Transcriptome profile of pecan scab resistant and susceptible trees from a pecan provenance collection

Pecan scab is a devastating disease that causes damage to pecan (Carya illinoinensis (Wangenh.) K. Koch) fruit and leaves. The disease is caused by the fungus Venturia effusa (G. Winter) and the main management practice for controlling the disease is by application of fungicides at 2-to-3-week intervals throughout the growing season. Besides disease-related yield loss, application of fungicides can result in considerable cost and increases the likelihood of fungicide resistance developing in the pathogen. Resistant cultivars are available for pecan growers; although, in several cases resistance has been overcome as the pathogen adapts to infect resistant hosts. Despite the importance of host resistance in scab management, there is little information regarding the molecular basis of genetic resistance to pecan scab.The purpose of this study was to elucidate mechanisms of natural pecan scab resistance by analyzing transcripts that are differentially expressed in pecan leaf samples from scab resistant and susceptible trees. The leaf samples were collected from trees in a provenance collection orchard that represents the natural range of pecan in the US and Mexico. Trees in the orchard have been exposed to natural scab infections since planting in 1989, and scab ratings were collected over three seasons. Based on this data, ten susceptible trees and ten resistant trees were selected for analysis. RNA-seq data was collected and analyzed for diseased and non-diseased parts of susceptible trees as well as for resistant trees. A total of 313 genes were found to be differentially expressed when comparing resistant and susceptible trees without disease. For susceptible samples showing scab symptoms, 1,454 genes were identified as differentially expressed compared to non-diseased susceptible samples. Many genes involved in pathogen recognition, defense responses, and signal transduction were up-regulated in diseased samples of susceptible trees, whereas differentially expressed genes in pecan scab resistant samples were generally down-regulated compared to non-diseased susceptible samples.Our results provide the first account of candidate genes involved in resistance/susceptibility to pecan scab under natural conditions in a pecan orchard. This information can be used to aid pecan breeding programs and development of biotechnology-based approaches for generating pecan cultivars with more durable scab resistance.

Exposure levels and health implications of fungicides, neonicotinoid insecticides, triazine herbicides and their associated metabolites in pregnant women and men

Exposure to pesticides can pose a series of advance effects on human health. However, the exposure levels and health implications of the current use pesticides and their metabolites in both men and pregnant women remain unclear. In this study, an analytical method was developed to quantify fungicides, neonicotinoid insecticides, triazine herbicides, and their metabolites in the human serum. Fifty of the 73 target pesticides and metabolites were detected in the human serum of men and pregnant women from Wuxi, China, which included 11 triazine herbicides and metabolites, 17 neonicotinoid insecticides and metabolites, and 22 fungicides. Fungicides had the highest cumulative concentration (49.5 ng/mL), followed by neonicotinoid insecticides and metabolites (6.38 ng/mL), and triazine herbicides and metabolites (5.10 ng/mL). Moreover, the estimated daily intake (EDI) of fungicides was 10.4 and 12.7 times higher than that of triazine herbicides (included their metabolites) and neonicotinoid insecticides (included their metabolites), respectively. Of the three categories of pesticides, exposure to fungicides contributed to the highest exposure risk within the hazard quotient in the range of 5.1 × 10-3-0.17. Correlation analysis revealed that the pesticide exposure levels in human serum were correlated with their maximum residue levels in vegetables and fruits. Pesticide exposure has also been correlated with the weight and Body Mass Index (BMI) of humans based on structural equation modeling. This study provides new insights into the exposure of men and pregnant women to a cocktail of fungicides, neonicotinoid insecticides, triazine herbicides and their metabolites.

Architecture and potential roles of a delta-class glutathione S-transferase in protecting honey bee from agrochemicals

The European honey bee, Apis mellifera, serves as the principle managed pollinator species globally. In recent decades, honey bee populations have been facing serious health threats from combined biotic and abiotic stressors, including diseases, limited nutrition, and agrochemical exposure. Understanding the molecular mechanisms underlying xenobiotic adaptation of A. mellifera is critical, considering its extensive exposure to phytochemicals and agrochemicals present in the environment. In this study, we conducted a comprehensive structural and functional characterization of AmGSTD1, a delta class glutathione S-transferase (GST), to unravel its roles in agrochemical detoxification and antioxidative stress responses. We determined the 3-dimensional (3D) structure of a honey bee GST using protein crystallography for the first time, providing new insights into its molecular structure. Our investigations revealed that AmGSTD1 metabolizes model substrates, including 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrophenyl acetate (PNA), phenylethyl isothiocyanate (PEITC), propyl isothiocyanate (PITC), and the oxidation byproduct 4-hydroxynonenal (HNE). Moreover, we discovered that AmGSTD1 exhibits binding affinity with the fluorophore 8-Anilinonaphthalene-1-sulfonic acid (ANS), which can be inhibited with various herbicides, fungicides, insecticides, and their metabolites. These findings highlight the potential contribution of AmGSTD1 in safeguarding honey bee health against various agrochemicals, while also mitigating oxidative stress resulting from exposure to these substances.

