Due to the natural destructiveness and persistence of the southern corn leaf blight (SCLB) fungus Bipolaris maydis (Nisikado et Miyake) Shoem, the characterization of B. maydis field isolates is essential to guide the rational distribution of resistant materials in corn-growing regions. In the present study, 102 field isolates collected from seven locations covering the entire region of Fujian Province, China, were assessed for mating type distribution, genetic diversity, and pathogenicity toward local sweet corn cultivars. Mating type detection via polymerase chain reaction indicated that 36.3 and 63.7% of isolates were MAT1-1 and MAT1-2, respectively; more than 80% of these isolates were confirmed using cross assays with known mating type isolates. Thirteen intersimple sequence repeat (ISSR) markers within and among two mating type populations revealed a high level of DNA polymorphism for all combined isolates and between MAT1-1 and MAT1-2 populations. The MAT1-2 population was more diverse based on DNA polymorphism than the MAT1-1 population. The value of G_STwas 0.0070, ranging from 0.0399 to 0.3044 based on analysis of combined isolates and individual regional populations, respectively, suggesting the presence of genetic differentiation in the two mating type populations from different locations. Pathogenicity assays revealed that both MAT1-1 and MAT1-2 populations were pathogenic to all 11 local sweet corn cultivars tested in this study. The potential of sexual reproduction, existence of genetic diversity in the two mating type populations, and pathogenicity suggest that B. maydis populations have independently clonally adapted under natural field conditions during corn cultivation.

Asparagus stem blight caused by Phomopsis asparagi is a major hindrance to asparagus production worldwide. Currently, fungicides are used to manage the disease in commercial production, but resistance to common fungicides has emerged in the wild population. In the present study, 132 isolates of P. asparagi collected from different provinces in China were tested for sensitivities to pyraclostrobin, tebuconazole, and fluazinam. We also determined the efficacies of six fungicides against P. asparagi. The frequency distributions of EC₅₀ values of the isolates tested were unimodal, but the curves for pyraclostrobin and tebuconazole had long right-hand tails. The mean EC₅₀ values for pyraclostrobin, tebuconazole, and fluazinam were 0.0426 ± 0.0029, 0.6041 ± 0.0416, and 0.0314 ± 0.0013 μg/ml, respectively. In addition, the EC₅₀ values for pyraclostrobin were very similar with or without salicylhydroxamic acid (SHAM), 20 μg/ml, indicating that SHAM is not needed to determine the sensitivity of P. asparagi to pyraclostrobin when using the mycelial growth inhibition assay. In greenhouse assays, Merivon (42.4% fluxapyroxad plus pyraclostrobin SC), Frown-cide (500 g/liter fluazinam SC), Cabrio (250 g/liter pyraclostrobin EC), and Nativo (75% trifloxystrobin plus tebuconazole WG) showed excellent preventive efficacy against P. asparagi. And these fungicides were more effective before inoculation than when they were applied after inoculation (P < 0.05). Therefore, these fungicides should be applied prior to infection to control stem blight. In field trials, Frown-cide, Merivon, Nativo, and Cabrio also performed good control effects, ranging from 75.2 to 86.0% in 2017 and 75.4 to 87.1% in 2018. We demonstrated that Frown-cide, Merivon, Nativo, and Cabrio had considerable potential to manage asparagus stem blight. In addition, rotations of these fungicides are essential for precluding or delaying the development of resistance and for controlling the disease.

White button mushroom, Agaricus bisporus (Lange) Imbach, is the most extensively cultivated and edible mushroom worldwide. The production of A. bisporus is commonly affected by wet bubble disease (WBD), imposing a significant economic burden in China. Although studies have shown that this disease is caused by fungi of the Mycogone genus, the pathogen has not been fully characterized. In this study, 802 samples of diseased fruiting bodies of A. bisporus were collected from nine major mushroom-cultivating provinces in China, yielding a total of 586 Mycogone isolates. The morphologic characteristics of these isolates were observed and compared, and multilocus phylogenetic analyses (internal transcribed spacer [ITS], ACT, TEF1-α, TUB, RPB2, and large ribosomal subunit [LSU]) were performed on the selected representative isolates. Three Mycogone species were identified: a new species, M. xinjiangensis; M. perniciosa; and M. rosea. Mycogone rosea was the first ever reported in China. Furthermore, M. rosea was found to be the most prevalent species (54.95% of all isolates) in all the sampled areas, except in Hubei and Xinjiang, followed by M. perniciosa (39.93%) and M. xinjiangensis (5.12%). Pathogenicity tests on the fruiting body and mushroom bed substantiated Koch’s postulates by the development of mildly different symptoms after inoculation with each species. This study, therefore, enhances our knowledge of the species associated with WBD in A. bisporus and provides useful insights for preventing WBD and allied diseases.

