Plant Pathogenic Fungus Fusarium Research Articles

A novel ormycovirus isolated from the plant-pathogenic fungus Fusarium graminearum.

In this study, we identified a novel mycovirus, Fusarium graminearum ormycovirus 1 (FgOV1), from the pathogenic fungus Fusarium graminearum. The virus has two RNA segments, RNA1 and RNA2, with lengths of 2,591 and 1,801 nucleotides, respectively, excluding the polyA tail. Each segment contains a single open reading frame (ORF). The ORF in RNA1 encodes an RNA-dependent RNA polymerase, while the ORF in RNA2 encodes a hypothetical protein. Phylogenetic analysis showed that FgOV1 belongs to the gammaormycovirus clade, whose members are related to betaormycoviruses. To our knowledge, this is the first report of an ormycovirus in Fusarium graminearum.

Oxaloacetate anaplerosis differently contributes to pathogenicity in plant pathogenic fungi Fusarium graminearum and F. oxysporum.

Anaplerosis refers to enzymatic reactions or pathways replenishing metabolic intermediates in the tricarboxylic acid (TCA) cycle. Pyruvate carboxylase (PYC) plays an important anaplerotic role by catalyzing pyruvate carboxylation, forming oxaloacetate. Although PYC orthologs are well conserved in prokaryotes and eukaryotes, their pathobiological functions in filamentous pathogenic fungi have yet to be fully understood. Here, we delve into the molecular functions of the ortholog gene PYC1 in Fusarium graminearum and F. oxysporum, prominent fungal plant pathogens with distinct pathosystems, demonstrating variations in carbon metabolism for pathogenesis. Surprisingly, the PYC1 deletion mutant of F. oxysporum exhibited pleiotropic defects in hyphal growth, conidiation, and virulence, unlike F. graminearum, where PYC1 deletion did not significantly impact virulence. To further explore the species-specific effects of PYC1 deletion on pathogenicity, we conducted comprehensive metabolic profiling. Despite shared metabolic changes, distinct reprogramming in central carbon and nitrogen metabolism was identified. Specifically, alpha-ketoglutarate, a key link between the TCA cycle and amino acid metabolism, showed significant down-regulation exclusively in the PYC1 deletion mutant of F. oxysporum. The metabolic response associated with pathogenicity was notably characterized by S-methyl-5-thioadenosine and S-adenosyl-L-methionine. This research sheds light on how PYC1-mediated anaplerosis affects fungal metabolism and reveals species-specific variations, exemplified in F. graminearum and F. oxysporum.

Manure amendments and fungistasis, and relation with protection of wheat from Fusarium graminearum

Certain soils promote crop health because they are pathogen-suppressive (i.e., fungistatic) or disease-suppressive, but the effect of soil management on these properties is not fully understood. Here, we tested the hypothesis that manure could favor fungistasis by screening 26 manured or non-manured wheat fields from Serbia for their ability to control survival/growth of the fungal plant pathogen Fusarium graminearum Fg1. Quantitative PCR showed that the pathogen grew after inoculation in all 26 autoclaved soils. In absence of autoclaving, the pathogen was stable or grew in 16 soils (37 % manured) but declined in the 10 others (70 % manured). For most soils, there was no significant link between soil chemistry and fungistasis, except with Mionica in western/central Serbia. Mionica soils MI2 and MI3, which had received manure, exhibited higher levels of organic matter and potassium compared with soils MI4 and MI5, which had not received manure and were non-fungistatic. Using Mionica soils, we then tested the hypothesis that fungistatic (manured) soils rather than non-fungistatic (non-manured) soils would protect wheat from F. graminearum disease. Indeed, fungistatic soils were suppressive to wheat damping-off. Non-fungistatic soil MI4 was conducive, as expected, but non-fungistatic soil MI5 turned out to be suppressive. Metabarcoding showed that the structure of prokaryotic and fungal rhizosphere communities depended mostly on field location, with a significant effect of F. graminearum inoculation. In conclusion, our findings show that certain farming practices (here, manure amendments) may promote soil fungistasis towards F. graminearum. However, both fungistatic and non-fungistatic soils can be suppressive to F. graminearum disease in wheat, and their differences in rhizosphere microbiota suggest different phytoprotection mechanisms.

Inhibition of fusarium graminearum growth and spore germination by a streptomyces amritsarensis strain capable of killing and growing on microcystis scum.