A novel 2D-GO@WS2 electrochemical platform for the determination of thiram fungicide

In this paper, the determination of Thiram fungicide by a novel modified screen-printed carbon electrode (SPCE) fabricated modifying the working electrode (WE) with 2D-GO/WS2 nanohybrid composites, is reported. Scanning electron microscopy (SEM), Raman spectroscopy, and fluorescence analysis (PL) were used to reveal the morphological and microstructural characteristics of the 2D-GO/WS2 nanohybrids with different graphene oxide:tungsten disulphide (GO:WS2) ratio. Electrochemical characterization demonstrated that the 2D-WS2/GO nanohybrids having a GO:WS2 ratio = 2:1 shows the highest electrocatalytic activity towards oxidation of Thiram. The developed sensor permits the quantification of Thiram in the linear range 0.083-0.33 µM with a limit of detection (LOD) of 0.02 µM, which is below the legal limits for this fungicide in drinking water or foods.

Mefentrifluconazole-Resistant Risk and Resistance-Related Point Mutation in FpCYP51B of Fusarium pseudograminearum

Mefentrifluconazole, a triazole fungicide, exhibits remarkable efficacy in combating Fusarium spp. The mean EC50 value of mefentrifluconazole against 124 isolates of Fusarium pseudograminearum was determined to be 1.06 μg/mL in this study. Fungicide taming produced five mefentrifluconazole-resistant mutants with resistance factors ranging from 19.21 to 111.34. Compared to the original parental isolates, the fitness of three resistant mutants was much lower, while the remaining two mutants displayed enhanced survival fitness. There was evidence of positive cross-resistance between tebuconazole and mefentrifluconazole. Mefentrifluconazole resistance in F. pseudograminearum can be conferred by FpCYP51BL144F, which was identified in four mutants according to molecular docking and site-directed transformation experiments. Overexpression of FpCYP51s was also detected in the resistant mutants. In conclusion, mefentrifluconazole has a low-to-medium resistance risk in F. pseudograminearum, and the L144F mutation in FpCYP51B and the increased expression level of FpCYP51s may be responsible for mefentrifluconazole resistance in F. pseudograminearum.

Heavy metal status in cocoa (Theobroma cacao L.) soils and beans: the case of Abuakwa North Municipality of Eastern Region, Ghana

In recent times, public concerns over the potential accumulation of heavy metals in agricultural soils and crops due to the excessive use of agrochemicals are increasing. This study was conducted in the Abuakwa North Municipality of Eastern Region, Ghana, to assess the status of heavy metals in cocoa soils and beans. Cocoa farms aged between 10 and 20 years and have received agrochemicals for at least 5 years were selected, and their adjacent forests were used as controls. Soil samples and cocoa pods were collected randomly and processed for laboratory analysis. The study discovered that across the sampling sites, heavy metal concentrations in soil were below permissible limits. However, contamination factor and geo-accumulation index results revealed that Tontro cocoa farms were considerably contaminated and moderately polluted respectively with Cu, probably due to long-term fungicide application. The concentrations of Fe (39.3-47.1 mg kg-1) and Zn (54.8-70.0 mg kg-1) in the cocoa beans across the communities were below the FAO/WHO's safe limit of 99.4 mg kg-1 and 73.0 mg kg-1 respectively. Lead (0.03-0.06 mg kg-1) and Cd (0.12-0.20 mg kg-1) concentrations were below the EU's maximum allowable level and Codex Alimentarius Commission's limit of 1.0 mg kg-1 respectively. However, bean Cu content in the Tontro farm (51.5 mg kg-1) was slightly above the EU's recommended maximum limit of 50.0 mg kg-1, possibly due to the continuous application of copper-based fungicides. The study showed that, overall, agrochemicals used for cocoa farming in Abuakwa North Municipality of Ghana did not cause serious harm to the soils and beans, since the mean metal concentrations were not alarming and guarantee public health safety.

