Plant Pathogenic Fungi Research Articles

Evaluating the biocontrol efficacy of beneficial soil microbes against the Fusarium wilt disease of tomato

Tomato is one of the most important agricultural crops in the world as it is a rich source of vitamins A and C. The quality and the quantity of tomato fruits is severely affected by the fungal plant pathogens. Fungal diseases are among the most dangerous biological stresses that cause severe damage to tomato crops in many countries. Fusarium wilt disease in tomato caused by Fusarium oxysporum f. sp. lycopersici, become a major concern of yield loss worldwide. This study evaluated the efficacy of multiple antagonistic biocontrol agents, including Trichoderma species and non-pathogenic F. oxysporum, in mitigating Fusarium wilt. Pathogenic F. oxysporum strains were isolated from diseased tomato plants, while biocontrol agents were cultured from rhizosphere soil of healthy tomato plants. In vitro dual-culture assays demonstrated that non-pathogenic F. oxysporum inhibited pathogenic strains by 86.8% (±4.8) at 7 days post-inoculation (dpi), significantly higher than T. harzianum, which achieved 62.8% (±6.2) inhibition (p < 0.01). Other Trichoderma strains, such as T. viride and T. asperellum, showed moderate inhibition levels of 54.3% (±2.3) and 51.9% (±5.9), respectively. Greenhouse pot trials reinforced these in vitro results, with non-pathogenic F. oxysporum achieving a significant disease reduction of 77.0% (±3.0) in Fusarium wilt incidence, followed by T. harzianum at 64.8% (±2.7) (p < 0.01). Statistically significant improvements in plant growth were also recorded in treated plants. T. harzianum increased shoot length by 25.6% (±3.1) and root weight by 22.4% (±2.9) compared to control plants, while non-pathogenic Fusarium enhanced root length by 30.2% (±3.4) and overall biomass by 28.7% (±3.8) (p < 0.01). Data were analyzed using ANOVA, followed by LSD for pairwise comparisons, confirming the efficacy of these biocontrol agents in reducing disease incidence and promoting plant growth. These findings underscore the potential of antagonistic biocontrol agents as viable, sustainable alternatives to chemical fungicides for managing Fusarium wilt in tomato production systems, supporting both plant health and environmental resilience.

Diversity of Colletotrichum Species Causing Anthracnose in Chayote in Brazil, with a Description of Two New Species in the C. magnum Complex

Anthracnose caused by Colletotrichum species is the most important disease of chayote (Sicyos edulis) in Brazil. The etiology of chayote anthracnose has been assigned to the species C. orbiculare, an important plant pathogenic fungus also reported as the causal agent of anthracnose in other cucurbits worldwide. However, there is no recent survey of the Colletotrichum species causing anthracnose in chayote in Brazil. In this study, Colletotrichum isolates associated with anthracnose on the fruit and leaves of chayote, from various producing regions in Brazil, were collected and identified. Haplotype analysis based on sequences of the β-tubulin genomic region (TUB2) of 44 Colletotrichum isolates was carried out as a first measure of genetic diversity. A subset of 22 isolates were sequenced using the partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the rDNA ITS (ITS) region. Maximum likelihood analysis was performed using the concatenated sequences. The multilocus sequence analysis revealed four previously described species, Colletotrichum chrysophilum, C. menezesiae, C. plurivorum, and C. karsti, and two novel species, named C. cucurbitacearum and C. sicyi. All species were able to induce typical symptoms of anthracnose in chayote fruits but varied in their aggressiveness. The species C. menezesiae and C. sicyi were the most aggressive, while C. plurivorum was the least aggressive. The species C. orbiculare was not found to cause chayote anthracnose in Brazil.