Developing energy-saving and ecofriendly strategies for treating harvested Microcystis biomass. Streptomyces amritsarensis HG-16 was first reported to effectively kill various morphotypes of natural Microcystis colonies at very high cell densities. Concurrently, HG-16 grown on lysed Microcystis maintained its antagonistic activity against plant pathogenic fungus Fusarium graminearum. It could completely inhibit spore germination and destroy mycelial structure of F. graminearum. Transcriptomic analysis revealed that HG-16 attacked F. graminearum in a comprehensive way: interfering with replication, transcription, and translation processes, inhibiting primary metabolisms, hindering energy production and simultaneously destroying stress-resistant systems of F. graminearum. The findings of this study provide a sustainable and economical option for resource reclamation from Microcystis biomass: utilizing Microcystis slurry to propagate HG-16, which can subsequently be employed as a biocontrol agent for managing F. graminearum.

Field isolates of Beauveria bassiana exhibit biological heterogeneity in multitrophic interactions of agricultural importance

Beauveria bassiana (Bb) is a widespread entomopathogenic fungus widely used in agriculture for crop protection. Other than pest control, fungi belonging to the B. bassiana complex represent an important microbial resource in agroecosystems, considering their multiple interactions with other microorganisms as antagonists of phytopathogens, or with plants as endophytic colonizers and growth promoters. Here, we characterised field collected or commercial isolates of B. bassiana relative to the environmental factors that affect their growth. We further compared the metabolome, the entomopathogenic potential and biocontrol activity of the tested isolates respectively on the insect pest Spodoptera littoralis or against the fungal plant pathogen Fusarium oxysporum. Our analysis revealed that the B. bassiana complex is characterised by a high level of inter-isolate heterogeneity in terms of nutritional requirements, establishment of intra- or inter-kingdom interactions, and the nature of metabolites produced. Interestingly, certain B. bassiana isolates demonstrated a preference for low nutrient plant-derived media, which hints at their adaptation towards an endophytic lifestyle over a saprophytic one. In addition, there was a noticeable variation among different B. bassiana isolates in their capacity to kill S. littoralis larvae in a contact infection test, but not in an intrahaemocoelic injection experiment, suggesting a unique level of adaptability specific to the host. On the other hand, most B. bassiana isolates exhibited similar biocontrol efficacy against the soil-dwelling ascomycete F. oxysporum f. sp. lycopersici, a pathogen responsible for vascular wilt disease in tomato plants, effectively averting wilting. Overall, we show that the effectiveness of B. bassiana isolates can greatly vary, emphasising the importance of isolate selection and nutritional adaptability consideration for their use in sustainable agriculture.

Edeine B1 produced by Brevibacillus brevis reduces the virulence of a plant pathogenic fungus by inhibiting mitochondrial respiration.

Plant pathogenic fungi cause serious diseases, which result in the loss of crop yields and reduce the quality of crops worldwide. To counteract the escalating risks of chemical fungicides, interest in biological control agents to manage plant diseases has significantly increased. In this study, we comprehensively screened microbial culture filtrates using a yeast screening system to find microbes exhibiting respiratory inhibition activity. Consequently, we found a soil-borne microbe Brevibacillus brevis HK544 strain exhibiting a respiration inhibitory activity and identified edeine B1 (EB1) from the culture filtrate of HK544 as the active compound of the respiration inhibition activity. Furthermore, against a plant pathogenic fungus Fusarium graminearum, our results showed that EB1 has effects on multiple aspects of respiration with the downregulation of most of the mitochondrial-related genes based on transcriptome analysis, differential EB1-sensitivity from targeted mutagenesis, and the synergistic effects of EB1 with electron transport chain complex inhibitors. With the promising plant disease control efficacy of B. brevis HK544 producing EB1, our results suggest that B. brevis HK544 has potential as a biocontrol agent for Fusarium head blight.IMPORTANCEAs a necrotrophic fungus, Fusarium graminearum is a highly destructive pathogen causing severe diseases in cereal crops and mycotoxin contamination in grains. Although chemical control is considered the primary approach to control plant disease caused by F. graminearum, fungicide-resistant strains have been detected in the field after long-term continuous application of fungicides. Moreover, applying chemical fungicides that trigger mycotoxin biosynthesis is a great concern for many researchers. Biocontrol of Fusarium head blight (FHB) by biological control agents (BCAs) represents an alternative approach and could be used as part of the integrated management of FHB and mycotoxin production. The most extensive studies on bacterial BCAs-fungal communications in agroecosystems have focused on antibiosis. Although many BCAs in agricultural ecology have already been used for fungal disease control, the molecular mechanisms of antibiotics produced by BCAs remain to be elucidated. Here, we found a potential BCA (Brevibacillus brevis HK544) with a strong antifungal activity based on the respiration inhibition activity with its active compound edeine B1 (EB1). Furthermore, our results showed that EB1 secreted by HK544 suppresses the expression of the mitochondria-related genes of F. graminearum, subsequently suppressing fungal development and the virulence of F. graminearum. In addition, EB1 exhibited a synergism with complex I inhibitors such as rotenone and fenazaquin. Our work extends our understanding of how B. brevis HK544 exhibits antifungal activity and suggests that the B. brevis HK544 strain could be a valuable source for developing new crop protectants to control F. graminearum.

