Background: Peanut (Arachis hypogaea), a vital oil and food crop globally, is susceptible to web blotch which is a significant foliar disease caused by Phoma arachidicola Marasas Pauer&Boerema leading to substantial yield losses in peanut production. Calcium treatment has been found to enhance plant resistance against pathogens. Results: This study investigates the impact of exogenous calcium on peanut resistance to web blotch and explores its mechanisms. Greenhouse experiments revealed that exogenous calcium treatment effectively enhanced resistance to peanut web blotch. Specifically, amino acid calcium and sugar alcohol calcium solutions demonstrated the best induced resistance effects, achieving reduction rates of 61.54% and 60% in Baisha1016, and 53.94% and 50% in Luhua11, respectively. All exogenous calcium treatments reduced malondialdehyde (MDA) and relative electrical conductivity (REC) levels in peanut leaves, mitigating pathogen-induced cell membrane damage. Exogenous calcium supplementation led to elevated hydrogen peroxide (H₂O₂) content and superoxide anion (O₂^∙-) production in peanut leaves, facilitating the accumulation of reactive oxygen species (ROS) crucial for plant defense responses. Amino acid calcium and sugar alcohol calcium treatments significantly boosted activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in peanut leaves. Activation of these antioxidant enzymes effectively scavenged excess ROS, maintaining ROS balance and mitigating cellular damage. Conclusions: In summary, exogenous calcium treatment triggered ROS production, which was subsequently eliminated by the activation of antioxidant enzymes, thereby reducing cell membrane damage and inducing defense responses against peanut web blotch.

Elsinochromes (ESCs) are virulence factors produced by Elsinoë arachidis which is the cause of peanut scab. However, the biosynthesis pathway of ESCs in E. arachidis has not been elucidated and the potential pathogenic mechanism of E. arachidis is poorly understood. In this study, we report a high-quality genome sequence of E. arachidis. The size of the E. arachidis genome is 33.18Mb, which is comparable to the Ascomycota genome (average 36.91 Mb), encoding 9174 predicted genes. The self-detoxification family including transporters and cytochrome P450 enzymes were analysis, candidate effectors and cell wall degrading enzymes were investigated as the pathogenicity genes by using PHI and CAZy databases. Additionally, the E. arachidis genome contains 24 secondary metabolism gene clusters, in which ESCB1 was identified as the core gene of ESC biosynthesis. Taken together, the genome sequence of E. arachidis provides a new route to explore its potential pathogenic mechanism and the biosynthesis pathway of ESCs.

Rhizoctonia solani Kühn is an important fungal pathogen that causes serious crop yield losses worldwide. The application of nanoscale strategies based on RNA interference (RNAi) represents an environmentally friendly and efficient approach for plant disease control. In this study, R. solani glycosyl hydrolase family 1 (RsGH1), which functions as a cell wall degrading enzyme (CWDE), and was screened as a prospective RNAi target gene for managing R. solani AG3 TB. Additionally, a novel nanosystem for loading and stabilization of double-stranded RNA (dsRNA) was developed. When the mass ratio of ε-poly-L-lysine (ε-PL) to carboxymethyl chitosan (CMCS) is 1:1, ε-PL can spontaneously conjugate with CMCS to form nanoscale spherical particles by electrostatic interaction, hydrogen bonding and Van der Waals forces. Compared with ε-PL alone, the introduction of CMCS resulted in more regular and uniform nanoparticles. dsRsGH1 spontaneously binds with ε-PL@CMCS, which is referred to as dsRsGH1@ε-PL@CMCS. ε-PL@CMCS protected dsRNA from RNase A degradation effectively. The combination of dsRsGH1 with ε-PL@CMCS remarkably improved the deposition and adhesion of dsRsGH1 droplets on Nicotiana tabacum (N. tabacum) leaves. The application of ε-PL@CMCS improved the RNAi efficiency of dsRsGH1 and prolonged its protective duration on crops. dsRsGH1 derived from R. solani AG3 TB also exhibited broad-spectrum activity against R. solani AG1-IA in rice and maize plants. In this study, a self-assembled multi-component nano-fungicide was designed based on dsRNA and nanocarriers. This work proposes an eco-friendly strategy to manage R. solani.

Aconitum kusnezoffii is a perennial medicinal plant belong to the Ranunculaceae family and distributed mainly in Northeast and North China. In July of 2018, a typical southern blight disease of A. kusnezoffii was observed in commercial fields of Qingyuan County, Fushun City, Liaoning Province, China. The fungus mainly infected stem base and tuberous roots of the plant by wrapping the hyphae and absorbing nutrition, resulting in tuberous root wilted or whole plant death. Morphological characteristics of colony and sclerotia of three representative strains isolated from the diseased plants differed obviously from those of Sclerotium rolfsii isolated from A. carmichaeli. Sclerotia were large (0.8-5.1 mm size), reddish-brown, irregular and pitted surfaces, and the hyphae was white, compact or fluffy, with a growth rate ranging from 8.0 mm/d to 10.1 mm/d. Phylogenetic analysis of the internal transcribed spacer and the large subunit sequences showed that three strains isolated from A. kusnezoffii formed a unique and well supported clade that groups with the reference isolates of S. delphinii. Based on phylogentic analysis, cultural and morphological characteristics, the three isolates of A. kusnezoffii were identified as S. delphinii. The optimum temperature for mycelial growth of the three tested isolates were 30℃ and sclerotia formed and matured more easily at 20℃. Light promoted the growth of mycelial, while dark was beneficial to the formation and maturation of sclerotia. The pathogenicity of S. delphinii showed stronger than S. rolfsii at low temperature (20℃). This is the first report of S. delphinii causing southern blight on A. kusnezoffii in China and this finding would provide a basis for disease accurate diagnosis and the development of effective management strategies.

Panax ginseng C. A. Meyer is one of the most important medicinal herbs in China. It is known for its high medicinal value and economic value. The ginseng root rust rot (RRR) has always been one of the important diseases troubling the ginseng industry. The yield reduction rate of RRR is ~30%. To understand why the Cylindrocarpon species bring about the ginseng RRR in Northeastern China, this study isolates 45 strains from samples collected in Liaoning, Jilin, and Heilongjiang provinces. The rDNA-internal transcribed spacer (ITS) sequence was analyzed to identify the pathogenic species. The morphological characteristics of colonies and conidia of each strain on potato dextrose agar (PDA) medium were observed, and the pathogenicity difference between different pathogenic species was analyzed by pricking method and determining the cell wall degrading enzyme activity. The BLAST alignment analysis shows that the homology of rDNA-ITS between 45 strains and Cylindrocarpon is more than 99%, among which 28 are identified as Cylindrocarpon destructans, three are identified as C. destructans var. destructans, and 14 are identified as Ilyonectria robusta. The colony diameters of all 45 isolated range from 4.21 ± 0.16a to 7.78 ± 0.25c cm after several days of incubation. Among all the species, I. robusta has the fastest growth rate, and C. destructans var. destructans has the slowest growth rate. Pathogenicity test results show that the pathogenicity of C. destructans var. destructans is the strongest, followed by C. destructans. I. robusta has relatively weak pathogenicity.