Luyang Song

Background/Objectives: Wheat root and crown rot, caused by Fusarium pseudograminearum, Fusarium graminearum, and Bipolaris sorokiniana, are devastating soil-borne diseases that cause substantial yield losses worldwide. Endophytic fungi are promising sources of bioactive metabolites for agricultural applications. This study aimed to isolate and characterize an endophytic fungus with antifungal activity against major wheat pathogens, identify its active compound, and investigate the underlying transcriptional response. Methods: An endophytic strain Y2 was isolated from Hedyotis diffusa leaves and identified through morphological and phylogenetic analysis based on TEF-1α and RPB2 sequences. Pathogenicity of strain Y2 was evaluated on wheat stem bases. The bioactive compound was purified by HPLC and identified by HR-ESI-MS and NMR. Antifungal activity was assessed using dual-culture and microbroth dilution assays. Transcriptomic analysis (RNA-seq) was performed on F. pseudograminearum treated with equisetin, with qRT-PCR validation of seven representative differentially expressed genes. Results: Strain Y2 was identified as Fusarium incarnatum or a closely related member of the F. incarnatum–equiseti species complex (FIESC) and confirmed to be non-pathogenic to wheat. The purified bioactive compound was characterized as equisetin, which exhibited significant antifungal activity with MIC values of 16, 32, and 64 μg/mL against F. pseudograminearum, B. sorokiniana, and F. graminearum, respectively. Transcriptomic analysis revealed that equisetin treatment induced a polarized transcriptional response in F. pseudograminearum, characterized by strong upregulation of ribosome and translation-related genes and widespread downregulation of other metabolic pathways, particularly nitrogen metabolism. qRT-PCR validation of seven representative genes confirmed the reliability of the RNA-seq data. Conclusions: Our findings demonstrate that equisetin is the active antifungal metabolite produced by F. incarnatum Y2, with potent in vitro activity against major wheat root and crown rot pathogens. The transcriptomic data provide insights into the potential mechanism of action, while the non-pathogenic nature of strain Y2 supports its biosafety. Although these results highlight equisetin as a promising lead compound for antifungal development, further in planta efficacy and safety studies are required before it can be considered for practical biocontrol.

Microbiome-guided crop protection increasingly emphasizes the chemical basis of disease suppression. Here, we identify Streptomyces aurantiacus YS-4, a rhizosphere-enriched actinobacterium selectively recruited by resistant cultivars of Salvia miltiorrhiza, as a producer of metacycloprodigiosin, a previously reported secondary metabolite that is reported for the first time in this strain and further investigated for its role in suppressing Fusarium oxysporum-induced root rot in S. miltiorrhiza. Metacycloprodigiosin inhibited Fusarium oxysporum growth by 81.66% at 200 μg mL^-1 and induced extensive cellular and transcriptional changes related to membrane function and virulence-associated pathways. Transmission electron microscopy confirmed severe hyphal damage, while transcriptomic profiling revealed broad downregulation of virulence-associated genes. Pot experiments demonstrated that YS-4 application alleviated root rot symptoms and enhanced plant biomass. Collectively, these findings establish a direct link between metabolite chemistry and pathogen suppression, advancing molecular understanding of plant-fungal interactions and highlighting metacycloprodigiosin as a promising biocontrol agent for sustainable management of crops.

Macrophomina phaseolina is a widely distributed soilborne phytopathogenic fungus that causes destructive diseases such as charcoal rot and stem canker, posing serious threats to crop yield and quality. In recent years, mycoviruses have gained attention as potential biological control agents. In this study, a novel double-stranded RNA (dsRNA) virus was identified from M. phaseolina strain 22C-8, isolated from sesame (Sesamum indicum L.) charcoal rot samples in Fuyang, Anhui Province, China. The viral genome comprised four dsRNA segments, each encoding a single open reading frame (ORF) predicted to encode RNA-dependent RNA polymerase (RdRp), coat protein (CP), and two hypothetical proteins. Phylogenetic analysis classified the virus as a new member of the genus Betachrysovirus in the family Chrysoviridae, and it was designated Macrophomina phaseolina chrysovirus 2 (MpChrV2). Pathogenicity assays in sesame seedlings revealed that MpChrV2 infection significantly reduced the virulence of M. phaseolina strain 22C-8. In contrast, virus-free derivatives (22C-8-VF18), obtained via protoplast regeneration, caused more severe symptoms and exhibited enhanced growth rates, indicating that MpChrV2 alters fungal physiology and pathogenicity. These findings suggest that MpChrV2 possesses a typical hypovirulence phenotype and holds promise as a biocontrol agent for sesame charcoal rot.

Bemisia tabaci is distributed globally and incurs considerable economic and ecological costs as an agricultural pest and viral vector. The entomopathogenic fungus Metarhizium anisopliae has been known for its insecticidal activity, but its impacts on whiteflies are understudied. We investigated how infection with the semi-persistently transmitted Cucurbit chlorotic yellows virus (CCYV) affects whitefly susceptibility to M. anisopliae exposure. We discovered that viruliferous whiteflies exhibited increased mortality when fungus infection was present compared to non-viruliferous insects. High throughput 16S rRNA sequencing also revealed significant alterations of the whitefly bacterial microbiome diversity and structure due to both CCYV and fungal presence. Specifically, the obligate symbiont Portiera decreased in relative abundance in viruliferous whiteflies exposed to M. anisopliae. Facultative Hamiltonella and Rickettsia symbionts exhibited variability across groups but dominated in fungus-treated non-viruliferous whiteflies. Our results illuminate triangular interplay between pest insects, their pathogens, and symbionts—dynamics which can inform integrated management strategies leveraging biopesticides This work underscores the promise of M. anisopliae for sustainable whitefly control while laying the groundwork for elucidating mechanisms behind microbe-mediated shifts in vector competence.