Con7 is a key transcription regulator for conidiogenesis in the plant pathogenic fungus Fusarium graminearum.

The ascomycete fungus Fusarium graminearum is the primary cause of head blight disease in wheat and barley, as well as ear and stalk rot in maize. Given the importance of conidia and ascospores in the disease cycle of F. graminearum, precise spatiotemporal regulation of these biological processes is crucial. In this study, we characterized the Magnaporthe oryzae Con7p ortholog and discovered that FgCon7 significantly influences various crucial aspects of fungal development and pathogenicity. Notably, overexpression of FgABAA partially restored developmental defects in the FgCON7 deletion mutant. ChIP-qPCR analysis confirmed a direct genetic link between FgABAA and FgCON7. Furthermore, our research revealed a clear correlation between FgCon7 and chitin accumulation and the expression of chitin synthase genes. These findings offer valuable insights into the genetic mechanisms regulating conidiation and the significance of mycelial differentiation in this plant pathogenic fungus.

Euwallacea perbrevis (Schedl, 1951) and associated novel fungal symbiont, Fusarium sp.: A potential cause of wilting in cocoa, Theobroma cacao in India

Cocoa is a commercially important beverage crop that faces new challenges in the context of climate change, which can alter pest and disease dynamics in cocoa plantations. In the Dakshina Kannada district of Karnataka, India, an abrupt increase in cocoa wilt was observed during the 2017–18 and 2018–19 seasons. Systematic examination of affected trees revealed consistent attacks of Euwallacea perbrevis (Schedl, 1951; Coleoptera: Curculionidae: Scolytinae). In-depth studies of the wilted trees revealed the association of the plant pathogenic fungus Fusarium sp. with Euwallacea perbrevis. The identity of the obtained pure culture from the insect and infected tree was confirmed as Fusarium sp. using amplification of ribosomal DNA, RNA polymerase II largest subunit (RPB1) and translation elongation factor 1 (Tef1) genes. Notably, this study reports a remarkable case of mutualistic association between ambrosia beetles and Fusarium sp., belonging to the Fusarium solani species complex (FSSC), rather than the Ambrosia Fusariumclade (AFC). This finding highlights the intriguing diversity of mutualistic relationships in nature and sheds new light on the complex interactions between organisms. The present study also investigated the impact of rainfall on the colonization and spread of the Euwallacea-Fusarium complex. The findings revealed that rainfall was identified as a predisposing factor for the incidence and spread of attacks. Additionally, the study conducted a comprehensive analysis of the modeling of Euwallacea-Fusarium complex spread over a specific period of time.

Synthesis, antifungal, antibacterial activity, and computational evaluations of some novel coumarin-1,2,4-triazole hybrid compounds

Effective plant pathogen control presents an important challenge. Pesticide resistance and associated health and environmental problems demonstrate the need for novel, safe active ingredients for plant protection. Since both coumarins and 1,2,4-triazoles show pesticidal activity, in this study, we evaluated the antimicrobial activity of coumarin-1,2,4-triazole hybrids against plant pathogenic fungi (Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum), bacterial plant pathogens (Pseudomonas syringae and Rhodococcus fascians), and beneficial bacteria (Bacillus mycoides and Bradyrhizobium japonicum). Coumarin-1,2,4-triazoles inhibited the growth of S. sclerotiorum and F. oxysporum, while no antibacterial effect on either pathogens or soil-beneficial bacteria was observed. A quantitative structure–activity relationship models for antifungal activities on S. sclerotiorum and F. oxysporum, developed using Dragon descriptors, can explain 79% and 77% of the compounds inhibitory activity, respectively. According to molecular docking, title compounds are potential sterol 14α-demethylase inhibitors, with 7-((5-mercapto-4-(p-tolyl)-4H-1,2,4-triazol-3-yl)methoxy)-4-methyl-2H-chromen-2-one as the promising candidate for further research in plant protection.

