Cinerea Strains Research Articles

Characterization of Botrytis cinerea, the causal agent of tomato grey mould, and its biocontrol using Bacillussubtilis

Botrytis cinerea infects more than 1400 plant species globally, resulting in severe damage pre- and post-harvest. This study aimed to isolate and identify B. cinerea from tomato plants from local greenhouses and assess the inhibitory capacities of local Bacillus strains against B. cinerea. Various B. cinerea strains isolated from infected tomato plants exhibited characteristic symptoms. The ITS sequences and phylogenetic analysis of isolates exhibited 99 % homology with B. cinerea. Pathogenicity tests on healthy tomato vegetative growth or detached leaves using QB13, QBuk1, and QUna fungal isolates fulfilled Koch's postulates. Symptomatic characteristics resulting from the artificial inoculations of tomato grey mould closely resembled those of the original diseased leaves and stems collected from the field after 7 DPI when seven strains of Bacillus subtilis (64C1, 88D, 65D, 64C2, 41D1, 23A2, and 102) tested in-vitro against B. cinerea demonstrated that all of Bacillus subtilis isolates displayed notably strong antagonistic effects against B. cinerea. Mycelial growth inhibition ranged from 37 % (isolate 65D) to 60 % (isolate 102) compared to the untreated control. The most substantial inhibitory effects against B. cinerea were statistically observed with isolates 88D and 102, which exhibited inhibition rates of 58 % and 60 %, respectively. Morphological and molecular identification and pathogenicity analysis revealed that all 20 B. cinerea isolates obtained from infected tomato plants from greenhouses exhibited a highly pathogenic effect on tomato plants. This study states the basis for developing natural biocontrol agents to combat grey mould caused by B. cinerea on tomato plants.

Exploring SDHI fungicide resistance in Botrytis cinerea through genetic transformation system and AlphaFold model-based molecular docking.

Gray mold caused by Botrytis cinerea is one of the most serious diseases affecting strawberry. Succinate dehydrogenase inhibitor (SDHI) fungicides have been used for more than a decade to control the disease. Monitoring resistance and improving in-depth understanding of resistance mechanisms are essential for the control of B. cinerea. In this study, resistance monitoring of a SDHI fungicide boscalid was conducted on B. cinerea isolated from strawberries in Korea during 2020 and 2021, with resistance rates of 76.92% and 72.25%, respectively. In resistant strains, mutations P225F/H and H272R were found in SdhB, with P225F representing the dominant mutation type. Simultaneous mutations G85A, I93V, M158V, and V168I in SdhC were detected in 54.84% of sensitive strains. Sensitivity profiles of different Sdh genotypes of B. cinerea strains to six SDHIs were determined in vitro and in vivo. In addition, the mutation(s) were genetically validated through in situ SdhB (SdhC) expression. Docking assays between SDHIs and AlphaFold model-based Sdh complexes revealed generally consistent patterns with their in vitro phenotypes. Resistance of B. cinerea to SDHI fungicide on strawberry was systematically investigated in this study. Deciphering of SDHI resistance through the genetic transformation system and AlphaFold model-based molecular docking will provide valuable insights into other target site-based fungicide resistance in fungal pathogens. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Degradation-Risk-Inspired Optimization of the Antifungal Oxazolinyl Aniline Lead by a Fusion of Triazole with Nicotinamide.

The discovery of readily available and easily modifiable new models is a crucial and practical solution for agrochemical innovation. Antifungal function-oriented fusion of triazole with the prevalidated lead (R)-LE001 affords a novel framework with a broad and enhanced antifungal spectrum. Characterized by the easy accessibility and adjustability of [1,2,4]triazolo[4,3-a]pyridine, modular fine-tuning provided a set of unprecedented leads (e.g., Z23, Z25, Z26, etc.) with superior antifungal potentials than the positive control boscalid. Candidate Z23 exhibited a more promising antifungal activity against Sclerotinia sclerotiorum, Botrytis cinerea, and Phytophthora capsici with EC50 values of 0.7, 0.6, and 0.5 μM, respectively. This candidate could effectively control boscalid-resistant B. cinerea strains and also exhibit good vivo efficacy in controlling gray mold. Noteworthily, both the SDH-inhibition and the efficiency against Oomycete P. capsici are quite distinct from that of the positive control boscalid. A molecular docking simulation also differentiates Z23 from boscalid. These findings highlight the potential of [1,2,4]triazolo[4,3-a]pyridine amide as a novel antifungal model.

