Effect of surfactants and temperature on germination and vegetative growth of Beauveria bassiana

Spray inoculation and image analysis-based quantification of powdery mildew disease severity on pea leaves

Pea (Pisum sativum) is an important agricultural legume crop, but powdery mildew disease caused by the biotrophic fungus Erysiphe pisi regularly limits its annual yield. Assays to evaluate the efficacy of potential antifungal compounds or resistance genes for disease control require a simple fungal inoculation method that provides control over the initial inoculum concentration and enables uniform inoculum distribution within a leaf and across replicates as well as a method for the quantitative assessment of disease severity. Here, we present an easy spray inoculation method for the uniform distribution of a defined concentration of E. pisi conidia on the leaves of pea plants and a semi-automated image analysis-based quantification of disease symptoms. The uniformity in conidial distribution was validated using a novel grading system termed the uniformity index. In addition, RT-qPCR was used to validate the reproducibility of the spray inoculation method and image analysis-based disease quantification. These procedures permit the accurate quantification of powdery mildew disease severity at macroscopic and molecular levels.•Uniform and reproducible inoculum distribution on leaves using a simple and inexpensive spray device•Rapid and reproducible quantification of powdery mildew disease symptoms using open-source software without the requirement of computational expertise.

Can Beauveria bassiana (Bals.-Criv.) Vuill. Control the Key Fruit Pests of the European Chestnut Tree, under Field Conditions?

The chestnut moth (Cydia splendana Hübner) and the chestnut weevil (Curculio elephas Gyllenhal) cause serious damage to European producers and companies that transform and market the chestnut. The objective of the present work was to evaluate, under field conditions, the possibilities of Beauveria bassiana (Bals.-Criv.) Vuill. to infect and kill the larvae of the two main carpophagous pests of European chestnut, in treatments directed at the soil. For this purpose, the surfaces of vases were sprayed with two concentrations of conidia/mL 5 × 10⁷ (T1) and 1 × 10⁸ (T2). The control (T0) was sprayed with distilled water. Larval mortality and infection were evaluated on five dates (D8 to D220). Confirmation of the fungus present in the larva was performed by molecular analysis. The results obtained are promising for the use of B. bassiana as a biological control agent against these key pests of the chestnut crop. There were no significant differences in mortality between the T1 and T2 modalities, however, they were significantly higher than the control. In the case of total mortality (dead and infected larvae), no significant differences were observed for C. elephas either. In the case of C. splendana, the T2 modality obtained better results in terms of total mortality.

Effect of ultraviolet radiation on Beauveria bassiana virulence and development of protective formulations

Locusta migratoria is a serious agricultural pest in China. Beauveria bassiana is one of the most important pathogens of grasshoppers and locusts. The effects of ultraviolet light were evaluated on the B. bassiana strain BbZJ1. The results showed that 253.7 and 360 nm wavelength UV (Ultra Violet) did not affect the germination of B. bassiana after its recovery from UV treatments. Nevertheless, the virulence of B. bassiana BbZJ1 after its recovery from radiation of UV (253.7 nm) increased. The mortality rates were 85.00% for the BbZJ1 control, was 96.67% for BbZJ1 recovered from radiation of UV (253.7 nm) for 60 min. After treatment with 253.7 nm UV radiation for 60 min, the expression levels of stress-resistant genes BbAlg9 and Bbadh2 in BbZJ1 strain were 2.68 and 2.29 times higher than those in the control group, respectively. Meanwhile, the B. bassiana prepared in 5% groundnut oil showed highest tolerance levels to the ultraviolet radiation. The 5% groundnut oil was the most suitable potential UV-protectant for B. bassiana in terms of cost and availability.

Effects of the Entomopathogenic Fungus Mucor hiemalis BO-1 on the Physical Functions and Transcriptional Signatures of Bradysia odoriphaga Larvae

Mucor hiemalis BO-1 is an entomopathogenic fungus that infects Bradysia odoriphaga, a destructive root maggot. M. hiemalis BO-1 possesses stronger pathogenicity to the larvae than to other stages of B. odoriphaga, and provides satisfactory field control. However, the physiological response of B. odoriphaga larvae to infection and the infection mechanism of M. hiemalis are unknown. We detected some physiological indicators of diseased B. odoriphaga larvae infected by M. hiemalis BO-1. These included changes in consumption, nutrient contents, and digestive and antioxidant enzymes. We performed transcriptome analysis of diseased B. odoriphaga larvae, and found that M. hiemalis BO-1 showed acute toxicity to B. odoriphaga larvae and was as toxic as some chemical pesticides. The food consumption of diseased B. odoriphaga after inoculation with M. hiemalis spores decreased significantly, and there was a significant decrease in total protein, lipid, and carbohydrates in diseased larvae. Key digestive enzymes (protease, α-amylase, lipase, and cellulase) were significantly inhibited during infection. Peroxidase maintained high activity, and the activity of other antioxidant enzymes (catalase, superoxide dismutase, and glutathione S-transferases) first increased and then decreased. Combined with the transcriptional signatures of diseased B. odoriphaga larvae, M. hiemalis BO-1 infection resulted in decreased food consumption, reduced digestive enzyme activity, and altered energy metabolism and material accumulation. Infection was also accompanied by fluctuations in immune function, such as cytochrome P450 and the Toll pathway. Therefore, our results laid a basis for the further study of the interactions between M. hiemalis BO-1 and B. odoriphaga and promoted the genetic improvement of entomopathogenic fungi.