Impact of Tea Tree Cultivation on Soil Microbiota, Soil Organic Matter, and Nitrogen Cycling in Mountainous Plantations

This study focused on examining the early stages of tea cultivation (1, 3, and 5 years) in mountainous tea plantations. It specifically aimed to investigate the changes in soil micro-ecology at different locations (inter-row, terrace surfaces, and terrace walls). It was revealed that as tea tree cultivation progressed over the years, bacterial diversity and co-occurrence networks annually decreased in different locations. The results of soil physicochemical index analysis showed that the soil’s available nutrients and the activities of cellulase and protease increased. Furthermore, the amplitude of variation of these indexes in the inter-row soil was significantly higher than that on the terrace surfaces and the terrace walls (p < 0.05). Alterations occurred in the soil microbial community structure, with an enrichment of bacterial genera such as Sinomonas, Granulicella, and Sphingomonas, as well as fungal genera such as Trichoderma, Penicillium, and Talaromyces; an increase in the proportion of plant pathogenic fungi (Cladosporium, Fusarium, and Curvularia) was observed in the inter-row soil. The results of soil microbial function prediction showed that nitrification and nitrogen fixation decreased, but denitrification increased (p < 0.05). In conclusion, cultivating tea trees in mountainous terraced plantations significantly impacted the soil microbial community, accelerated the metabolism of soil organic matter, disrupted soil nitrogen cycling functions, and increased the presence of plant pathogenic fungal pathogens. Moreover, the changes in the structure and functions of the soil microbial community demonstrate a spatial distance effect across different terrace locations.

Proteomic Analysis of Cell Wall Proteins with Various Linkages in Fusarium graminearum.

The fungal cell wall, primarily comprising a glucan-chitin matrix and cell wall proteins (CWPs), serves as a key mediator for fungal interactions with the environment and plays a pivotal role in virulence. In this study, we employed a comprehensive proteomics approach to analyze the CWPs in the plant pathogenic fungus Fusarium graminearum. Our methodology successfully extracted and identified 1373 CWPs, highlighting their complex linkages, including noncovalent bonds, disulfide bridges, alkali-sensitive linkages, and glycosylphosphatidylinositol (GPI) anchors. A significant subset of these proteins, enriched in Gene Ontology terms, suggest multifunctional roles of CWPs. Through the integration of transcriptomic and proteomic data, we observed differential expression patterns of CWPs across developmental stages. Specifically, we focused on two genes, Fca7 and Cpd1, which were upregulated in planta, and confirmed their localization predominantly outside the plasma membrane, primarily in the cell wall and periplasmic space. The disruption of FCA7 reduced virulence on wheat, aligning with previous findings and underscoring its significance. Overall, our findings offer a comprehensive proteomic profile of CWPs in F. graminearum, laying the groundwork for a deeper understanding of their roles in the development and interactions with host plants.

Segmental duplications drive the evolution of accessory regions in a major crop pathogen.

Many pathogens evolved compartmentalized genomes with conserved core and variable accessory regions (ARs) that carry effector genes mediating virulence. The fungal plant pathogen Fusarium oxysporum has such ARs, often spanning entire chromosomes. The presence of specific ARs influences the host range, and horizontal transfer of ARs can modify the pathogenicity of the receiving strain. However, how these ARs evolve in strains that infect the same host remains largely unknown. We defined the pan-genome of 69 diverse F. oxysporum strains that cause Fusarium wilt of banana, a significant constraint to global banana production, and analyzed the diversity and evolution of the ARs. Accessory regions in F. oxysporum strains infecting the same banana cultivar are highly diverse, and we could not identify any shared genomic regions and in planta-induced effectors. We demonstrate that segmental duplications drive the evolution of ARs. Furthermore, we show that recent segmental duplications specifically in accessory chromosomes cause the expansion of ARs in F. oxysporum. Taken together, we conclude that extensive recent duplications drive the evolution of ARs in F. oxysporum, which contribute to the evolution of virulence.