First report of Botrytis cinerea in South African blueberry orchards

AbstractThe South African blueberry industry has grown consistently over the past few years due to an increase in local and international demand. Like many other crops, blueberries are susceptible to grey mould caused by Botrytis cinerea, resulting in significant reductions in yield. In this study, Botrytis isolates were recovered from symptomatic blueberry fruit, flowers, leaves and undifferentiated buds, but were not found as endophytes in healthy tissues. Phylogenetic analysis of the concatenated glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60) and DNA-dependent RNA polymerase subunit II (RPB2) genes identified 88 isolates as B. cinerea strains as well as a single B. pelargonii strain. The results presented in this study are the first to contribute towards the characterisation of B. cinerea populations in South African blueberry orchards.

Antifungal Potential of Carnosic Acid from Salvia somalensis against Phytopathogenic Fungi

The aims of the present study were (i) to characterize the dichloromethane extract of the fresh aerial parts of S. somalensis, cultivated in Liguria (Italy), (ii) to quantify carnosic acid production and (iii) to find an eco-friendly alternative approach to control diseases caused by phytopathogenic fungi. The phytochemical investigation yielded several known terpenoids, as well as a diterpene, 4α,9α-epoxy-2H-dibenzo[a,d]cyclohepten-7(5H)-one, not previously described as a plant metabolite before. The results showed a noteworthy quantity of carnosic acid (113.90 µg/mg of dried extract). The potential antifungal activity of the plant surface extract and carnosic acid against five phytopathogenic fungi (Colletotrichum coccodes, Fusarium oxysporum, Sclerotinia sclerotiorum, Botrytis cinerea and Rhizoctonia solani) was considered. A complete inhibition of C. coccodes, S. sclerotiorum and R. solani mycelium growth was observed by carnosic acid at 500 µg/mL. High inhibition values were observed against B. cinerea and F. oxysporum compared to reference active ingredients. Four different B. cinerea strains exhibited a pronounced sensitivity to carnosic acid, as well as those originating from agricultural crop scenarios where a high load of active ingredient for gray mold control was historically adopted. Additionally, the formation and development of the germinative tube in B. cinerea were greatly slowed down.

Membrane protein Bcsdr2 mediates biofilm integrity, hyphal growth and virulence of Botrytis cinerea

Grey mould caused by Botrytis cinerea is a devastating disease responsible for large losses to agricultural production, and B. cinerea is a necrotrophic model fungal plant pathogen. Membrane proteins are important targets of fungicides and hotspots in the research and development of fungicide products. Wuyiencin affects the permeability and pathogenicity of B. cinerea, parallel reaction monitoring revealed the association of membrane protein Bcsdr2, and the bacteriostatic mechanism of wuyiencin was elucidated. In the present work, we generated and characterised ΔBcsdr2 deletion and complemented mutant B. cinerea strains. The ΔBcsdr2 deletion mutants exhibited biofilm loss and dissolution, and their functional activity was illustrated by reduced necrotic colonisation on strawberry and grape fruits. Targeted deletion of Bcsdr2 also blocked several phenotypic defects in aspects of mycelial growth, conidiation and virulence. All phenotypic defects were restored by targeted gene complementation. The roles of Bcsdr2 in biofilms and pathogenicity were also supported by quantitative real-time RT-PCR results showing that phosphatidylserine decarboxylase synthesis gene Bcpsd and chitin synthase gene BcCHSVII were downregulated in the early stages of infection for the ΔBcsdr2 strain. The results suggest that Bcsdr2 plays important roles in regulating various cellular processes in B. cinerea.Key points• The mechanism of wuyiencin inhibits B. cinerea is closely associated with membrane proteins.• Wuyiencin can downregulate the expression of the membrane protein Bcsdr2 in B. cinerea.• Bcsdr2 is involved in regulating B. cinerea virulence, growth and development.

