caulivora is a fungal pathogen causing stem canker in soybean worldwide. The generation of genomic and transcriptomic information of this ascomycete, together with a comparative genomic approach with other pathogens of this genus, will contribute to get insights into the molecular basis of pathogenicity strategies used by D. caulivora and other Diaporthe species.ResultsIn the present work, the nuclear genome of D. caulivora isolate (D57) was resolved, and a comprehensive annotation based on gene expression and genomic analysis is provided. Diaporthe caulivora D57 has an estimated size of 57,86 Mb and contains 18,385 predicted protein-coding genes, from which 1501 encode predicted secreted proteins. A large array of D. caulivora genes encoding secreted pathogenicity-related proteins was identified, including carbohydrate-active enzymes (CAZymes), necrosis-inducing proteins, oxidoreductases, proteases and effector candidates. Comparative genomics with other plant pathogenic Diaporthe species revealed a core secretome present in all Diaporthe species as well as Diaporthe-specific and D. caulivora-specific secreted proteins. Transcriptional profiling during early soybean infection stages showed differential expression of 2659 D. caulivora genes. Expression patterns of upregulated genes and gene ontology enrichment analysis revealed that host infection strategies depends on plant cell wall degradation and modification, detoxification of compounds, transporter activities and toxin production. Increased expression of effectors candidates suggests that D. caulivora pathogenicity also rely on plant defense evasion. A high proportion of the upregulated genes correspond to the core secretome and are represented in the pathogen-host interaction (PHI) database, which is consistent with their potential roles in pathogenic strategies of the genus Diaporthe.ConclusionsOur findings give novel and relevant insights into the molecular traits involved in pathogenicity of D. caulivora towards soybean plants. Some of these traits are in common with other Diaporthe pathogens with different host specificity, while others are species-specific. Our analyses also highlight the importance to have a deeper understanding of pathogenicity functions among Diaporthe pathogens and their interference with plant defense activation.

Characterization of Two Fusarium solani Species Complex Isolates from the Ambrosia Beetle Xylosandrus morigerus.

Ambrosia beetles are insect vectors of important plant diseases and have been considered as a threat to forest ecosystems, agriculture, and the timber industry. Several factors have been suggested as promoters of the pathogenic behavior of ambrosia beetles; one of them is the nature of the fungal mutualist and its ability to establish an infectious process. In Mexico, Xylosandrus morigerus is an invasive ambrosia beetle that damages many agroecosystems. Herein, two different isolates from the X. morigerus ambrosia beetle belonging to the Fusarium genus are reported. Both isolates belong to the Fusarium solani species complex (FSSC) but not to the Ambrosia Fusarium clade (AFC). The two closely related Fusarium isolates are pathogenic to different forest and agronomic species, and the morphological differences between them and the extracellular protease profile suggest intraspecific variability. This study shows the importance of considering these beetles as vectors of different species of fungal plant pathogens, with some of them even being phylogenetically closely related and having different pathogenic abilities, highlighting the relevance of the fungal mutualist as a factor for the ambrosia complex becoming a pest.

Different requirement of immunity pathway components by oomycete effectors-induced cell death

Plant pathogenic oomycete species pose a worldwide threat to crop production and ecosystems. During infection, oomycete pathogens secrete a series of effectors to manipulate plant immunity. Many of these effectors, which are indicated as avirluence gene candidates, will use components of immunity pathway to induce cell death in plants. This response given by plants is known as effector-triggered immunity (ETI). The identification of avirulence genes from pathogenic oomycete species opens a way to investigating their virulence function and uncovering related R gene repertoires in resistant plants. In this study, we screened eight cell death-inducing effectors from oomycete species in N. benthamiana and tested the requirements of ETI signaling components to induce cell death. SGT1 was required for PsAvh163- and PcRXLR25-mediated cell death, while silencing NbHSP90 abolished PcRXLR25-, PsAvh163-, PsAvh241- and PsCRN63-triggered cell death. The cell death induced by the tested effectors does not depend on EDS1, NDR1, NRG1 and ADR1. PcRXLR25- and PsAvh163-induced cell death was found to require NRC2/3/4, indicating that these two effectors are avirulence protein candidates. Finally, we found that auto-activated NRC2/3/4 also required SGT1 and HSP90 to induce hypersensitive response.