Silver nanoparticles improve the fungicidal properties of Rhazya stricta decne aqueous extract against plant pathogens

One of the most promising, non-toxic, and biocompatible developments for many biological activities is the green synthesis of nanoparticles from plants. In this work, we investigated the antifungal activity of silver nanoparticles (AgNPs) biosynthesized from Rhazya stricta aqueous extract against several plant pathogenic fungi. UV-visible spectroscopy, Zeta potential analysis, Fourier-transform infrared spectroscopy (FTIR), and transmitted electron microscopy (TEM) were used to analyze the biosynthesized AgNPs. Drechslera halodes, Drechslera tetramera, Macrophomina phaseolina, Alternaria alternata, and Curvularia australiensis were tested for their potential antifungal activity. Surface Plasmon Resonance (SPR) of Aq. AgNPs and Alkaline Aq. AgNPs was observed at 405 nm and 415 nm, respectively. FTIR analysis indicated hydroxyl, nitrile, amine, and ketone functional groups. Aq. AgNPs and Alka-line Aq. AgNPs had velocities of - 27.7 mV and - 37.9 mV and sizes of 21-90 nm and 7.2-25.3 nm, respectively, according to zeta potential studies and TEM. The antifungal examination revealed that all species' mycelial development was significantly inhibited, accompanied by severe ultra-structural alterations. Among all treatments, Aq. AgNPs were the most effective fungicide. M. phaseolina was statistically the most resistant, whereas A. alternata was the most vulnerable. To the best of our knowledge, this is the first report on R. stricta's antifungal activity against these species.

Exploring Factors Conditioning the Expression of Botryosphaeria Dieback in Grapevine for Integrated Management of the Disease

Species from the Botryosphaeriaceae family are the causal agents of Botryosphaeria dieback (BD), a worldwide grapevine trunk disease. Because of their lifestyle and their adaptation to a wide range of temperatures, these fungi constitute a serious threat to vineyards and viticulture, especially in the actual context of climate change. Grapevine plants from both nurseries and vineyards are very susceptible to infections by botryosphaeriaceous fungi due to several cuts and wounds made during their propagation process and their entire life cycle, respectively. When decline becomes chronic or apoplectic, it reduces the longevity of the vineyard and affects the quality of the wine, leading to huge economic losses. Given the environmental impact of fungicides, and their short period of effectiveness in protecting pruning wounds, alternative strategies are being developed to fight BD fungal pathogens and limit their propagation. Among them, biological control has been recognized as a promising and sustainable alternative. However, there is still no effective strategy for combating this complex disease, conditioned by both fungal life traits and host tolerance traits, in relationships with the whole microbiome/microbiota. To provide sound guidance for an effective and sustainable integrated management of BD, by combining the limitation of infection risk, tolerant grapevine cultivars, and biological control, this review explores some of the factors conditioning the expression of BD in grapevine. Among them, the lifestyle of BD-associated pathogens, their pathogenicity factors, the cultivar traits of tolerance or susceptibility, and the biocontrol potential of Bacillus spp. and Trichoderma spp. are discussed.

Cloud point extraction of carbendazim fungicide from strawberry samples and amperometric detection with boron doped diamond

The cloud point extraction (Tergitol® surfactant) method was used for the first time to extract and preconcentrate the fungicide carbendazim (CBZ) from strawberry samples, while electrochemical detection (boron doped diamond electrode) in association with high performance liquid chromatography (HPLC-EC) was used for the determination of CBZ. The variables of bath temperature, ultrasonic stirring time, mass of NaCl and amount of surfactant were investigated using a 24 full factorial design. Limits of detection (LOD, S/N = 3) and quantification (LOQ) of 3.42 × 10-8 mol/L (or 6.54 µg/L) and 6.84 × 10-8 mol/L (or 13.1 µg/L), respectively, were obtained for the CPE processes, considering the value of the preconcentration factor obtained (9.12). The method was validated based on linearity, intra-day and inter-day recovery tests, accuracy and precision. The proposed method was applied to strawberry samples from local commercial establishments and different procedures for washing and sanitizing strawberry fruits were also evaluated.