First report of Botrytis cinerea causing grey mold on Corydalis yanhusuo in Panan, China.

Yanhusuo (Corydalis yanhusuo (Y. H. Chou & Chun C. Hsu) W. T. Wang ex Z.Y. Su & C.Y. Wu), a perennial herbaceous plant of the Papaveraceae family and genus Corydalis, is also known as Yuanhu and used as medicine by its tuberous roots. It is mainly planted in Zhejiang, Jiangsu and Anhui provinces of China, with the best quality produced in Panan County of Zhejiang province. Yanhusuo has the effects of promoting blood circulation, invigorating the flow of qi and relieving pain, and is widely used in Chinese traditional medicines. In surveys carried out in summer of 2020-2023, grey mold disease was found occurred on C. yanhusuo in Panan County. This disease begins at April, and lasts to July, with incidence of 20% to 70%. The diseased plants showed a large number of gray mold layers adhere to the leaves. When the disease infects from the leaf tips, it form V-shaped lesions; when the leaves are severely infected, the entire leaves die, shrink, curl, and have a large number of gray mold layers on the surface. To identify the causal agent of this leaf disease, diseased leaves were collected from Yanhusuo field at Panan County of Zhejiang province in China since 2020, and tissues at the junction of the healthy and diseased areas were cut off, disinfected with 75% ethanol for 30 seconds, rinsed with sterile water for 3 times for 1 minute each time, air-dried under sterile conditions, and then were inoculated in PDA medium and cultured in a 25℃ incubator. After 2-3 days, picked the edge hyphae of the fungi that grew on the PDA plate and cultured them on a new PDA plate. After 5 days, picked the single spore and inoculated on a new PDA plate for continuous cultivation until pure culture strains were obtained. Thirty strains were isolated from 30 samples that collected from 3 Yanhusuo fields in Panan County. One of the thirty purified strains was named "YH8" for further identification. When cultured on PDA medium, mycelia were initially whitish and turned gray with age. The hyphae accumulate into clusters, and no sclerotia are produced during the cultivation. The conidiophores are slender, septate. The base of the conidiophore is enlarged or slightly enlarged. The conidiophore often has branches and produces a large number of conidia, which are similar to grape clusters. The conidia are monosporous, ovoid, and colorless, 6.08 μm-12.76 μm×8.42 μm-19.34 μm, with an average size of 9.55 μm×14.50 μm. To further identify the species, YH8 genomic DNA was extracted, and the internal transcribed spacer (ITS), heat shock protein (HSP60), and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) genes were amplified with the primers ITS1/4 (White et al. 1990), HSP60-F/HSP60-R, and G3PDH-F/G3PDH-R (Staats et al. 2005), respectively. A multilocus phylogenetic tree was constructed with the ITS, HSP60, and G3PDH reference sequences, and the sequences of PCR amplicons (Genbank number: PP388281, PP376066 and PP376067) were 100% (518 bp out of 518 bp), 99% (994 bp out of 995 bp) and 100% (880 bp out of 880 bp) identical to the Botrytis cinerea strain 5-3, respectively, and the grouping of strain YH8 was supported by 99% bootstrap value. To fulfill the Koch's postulates, spore suspension (approximately 103 CFU/mL) of YH8 was sprayed onto leaves of 3-week Yanhusuo seedlings, and sterile water was sprayed as negative control, 15 seedlings for each treatment, and the experiments was repeated for times. The seedlings were incubated in a growth chamber under 28℃ and 80% humidity. Seven days after inoculation, leaves of noninoculated controls were green and healthy, while the seedlings inoculated with spore suspension of YH8 showed lesions and molds, which were same with field symptoms. The causal pathogen was then reisolated from the lesions, and the gained pathogen showed same colony and spore morphology with YH8, which suggested the confirmation of Koch's postulates. Based on the morphological characteristics and molecular identification, the strain YH8 was identified as B. cinerea. To our knowledge, this is the first report of B. cinerea causing gray mold on the Corydalis yanhusuo in China. This report will provide guide to growers and local technicians for diagnostic and controlling grey mold disease of Yanhusuo.