PnSCR82, a small cysteine-rich secretory protein of Phytophthora nicotianae, can enhance defense responses in plants

A number of plant pathogenic species of Phytophthora are known to produce different classes of secretory proteins during interactions with their hosts. Although several small cysteine-rich (SCR) secretory proteins, conserved in oomycete pathogens, have been identified in Phytophthora, their specific involvement in these interactions remains unknown. In this study, an SCR effector encoded by PnSCR82 in P. nicotianae was identified and shown to have similarities to P. cactorum phytotoxic protein, PcF (Phytophthora cactorum Fragaria). Agroinfection with potato virus X vector, PnSCR82, was capable of inducing plant hypersensitive cell death in Nicotiana benthamiana and Solanum lycopersicum. Real-time PCR results indicated that transiently expressed PnSCR82 in N. benthamiana leaves activated the jasmonate, salicylic acid and ethylene signaling pathways. Transient expression of PnSCR82 enhanced plant resisitance to P. capsici. In summary, our results demonstrated that P. nicotianae PnSCR82 elicits defensive responses in N. benthamiana and may potentially play a significant role in future crop protection programs.

Screening of Antimicrobial Activities and Lipopeptide Production of Endophytic Bacteria Isolated from Vetiver Roots.

The exploration of certain microbial resources such as beneficial endophytic microorganisms is considered a promising strategy for the discovery of new antimicrobial compounds for the pharmaceutical industries and agriculture. Thirty-one endophytic bacterial strains affiliated with Bacillus, Janthinobacterium, Yokenella, Enterobacter, Pseudomonas, Serratia, and Microbacterium were previously isolated from vetiver (Chrysopogon zizanioides (L.) Roberty) roots. These endophytes showed antifungal activity against Fusarium graminearum and could be a source of antimicrobial metabolites. In this study, in particular, using high-throughput screening, we analyzed their antagonistic activities and those of their cell-free culture supernatants against three species of Fusarium plant pathogens, a bacterial strain of Escherichia coli, and a yeast strain of Saccharomyces cerevisiae, as well as their capacity to produce lipopeptides. The results showed that the culture supernatants of four strains close to B. subtilis species exhibited antimicrobial activities against Fusarium species and E. coli. Using mass spectrometry analyses, we identified two groups of lipopeptides (surfactins and plipastatins) in their culture supernatants. Whole-genome sequencing confirmed that these bacteria possess NRPS gene clusters for surfactin and plipastatin. In vitro tests confirmed the inhibitory effect of plipastatin alone or in combination with surfactin against the three Fusarium species.

Evaluation of the mycobiome of ballast water and implications for fungal pathogen distribution

Marine transport has the potential to alter the geographic range of microorganisms through ballast water movement. Recent culture-independent studies investigated the bacteriome of ballast water, but no prior studies have examined the mycobiome. Here were examined 60 ballast and harbor samples from 4 major ports and 5 ocean samples using culture-independent techniques to determine (1) the composition of harbor and ballast water mycobiomes; (2) if ballast contained human and environmentally relevant fungal pathogens; and (3) the potential risk of introduction to coastal ecosystems. Results indicate that ballast water and harbor water contain a diverse mycobiome and that ballast water may contain fungal taxa that are relevant human and marine fish pathogens. Fungal genera were identified that contain known coral and coastal plant pathogen species; however, species-level identification of these potential pathogens could not be conclusively resolved. Ballast and harbor mycobiomes contained similar taxa, suggesting that environmental filtering may not inhibit the spread of fungal taxa between these ecosystems. This study highlights the potential risks of ballast movement and suggests further research of the ballast mycobiome is needed.

An Addition to pestalotioid fungi in China: Neopestalotiopsis fragariae sp. nov. causing leaf spots on Fragaria × ananassa

Pestalotioid fungi are widely distributed and cause diseases on a myriad of crops, including strawberries. In this study, we introduce a new species, Neopestalotiopsis fragariae, that has been isolated from a leaf spot of strawberry in Guangdong Province, China. Neopestalotiopsis fragariae is classified as a new taxon based on the morphology and phylogenetic analysis of the combined ITS, β-TUB and TEF-1α sequence data, together with pairwise homoplasy index results. To our knowledge, this is the first report of N. fragariae that causes leaf spots on strawberries in China. This study provides novel data about the plant-pathogenic species associated with strawberries.