Polyphenols-Rich Extract of Calotropis procera Alone and in Combination with Trichoderma Culture Filtrate for Biocontrol of Cantaloupe Wilt and Root Rot Fungi

Fungal diseases have always been a major problem for cantaloupe crops; however, synthetic fungicides are hazardous to humans and the environment. Consequently, a feasible alternative to fungicides without side effects could be by using bio agents and naturally occurring plants with antibacterial potential. This study has achieved a novel procedure for managing wilt and root rot diseases by potentially using Trichoderma sp. culture filtrates in consortium with plant extract of Calotropis procera, Rhizoctonia solani, Fusarium oxysporum, and Pythium ultimum, which were isolated from infected cantaloupe roots with identified root rot symptoms. The antagonistic activity of four Trichoderma isolates and analysis of antibiotics and filtrate enzymes of the most active Trichoderma isolate were determined as well as phytochemical analysis of C. procera plant extract using HPLC-UV. The obtained results showed that all Trichoderma isolates considerably lowered the radial growth of P. ultimum, R. solani, and F. oxysporum in varying degrees. The scanning electron micrographs illustrate the mycoparasitic nature of Trichoderma sp. on F. oxysporum. The phytochemical analysis of C. procera indicated that phenolic contents were the major compounds found in extracts, such as vanillin (46.79%), chlorogenic acid (30.24%), gallic acid (8.06%), and daidzein (3.45%) but including only a low amount of the flavonoid compounds rutin, naringenin, and hesperetin. The Pot experiment's findings showed that cantaloupe was best protected against wilting and root rot diseases when it was treated with both Trichoderma sp. culture filtrates (10%) and C. procera extract of (15 mg/mL), both alone and in combination. This study demonstrates that the application of bio agent Trichoderma spp. filtrate with C. procera phenol extract appears useful for controlling wilting and root rot disease in cantaloupe. This innovative approach could be used as an alternative to chemical fungicide for the control of wilting and rot root diseases.

Fungi increases kelp (Ecklonia radiata) remineralisation and dissolved organic carbon, alkalinity, and dimethylsulfoniopropionate (DMSP) production

Fungi are key players in terrestrial organic matter (OM) degradation, but little is known about their role in marine environments. Here we compared the degradation of kelp (Ecklonia radiata) in mesocosms with and without fungicides over 45 days. The aim was to improve our understanding of the vital role of fungal OM degradation and remineralisation and its relevance to marine biogeochemical cycles (e.g., carbon, nitrogen, sulfur, or volatile sulfur). In the presence of fungi, 68 % of the kelp detritus degraded over 45 days, resulting in the production of 0.6 mol of dissolved organic carbon (DOC), 0.16 mol of dissolved inorganic carbon (DIC), 0.23 mol of total alkalinity (TA), and 0.076 mol of CO2, which was subsequently emitted to the atmosphere. Conversely, when fungi were inhibited, the bacterial community diversity was reduced, and only 25 % of the kelp detritus degraded over 45 days. The application of fungicides resulted in the generation of an excess amount of 1.5 mol of DOC, but we observed only 0.02 mol of DIC, and 0.04 mol of TA per one mole of kelp detritus, accompanied by a CO2 emission of 0.081 mol. In contrast, without fungi, remineralisation of kelp detritus to DIC, TA, dimethyl sulfide (DMS), dimethylsulfoniopropionate (DMSP) and methanethiol (MeSH) was significantly reduced. Fungal kelp remineralisation led to a remarkable 100,000 % increase in DMSP production. The observed substantial changes in sediment chemistry when fungi are inhibited highlight the important biogeochemical role of fungal remineralisation, which likely plays a crucial role in defining coastal biogeochemical cycling, blue carbon sequestration, and thus climate regulation.

Assessment of Candidate Reference Genes for Gene Expression Studies Using RT-qPCR in Colletotrichum fructicola from Litchi

Litchi (Litchi chinensis Sonn.) is a tropical fruit originating from southern China that is currently cultivated in subtropical and tropical regions worldwide. Litchi anthracnose, caused by Colletotrichum fructicola, a dominant species of Colletotrichum spp., is an important disease of litchi that damages the fruits in fields and in post-harvest storage. Real-time quantitative PCR (RT-qPCR) is a common technique with which to detect the expression of and function of target genes quickly and precisely, and stable reference genes are crucial. However, there is no comprehensive information on suitable reference genes of C. fructicola present. Here, we designed eight candidate genes (GAPDH, α-tubulin, 18S, β-tubulin, EF1a, TATA, RPS5, and EF3) using RefFinder software (programs: geNorm, ΔCt, BestKeeper, and NormFinder) to investigate their reliability in the detection of C. fructicola under five different treatments (fungal development stage, temperature, UV, culture medium, and fungicide). The results showed the optimal reference genes under different conditions: EF1a and α-tubulin for developmental stage; α-tubulin and β-tubulin for temperature; α-tubulin and RPS5 for UV treatment; RPS5 and α-tubulin for culture medium; α-tubulin, GAPDH, and TATA for fungicide treatments. The corresponding expression patterns of HSP70 (Heat shock protein 70) were significantly different when the most and the least stable reference genes were selected when treated under different conditions. Our study provides the first detailed list of optimal reference genes for the analysis of gene expression in C. fructicola via RT-qPCR, which should be useful for future functional studies of target genes in C. fructicola.