A novel isatin Schiff based cerium complex: synthesis, characterization, antimicrobial activity and molecular docking studies

In this work, a novel isatin-Schiff base L2 had been synthesized through a simple reaction between isatin and 2-amino-5-methylthio-1,3,4-thiadiazole. The produced Schiff base L2 was then subjected to a hydrothermal reaction with cerium chloride to produce the cerium (III)-Schiff base complex C2. Several spectroscopic methods, including mass spectra, FT-IR, elemental analysis, UV–vis, 13C-NMR, 1H-NMR, Thermogravimetric Analysis, HR-TEM, and FE-SEM/EDX, were used to completely characterize the produced L2 and C2. A computer simulation was performed using the MOE software program to find out the probable biological resistance of studied compounds against the proteins in some types of bacteria or fungi. To investigate the interaction between the ligand and its complex, we conducted molecular docking simulations using the molecular operating environment (MOE). The docking simulation findings revealed that the complex displayed greater efficacy and demonstrated a stronger affinity for Avr2 effector protein from the fungal plant pathogen Fusarium oxysporum (code 5OD4) than the original ligand. The antibacterial activity of the ligand and its Ce3+ complex were applied in vitro tests against different microorganism. The study showed that the complex was found to be more effective than the ligand.

Sulfur metabolism-mediated fungal glutathione biosynthesis is essential for oxidative stress resistance and pathogenicity in the plant pathogenic fungus Fusarium graminearum.

Fusarium graminearum is a destructive fungal pathogen that causes Fusarium head blight (FHB) on a wide range of cereal crops. To control fungal diseases, it is essential to comprehend the pathogenic mechanisms that enable fungi to overcome host defenses during infection. Pathogens require an oxidative stress response to overcome host-derived oxidative stress. Here, we identify the underlying mechanisms of the Fgbzip007-mediated oxidative stress response in F. graminearum. ChIP-seq and subsequent genetic analyses revealed that the role of glutathione in pathogenesis is not dependent on antioxidant functions in F. graminearum. Altogether, this study establishes a comprehensive framework for the Fgbzip007 regulon on pathogenicity and oxidative stress responses, offering a new perspective on the role of glutathione in pathogenicity.

Determination of Antifungal Activity of Leaf Extracts from Hypericum ssp. Against Plant Pathogenic Fungi Fusarium oxysporum and Alternaria Alternata

In this study, the antifungal activity of ethanol extracts of three plant species of Hypericum perforatum, Hypericum scabrum and Hypericum origanifolium were evaluated for against two plant pathogenic fungal species of Fusarium oxysporum and Alternaria alternata.The antifungal activities of Hypericum ssp. extracts (3, 15, 45, 80, 120, 200, 240, 300 ppm) were tested against fungi. Ethanol 30% as control; Commercial fungicide (1 μg/mL) was used as a positive control. All Hypericum ssp. plant extracts were effective in different rates against the fungi depending on the doses. In addition, IC50 values of the three selected plant Hypericum ssp. leaf extract against pathogenic fungus F.oxysporum and A. alternata were determined with of probit analysis. In terms of the IC50 values, the antifungal activity of H. perforatum plant exract against F.oxysporum (122.525 μg/mL) > A.alternata (108.484 μg/mL). On the other hand, IC50 values of H. scabrum against A.alternata (126.390 μg/mL) > F.oxysporum (113.714 μg/mL). Moreover, the IC50 value of H. origanifolium against two pathogenic fungi was calculated as F.oxysporum (159.931 μg/mL) > A.alternata (55.759 μg/mL). Results showed that H.origanifolium has the best fungicidal activity, with IC50 value of 55.759 μg/mL against A.alternata and H.scabrum 113.717 μg/mL against F.oxysporum. However, the highest concentrations (300 ppm) caused completely inhibition in the both fungi mycelial growth followed by lower concentrations of plant extracts. A. alternata were the sensitive fungal species, while the F. oxysporum were a more resistant to the Hypericum ssp. extracts. Based on the antifungal activity tests, these plants extracts this may have effective as the new natural fungicide protecting crops against fungal diseases.

The Fusarium graminearum Transporters Abc1 and Abc6 Are Important for Xenobiotic Resistance, Trichothecene Accumulation, and Virulence to Wheat.