The effect of thymus syriacus plant extract on the main physical and antibacterial activities of ZnO nanoparticles synthesized by SILAR method

This study aimed to determine the main physical properties of green synthesized ZnO nanoparticles (ZnO-NPs) using Thymus syriacus plant extract and their antibacterial activities against eight different Gram-positive and Gram-negative plant bacterial disease agents. The surface morphological, structural, optical and electrical attributes of the ZnO films were analyzed by various types of characterization techniques. The authors have observed that the microstructural and surface morphological properties considerably changed by using T. syriacus plant extract. UV–Vis. analysis showed that the bandgap values are increased from 3.17 to 3.28 eV with the T. syriacus content in the growth solution. Impedance measurements presented an increase of the semicircle diameters with the increase % of T. syriacus. The antibacterial effectiveness of ZnO-NPs was evaluated against plant pathogenic bacterial species by using the agar disc diffusion method. Established on inhibition zone diameter values, ZnO-NPs displayed varying levels of antibacterial activities against all bacterial species tested. Gram-positive bacterial species were found more sensitive than Gram-negative species. In comparison, the highest antibacterial activity was displayed against Clavibacter michiganensis subsp. michiganensis and Bacillus subtilis subsp. subtilis, the lowest antibacterial activity was recorded for Pseudomonas corrugata. The present research findings suggest that the green synthesized ZnO-NPs have a prospective to be used as optoelectronic materials and antibacterial agents against plant pathogenic bacterial disease.

Tad pilus-mediated twitching motility is essential for DNA uptake and survival of Liberibacters.

Axenically cultured Liberibacter crescens (Lcr) is a closely related surrogate for uncultured plant pathogenic species of the genus Liberibacter, including 'Candidatus L. asiaticus' (CLas) and 'Ca. L. solanacearum' (CLso). All Liberibacters encode a completely conserved gene repertoire for both flagella and Tad (Tight Adherence) pili and all are missing genes critical for nucleotide biosynthesis. Both flagellar swimming and Tad pilus-mediated twitching motility in Lcr were demonstrated for the first time. A role for Tad pili in the uptake of extracellular dsDNA for food in Liberibacters was suspected because both twitching and DNA uptake are impossible without repetitive pilus extension and retraction, and no genes encoding other pilus assemblages or mechanisms for DNA uptake were predicted to be even partially present in any of the 35 fully sequenced Liberibacter genomes. Insertional mutations of the Lcr Tad pilus genes cpaA, cpaB, cpaE, cpaF and tadC all displayed such severely reduced growth and viability that none could be complemented. A mutation affecting cpaF (motor ATPase) was further characterized and the strain displayed concomitant loss of twitching, viability and reduced periplasmic uptake of extracellular dsDNA. Mutations of comEC, encoding the inner membrane competence channel, had no effect on either motility or growth but completely abolished natural transformation in Lcr. The comEC mutation was restored by complementation using comEC from Lcr but not from CLas strain psy62 or CLso strain RS100, indicating that unlike Lcr, these pathogens were not naturally competent for transformation. This report provides the first evidence that the Liberibacter Tad pili are dynamic and essential for both motility and DNA uptake, thus extending their role beyond surface adherence.

Major Streptomyces species associated with fissure scab of potato in South Africa including description of Streptomyces solaniscabiei sp. nov.

Streptomyces species are the causal agents of several scab diseases on potato tubers. A new type of scab symptom, caused by Streptomyces species, was observed in South Africa from 2010 onwards. The disease was initially thought to be caused by a single Streptomyces species, however, subsequent isolations from similar symptoms on other potato tubers revealed diversity of the Streptomyces isolates. The objective of this study was to characterise these isolates in order to determine what are the major species involved in the disease. This was done by sequencing and phylogenetic analyses of the 16S rDNA as well as five housekeeping genes, investigation of growth on different culture media, standard phenotypic tests and scanning electron microscopy of culture morphology. The presence of the pathogenicity island (PAI) present in plant pathogenic Streptomyces species was also investigated. The genomes of eight isolates, selected from the three main clades identified, were sequenced and annotated to further clarify species boundaries. Three isolates of each of the three main clades were also inoculated onto susceptible potato cultivars in order to establish the pathogenicity of the species. The results of the phylogenetic and genome analyses revealed that there are three main species involved, namely, Streptomyces werraensis, Streptomyces pseudogriseolus and a novel Streptomyces species that is described here as Streptomyces solaniscabiei sp. nov., with strain FS70T (= PPPPB BD 2226T = LMG 32103T) as the type strain. The glasshouse trial results showed that all three of the Streptomyces species are capable of producing fissure scab symptoms. None of the Streptomyces isolates from fissure scab contained the full PAI and the mechanism of disease initiation still needs to be determined. Genomic comparisons also indicated that S. gancidicus Suzuki 1957 (Approved Lists 1980) is a later heterotypic synonym of S. pseudogriseolus Okami and Umezawa 1955 (Approved Lists 1980).