In vitro Antifungal Effects of Various Essential Oils against Aspergillus Crown Rot of Peanut

Synthetic fungicides that combat plant pathogenic fungi can enhance crop yields, ensuring stable crop production and market quality. However, the increase in the use of fungicides may cause to development of fungicide-resistant pathogen strains and the accumulation of fungicide residues in the food chain above safe limits. This situation underscores the need for improved fungal disease management through alternatives to synthetic fungicides. These alternatives include plant-derived compounds such as essential oils and extracts. Essential oils are known to be potent antifungal compounds against both human and plant pathogens. Aspergillus niger is a toxin-producing fungal disease agent that causes Aspergillus crown rot in peanuts. In this study, the antifungal activities of nine different essential oils from Foeniculum vulgare, Lippia citriodora, Origanum majorana, Origanum minutiflorum, Origanum onites, Origanum syriacum, Origanum vulgare, Salvia aramiensis and Thymus syriacus plants were evaluated against A. niger under in vitro conditions by using disc diffusion test. Among the nine essential oils tested, the highest antifungal activities were displayed by O. vulgare essential oil (with an inhibition zone diameter of 49.33 mm) which was followed by T. syriacus, O. onites, O. syriacum and O. minutiflorum essential oils (48.67, 47.00, 46.33 and 43.33 mm, respectively). The essential oils of F. vulgare, L. citriodora, and O. majorana showed relatively lower antifungal effects. The essential oil of S. aramiensis did not show antifungal effect against pathogen. The results indicated that plant essential oils could be valuable in promoting research aimed at developing new antifungal agent(s) for fungal disease management. However, further studies are needed to optimize the in vivo application conditions of essential oils against A. niger.

Mangifera indica L. leaf assisted biosynthesis and characterization of silver nanoparticles and their antifungal activity against plant pathogen Aspergillus niger Tiegh.

The biosynthesis of silver nanoparticles is an emerging field in nanotechnology. There are several different methods to prepare silver nanoparticles depending upon their uses such as in the pharmaceutical and textile industries, and the field of medicine. One of the most important applications of silver nanoparticles is their antifungal activity against different plant pathogenic fungi. In this study, a cost-effective and environment-friendly method was used to synthesize silver nanoparticles using leaf extract of different varieties of Mangifera indica L. The varieties used in this study were Fajri, Malta, Sinduri, Sufaid Chaunsa, and Langra. The aqueous extract of the leaves of mango acted as reducing and stabilizing agents for the silver nanoparticles. The formation of silver nanoparticles was confirmed by the UV-Vis spectroscopy in which a surface plasmon resonance peak within the range of 448-454 nm was observed. FTIR analysis was also performed which showed the bands between 3738 cm-1 to 432 cm-1 which confirmed the presence of different chemical groups. Silver nanoparticles were further characterized by the scanning electron microscopy which revealed the sizes of the nanoparticles within the range of 12-235 nm. After characterization, the antifungal activity of biosynthesized silver nanoparticles was evaluated. From the results, it was concluded that all the varieties showed a greater inhibitory effect at the concentration of 100 mg/L, but it was observed that silver nanoparticles prepared by the leaf extract of cv. Fajri exhibited a greater inhibitory effect against Aspergillus niger having a percent inhibition of 79.8%.

Structural characterization, in-silico studies, and antifungal activity of 5-methylmellein isolated from endophytic Alternaria burnsii.

The present investigation focused on exploring the potential of fungal endophytes as a valuable source of bioactive compounds with diverse applications. The phenolic compound 5-methylmellein was isolated for the first time from Alternaria burnsii, an endophytic fungus associated with Morus alba Linn. The compounds were structurally characterized using comprehensive spectral analysis, including 1H-, 13C, and 2D-NMR, as well as HRESI-MS. The study investigated the antifungal activity of 5-methylmellein against several plant pathogenic fungi, including Botrytis cinerea, Colletotrichum gloeosporioides, Cercospora beticola, and Rhizoctonia solani. In vitro assays showed significant inhibition of various plant pathogenic fungi, and the IC50 values ranging from 34.59 ± 1.03a µg/mL to 44.76 ± 1.03b µg/mL against the tested fungi. In vivo experiments on apples and grapes revealed that 5-Methylmellein significantly reduced fruit decay caused by Botrytis cinerea. The wound incidence in the control group reached 95.78%, while the treated groups exhibited a reduction of 37.54% after 15days. These findings underscore the potential of 5-methylmellein as a potent antifungal agent, suggesting its eco-friendly application in agriculture for managing fruit decay.

Chickpea NCR13 disulfide cross-linking variants exhibit profound differences in antifungal activity and modes of action.