Taxonomy-guided selection of Paraburkholderia busanensis sp. nov.: a versatile biocontrol agent with mycophagy against Colletotrichum scovillei causing pepper anthracnose

IMPORTANCE

Traditional control methods for postharvest diseases rely on fungicides, which cause human health and environmental concerns. This study introduces a taxonomy-guided strategy for selecting biocontrol agents. By focusing on Paraburkholderia group, which harbors diverse plant-beneficial strains, the inadvertent selection of harmful strains was circumvented, thereby obviating the need for laborious in vitro screening assays. A highly promising candidate, strain P39, has been identified, exhibiting remarkable biocontrol activity against Colletotrichum scovillei. Through comprehensive genomic, physiological, and biochemical analyses, P39 was characterized as a novel species within the Paraburkholderia genus and designated Paraburkholderia busanensis. Moreover, these findings deepen our understanding of bacterial-fungal interactions, as they elucidate a potential pathway for the utilization of fungal chitin, thereby enhancing our understanding of bacterial mycophagy. P. busanensis is a promising source of antifungal volatiles and putative novel secondary metabolites.

Double-stranded RNA prevents and cures infection by rust fungi

Fungal pathogens that impact perennial plants or natural ecosystems require management strategies beyond fungicides and breeding for resistance. Rust fungi, some of the most economically and environmentally important plant pathogens, have shown amenability to double-stranded RNA (dsRNA) mediated control. To date, dsRNA treatments have been applied prior to infection or together with the inoculum. Here we show that a dsRNA spray can effectively prevent and cure infection by Austropuccinia psidii (cause of myrtle rust) at different stages of the disease cycle. Significant reductions in disease coverage were observed in plants treated with dsRNA targeting essential fungal genes 48 h pre-infection through to 14 days post-infection. For curative treatments, improvements in plant health and photosynthetic capacity were seen 2-6 weeks post-infection. Two-photon microscopy suggests inhibitory activity of dsRNA on intercellular hyphae or haustoria. Our results show that dsRNA acts both preventively and curatively against myrtle rust disease, with treated plants recovering from severe infection. These findings have immediate potential in the management of the more than 10-year epidemic of myrtle rust in Australia.

Protecting-group free synthesis of glycoconjugates displaying dual fungicidal and plant defense-eliciting activities

A straightforward synthesis of carbohydrate templated isoxazolidines is described, by reaction of unprotected glycosylhydroxylamines (operating as 1,3-dipoles) with methyl acrylate using microwave activation. Rhamno- and erythro-isoxazolidines are recognized by plant cells, resulting in a strong ROS-production as a plant immune response, and exert a high antifungal activity against Botrytis cinerea.

New 2,4-dihydro-1H-1,2,4-triazole-3-selones and 3,3'-di(4H-1,2,4-triazolyl)diselenides. Synthesis, biological evaluation, and in silico studies as antibacterial and fungicidal agents

The reaction of aromatic ring-substituted isoselenocyanates with 2-thiopheacetic and 4-pyridinecarboxylic acid hydrazides yielded selenosemicarbazides which were further converted into previously unknown 1,2,4-triazole-3-selones and 3,3'-di(4H-1, 2,4-triazolyl)diselenides. The structures of the obtained compounds were studied by NMR spectroscopy, IR spectroscopy, and high-resolution mass spectroscopy (HR-MS). The bactericidal and fungicidal activity of some obtained compounds was evaluated in molecular modeling studies such as docking and simulation studies. The compound 3ba was reported as the most promising compound to show robust binding energy with different antibacterial and antifungal compounds. The compounds were observed in strong hydrophilic and hydrophobic interactions and remained in stable binding conformation with the receptor enzymes. Furthermore, the interatomic interaction energies were dominated by Van der Waals and electrostatic energies indicating the formation of stable complexes.