Biological and Molecular Characterization of a Jumbo Bacteriophage Infecting Plant Pathogenic Ralstonia solanacearum Species Complex Strains.

A jumbo phage infecting Ralstonia solanacearum species complex strains, designated RsoM2USA, was isolated from soil of a tomato field in Florida, United States, and belongs to the family Myoviridae. The phage has a long latent period of 270 min and completed its infection cycle in 360 min with a burst size of approximately 32 particles per cell. With a genome size of 343,806 bp, phage RsoM2USA is the largest Ralstonia-infecting phage sequenced and reported to date. Out of the 486 ORFs annotated for RsoM2USA, only 80 could be assigned putative functions in replication, transcription, translation including 44 tRNAs, and structure with the main structural proteins experimentally confirmed. Phylogenetic analyses placed RsoM2USA in the same clade as Xanthomonas phage XacN1, prompting a proposal of a new genus for the two jumbo phages. Jumbo phage RsoM2USA is a lytic phage and has a wide host range, infecting each of the three newly established Ralstonia species: R. solanacearum, R. pseudosolanacearum, and R. syzygii, and significantly reduced the virulence of its susceptible R. solanacearum strain RUN302 in tomato plants, suggesting that this jumbo phage has the potential to be developed into an effective control against diseases caused by R. solanacearum species complex strains.

Genomics-Informed Multiplex PCR Scheme for Rapid Identification of Rice-Associated Bacteria of the Genus Pantoea.

The genus Pantoea forms a complex of more than 25 species, among which several cause diseases of various crop plants, including rice. Notably, strains of Pantoea ananatis and P. stewartii have been repeatedly reported to cause bacterial leaf blight of rice, whereas other authors have observed that P. agglomerans can also cause bacterial leaf blight of rice. The contribution of these and perhaps other species of Pantoea to plant diseases and yield losses of crop plants is currently not well documented, partly due to the lack of efficient diagnostic tools. Using 32 whole-genome sequences of the three major plant-pathogenic Pantoea spp., a set of PCR primers that detect each of the three species P. agglomerans, P. ananatis, and P. stewartii was designed. A multiplex PCR scheme which can distinguish these three species and also detects members of other Pantoea spp. was further developed. Upon validation on a set of reference strains, 607 suspected Pantoea strains that were isolated from rice leaves or seed originating from 11 African countries were screened. In total, 41 P. agglomerans strains from 8 countries, 79 P. ananatis strains from 9 countries, 269 P. stewartii strains from 9 countries, and 218 unresolved Pantoea strains from 10 countries were identified. The PCR protocol allowed detection of Pantoea bacteria grown invitro, in planta, and in rice seed. The detection threshold was estimated as total genomic DNA at 0.5 ng/µl and heated cells at 1 × 104 CFU/ml. This new molecular diagnostic tool will help to accurately diagnose major plant-pathogenic species of Pantoea. Due to its robustness, specificity, sensitivity, and cost efficiency, it will be very useful for plant protection services and for the epidemiological surveillance of these important crop-threatening bacteria.

Importance of Molecular Data to Identify Fungal Plant Pathogens and Guidelines for Pathogenicity Testing Based on Koch's Postulates.

Fungi are an essential component of any ecosystem, but they can also cause mild and severe plant diseases. Plant diseases are caused by a wide array of fungal groups that affect a diverse range of hosts with different tissue specificities. Fungi were previously named based only on morphology and, in many cases, host association, which has led to superfluous species names and synonyms. Morphology-based identification represents an important method for genus level identification and molecular data are important to accurately identify species. Accurate identification of fungal pathogens is vital as the scientific name links the knowledge concerning a species including the biology, host range, distribution, and potential risk of the pathogen, which are vital for effective control measures. Thus, in the modern era, a polyphasic approach is recommended when identifying fungal pathogens. It is also important to determine if the organism is capable of causing host damage, which usually relies on the application of Koch’s postulates for fungal plant pathogens. The importance and the challenges of applying Koch’s postulates are discussed. Bradford Hill criteria, which are generally used in establishing the cause of human disease, are briefly introduced. We provide guidelines for pathogenicity testing based on the implementation of modified Koch’s postulates incorporating biological gradient, consistency, and plausibility criteria from Bradford Hill. We provide a set of protocols for fungal pathogenicity testing along with a severity score guide, which takes into consideration the depth of lesions. The application of a standard protocol for fungal pathogenicity testing and disease assessment in plants will enable inter-studies comparison, thus improving accuracy. When introducing novel plant pathogenic fungal species without proving the taxon is the causal agent using Koch’s postulates, we advise the use of the term associated with the “disease symptoms” of “the host plant”. Where possible, details of disease symptoms should be clearly articulated.