Small cysteine-rich antifungal peptides with multi-site modes of action (MoA) have potential for development as biofungicides. In particular, legumes of the inverted-repeat lacking clade express a large family of nodule-specific cysteine-rich (NCR) peptides that orchestrate differentiation of nitrogen-fixing bacteria into bacteroids. These NCRs can form 2 or 3 intramolecular disulfide bonds and a subset of these peptides with high cationicity exhibits antifungal activity. However, the importance of intramolecular disulfide pairing and MoA against fungal pathogens for most of these plant peptides remains to be elucidated. Our study focused on a highly cationic chickpea NCR13, which has a net charge of +8 and contains six cysteines capable of forming three disulfide bonds. NCR13 expression in Pichia pastoris resulted in formation of two peptide folding variants, NCR13_PFV1 and NCR13_PFV2, that differed in the pairing of two out of three disulfide bonds despite having an identical amino acid sequence. The NMR structure of each PFV revealed a unique three-dimensional fold with the PFV1 structure being more compact but less dynamic. Surprisingly, PFV1 and PFV2 differed profoundly in the potency of antifungal activity against several fungal plant pathogens and their multi-faceted MoA. PFV1 showed significantly faster fungal cell-permeabilizing and cell entry capabilities as well as greater stability once inside the fungal cells. Additionally, PFV1 was more effective in binding fungal ribosomal RNA and inhibiting protein translation in vitro. Furthermore, when sprayed on pepper and tomato plants, PFV1 was more effective in reducing disease symptoms caused by Botrytis cinerea, causal agent of gray mold disease in fruits, vegetables and flowers. In conclusion, our work highlights the significant impact of disulfide pairing on the antifungal activity and MoA of NCR13 and provides a structural framework for design of novel, potent antifungal peptides for agricultural use.

A novel antifungal peptide, SP1.2, from Rhodopseudomonas palustris against the rice blast pathogen.

Rice blast has a significant detrimental impact on rice yields, so developing efficient biological control technologies is an effective means for rice blast prevention and control. The GroEL protein has proven to be effective at preventing and managing the pathogenicity of rice blast. Here, we analyzed the amino acid sequence of the GroEL protein and synthesized the '60 kDa chaperonin signature' (350-373 amino acids) peptide SP1.2, which has potent antifungal activity. Notably, the SP1.2 peptide exhibited potent fungicidal activity against Magnaporthe oryzae, effectively inhibiting appressorium germination. Electron microscopy revealed that SP1.2 disrupted the fungal plasma membrane and bound to multiple bioactive phosphoinositides in vitro, triggering the production of reactive oxygen species. Furthermore, it also caused an increase in the acetylation of M. oryzae and induced autophagy in cells. The spray application of SP1.2 significantly reduced the number of disease spots caused by the fungal pathogen M. oryzae in rice, enhancing the defense response of rice plants. Field trials showed that the control effect was 64.59% after spraying SP1.2. Our study illustrates the antifungal activity of the structurally unique SP1.2 peptide against plant fungal pathogens and paves the way for the future development of this class of peptides as antifungal agents. © 2024 Society of Chemical Industry.

Applying Wheat-Associated Bacteria's producing Volatile Organic Compounds (VOCs) antagonistic to plant pathogenic fungi

Applying Wheat-Associated Bacteria's producing Volatile Organic Compounds (VOCs) antagonistic to plant pathogenic fungi

Bacillus velezensis SS-20 as a potential and efficient multifunctional agent in biocontrol, saline-alkaline tolerance, and plant-growth promotion

