Phaeobotryon rhois is an important pathogenic fungus that causes dieback and canker disease of woody hosts. A novel mycovirus, tentatively named "Phaeobotryon rhois victorivirus 1 " (PrVV1), was identified in P. rhois strain SX8-4. The PrVV1 has a double-stranded RNA (dsRNA) genome that is 5,224 base pairs long and contains two open reading frames (ORF1 and ORF2), which overlap at a AUGA sequence. ORF1 encodes a polypeptide of 786 amino acids (aa) that contains the conserved coat protein (CP) domain of victoriviruses, while ORF2, encodes a large polypeptide of 826 aa that contains the conserved RNA-dependent RNA polymerase (RdRp) domain of victoriviruses. Our analysis of genomic structure, homology, and phylogeny indicated that PrVV1 is a novel member of the genus Victorivirus in the family Totiviridae. This is the first report of the complete genome sequence of a victorivirus that infects P. rhois.

Fusarium wilt of bitter gourd is a soil-borne disease caused by Fusarium oxysporum f. sp. momordicae Sun ＆ Huang（FOM）, which seriously affects the production of bitter gourd. Clarifying the pathogenic mechanism of FOM has important guiding significance for the prevention and control of Fusarium wilt of bitter gourd, but the pathogenic mechanism of FOM is still unclear. In the previous analysis of the differentially expressed genes in the transcriptomes of the strong pathogenic strain SD-1 and the weak pathogenic strain SD-V（carrying mycoviruses） of FOM, it was found that the expression level of FoHAD-type II was significantly down-regulated in SD-V strain. Therefore, we speculated that this gene may be involved in the pathogenic process of FOM. In this study, based on the principle of homologous recombination, the fusion fragment of FoHAD-type Ⅱ was obtained by Split-Marker PCR, the gene knockout mutant was obtained by PEG-mediated protoplast transformation, and the complementary mutant was obtained by Agrobacterium transformation method. The biological characteristics and pathogenicity of the mutants were tested and analyzed. The results showed that the growth rate and spore production of the FoHAD-type Ⅱ gene knockout mutant on the PDA medium were not significantly different from the wild-type strain, and there were no significant differences in the morphology of hyphal tips and spores. However, the vegetative growth of the knockout mutant was defective, manifested as different colony morphology, reduced aerial hyphae, significantly reduced virulence, and increased sensitivity to osmotic stress. The pathogenicity of the complemented mutant was consistent with that of the wild-type strain. Therefore, these findings suggested that FoHAD-type Ⅱ is not involved in the growth and development of FOM, but plays an important role in the pathogenic process of FOM, which may be related to the decline of pathogenicity of FOM caused by mycovirus. The results of this study provide a basis for the subsequent exploration of the pathogenic mechanism of FOM and a reference for the study of the hypovirulence mechanism of mycoviruses.

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.

In order to effectively control jujube dry rot disease,47 fungal isolates of jujube dry rot plaques from different sources were identified and characterized by using sequence analysis of internal transcribed spacer（ITS） and elongation factor 1 α（EF-1α） genes and indoor inoculation method,and their distribution characteristics and virulence differences were analyzed. The distribution characteristics and differences in pathogenicity were also studied. The results showed that Botryosphaeria dothidea,Spencermartinsia viticola,Diplodia mutila,D. seriata,and Phaeobotryon rhois were identified as the major pathogens causing jujube dry rot. Among them,the isolation frequency of S. viticola was the highest（65.96%）,followed by that of B. dothidea（17.02%）. The dominant pathogens were different in different regions. B. dothidea and D. seriata were the predominant species in Henan and Hebei areas,and S. viticola was the predominant species in Shanxi,Gansu,and Ningxia areas. The pathogenicity of different pathogens to jujube tree was different,and the results indicated that the pathogenicity of B. dothidea was the highest and that of P. rhois was the weakest. The results of this study showed that the pathogens of jujube dry rot were mainly composed of 5 species in the Botryosphaericeae family,and the dominant pathogens were different in different regions. In terms of pathogenicity,the pathogenicity of different strains of the same pathogen varies in different regions,and the pathogenicity of different strains of pathogens in the same region also varies. The results of this study provide reference for the precise prevention and control of jujube dry rot in different areas.

Abstract Fusarium pseudograminearum is a pathogenic fungus causeing crown rot. Only two mycovirus have been reported in F. pseudograminearum thus 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 study to report a fusarivirus that infects F. pseudograminearum.

A novel mycovirus named Fusarium oxysporum alternavirus 1(FoAV1) was identified as infecting Fusarium oxysporum strain BH19, which was isolated from a fusarium wilt diseased stem of Lilium brownii. The genome of FoAV1 contains four double-stranded RNA (dsRNA) segments (dsRNA1, dsRNA 2, dsRNA 3 and dsRNA 4, with lengths of 3.3, 2.6, 2.3 and 1.8 kbp, respectively). Additionally, dsRNA1 encodes RNA-dependent RNA polymerase (RdRp), and dsRNA2- dsRNA3- and dsRNA4-encoded hypothetical proteins (ORF2, ORF3 and ORF4), respectively. A homology BLAST search, along with multiple alignments based on RdRp, ORF2 and ORF3 sequences, identified FoAV1 as a novel member of the proposed family "Alternaviridae". Evolutionary relation analyses indicated that FoAV1 may be related to alternaviruses, thus dividing the family "Alternaviridae" members into four clades. In addition, we determined that dsRNA4 was dispensable for replication and may be a satellite-like RNA of FoAV1-and could perhaps play a role in the evolution of alternaviruses. Our results provided evidence for potential genera establishment within the proposed family "Alternaviridae". Additionally, FoAV1 exhibited biological control of Fusarium wilt. Our results also laid the foundations for the further study of mycoviruses within the family "Alternaviridae", and provide a potential agent for the biocontrol of diseases caused by F. oxysporum.

Aplosporella javeedii is a pathogenic fungus that causes canker and dieback of jujube in China. In this study, we report a new mycovirus, Aplosporella javeedii partitivirus 1 (AjPV1), isolated from A. javeedii strain NX55-3. The AjPV1 genome contains two double-stranded RNA elements (dsRNA1 and dsRNA2). The size of dsRNA1 is 2,360 bp, and it encodes a putative RNA-dependent RNA polymerase (RdRp), while dsRNA2 is 2,301 bp in length and encodes a putative capsid protein (CP). The sequences of RdRp and CP have significant similarity to those of members of the family Partitiviridae. Sequence alignment and phylogenetic analysis showed that AjPV1 is a new member of the family Partitiviridae that is related to members of the genus Betapartitivirus. To our knowledge, AjPV1 is the first mycovirus reported from A. javeedii.