Colletotrichum Corda is one of the most important plant pathogens that has a wide range of hosts including apple (Velho et al. 2016), coffee (Prihastuti et al. 2009), and many other species of plants. Meanwhile, anthracnose on tea plants (Camellia sinensis) caused by Colletotrichum spp. is one of the most severe diseases. During 2014 and 2015, a leaf and twig blight occurred with a disease incidence of 20 to 40% on tea plants in growing regions of Jiaoling County, in Guangdong Province. Symptoms began as small, water-soaked lesions on young leaves, and later became larger, semicircular or irregular, dark brown, reddish-brown at the margin. At later stages, the lesions became grayish white with black acervuli on surface. Six Colletotrichum-like isolates were isolated from symptomatic leaves on PDA, and pure cultures were obtained by single-spore isolation. All isolates initially produced white fluffy aerial hyphae and turned dark grayish with bright orange conidial masses. Ascomata 109.2 to 252.6 × 97.1 to...

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most important diseases of oilseed rape in the world. Because of the absence of resistant varieties and the disadvantages of chemical control, application of antifungal microbes has become an eco-friendly and effective measure to control this disease. In this study, Bacillus subtilis strain RSS-1, isolated from soil samples, was identified based on morphological, physiological and biochemical tests, and DNA gyrase subunit A (gyrA), gyrB, DNA-directed RNA polymerase subunit beta (rpoB) and rpoC gene sequence analysis. It significantly inhibited mycelial growth and sclerotial production of S. sclerotiorum in vitro. In greenhouse experiments, all three tested concentrations (10⁶, 10⁷, 10⁸ cfu mL⁻¹) of cell fermentation broth and culture filtrate significantly reduced the severity of sclerotinia stem rot on oilseed rape (P < 0.05). RSS-1 was more effective at reducing disease severity when applied 24 h before inoculation with S. sclerotiorum than at 24 h post inoculation, suggesting that RSS-1 should be applied as a prophylactic rather than a curative biological agent. Colonization tests indicated that the population density of RSS-1 on rapeseed leaves significantly decreased (P < 0.05) over 6 days. However, RSS-1 could stably colonize in rhizospheric soil of rapeseed over 30 days. Challenge inoculation tests showed that RSS-1 significantly inhibited the activities of polygalacturonase and cellulase and accumulation of oxalic acid during the S. sclerotiorum infection. These results suggest that RSS-1 was a potential biological agent for controlling sclerotinia stem rot caused by S. sclerotiorum on oilseed rape.

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.

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...