The versatile strain Bacillus velezensis SS-20 was studied to determine its agricultural benefits, including its ability to antagonize fungi, promote plant growth, and tolerate saline-alkaline conditions. Firstly, strain SS-20 was found to be an antagonist of plant pathogenic fungi such as Magnaporthe oryzae, Rhizoctonia solani, and Fusarium oxysporum, with control effects up to 82.07 %, 46.57 %, and 23.09 %, respectively. The hyphae of pathogenic fungi treated with SS-20 and its fermentation product were abnormal, swollen, deformed, and distorted. Meanwhile, strain SS-20 dissolved inorganic phosphorus (phosphate solubilization efficiency, 45.95 %), and produced siderophore (siderophore units, 54.18 ± 4.19 %), and poly-γ-glutamic acid (γ-PGA) (13.35 ± 2.61 g/L). Strain SS-20 significantly increased plant height, aboveground fresh weight, and root dehydrogenase activity compared to the control treatment under non-saline conditions (p < 0.05). In addition, strain SS-20 showed significant saline-alkaline tolerance, surviving in 10 % NaCl and pH 9.5, and enhanced plant growth under simulated saline-alkali conditions. Whole-genome sequencing analysis revealed that the chromosome of B. velezensis SS-20 consists of 3,929,792-bp with 46.5 % guanine-cytosine content and 4015 coding sequences. The antiSMASH analysis identified 12 gene clusters within strain SS-20 that encode antimicrobial compounds such as surfactin, fengycin, butirosin A/butirosin B, macrolactin H, bacillibactin, difficidin, and bacilysin, thereby corroborating the strain's biocontrol capabilities. Genes related to plant growth promotion, including siderophores, γ-PGA, indole acetic acid production, phosphate solubilization, glycine-betaine production, and Na+/H+ antiporters, were also annotated. In conclusion, B. velezensis SS-20 represents a promising biotic resource for enhancing plant growth and protecting against environmental stresses.

Insect-derived bacteria as biocontrol tool and a potent suppressor of plant pathogenic fungi in tomato cultivation

Sustainable agriculture is increasingly emphasized, focusing on microorganisms' role in maintaining soil fertility and inhibiting plant pathogens. Seeking novel sources of plant-beneficial bacteria, our study explores insects due to their established associations with plants and bacteria. The insect gut, hosting various bacteria, may hold microbes protecting against fungal infections, particularly plant pathogens. Traditional sources of plant growth-promoting bacteria are the rhizosphere and host plant tissues; however, insects serve as diverse bacterial reservoirs in the environment. This study aimed to identify insect-gut-derived bacteria with antifungal properties and cellulase enzyme production, predicting high plant tissue colonization abilities. Cellulase, crucial for breaking down cellulose, is essential for both industry and the environment. We sought to assess the potential of these bacteria as biocontrol agents against plant pathogenic fungi, with a focus on tomato plants. Bacterial isolates from insect bodies, including Lactococcus lactis, Pantoea ananatis, and Serratia liquefaciens, exhibited robust antifungal properties and cellulase activity. In vitro tests and glasshouse tests, confirmed their ability to inhibit the growth of plant-pathogenic fungi, indicating potential for biological control. Moreover, selected strains demonstrated high cellulase enzyme activity, vital for nutrient competition and rapid colonization of plant surfaces. The study introduces insect-gut-derived bacteria as promising biocontrol agents against plant pathogenic fungi. The identified strains, capable of inhibiting fungal growth and producing cellulase, offer sustainable alternatives to synthetic fungicides for protecting tomato plants. The findings advance agricultural practices by harnessing insect-associated bacteria, contributing to eco-friendly and efficient pest management strategies in modern agriculture.

Design and synthesis of camphor-thiazole derivatives as potent antifungal agents: structure-activity relationship and preliminary mechanistic study.

Plant pathogenic fungi pose a severe threat to crop yield and food security. This study aims to investigate the potential antifungal activity and mechanism of action of camphor-thiazole derivatives against six plant pathogenic fungi. A novel series of camphor-thiazole derivatives were designed, synthesized and evaluated for their antifungal effects against Rhizoctonia solani, Fusarium graminearum, Valsa mali, Alternaria solani, Colletotrichum orbiculare and Botryitis cinerea. Most of the synthesized camphor-thiazole derivatives exhibited notable antifungal activity. Amongst them, compounds C5, C10 and C17 showed significant activity against R. solani with median effective concentrations (EC50) values in the range 3-4 μg mL-1, demonstrating superior antifungal efficacy to the control drug boscalid (EC50 = 1.23 μg mL-1). Structure-activity relationship and density functional theory analysis emphasized the critical role of substituent selection in optimizing the biological activity of these compounds. Moreover, preliminary mechanistic studies revealed that compound C5 induced abnormal mycelial and cellular morphology in R. solani as observed using scanning and transmission electron microscopy, and triggered the production and accumulation of reactive oxygen species. Additionally, the increased concentration of C5 resulted in enhanced cell membrane permeability. In this study, the designed and optimized compound C5 emerged as a promising candidate for potent antifungal agents. The results demonstrate that synthesized camphor-thiazole derivatives possess potent antifungal activity and can serve as lead compounds for further optimization in antifungal agent development. © 2024 Society of Chemical Industry.