Photodynamic Inactivation in agriculture: combating fungal phytopathogens resistant to conventional treatment

Botrytis cinerea is a severe threat in agriculture, as it can infect over 200 different crop species with gray mold affecting food yields and quality. The conventional treatment using fungicides lead to emerging resistance over the past decades. Here, we introduce Photodynamic Inactivation (PDI) as a strategy to combat B. cinerea infections, independent of fungicide resistance. PDI uses photoactive compounds, which upon illumination create reactive oxygen species toxic for killing target organisms. This study focuses on different formulations of sodium–magnesium–chlorophyllin (Chl, food additive E140) as photoactive compound in combination with EDTA disodium salt dihydrate (Na2EDTA) as cell-wall permeabilizer and a surfactant. In an in vitro experiment, three different photosensitizers (PS) with varying Chl and Na2EDTA concentrations were tested against five B. cinerea strains with different resistance mechanisms. We showed that all B. cinerea mycelial spheres of all tested strains were eradicated with concentrations as low as 224 µM Chl and 3.076 mM Na2EDTA (LED illumination with main wavelength of 395 nm, radiant exposure 106 J cm−2). To further test PDI as a Botrytis treatment strategy in agriculture a greenhouse trial was performed on B. cinerea infected bell pepper plants (Capsicum annum L). Two different rates (560 or 1120 g Ha−1) of PS formulation (0.204 M Chl and 1.279 M Na2EDTA) and a combination of PS formulation with 0.05% of the surfactant BRIJ L4 (560 g Ha−1) were applied weekly for 4 weeks by spray application. Foliar lesions, percentage of leaves affected, percentage of leaf area diseased and AUDPC were significantly reduced, while percentage of marketable plants were increased by all treatments compared to a water treated control, however, did not statistically differ from each other. No phytotoxicity was observed in any treatment. These results add to the proposition of employing PDI with the naturally sourced PS Chl in agricultural settings aimed at controlling B. cinerea disease. This approach seems to be effective regardless of the evolving resistance mechanisms observed in response to conventional antifungal treatments.Graphical abstract

Characterization of two novel fusariviruses co-infecting a single isolate of phytopathogenic fungus Botrytis cinerea.

A wide diversity of mycoviruses has been reported from Botrytis species, some with the potential to suppress the pathogenic abilities of this fungus. Considering their importance, this study was devised to find potential hypovirulence-associated mycoviruses found in Botrytis cinerea strains isolated from Pakistani strawberry fields. Here we report the complete genome characterization of two fusariviruses co-infecting a single isolate of phytopathogenic fungus B. cinerea (Kst14a). The viral genomes were sequenced by deep sequencing using total RNA fractions of the Kst14a isolate. The identified viruses were tentatively namedBotrytis cinerea fusarivirus 9 (BcFV9) and Botrytis cinerea fusarivirus 3a (BcFV3a). Both viruses had a single-segmented (ssRNA) genome having a size of 6424 and 8370 nucleotides encoding two discontinuous open reading frames (ORFs). ORF-1 of both mycoviruses encodes for a polyprotein having a conserved domain of RNA-dependent RNA polymerase (RdRP) and a helicase domain (Hel) which function in RNA replication, while ORF2 encodes a hypothetical protein with an unknown function, respectively. Phylogenetic analysis indicated that BcFV9 made a clade with the genus Alphafusarivirus and BcFV3a fall in the genus Betafusarivirus in the family Fusariviridae. To our knowledge, this is the first report of two fusariviruses identified in isolates of B. cinerea from Pakistan. Both mycoviruses successfully transfected to a compatible strain of B. cinerea (Mst11). A comparison of virus-free (VF) and virus-infected (VI) isogenic lines showed the presence of these viruses was causing hypovirulence in infected strains. Virus-infected strains also had a small lesion size while testing the pathogenicity via apple assay.