Transcriptome data for Hevea brasiliensis associated with powdery Mildew infection

The Hevea brasiliensis or rubber tree belongs to the Euphorbiaceae family and is the only economically viable natural rubber source worldwide. The development of enhanced rubber tree clones with agronomically important traits is critical due to the growing demand for natural rubber around the world. Throughout the years, numerous disease-causing pathogens of H. brasiliensis have been identified and studied. One of the more prominent diseases affecting H. brasiliensis is powdery mildew caused by Oidium heveae. Oidium heveae primarily infects the newly formed leaves and buds of H. brasiliensis. Severe Oidium heveae infections cause extensive defoliation and yield loss. We performed RNA sequencing (RNA-Seq) for healthy and O. heveae-infected leaf tissues from RRIM 2025 and RRIM 929 rubber tree clones using the Illumina HiSeq 2000 platform. RNA-Seq generated 92007684 (12.9 GB) and 96070286 (13.5 GB) paired raw reads for healthy H. brasiliensis clones RRIM 2025 and RRIM 929 respectively. Similarly, RNA-Seq generated 93747858 (13.2 GB) and 93324564 (13.1 GB) paired raw reads for disease-infected H. brasiliensis clones RRIM 2025 and RRIM 929 respectively. The raw data were deposited in the NCBI under bio-project accession number PRJNA723431. The raw reads were quality trimmed and the reference-based transcriptome assembly was generated using the H. brasiliensis genome (ASM165405v1). The data were used to identify between the significantly differentially expressed genes of the healthy and diseased samples.

Identification and Pathogenicity of a New Entomopathogenic Fungus, Mucor hiemalis (Mucorales: Mucorales), on the Root Maggot, Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae), the Chinese chive root maggot, is a destructive pest of Allium vegetables and flowers that causes severe losses in northern China. Novel biological control technologies are needed for controlling this pest. We identified a new entomopathogenic fungus isolated from infected B. odoriphaga larvae and evaluated the susceptibility of the biological stages of B. odoriphaga and the effects of temperature on fungus growth and pathogenicity. Based on morphological characteristics and molecular phylogeny, the fungus was identified as Mucor hiemalis BO-1 (Mucorales: Mucorales). This fungus had the strongest virulence to B. odoriphaga larvae followed by eggs and pupae, while B. odoriphaga adults were not susceptible. A temperature range of 18-28°C was optimum for the growth and sporulation of M. hiemalis BO-1 and virulence to B. odoriphaga larvae. At 3 and 5 d after inoculation with 105 spores/ml at 23°C, the survival rates were 24.8% and 4.8% (2nd instar larvae), respectively, and 49.6% and 12.8% (4th instar larvae), respectively. The potted plant trials confirmed that M. hiemalis BO-1 exerted excellent control efficiency against B. odoriphaga larvae, and the control exceeded 80% within 5 d when the spore concentration applied exceeded 107 spores/ml. In conclusion, these findings supported the hypotheses that this fungus could serve as an effective control agent against B. odoriphaga larvae and is worth being further tested to determine its full potential as a biocontrol agent.

Analysis of Biodegradation of the Synthetic Pyrethroid Cypermethrin by Beauveria bassiana

Entomopathogenic fungi like Beauveria bassiana play a crucial role in natural control of arthropod pests which are being used in Integrated Pest Management programs. Assessing the compatibility of biological and chemical counterparts used in IPM programs is essential to achieve successful results in pest management. Behavior of four isolates of B. bassiana (ITCC 913, ARSEF 2860, ARSEF 1166, and ARSEF 3041) was tested in the presence of the pyrethroid insecticide cypermethrin. Spore germination and growth bioassays were conducted to assess the impact of cypermethrin on germination and growth. Though growth was not totally inhibited, there was retardation in the germination of spores and growth of the mycelium. Under this condition, ITCC 913 showed highest tolerance toward cypermethrin. Further analysis of the culture crude extracts by GC-MS revealed degradation of the insecticide by B. bassiana and putative intermediates of the degradation pathway were identified. This study reveals the potential of the entomopathogen B. bassiana in degradation of the pyrethroid insecticide cypermethrin. In conclusion, this potentiality of the studied fungus may help in the IPM strategies and find its role in degradation of such chemical pesticide compounds for utilization as a biodegradation agent further.