Intensive vegetable production under plastic mulch: A field study on soil plastic and pesticide residues and their effects on the soil microbiome

Intensive agriculture relies on external inputs to reach high productivity and profitability. Plastic mulch, mainly in the form of Low-Density Polyethylene (LDPE), is widely used in agriculture to decrease evaporation, increase soil temperature and prevent weeds. The incomplete removal of LDPE mulch after use causes plastic contamination in agricultural soils. In conventional agriculture, the use of pesticides also leaves residues accumulating in soils. Thus, the objective of this study was to measure plastic and pesticide residues in agricultural soils and their effects on the soil microbiome. For this, we sampled soil (0-10 cm and 10-30 cm) from 18 parcels from 6 vegetable farms in SE Spain. The farms were under either organic or conventional management, where plastic mulch had been used for >25 years. We measured the macro- and micro-light density plastic debris contents, the pesticide residue levels, and a range of physiochemical properties. We also carried out DNA sequencing on the soil fungal and bacterial communities. Plastic debris (>100 μm) was found in all samples with an average number of 2 × 103 particles kg-1 and area of 60 cm2 kg-1. We found 4-10 different pesticide residues in all conventional soils, for an average of 140 μg kg-1. Overall, pesticide content was ∼100 times lower in organic farms. The soil microbiomes were farm-specific and related to different soil physicochemical parameters and contaminants. Regarding contaminants, bacterial communities responded to the total pesticide residues, the fungicide Azoxystrobin and the insecticide Chlorantraniliprole as well as the plastic area. The fungicide Boscalid was the only contaminant to influence the fungal community. The wide spread of plastic and pesticide residues in agricultural soil and their effects on soil microbial communities may impact crop production and other environmental services. More studies are required to evaluate the total costs of intensive agriculture.

Occurrence of Aspergillus fumigatus azole resistance in soils from Switzerland

Aspergillus fumigatus is a fungal species causing diverse diseases in humans. The use of azoles for treatments of A. fumigatus diseases has resulted in azole resistance. Azoles are also widely used in the environment for crop protection, which resulted in azole resistance. Resistance is primarily due to mutations in cyp51A, which encodes the target protein for azoles. Here we addressed the occurrence of azole resistance in soils from a vast part of Switzerland. We aimed to associate the use of azoles in the environment with the occurrence of azole resistance. We targeted sample sites from different agricultural environments as well as sites with no agricultural practice (natural sites and urban sites). Starting from 327 sites, 113 A. fumigatus isolates were recovered (2019-2021), among which 19 were azole-resistant (15 with TR34/L98H and four with TR46/Y121F/T289A resistance mutations in cyp51A). Our results show that azole resistance was not associated with a specific agricultural practice. Azoles could be chemically detected in investigated soils, however, their presence was not associated with the occurrence of azole-resistant isolates. Interestingly, genetic markers of resistance to other fungicides were detected but only in azole-resistant isolates, thus reinforcing the notion that A. fumigatus cross-resistance to fungicides has an environmental origin. In conclusion, this study reveals the spreading of azole resistance in A. fumigatus from the environment in Switzerland. The proximity of agricultural areas to urban centers may facilitate the transmission of resistant strains to at-risk populations. Thus, vigilant surveillance is required to maintain effective treatment options for aspergillosis.

A Loop-Mediated Isothermal Amplification Assay for the Identification of Botrytis fragariae in Strawberry

Gray mold in strawberry is caused by multiple species of Botrytis, including Botrytis cinerea, B. pseudocinerea, B. fragariae, and B. mali. The species B. cinerea and B. fragariae are widespread in production regions of the eastern United States and Germany, and their distinction is important for disease management strategies. Currently, the only way to differentiate these species in field samples is by PCR, which is time consuming, labor intensive, and costly. In this study, a loop-mediated isothermal amplification (LAMP) technique was developed based on species-specific NEP2 gene nucleotide sequences. The designed primer set specifically amplified B. fragariae DNA and no other Botrytis spp. (B. cinerea, B. mali, and B. pseudocinerea) or plant pathogens. The LAMP assay was able to amplify fragments from DNA extracted from infected fruit using a rapid DNA extraction protocol, confirming its ability to detect low amounts of B. fragaria DNA from field-infected fruit. In addition, a blind test was performed to identify B. fragariae in 51 samples collected from strawberry fields in the eastern United States using the LAMP technique. The B. fragariae samples were identified with a reliability of 93.5% (29 of 32), and none of the B. cinerea, B. pseudocinerea, or B. mali samples included in the test were amplified in 10 min. Our results show that the LAMP technique is a specific and reliable method for the detection of B. fragariae from infected fruit tissue and can help to control this important disease in the field.