Long-term grazing effects on soil-borne pathogens are driven by temperature

Soils support a highly diverse community of plant pathogens, which are highly responsive to global change. Climate and livestock grazing are the main global changes in grasslands, yet, how long-term grazing alone, and in interaction with climate, influence the distribution of soil-borne plant pathogens remain virtually unknown. Here, we present the first long-term regional-scale experimental investigation on the impacts of livestock grazing on soil-borne fungal plant pathogens and their association with plant community across 10 experimental sites spanning a climate gradient in the steppe in Northern China. Our results showed that long-term grazing effects on the diversity and proportion of soil-borne fungal plant pathogens are strongly controlled by temperature, with grazing increasing pathogen richness and proportions largely in cooler grasslands. We further show that long-term grazing supported stronger connections between soil-borne fungal pathogens and plant communities. Our work demonstrates that climate controls the effects of grazing on plant pathogens, which is critical to understand and manage grasslands in a changing world.

Blue Light Emitting Electron-Rich Triphenylamine Decorated Stilbene Derivatives for the Bio-Imaging Application

The stilbene functionalized star and bent shaped π-conjugate organic donor-donor (D-π-D) molecules with decorated triphenylamine central core were synthesized via Michaelis-Arbuzov and Wittig-Horner Reaction with excellent regio-specific. The photo-physical investigations clearly indicate the synthesized molecules have excellent optical properties with UV-visible regions and hypochromic shifts. The intra-molecular charge transfer (ICT) absorption of bent and star-shaped molecules was found in the region of 369–390 and 382–390 nm. The star and bent-shaped molecules exhibited emission maximums between 444–490 and 437–476 nm. While increasing the solvent polarity, the emission maximum of TDMSPA and DMSNDMPA molecules were observed in red-shift. The excited state dipole moment changed when compared to ground state due to the triphenylamine core confirmed by the Lippert-Mataga plot. The density functional theory is good evidence; the TDMSPA molecule has a twisted configuration and supports optical and electrochemical studies. Time-correlated single photon counting (TCSPC) technique showed that the excited state fluorescence lifetime of the stilbene molecules was found to be 2.25 and 2.18 ns for star and bent shaped molecules, respectively. The synthesized molecules exhibit significantly low band-gap energies between HOMO and LUMO, and the values are observed in the range between 2.86 and 2.91 eV. The triphenylamine core-based π-conjugate organic chromophore is widely used as a bio-imaging agent in Rhizoctonia oryzae (Plant fungal pathogen) as the model and the TDMSPA was an excellent bio-imaging agent and biocompatibility with fungal and bacterial cells.

The Role of Oxalic Acid in Clarireedia jacksonii Virulence and Development on Creeping Bentgrass.

Dollar spot is a destructive foliar disease of amenity turfgrass caused by Clarireedia spp. fungi, mainly C. jacksonii, on the Northern United States region's cool-season grass. Oxalic acid (OA) is an important pathogenicity factor in related fungal plant pathogens such as Sclerotinia sclerotiorum; however, the role of OA in the pathogenic development of C. jacksonii remains unclear due to its recalcitrance to genetic manipulation. To overcome these challenges, a CRISPR/Cas9-mediated homologous recombination approach was developed. Using this novel approach, the oxaloacetate acetylhydrolase (oah) gene that is required for the biosynthesis of OA was deleted from a C. jacksonii wild-type (WT) strain. Two independent knockout mutants, ΔCjoah-1 and ΔCjoah-2, were generated and inoculated on potted creeping bentgrass along with a WT isolate and a genome sequenced isolate LWC-10. After 12 days, bentgrass inoculated with the mutants ΔCjoah-1 and ΔCjoah-2 exhibited 59.41% lower dollar spot severity compared with the WT and LWC-10 isolates. OA production and environmental acidification were significantly reduced in both mutants when compared with the WT and LWC-10. Surprisingly, stromal formation was also severely undermined in the mutants in vitro, suggesting a critical developmental role of OA independent of plant infection. These results demonstrate that OA plays a significant role in C. jacksonii virulence and provide novel directions for future management of dollar spot. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Fungus Fighters: Wood Ants (Formica polyctena) and Their Associated Microbes Inhibit Plant Pathogenic Fungi

