This study investigated the biodiversity, phylogeny, and antifungal activity of endophytic fungi isolated from Zanthoxylum bungeanum. A total of 940 isolates obtained were grouped into 93 morphotypes, 43 species, and 23 genera, which were authenticated by molecular identification based on rDNA internal transcribed spacer (ITS) sequence analysis. A high diversity of endophytic fungi from Z. bungeanum are observed with high species richness S (43), Margalef index D′ (6.1351), Shannon–Wiener index H′ (3.2743), Simpson diversity index D_s (0.9476), PIE index (0.9486), and evenness Pielou index J (0.8705) but a low dominant index λ (0.0524). Significant tissue specificity of the endophytic fungi was observed in Z. bungeanum, and the highest species richness and diversity indexes were obtained in the stem. Phylogenetic analyses of the 93 endophytic isolates were carried out by the neighbor-joining (NJ) method to demonstrate their evolutionary processes. Antifungal activities of endophytic fungi were assayed and eight endophytic isolates showed strong and long-lasting inhibition against host pathogenic fungi Fusarium sambucinum and Pseudocercospora zanthoxyli. Here, for the first time, we systematically demonstrate the biodiversity, phylogeny, and antifungal activity of endophytic fungi associated with Z. bungeanum and reveal the value of sampling different tissues of a given plant to obtain the greatest endophyte species diversity, which might offer a framework for further investigation and utilization of endophytic fungi as aunique source of interesting and useful bioactive compounds.

Oligosaccharide elicitors from pathogens have been shown to play major roles in host plant defense responses involving plant–pathogen chemoperception and interaction. In the present study, chitosan and oligochitosan were prepared from pathogen Fusarium sambucinum, and their effects on infection of Zanthoxylum bungeanum stems were investigated. Results showed that oligochitosan inhibited the infection of the pathogen, and that the oligochitosan fraction with a degree of polymerization (DP) between 5 and 6 showed the optimal effect. Oligochitosan DP5 was purified from fraction DP5-6 and was structurally characterized using electrospray ionization mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Oligochitosan DP5 showed significant inhibition against the infection of the pathogenic fungi on host plant stems. An investigation of the mechanism underlying this effect showed that oligochitosan DP5 increased the activities of defensive enzymes and accumulation of phenolics in host Z. bungeanum. These results suggest that oligochitosan from pathogenic fungi can mediate the infection of host plants with a pathogen by acting as an elicitor that triggers the defense system of a plant. This information will be valuable for further exploration of the interactions between the pathogen F. sambucinum and host plant Z. bungeanum.

In this report, the effects of two oligochitosans, i.e., oligochitosan A (OCHA) and oligochitosan B (OCHB), on control of dry rot of Zanthoxylum bungeanum (Z. bungeanum) caused by Fusarium sambucinum (F. sambucinum) were evaluated. First, both oligochitosans show desirable ability to decrease the infection of F. sambucinum. Second, the oligochitosans strongly inhibit the radial colony and submerged biomass growth of F. sambucinum. Lastly, these oligochitosans are capable of increasing the activities of phenylalanine ammonia lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) significantly, as well as enhancing the content of total phenolics in Z. bungeanum stems. These findings indicate that the protective effects of OCHA and OCHB on Z. bungeanum stems against dry rot may be associated with the direct fungitoxic function against pathogen and the elicitation of biochemical defensive responses in Z. bungeanum stems. The outcome of this report suggests that oligochitosans may serve as a promising natural fungicide to substitute, at least partially, for synthetic fungicides in the disease management of Z. bungeanum.

Background: Fusarium zanthoxyli is a destructive pathogen causing stem canker in prickly ash, an ecologically and economically important forest tree. However, the genome lack of F. zanthoxyli has hindered research on its interaction with prickly ash and the development of precise control strategies for stem canker. Results: In this study, we sequenced and annotated a relatively high-quality genome of F. zanthoxyli with a size of 43.39 Mb, encoding 11,316 putative genes. Pathogenicity-related factors are predicted, comprising 495 CAZymes, 217 effectors, 156 CYP450s, and 202 enzymes associated with secondary metabolism. Besides, a comparative genomics analysis revealed Fusarium and Colletotrichum diverged from a shared ancestor approximately 141.1 ~ 88.4 million years ago (MYA). Additionally, a phylogenomic investigation of 12 different phytopathogens within Fusarium indicated that F. zanthoxyli originated approximately 34.6 ~ 26.9 MYA, and events of gene expansion and contraction within them were also unveiled. Finally, utilizing conserved domain prediction, the results revealed that among the 59 unique genes, the most enriched domains were PnbA and ULP1. Among the 783 expanded genes, the most enriched domains were PKc_like kinases and those belonging to the APH_ChoK_Like family. Conclusion: This study sheds light on the genetic basis of F. zanthoxyli’s pathogenicity and evolution which provides valuable information for future research on its molecular interactions with prickly ash and the development of effective strategies to combat stem canker.

Stem canker of Zanthoxylum bungeanum is a destructive forest disease, caused by Fusarium zanthoxyli, poses a serious threat to the cultivation of Z. bungeanum. The lack of research on effector proteins in F. zanthoxyli has severely limited our understanding of the molecular interactions between F. zanthoxyli and Z. bungeanum, resulting in insufficient effective control technologies for this disease. In this study, a total of 137 effector proteins (FzEPs) were predicted and characterized based on whole genome of F. zanthoxyli, with an average length of 215 amino acids, 8 cysteine residues, and a molecular weight of 23.06 kD. Besides, the phylogenetic evolution, conserved motifs, domains and annotation information of all the 137 effectors were comprehensively demonstrated. Moreover, transcriptomic analysis indicated that 24 effector genes were significantly upregulated in the early infection stages of F. zanthoxyli, which was confirmed by RT-qPCR. Following, the 24 effector DEGs were cloned and transiently over-expressed in the leaves of tobacco to evaluate their effects on the plant’s innate immunity. It was found that effector proteins FzEP94 and FzEP123 induced pronounced programmed cell death (PCD), callose deposition, and reactive oxygen species (ROS) burst in tobacco leaves, whereas FzEP83 and FzEP93 significantly suppressed PCD induced by INF1, accompanied by a less pronounced callose accumulation and ROS burst. In this study, we systematically characterized and functionally analyzed the effector proteins of F. zanthoxyli, successfully identifying four effector proteins that can impact the innate immune response of plants. These findings enhance our understanding of effector protein functions in F. zanthoxyli and offer valuable insights for future research on molecular interactions between F. zanthoxyli and Z. bungeanum.