Meta-Analytic Modeling of the Severity-Yield Relationships in Soybean Frogeye Leaf Spot Epidemics

Frogeye leaf spot (FLS), caused by Cercospora sojina, is an important foliar disease affecting soybean in the United States. A meta-analytic approach including 39 fungicide trials conducted from 2012 to 2021 across eight states (Alabama, Arkansas, Illinois, Iowa, Kentucky, Louisiana, Mississippi, Tennessee) was used to assess the relationship between FLS severity and soybean yield. Correlation and regression analyses were performed separately to determine Fisher's transformation of correlation coefficients (Zr), intercept (β0) and slope (β1). Disease pressure (low severity, ≤34.5; high severity, >34.5%) and yield class (low, ≤3,352; high, >3,352 kg/ha) were included as categorical moderators. Pearson's [Formula: see text], obtained from back-transforming the [Formula: see text]r estimated by an overall random-effects model, showed a significant negative linear relationship between FLS severity and yield ([Formula: see text] = -0.60). The [Formula: see text]r was affected by disease pressure (P = 0.0003) but not by yield class (P = 0.8141). A random-coefficient model estimated a slope of -19 kg/ha for each percent severity for a mean attainable yield of 3,719.9 kg/ha. Based on the overall mean (95% CI) of the intercept and slope estimated by the random-coefficients model, the estimated overall relative damage coefficient was 0.51% (0.36 to 0.69), indicating that a percent increase in FLS severity reduced yield by 0.51%. The best model included yield class as a covariate, and population-average intercepts differed significantly between low (3,455.1 kg/ha) and high (3,842.7 kg/ha) yield classes. This highlights the potential impact of FLS on soybean yield if not managed and may help in disease management decisions.

Major Fusarium species and mycotoxins associated with freshly harvested maize grain in Uruguay

Fusarium species are common fungal pathogens of maize. Fusarium graminearum and Fusarium verticillioides, among others, can cause maize ear rot, and they are also mycotoxin producers. The aims of this work were to determine the frequency and diversity of Fusarium species in Uruguayan maize kernels, evaluate the toxigenic potential of the isolates, determine toxin contamination levels on freshly harvested grain, and assess the sensitivity of main Fusarium species against fungicides. Fusarium verticillioides was the most frequent species isolated, followed by Fusarium graminearum sensu stricto. Of F. verticillioides isolates studied for fumonisin production, 72% produced fumonisin B1 and 32% fumonisin B2. Considering in vitro toxin production by F. graminearum sensu stricto isolates, deoxynivalenol was the main toxin produced, followed by zearalenone and nivalenol. Fumonisins were the most frequently found toxins on freshly harvested maize samples (98% in 2018 and 86% in 2019), and also, fumonisin B1 was the toxin with highest concentration in both years studied (4860 µg/kg in 2018 and 1453 µg/kg in 2019). Deoxynivalenol and zearalenone were also found as contaminants. Metconazole and epoxiconazole were the most effective fungicides tested on F. verticillioides isolates. Fusarium graminearum sensu stricto isolates also were more sensitive to metconazole compared to other fungicides; nevertheless, epoxiconazole was less efficient in controlling this species. This is the first study that reports Fusarium species and mycotoxin contamination levels associated with maize grain in Uruguay. Its detection is the main step to develop management strategies in order to minimize fungal infection in maize crops.

Disease decreases variation in host community structure in an old-field grassland

Disease may drive variation in host community structure by modifying the interplay of deterministic and stochastic processes that shape communities. For instance, deterministic processes like ecological selection can benefit species less impacted by disease. When communities have higher levels of disease and disease consistently selects for certain host species, this can reduce variation in host community composition. On the other hand, when host communities are less impacted by disease and selection is weaker, stochastic processes (e.g., drift, dispersal) may play a bigger role in host community structure, which can increase variation among communities. While effects of disease on host community structure have been quantified in field experiments, few have addressed the role of disease in modulating variation in structure among host communities. To address this, we conducted a field experiment spanning three years, using a tractable system: foliar fungal pathogens in an old-field grassland community dominated by the grass Lolium arundinaceum, tall fescue. We reduced foliar fungal disease burden in replicate host communities (experimental plots in intact vegetation) in three fungicide regimens that varied in the seasonal duration of fungicide treatment and included a fungicide-free control. We measured host diversity, biomass, and variation in community structure among replicate communities. Disease reduction generally decreased plant richness and increased aboveground biomass relative to communities experiencing ambient levels of disease. These changes in richness and aboveground biomass were consistent across years despite changes in structure of the plant communities over the experiment's three years. Importantly, disease reduction amplified host community variation, suggesting that disease diminished the degree to which host communities were structured by stochastic processes. These results of experimental disease reduction both highlight the potential importance of stochastic processes in plant communities and reveal the potential for disease to regulate variation in host community structure.