An optimized sporulation method for the wheat fungal pathogen Pyrenophora tritici-repentis

BACKGROUND

The necrotrophic fungal pathogen Pyrenophora tritici-repentis (Ptr) causes tan (syn. yellow) spot of wheat and accounts for significant yield losses worldwide. Understanding the molecular mechanisms of this economically important crop disease is crucial to counteract the yield and quality losses of wheat globally. Substantial progress has been made to comprehend the race structure of this phytopathogen based on its production of necrotrophic effectors and genomic resources of Ptr. However, one limitation for studying Ptr in a laboratory environment is the difficulty to isolate high spore numbers from vegetative growth with mycelial contamination common. These limitations reduce the experimental tractability of Ptr.

RESULTS

Here, we optimized a multitude of parameters and report a sporulation method for Ptr that yields robust, high quality and pure spores. Our methodology encompasses simple and reproducible plugging and harvesting techniques, resulting in spore yields up to 1500 fold more than the current sporulation methods and was tested on multiple isolates and races of Ptr as well as an additional seven modern Australian Ptr isolates. Moreover, this method also increased purity and spore harvest numbers for two closely related fungal pathogens (Pyrenophora teres f. maculata and f. teres) that cause net blotch diseases in barley (Hordeum vulgare), highlighting the usability of this optimized sporulation protocol for the wider research community.

CONCLUSIONS

Large-scale spore infection and virulence assays are essential for the screening of wheat and barley cultivars and combined with the genetic mapping of these populations allows pinpointing and exploiting sources of host genetic resistance. We anticipate that improvements in spore numbers and purity will further advance research to increase our understanding of the pathogenicity mechanisms of these important fungal pathogens.

Phenotyping Brown Rot Susceptibility in Stone Fruit: A Literature Review with Emphasis on Peach

Plant disease phenotyping methodologies can vary considerably among testers and often suffer from shortcomings in their procedures and applications. This has been an important challenge in resistance breeding to brown rot, one of the most severe pre-and postharvest stone fruit diseases caused by Monilinia spp. Literature about methodologies for evaluating stone fruit susceptibility to brown rot is abundant but displays significant variations across the described approaches, limiting the ability to compare results from different studies. This is despite the fact that authors largely agree on the main factors influencing brown rot development, such as Monilinia inocula, environmental conditions, cultivars, fruit stage, and management practices. The present review first discusses ways to control or at least account for major factors affecting brown rot phenotyping studies. The second section describes in detail the different steps of fruit infection assays, comparing different protocols available in the literature with the objective of highlighting best practices and further improvement of phenotyping for brown rot susceptibility. Finally, experimental results from multi-year evaluation trials are also reported, highlighting year-to-year variability and exploring correlations of evaluation outcomes among years and assay types, suggesting that choice of phenotyping methodology must be carefully considered in breeding programs.

Human exposure to air contaminants in sports environments

The aim of this review was to investigate human exposure to relevant indoor air contaminants, predictors affecting the levels, and the means to reduce the harmful exposure in indoor sports facilities. Our study revealed that the contaminants of primary concern are the following: particulate matter in indoor climbing, golf, and horse riding facilities; carbon dioxide and particulate matter in fitness centers, gymnasiums, and sports halls; Staphylococci on gymnasium surfaces; nitrogen dioxide and carbon monoxide in ice hockey arenas; carbon monoxide, nitrogen oxide(s), and particulate matter in motor sports arenas; and disinfection by-products in indoor chlorinated swimming pools. Means to reduce human exposure to indoor contaminants include the following: adequate mechanical ventilation with filters, suitable cleaning practices, a limited number of occupants in fitness centers and gymnasiums, the use of electric resurfacers instead of the engine powered resurfacers in ice hockey arenas, carefully regulated chlorine and temperature levels in indoor swimming pools, properly ventilated pools, and good personal hygiene. Because of the large number of susceptible people in these facilities, as well as all active people having an increased respiratory rate and airflow velocity, strict air quality requirements in indoor sports facilities should be maintained.

Chemical vs entomopathogenic control of Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) via aerial application in eucalyptus plantations

The Thaumastocoris peregrinus spread to eucalyptus plantations in many countries. Chemical control is a questionable measure, mainly due to the environmental impact, high cost and moreover has the use restricted by the forest certifications. Bio-insecticides may have similar efficiency to chemical products to control T. peregrinus. The chemical thiamethoxam, thiamethoxam + lambda-cyhalothrin, acephate and the microbial Beauveria bassiana and Metarhizium anisopliae insecticides were tested at different doses to manage T. peregrinus. The products were sprayed on eucalyptus plants using aircraft and populations of this insect were counted before application and at 1, 14 and 21 days afterwards (DAA). Ten eucalyptus trees were evaluated per plot, with the collection of ten leaves from the middle third of the crown of each tree, and the number of T. peregrinus nymphs and adults obtained per leaf was determined. All the chemical insecticides had similar control at 1 DAA for T. peregrinus nymphs and adults. At 14 DAA, the number of T. peregrinus nymphs and adults on eucalyptus leaves was similar for the chemical and microbial insecticide treatments. At 21 DAA the control efficiency of T. peregrinus nymphs and adults was higher than 80% with all insecticides. The entomopathogenic insecticides have potential for aerial application to control T. peregrinus nymphs and adults and provide viable and environmentally-friendly alternative to manage this pest.