Plant diseases cost the global economy billions of US dollars every year. The problem has mainly been addressed by using chemical pesticides, but recently, the use of ants has shown promising effects against plant pathogens. However, the mechanisms accounting for these effects have not yet been determined. One possible explanation is antimicrobial microorganisms associated with ants. Through controlled laboratory experiments, we investigated the inhibitory effects of wood ants (Formica polyctena) and their associated microorganisms against economically important plant pathogenic fungi. All live ants, extracts from crushed ants, and extracts from washed ants significantly inhibited the apple brown rot (Monilinia fructigena) while yielding the growth of other microbes. Furthermore, all investigated wood ants transferred microorganisms to their surroundings within 10 s when walking across a surface. We isolated the most dominant microorganisms deposited by walking ants and from washed ant extracts (i.e., strains likely found on the surface of ants), resulting in four bacterial cultures and one yeast. Two of these isolates, strain I3 (most closely related to Pseudomonas sichuanensis and P. entomophila) and strain I1b (most closely related to Bacillus mycoides), showed inhibitory effects against apple brown rot and apple scab (Venturia inaequalis), while strain I3 also inhibited gray mold (Botrytis cinerea) and Fusarium head blight (Fusarium graminearum). These results suggest that wood ants have potential as biological control agents against commercially relevant plant pathogens, and that their inhibitory effect might be at least partially caused by antibiotic compounds produced by their associated microorganisms.

Genome-based analysis of biosynthetic potential from antimycotic Streptomyces rochei strain A144.

Streptomyces rochei is a species of Streptomyces with a diverse range of biological activities. S. rochei strain A144 was isolated from desert soils and exhibits antagonistic activity against several plant pathogenic fungi. The genome of S. rochei A144 was sequenced and revealed the presence of one linear chromosome and one plasmid. The chromosome length was found to be 8,085,429bp, with a GC content of 72.62%, while the Plas1 length was 177,399bp, with a GC content of 69.08%. Comparative genomics was employed to analyse the S. rochei group. There is a high degree of collinearity between the genomes of S. rochei strains. Based on pan-genome analysis, S. rochei has 10,315 gene families, including 4051 core and 2322 unique genes. AntiSMASH was used to identify the gene clusters for secondary metabolites, identifying 33 secondary metabolite genes on the A144 genome. Among them, 18 clusters were found to be >70% identical to known biosynthetic gene clusters (BGCs), indicating that A144 has the potential to synthesize secondary metabolites. The majority of the BGCs were found to be conserved within the S. rochei group, including those encoding polyketide synthases (PKS), terpenes, non-ribosomal peptide synthetases (NRPS), other ribosomally synthesised and post-translationally modified peptides (RiPP), nicotianamine-iron transporters, lanthipeptides, and a few other types. The S. rochei group can be a potential genetic source of useful secondary metabolites with applications in medicine and biotechnology.

Progress in the study of pathogenic factors of Sclerotinia sclerotiorum

Abstract. Sclerotinia sclerotiorum is a devastating soil-borne plant fungal pathogen that can infect over 600 plant species, including important economic crops such as rapeseed, soybeans, and peanuts. Sclerotinia-induced plant diseases are distributed worldwide, and the economic losses caused by sclerotinia fruiting bodies are considerable every year. This article combines relevant research results to discuss the research on Sclerotinia sclerotiorum from four aspects: the biological characteristics and harm of the fungus, the "two-stage" infection model, the roles of oxalic acid, hydrolytic enzymes, and other five pathogenic factors in the pathogenesis of Sclerotinia, and the prevention and control measures of sclerotinia fruiting body disease using traditional methods and HIGS technology.

Exploring mechanisms of gene expression control during Ustilago maydis teliospore germination

Fungal plant pathogens produce spores for survival and dispersion. Developing an understanding of the mechanisms involved in spore dormancy and germination will aid in mitigating the impact of diseases they cause. The thick-walled diploid teliospores of Ustilago maydis were used as a model for studying fungal spore dormancy and germination. These spores develop only in infected maize tissue and can remain dormant for long periods of time. Teliospores germinate under favourable conditions, resume meiosis, and produce basidiospores to initiate new rounds of infection. Previous research identified changing gene transcripts during teliospore germination, but analysis was hampered by asynchronous germination. The more comprehensive RNA-seq analysis of U. maydis teliospore germination presented here aimed to identify gene altered transcript levels detectable above the background of fluctuating changes resulting from asynchronous germination. The analyses identified 18 different patterns of gene transcript level changes. It also indicated that gene expression is controlled at the transcriptional and post-transcriptional levels. Gene ontology term enrichment analyses of these patterns revealed genes that are involved in cell morphogenesis, metabolism, and RNA metabolism.