The plant pathogenic fungus Fusarium graminearum is the causal agent of Fusarium head blight (FHB) disease on small-grain cereals. F. graminearum produces trichothecene mycotoxins such as deoxynivalenol (DON) that are required for full virulence. DON must be exported outside the cell to cause FHB disease, a process that may require the involvement of membrane-bound transporters. In this study, we show that the deletion of membrane-bound transporters results in reduced DON accumulation as well as reduced FHB symptoms on wheat. Deletion of the ATP-binding cassette (ABC) transporter gene Abc1 results in the greatest reduction in DON accumulation and virulence. Deletion of another ABC transporter gene, Abc6, also reduces FHB symptoms to a lesser degree. Combining deletions fails to reduce DON accumulation or virulence in an additive fashion, even when a ∆abc1 deletion is included. Heterologous expression of F. graminearum transporters in a DON-sensitive strain of yeast confirms Abc1 as a major DON resistance mechanism; furthermore, it suggests that Abc1 is directly participating in DON transport rather than facilitating DON transport though other means. Yeast expression further indicates that multiple transporters, including Abc1, play an important role in resistance to the wheat phytoalexin 2-benzoxazolinone (BOA) and other xenobiotics. Thus, Abc1 may contribute to virulence on wheat both by facilitating export of DON and by providing resistance to the wheat phytoalexin BOA. This research provides useful information that may aid in designing novel management techniques of FHB or other destructive plant diseases.

Transposon-based identification of genes involved in the rimocidin biosynthesis in Streptomyces rimosus M527.

The transposon mutagenesis strategy has been employed to generate random insertion mutants and analyze the correlation between genes and secondary metabolites in the genus Streptomyces. In this study, our primary objective was to identify an unknown gene involved in rimocidin biosynthesis and elucidate its role in rimocidin production in Streptomyces rimosus M527. To achieve this, we established a random mutant library of S. rimosus M527 using a Tn5 transposon-mediated random mutagenesis strategy. Among the 137 isolated mutants, M527-G10 and M527-W5 exhibited the most significant variations in antagonistic activity against the plant pathogenic fungus Fusarium oxysporum f. sp. cucumerinum. Specifically, M527-G10 displayed a 72.93% reduction, while M527-W5 showed a 49.8% increase in rimocidin production compared to the wild-type (WT) strain S. rimosus M527. Subsequently, we employed a plasmid rescue strategy to identify the insertion loci of the transposon in the genomes of mutants M527-G10 and M527-W5, revealing a response regulator transcription factor (rrt) and a hypothetical protein (hyp), respectively. The roles of rrt and hyp in rimocidin biosynthesis were determined through gene deletion, overexpression in the WT strain, and complemented expression in the transposon mutants. Notably, the gene-deletion mutants M527-ΔRRT and M527-ΔHYP exhibited similar behavior in rimocidin production compared to the corresponding transposon mutants M527-G10 and M527-W5, suggesting that transposon insertions in genes rrt and hyp led to alterations in rimocidin production. Furthermore, both gene deletion and overexpression of rrt and hyp had no discernible effects on cell growth. These results reveal that genes rrt and hyp have positive and negative impacts on rimocidin production in S. rimosus M527, respectively.

Evaluation of some bioactive compounds of <i>Azadirachta indica</i> extracts and its application as safe fungicide against different plant pathogenic fungi

Extracts of leaves, seeds and twigs of Azadirachta indica was carried out using Soxhlet extraction technique. These extracts were subjected to percent yield, in vitro phytochemical screening and antifungal activities (minimum fungicidal concentration (MFC), minimum inhibitory concentration (MIC), zone of inhibition and spore germination assay) against plant pathogenic fungi Cladosporium fulvum, Colletotrichum coccodes, Fusarium oxysporum and Rhizoctonia solani. The Soxhlet extractive solvents were methanol, ethanol, chloroform, ethyl acetate and n–hexane. The maximum extractive yield were calculated in ethanol leaves (26±1.5%), methanol leaves (22±01%), n–hexane seeds (32±0.8%) and ethanol seeds (24±01%), while twigs calculated minimum extractive yield. The phytochemicals screening findings confirmed the occurrence of terpenoids, phenols, flavonoids, glycosides, alkaloids, tannins and saponins. The antifungal activities observed that leaves and seeds extracts of neem might cause the inhibition of mycelium and spore germination of tested fungi, though the antifungal activities rate of under study fungal strains diverse with dissimilar concentration and nature of extracts. However the entire concentrations of extract and crude extract especially the methanol and ethanol extracts of neem seeds and leaves reduce the plant pathogenic fungi growth at noteworthy rate. It was concluded from our results that neem leaves and seeds extracts were effectual as antifungal agents against the entire under study fungal strains however the most sensitive fungi were Rhizoctonia solani and Fusarium oxysporum. The findings acquired from this study revealed that chemical constituents from neem seeds and leaves may be formulated as latent agrochemical fungicides.