Bacillus cereus MH778713 elicits tomato plant protection against Fusarium oxysporum.

AimThe genus Fusarium comprises plant pathogenic species with agricultural relevance. Fusarium oxysporum causes tomato wilt disease with significant production losses. The use of agrochemicals to control the Fusarium wilt of tomato is not environmentally friendly. Bacillus species, as biocontrol agents, provide a safe and sustainable means to control Fusarium‐induced plant diseases. In this study, the ability of Bacillus cereus MH778713, a strain isolated from root nodules of Prosopis laevigata, to protect tomato plants against Fusarium wilt was evaluated.Methods and results Bacillus cereus MH778713 and its volatiles inhibited the radial growth of F. oxysporum and stimulated tomato seedling growth in in vitro and in vivo tests. When tomato plants growing in the greenhouse were inoculated with B. cereus MH778713, the percentage of wilted plants decreased from 96% to 12%, indicating an effective crop protection against Fusarium wilt. Among the metabolites produced by B. cereus MH778713, hentriacontane and 2,4‐di‐tert‐butylphenol promoted tomato seedling growth and showed antifungal activity against the target pathogen.ConclusionThe inoculation of B. cereus MH778713 on tomato seedlings helped plants to manage Fusarium wilt, suggesting the potential of B. cereus MH778713 as a biocontrol agent.Significance and Impact of the StudyThese results complement our previous studies on chromium tolerance and bioremediation traits of B. cereus MH778713 by highlighting the potential of this metal‐resistant micro‐organism to boost crop growth and disease resistance.

Potential Human and Plant Pathogenic Species in Airborne PM10 Samples and Relationships with Chemical Components and Meteorological Parameters

A preliminary local database of potential (opportunistic) airborne human and plant pathogenic and non-pathogenic species detected in PM10 samples collected in winter and spring is provided, in addition to their seasonal dependence and relationships with meteorological parameters and PM10 chemical species. The PM10 samples, collected at a Central Mediterranean coastal site, were analyzed by the 16S rRNA gene metabarcoding approach, and Spearman correlation coefficients and redundancy discriminant analysis tri-plots were used to investigate the main relationships. The screening of 1187 detected species allowed for the detection of 76 and 27 potential (opportunistic) human and plant pathogens, respectively. The bacterial structure of both pathogenic and non-pathogenic species varied from winter to spring and, consequently, the inter-species relationships among potential human pathogens, plant pathogens, and non-pathogenic species varied from winter to spring. Few non-pathogenic species and even fewer potential human pathogens were significantly correlated with meteorological parameters, according to the Spearman correlation coefficients. Conversely, several potential plant pathogens were strongly and positively correlated with temperature and wind speed and direction both in winter and in spring. The number of strong relationships between presumptive (human and plant) pathogens and non-pathogens, and meteorological parameters slightly increased from winter to spring. The sample chemical composition also varied from winter to spring. Some potential human and plant pathogens were correlated with chemicals mainly associated with marine aerosol and/or with soil dust, likely because terrestrial and aquatic environments were the main habitats of the detected bacterial species. The carrier role on the species seasonal variability was also investigated.

The growth inhibitory potential of eudicot‐based preparations against plant pathogenic fungi

The infection of certain plants with pathogenic fungi species results in a significant loss in the production yield of these plants, some of which are with high economical importance. In the current study, we studied the growth inhibitory potential of several eudicot plant preparations (Lavandula angustifolia, Matricaria chamomilla L. and Saponaria officinalis L.) against certain plant pathogenic fungi species, namely, Phytophthora infestans, Rhizoctania solani, Fusarium oxysporum. f. sp. lycopersici and Macrophamina phaseolina. We found that solutions prepared with these plants mostly show concentration-dependent inhibitory effect on the growth of these fungi species. These plant-based anti-fungal preparations might potentially be used in the control of fungi species studied in the present study, in order to increase the production yield of their host plants. Further research is required to identify the mechanisms of action of these plant-based solutions on pathogenic fungi growth.