Molecular Biological Methods to Assess Different Botrytis cinerea Strains on Grapes

Botrytis cinerea is a well-known pathogen that can be challenging to control in crops, such as wine grapes. To adapt to the increasing problems of climate change and strain resistance, it is important to find new methods to detect Botrytis cinerea and differentiate strains. These methods include strain differentiation and classification by simple sequence repeats (SSRs) and early detection of the fungus by qPCR. Various strains were analysed using SSR markers and either agarose gel electrophoresis or capillary sequencing via PCR. A sensitive qPCR method was refined to achieve an early detection method for the pathogen. The results demonstrate promising ways to distinguish between strains using both agarose gel electrophoresis and capillary sequencing as well as to detect infection before it becomes visible on grapes. This can be used to further understand and analyse different Botrytis cinerea strain characteristics such as laccase activity, regional or annual effects. The early detection method can be used to better prepare growers for an impending infection so that targeted efforts can be made.

Carboxylesterase and Cytochrome P450 Confer Metabolic Resistance Simultaneously to Azoxystrobin and Some Other Fungicides in Botrytis cinerea.

Plant pathogens have frequently shown multidrug resistance (MDR) in the field, often linked to efflux and sometimes metabolism of fungicides. To investigate the potential role of metabolic resistance in B. cinerea strains showing MDR, the azoxystrobin-sensitive strain B05.10 and -resistant strain Bc242 were treated with azoxystrobin. The degradation half-life of azoxystrobin in Bc242 (9.63 days) was shorter than that in B05.10 (28.88 days). Azoxystrobin acid, identified as a metabolite, exhibited significantly lower inhibition rates on colony and conidia (9.34 and 11.98%, respectively) than azoxystrobin. Bc242 exhibited higher expression levels of 34 cytochrome P450s (P450s) and 11 carboxylesterase genes (CarEs) compared to B05.10 according to RNA-seq analysis. The expression of P450 genes Bcin_02g01260 and Bcin_12g06380, along with the CarEs Bcin_12g06360 in Saccharomyces cerevisiae, resulted in reduced sensitivity to various fungicides, including azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin, iprodione, and carbendazim. Thus, the mechanism of B. cinerea MDR is linked to metabolism mediated by the CarE and P450 genes.

First Report of Gray Mold Caused by Botrytis cinerea on Dragon Fruit (Hylocereus undatus) in Mexico.

The dragon fruit is native of Mexico, and Puebla is the third-largest producing state (SIAP 2023). In June 2023, field sampling was conducted in El Paraíso, Atlixco (18° 49' 5.275" N, 98° 26' 52.353" W), Puebla, Mexico. The mean temperature and relative humidity were 20 °C and 75% for seven consecutive days. Dragon fruits cv. 'Delight' close to harvest with gray mold symptoms were found in a commercial area of 2 ha, with an incidence of 35 to 40% and an estimated severity of 75% on infected fruit. The symptoms included necrosis at the apex, which later spread throughout the fruit, along with a soft, black rot covered in abundant mycelium and sporulation. The fungus was isolated from 40 symptomatic fruits by disinfesting pieces of necrotic tissue with 3% NaClO for one minute, rinsing with sterile distilled water (SDW), plating on Petri dishes with potato dextrose agar, and incubating at 25 °C in the dark. One isolate was obtained from each diseased fruit by the hyphal-tip method. The colonies were initially white with a growth rate of 1.15-1.32 cm per day and turned gray after 10 days; the mycelium was dense and aerial. Spherical and irregular sclerotia were formed, measuring 0.9-1.4 × 0.6-1.1 mm (n = 100). Each Petri dish produced 56-278 sclerotia (n = 40) after 11 days; these were initially white and gradually turned dark brown. Brown to olive conidiophores were straight, septate, and branched, measuring 1075-1520 × 10-21 μm, with elliptical hyaline to light brown conidia of 6.6-11.5 × 5-8.1 μm (n=100). The isolates were tentatively identified as Botrytis cinerea based on morphological characteristics (Ellis 1971). Two representative isolates were chosen for molecular identification and genomic DNA was extracted by the CTAB protocol. The ITS region and the heat shock protein (HSP60), RNA polymerase binding II (RPB2) and glyceraldehyde 3-phosphate dehydrogenase (G3PDH) genes were sequenced (White et al. 1990; Staats et al. 2005). The sequences of a representative isolate (BcPh5) were deposited in GenBank (ITS-OR582337; HSP60-OR636622; RPB2-OR636623; and G3PDH-OR636621). BLAST analysis of the partial sequences of ITS (479 bp), HSP60 (1006 bp), RPB2 (1126 bp), and G3PDH (907 bp) showed 100% similarity to B. cinerea isolates (GenBank: KM840848, MH796663, MK919495, MF480679). Phylogenetic analysis confirmed that BcPh5 clustered with B. cinerea strains. Pathogenicity was confirmed by inoculating the non-wounded surface of 20 detached dragon fruits cv. 'Delight' using the BcPh5 isolate by depositing 20 μl of a 105 conidia/ml suspension with a sterile syringe. The fruits were placed on the rim of a plastic container and inserted in a moisture box with 2 cm of water at the bottom. The box was covered with a plastic sheet to maintain humidity. Control fruits were inoculated with SDW. The inoculated fruits became covered with abundant white to gray mycelium, and soft rot developed within eight days, while no symptoms were observed on the controls. The fungus was re-isolated from the inoculated fruits as described above, fulfilling Koch's postulates. The pathogenicity tests were repeated three times. Gray mold caused by B. cinerea was also recently reported in Mexico on pomegranate (Hernández et al. 2023) and rose apple (Isodoro et al. 2023). As far as we know, this is the first report of B. cinerea causing gray mold on dragon fruit in Mexico. This research is essential for designing integrated management strategies against gray mold on dragon fruits.