Colletotrichum species associated with durian (Durio zibethinus Murray) in Hainan, China

Durian (Durio zibethinus Murray), the king of fruits, is an edible and economically important tropical fruit endemic to Southeast Asia. Durian is affected by Colletotrichum, which is one of the most important genera of plant pathogenic fungi, especially on tropical and subtropical crops. In this study, Colletotrichum species associated with durian in Hainan (China) which was a new region for durian cultivation were studied using phylogenetic and morphological analyses. The results of molecular identification based on internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin (TUB2) and the mating type locus MAT1-2 (ApMat) along with microscopic identification indicated that seven species from three species complexes were identified, including C. fructicola, C. siamense, C. queenslandicum and C. endophyticum from the gloeosporioides species complex; C.plurivorum and C. musicola from the orchidearum species complex, and C. gigasporum from the gigasporum species complex. Colletotrichum fructicola and C. siamense were the main Colletotrichum species associated with durian in Hainan. Pathogenicity tests showed that all seven species could infect durian leaves using a wound inoculation method but only C. fructicola, C. queenslandicum and C. endophyticum could infect using a non-wound inoculation method. The findings from this study enhance the knowledge of durian diseases and lay an essential foundation for devising effective disease management approaches. Further large-scale surveys are necessary, including sampling different sites and plant tissues, pathogenicity testing on a wider range of host genotypes and fungicide-sensitivity evaluation among and within the different Colletotrichum species collected.

Frequent genetic exchanges revealed by a pan-mitogenome graph of a fungal plant pathogen.

Mitochondria are present in almost all eukaryotic lineages. The mitochondrial genomes (mitogenomes) evolve separately from nuclear genomes, and they can therefore provide relevant insights into the evolution of their host species. Fusarium oxysporum is a major fungal plant pathogen that is assumed to reproduce clonally. However, horizontal chromosome transfer between strains can occur through heterokaryon formation, and recently, signs of sexual recombination have been observed. Similarly, signs of recombination in F. oxysporum mitogenomes challenged the prevailing assumption of clonal reproduction in this species. Here, we construct, to our knowledge, the first fungal pan-mitogenome graph of nearly 500 F. oxysporum mitogenome assemblies to uncover the variation and evolution. In general, the gene order of fungal mitogenomes is not well conserved, yet the mitogenome of F. oxysporum and related species are highly colinear. We observed two strikingly contrasting regions in the F. oxysporum pan-mitogenome, comprising a highly conserved core mitogenome and a long variable region (6-16 kb in size), of which we identified three distinct types. The pan-mitogenome graph reveals that only five intron insertions occurred in the core mitogenome and that the long variable regions drive the difference between mitogenomes. Moreover, we observed that their evolution is neither concurrent with the core mitogenome nor with the nuclear genome. Our large-scale analysis of long variable regions uncovers frequent recombination between mitogenomes, even between strains that belong to different taxonomic clades. This challenges the common assumption of incompatibility between genetically diverse F. oxysporum strains and provides new insights into the evolution of this fungal species.IMPORTANCEInsights into plant pathogen evolution is essential for the understanding and management of disease. Fusarium oxysporum is a major fungal pathogen that can infect many economically important crops. Pathogenicity can be transferred between strains by the horizontal transfer of pathogenicity chromosomes. The fungus has been thought to evolve clonally, yet recent evidence suggests active sexual recombination between related isolates, which could at least partially explain the horizontal transfer of pathogenicity chromosomes. By constructing a pan-genome graph of nearly 500 mitochondrial genomes, we describe the genetic variation of mitochondria in unprecedented detail and demonstrate frequent mitochondrial recombination. Importantly, recombination can occur between genetically diverse isolates from distinct taxonomic clades and thus can shed light on genetic exchange between fungal strains.