Honey bees and bumble bees may be exposed to pesticides differently when foraging on agricultural areas

In an agricultural environment, where crops are treated with pesticides, bees are likely to be exposed to a range of chemical compounds in a variety of ways. The extent to which different bee species are affected by these chemicals, largely depends on the concentrations and type of exposure. We quantified the presence of selected pesticide compounds in the pollen of two different entomophilous crops; oilseed rape (Brassica napus) and broad bean (Vicia faba). Sampling was performed in 12 sites in Ireland and our results were compared with the pollen loads of honey bees and bumble bees actively foraging on those crops in those same sites. Detections were compound specific, and the timing of pesticide application in relation to sampling likely influenced the final residue contamination levels. Most detections originated from compounds that were not recently applied on the fields, and samples from B. napus fields were more contaminated compared to those from V. faba fields. Crop pollen was contaminated only with fungicides, honey bee pollen loads contained mainly fungicides, while more insecticides were detected in bumble bee pollen loads. The highest number of compounds and most detections were observed in bumble bee pollen loads, where notably, all five neonicotinoids assessed (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) were detected despite the no recent application of these compounds on the fields where samples were collected. The concentrations of neonicotinoid insecticides were positively correlated with the number of wild plant species present in the bumble bee-collected pollen samples, but this relationship could not be verified for honey bees. The compounds azoxystrobin, boscalid and thiamethoxam formed the most common pesticide combination in pollen. Our results raise concerns about potential long-term bee exposure to multiple residues and question whether honey bees are suitable surrogates for pesticide risk assessments for all bee species.

Moving past neonicotinoids and honeybees: A systematic review of existing research on other insecticides and bees

Synthetic pesticides (e.g. herbicides, fungicides and insecticides) are used widely in agriculture to protect crops from pests, weeds and disease. However, their use also comes with a range of environmental concerns. One key concern is the effect of insecticides on non-target organisms such as bees, who provide pollination services for crops and wild plants. This systematic literature review quantifies the existing research on bees and insecticides broadly, and then focuses more specifically on non-neonicotinoid insecticides and non-honeybees. We find that articles on honeybees (Apis sp.) and insecticides account for 80% of all research, with all other bees combined making up 20%. Neonicotinoids were studied in 34% of articles across all bees and were the most widely studied insecticide class for non-honeybees overall, with almost three times as many studies than the second most studied class. Of non-neonicotinoid insecticide classes and non-honeybees, the most studied were pyrethroids and organophosphates followed by carbamates, and the most widely represented bee taxa were bumblebees (Bombus), followed by leaf-cutter bees (Megachile) and mason bees (Osmia). Research has taken place across several countries, with the highest numbers of articles from Brazil and the US, and with notable gaps from countries in Asia, Africa and Oceania. Mortality was the most studied effect type, while sub-lethal effects such as on behaviour were less studied. Few studies tested how the effect of insecticides were influenced by multiple pressures, such as climate change and co-occurring pesticides (cocktail effects). As anthropogenic pressures do not occur in isolation, we suggest that future research also addresses these knowledge gaps. Given the changing global patterns in insecticide use, and the increasing inclusion of both non-honeybees and sub-lethal effects in pesticide risk assessment, there is a need for expanding research beyond its current state to ensure a strong scientific evidence base for the development of risk assessment and associated policy.

Selection and Validation of Reference Genes for Reverse-Transcription Quantitative PCR Analysis in Sclerotium rolfsii

Reference genes are important for the accuracy of gene expression profiles using reverse-transcription quantitative PCR (RT-qPCR). However, there are no available reference genes reported for Sclerotium rolfsii; it actually has a pretty diverse and wide host range. In this study, seven candidate reference genes (UBC, β-TUB, 28S, 18S, PGK, EF1α and GAPDH) were validated for their expression stability in S. rolfsii under conditions of different developmental stages, populations, fungicide treatments, photoperiods and pHs. Four algorithm programs (geNorm, Normfinder, Bestkeeper and ΔCt) were used to evaluate the gene expression stability, and RefFinder was used to integrate the ranking results of four programs. Two reference genes were recommended by RefFinder for RT-qPCR normalization in S. rolfsii. The suitable reference genes were GAPDH and UBC across developmental stages, PGK and UBC across populations, GAPDH and PGK across fungicide treatments, EF1α and PGK across photoperiods, β-TUB and EF1α across pHs and PGK and GAPDH across all samples. Four target genes (atrB, PacC, WC1 and CAT) were selected for the validation of the suitability of selected reference genes. However, using one or two reference genes in combination to normalize the expression of target genes showed no significant difference in S. rolfsii. In short, this study provided reliable reference genes for studying the expression and function of genes in S. rolfsii.