Phytochemical analysis and antimicrobial activity of Tamarindus indica extracts against Fusarium oxysporum and Xanthomonas campestris

Abstract. Gitari FM, Githae EW, Kuria EK. 2023. Phytochemical analysis and antimicrobial activity of Tamarindus indica extracts against Fusarium oxysporum and Xanthomonas campestris. Intl J Trop Drylands 7: 73-82. Plant-pathogenic bacteria and fungi are a major threat to biodiversity and food security worldwide. The pathogens are difficult to control using cultural methods and have sometimes acquired resistance to conventional pesticides. This has necessitated the search for more efficient active compounds against them. One promising source of such compounds is tropical-medicinal plants such as Tamarindus indica L. This study first determined the phytochemical composition of T. indica extracts from different parts (leaves, bark, roots, and pods). Then it evaluated in-vitro the antimicrobial activity against plant pathogenic bacteria (Xanthomonas campestris) and fungi (Fusarium oxysporum). Crude extracts were obtained using different solvents (dichloromethane, methanol, and acetone). The analysis revealed the presence of nine pharmaco-active phytochemicals; methanol extracts had the highest concentrations of these phytochemicals. All extracts demonstrated inhibitory effects against F. oxysporum. However, the extracts did not show any antimicrobial effect against X. campestris. There was a significant difference (p<0.05) in the percentage of inhibition of F. oxysporum growth by different extracts. Generally, high growth inhibition was observed in media containing different plant extracts at 250 and 500 ppm concentrations. For acetone extracts, the highest inhibition (71.042%) was induced by root extract at a 250 ppm concentration, whereas for dichloromethane extracts, the highest inhibition (68.811%) was induced by 500 ppm of leaf extract. Methanol extracts from stem recorded the highest inhibition of 86.953% at concentrations of 125 ppm. This was followed by root extracts (75.169% inhibition) at 500 ppm. The T. indica, therefore, has great potential as a source of bio-pesticide for use in integrated pest management of F. oxysporum.

Assessing long-distance atmospheric transport of soilborne plant pathogens

Pathogenic fungi are a leading cause of crop disease and primarily spread through microscopic, durable spores adapted differentially for both persistence and dispersal via soil, animals, water, and/or the atmosphere. Computational Earth system models and air pollution models have been used to simulate atmospheric spore transport for aerial-dispersal-adapted (airborne) rust diseases, but the importance of atmospheric spore transport for soil-dispersal-adapted (soilborne) diseases remains unknown. While a few existing simulation studies have focused on intracontinental dispersion, transoceanic and intercontinental atmospheric transport of soilborne spores entrained in agricultural dust aerosols is understudied and may contribute to disease spread. This study adapts the Community Atmosphere Model, the atmospheric component of the Community Earth System Model, to simulate the global transport of the plant pathogenic soilborne fungus Fusarium oxysporum (F. oxy). Our sensitivity study assesses the model’s accuracy in long-distance aerosol transport and the impact of deposition rate on simulated long-distance spore transport in Summer 2020 during a major dust transport event from Northern Sub-Saharan Africa to the Caribbean and southeastern United States (U.S.). We find that decreasing wet and dry deposition rates by an order of magnitude improves representation of long-distance, trans-Atlantic dust transport. Simulations also suggest that a small number of spores can survive trans-Atlantic transport to be deposited in agricultural zones. This number is dependent on source spore parameterization, which we improved through a literature search to yield a global map of F. oxy spore distribution in source agricultural soils. Using this map and aerosol transport modeling, we show how potentially viable spore numbers in the atmosphere decrease with distance traveled and offer a novel danger index for modeled viable spore deposition in agricultural zones. Our work finds that intercontinental transport of viable spores to cropland is greatest between Eurasia, North Africa, and Sub-Saharan Africa, suggesting that future observational studies should concentrate on these regions.