Procymidone Application Contributes to Multidrug Resistance of Botrytis cinerea.

The necrotrophic pathogen Botrytis cinerea infects a broad range of plant hosts and causes substantial economic losses to many crops. Although resistance to procymidone has been observed in the field, it remains uncertain why procymidone is usually involved in multidrug resistance (MDR) together with other fungicides. Nine mutants derived from the B. cinerea strain B05.10 through procymidone domestication exhibited high resistance factors (RFs) against both procymidone and fludioxonil. However, the fitness of the mutants was reduced compared to their parental strain, showing non-sporulation and moderate virulence. Furthermore, the RFs of these mutants to other fungicides, such as azoxystrobin, fluazinam, difenoconazole, and pyrimethanil, ranged from 10 to 151, indicating the occurrence of MDR. Transcriptive expression analysis using the quantitative polymerase chain reaction (qPCR) revealed that the mutants overexpressed ABC transporter genes, ranging from 2 to 93.7-fold. These mutants carried single-point mutations W647X, R96X, and Q751X within BcBos1 by DNA sequencing. These alterations in BcBos1 conferred resistance to procymidone and other fungicides in the mutants. Molecular docking analysis suggested distinct interactions between procymidone and Bos1 in the B. cinerea standard strain B05.10 or the resistant mutants, suggesting a higher affinity of the former towards binding with the fungicide. This study provides a comprehensive understanding of the biological characteristics of the resistant mutants and conducts an initial investigation into its fungicide resistance traits, providing a reference for understanding the causes of multidrug resistance of B. cinerea in the field.

Design and Discovery of α-Oximido-arylacetamides as Novel Antifungal Leads.

The discovery of novel and easily accessible antifungal compounds is an imperative issue in agrochemical innovation. Our continuing research with the o-aminophenyloxazoline (NHPhOx) scaffold demonstrated the viability of introducing phenylacetamides for identifying novel antifungal leads. An antifungal function-oriented molecular evaluation was conducted for the previously identified lead R-LE008. Fine-tuning of the α-position and scaffold hopping of acid segment and NHPhOx enables α-oximido-arylacetamide as a novel antifungal model. The concomitant function-oriented diversification produces a panel of antifungal leads CN19, CN21b, CN28, and CN31 against Sclerotinia sclerotiorum and Botrytis cinerea. The crucial and multidimensional effect of the configuration of the acquired amides on the antifungal performance is demonstrated specifically by the separable CN21 isomers. The Z-isomer (CN21b), with an EC50 value of 0.97 μM against B. cinerea, is significantly more potent than its E-isomer (CN21a) and the positive control boscalid. More importantly, compound CN21b can efficiently inhibit resistant B. cinerea strains. CN21b demonstrates a better in vivo preventative effect (82.1%) than those of CN21a (48.1%) and boscalid (55.1%) at 100 μM. CN21b showed a distinct binding model from those of the boscalid and CN21a in the molecular docking simulation. A further morphological investigation by scanning electron microscopy revealed the different mycelia shrinkage of B. cinerea treated by CN21 isomers. The easy accessibility and cost-effectiveness demonstrated the practical potential of α-oximido-phenylacetamide containing NHPhOx as a new model for agrochemical innovation.