Root rot as a result of Salvia miltiorrhiza is a common root disease caused by Fusarium spp., which has become one of the main diseases affecting the production of S. miltiorrhiza. Currently, several hypovirulence-related mycoviruses have been identified in many phytopathogenic fungi, including Fusarium spp., which show potential as biological controls. In this study, we report a new mycovirus, Fusarium oxysporum partitivirus 1 (FoPV1), isolated from F. oxysporum strain FCR51, which is a causal agent of S. miltiorrhiza dry rot. The FoPV1 genome contains two double-stranded RNA segments (dsRNA1 and dsRNA2). The size of dsRNA1 is 1773 bp, and it encodes a putative RNA-dependent RNA polymerase (RdRp). The dsRNA2 is 1570 bp in length, encoding a putative capsid protein (CP). Multiple sequence alignments and phylogenetic analyses based on the amino acid sequences of the RdRp and the CP proteins indicated that FoPV1 appears to be a new member of the family Partitiviridae that is related to members of the genus Gammapartitivirus. Pathogenicity assay showed that FoPV1 confers hypervirulence to its host, F. oxysporum. This is the first report of a partitivirus infecting F. oxysporum and the first hypovirulence-related mycovirus from the causal agent of S. miltiorrhiza dry rot.

Plant diseases caused by pathogenic fungi pose a significant threat to agricultural production. This study reports on a strain YBS22 with broad-spectrum antifungal activity that was isolated and identified, and its active metabolites were purified and systematically studied. Based on a whole genome sequence analysis, the new strain YBS22 was identified as Streptomyces melanogenes. Furthermore, eight gene clusters were predicted in YBS22 that are responsible for the synthesis of bioactive secondary metabolites. These clusters have homologous sequences in the MIBiG database with a similarity of 100%. The antifungal effects of YBS22 and its crude extract were evaluated in vivo and vitro. Our findings revealed that treatment with the strain YBS22 and its crude extract significantly reduced the size of necrotic lesions caused by Magnaporthe oryzae on rice leaves. Further analysis led to the isolation and purification of an active compound from the crude extract of the strain YBS22, identified as N-formylantimycin acid methyl ester, an analog of antimycin, characterized by NMR and MS analyses. Consistently, the active compound can significantly inhibit the germination and development of M. oryzae spores in a manner that is both dose- and time-dependent. As a result, we propose that the strain YBS22 could serve as a novel source for the development of biological agents aimed at controlling rice blast disease.

Fusarium pseudograminearum is a pathogenic fungus causeing crown rot. Only two mycovirus have been reported in F. pseudograminearumthus far. Here, we report a fungal virus (mycovirus), Fusarium pseudograminearum fusarivirus 1 (FpFV1), isolated from the F. pseudograminearum strain ZZ-1. FpFV1 has a single-stranded positive-sense RNA (+ssRNA) genome of 6622 nucleotides containing four open reading frames (ORFs). ORF1 encodes for a large 1,550 amino acids (aa) polypeptide with a conserved RNA-dependent RNA polymerase (RdRp) and two helicase domains. The ORF2, ORF3 and ORF4 have overlapping regions and encode putative proteins of 154 aa, 53aa and 429aa, respectively. All three ORFs have unknown functions. Based on the genomic structure, homology searches, and phylogenetic analysis, FpFV1 could be a new member of the proposed “Fusariviridae”. This is the first report of a fusarivirus that infects F. pseudograminearum.

Fusarium oxysporum causes vascular wilt in more than 100 plant species, resulting in massive economic losses. A deep understanding of the mechanisms of pathogenicity and symptom induction by this fungus is necessary to control crop wilt. The YjeF protein has been proven to function in cellular metabolism damage-repair in Escherichia coli and to play an important role in Edc3 (enhancer of the mRNA decapping 3) function in Candida albicans, but no studies have been reported on related functions in plant pathogenic fungi. In this work, we report how the FomYjeF gene in F. oxysporum f. sp. momordicae contributes to conidia production and virulence. The deletion of the FomYjeF gene displayed a highly improved capacity for macroconidia production, and it was shown to be involved in carbendazim’s associated stress pathway. Meanwhile, this gene caused a significant increase in virulence in bitter gourd plants with a higher disease severity index and enhanced the accumulation of glutathione peroxidase and the ability to degrade hydrogen peroxide in F. oxysporum. These findings reveal that FomYjeF affects virulence by influencing the amount of spore formation and the ROS (reactive oxygen species) pathway of F. oxysporum f. sp. momordicae. Taken together, our study shows that the FomYjeF gene affects sporulation, mycelial growth, pathogenicity, and ROS accumulation in F. oxysporum. The results of this study provide a novel insight into the function of FomYjeF participation in the pathogenicity of F. oxysporum f. sp. momordicae.