Pith necrosis, an important disease of tomato worldwide, is caused by Pseudomonas corrugata (Buonaurio et al. 1993), P. mediterranea (Trantas et al. 2013), P. viridiflava, and Pectobacterium spp. (Malathrakis and Goumas 1987). More than 233 ha of tomato are harvested annually in Minqing County, Fujian Province, China. During spring 2015 and 2016, pith necrosis symptoms were observed on tomato with an incidence of 30 to 50% in production areas of Minqing County. Symptoms consisted of general plant wilting, yellowing and brown to black spots or lesions on stem, petiole and fruit stalk. Internally, pith tissues showed water-soaking, hollowing and soft rotting, and vascular tissue was yellow to brown in color. To characterize the pathogen, symptomatic tissue was surface sterilized in 0.5% sodium hypochlorite for 1 min, rinsed with sterile distilled water, and then ground in a few drops of sterile distilled water. Subsequently, suspensions were streaked onto nutrient agar and incubated for 48 h at 28°C. Isolat...

Acidovorax citrulli (Ac) is an important pathogenic bacterium causing bacterial fruit blotch (BFB) in Cucurbitaceae plants and is an important quarantine pest in China. This study was conducted to establish a rapid, convenient, and accurate visual method for detecting A. citrulli. A. citrulli-specific primers and a prober were designed based on the conserved region of the YD-repeat protein gene. Loop-mediated isothermal amplification combined with lateral flow dipstick (LAMP-LFD) was used to establish an assay for the rapid visual detection of A. citrulli by optimizing the reaction temperature and time. The specificity, sensitivity, and performance of the optimized LAMP-LFD assay were evaluated using the genomic DNA of the tested isolates, A. citrulli pure culture, infested seeds, commercial seeds, and leaf samples. The optimal assay temperature and time were 64 °C and 60 min, respectively. The assay specifically detected A. citrulli, and no cross-reactions were observed with the genomic DNA of other closely related species. The detection sensitivity of the LAMP-LFD for detecting pure genomic DNA, the bacterial suspension, bacterial amount on seeds (colony-forming units (CFU)·g⁻¹), and infection rate of seeds (%) were 1 fg·μL⁻¹, 8 CFU·mL⁻¹, 5 CFU·g⁻¹, and 0.05% infestation per reaction, respectively. The positive detection rate of the LAMP-LFD assay was 20–100% in seed samples (n = 1000 seeds) with 0.05–0.1% infestation. The LAMP-LFD assay rapidly and accurately detected A. citrulli in seeds and leaf tissues carrying pathogens. This assay thus offers the advantages of easy operation, rapidity, high specificity and sensitivity, low cost (no need for complex and expensive precision instruments), visualization of detection results, good stability, and strong applicability, which can be used for epidemiological studies and disease management.

Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum Owen (FOC) is a major disease affecting cucumber production. Developing environmentally friendly prevention and control strategies is essential for managing cucumber Fusarium wilt (CFW). Bacillus velezensis is a beneficial microorganism with biocontrol potential against plant diseases. To investigate the biocontrol efficacy and induced disease resistance mechanism of B. velezensis FJ17-4 against CFW, the biocontrol effect of FJ17-4 on CFW was determined through indoor pot cultivation experiments, and the transcriptome of cucumber root samples treated with FJ17-4 was sequenced and analyzed by RNA-Seq technology. The results showed that CFW incidence was significantly reduced after FJ17-4 treatment, with 68.75% control efficacy, higher than that of Kasugamycin. A total of 1041 differentially expressed genes (DEGs) were induced, including 477 upregulated and 564 downregulated genes. DEGs associated with plant–pathogen interaction pathways (such as carbon metabolism, phenylpropanoid biosynthesis and amino acid biosynthesis), calcium (Ca²⁺) signaling pathway, and plant hormone signaling pathways [such as salicylic acid (SA), ethylene (ET), and jasmonic acid (JA)] were induced. These responses activated the disease resistance system of cucumber against CFW. Quantitative RT-PCR validation of 10 annotated DEGs confirmed consistent expression trends with the transcriptomic data. The results indicate that FJ17-4-induced disease resistance involves multiple genes and coordinated regulation of metabolisms, with hormone-mediated defense signaling pathways playing important roles. The transcriptome sequencing data provides a scientific basis for exploring the induced disease resistance mechanism of FJ17-4 and developing environmentally friendly biocontrol strategies.