Multidrug resistance of Botrytis cinerea associated with its adaptation to plant secondary metabolites.

Fungicides are an effective way to control gray mold of grapes, but the pathogen Botrytis cinerea can develop resistance, overcoming the effectiveness of a fungicide that is repeatedly applied. More importantly, the emergence of multidrug resistance (MDR) in the field, where multiple fungicides with different modes of action simultaneously lose their efficacies, is a significant concern. MDR is associated with ATP-binding cassette (ABC) transporters of the pathogen, and certain plant secondary metabolites (PSMs) stimulate the upregulation of ABC transporters, we hypothesized that the pathogen's preadaptation to PSMs might contribute to MDR development. To test this in B. cinerea, ten PSMs, namely, resveratrol, reserpine, chalcone, flavanone, eugenol, farnesol, anethene, camptothecin, salicylic acid, and psoralen, were selected based on their association with ABC transporters involved in fungicide resistance. B. cinerea strain B05.10 was continuously transferred for 15 generations on potato dextrose agar amended with a PSM (PDAP), and sensitivities to PSMs and fungicides were examined on the 5th, 10th, and 15th generations. RNA was extracted from B. cinerea from the selected generations. After 15 generations of culture transfers, an up-regulation was observed in the expression of ABC transporter-encoding genes BcatrB, BcatrD, and BcatrK using quantitative polymerase chain reaction (qPCR). This upregulation was found to contribute to MDR of B. cinerea against two or more fungicides, among azoxystrobin, boscalid, fludioxonil, difenoconazole, prochloraz, and pyrimethanil. This finding was confirmed through genetic transformation. The decreased sensitivity of B. cinerea to fungicides was confirmed as a subsequent MDR phenotype after exposure to camptothecin, flavanone, and resveratrol. Besides, transcriptome analysis also revealed the upregulation of transcription factors related to ABC expression following resveratrol exposure. This suggests that PSMs contributed to inducing preadaptation of B. cinerea, leading to subsequent MDR.IMPORTANCEThe emergence of MDR in plant pathogens is a threat to plant disease management and leads to the use of excessive fungicides. Botrytis cinerea is of particular concern because its MDR has widely emerged in the field. Understanding its genesis is the first step for controlling MDR. In this study, the contribution of PSMs to MDR has been examined. Effective management of this pathogen in agroecosystems relies on a better understanding of how it copes with phytochemicals or fungicides.

Determination of the Mycovirome of a Necrotrophic Fungus.

Next-generation sequencing (NGS) of total RNA has allowed the detection of novel viruses infecting different hosts, such as fungi, increasing our knowledge on virus horizontal transfer events among different hosts, virus diversity, and virus evolution. Here, we describe the detailed protocols for the isolation of the plant pathogenic fungus Botrytis cinerea, from grapevine plants showing symptoms of the mold gray disease, the culture and maintenance of the isolated B. cinerea strains, the extraction of total RNA from B. cinerea strains for NGS, the bioinformatics pipeline designed and followed to detect mycoviruses in the sequenced samples, and the validation of the in silico detected mycoviruses by different approaches.

Synthesis and evaluation of imidazo[1,2-a]quinoxaline derivatives as potential antifungal agents against phytopathogenic fungi.

To discover novel and effective potential agricultural antifungal agents, various kinds of imidazo[1,2-a]quinoxaline derivatives were designed, and synthesized from available and inexpensive reagents. Their antifungal activities were first evaluated against ten typical phytopathogenic fungi. The in vitro antifungal activity showed that some compounds exhibited more obvious broad-spectrum fungicidal activity than the two commercially-available fungicides chlorothalonil and hymexazol. Valsa mali and Botrytis cinerea strains exhibited the highest susceptibility with EC50 values of 1.4-27.0μg/mL to more than ten compounds. Compounds 5c and 5f showed the most promising inhibitory effects against Valsa mali (EC50 = 5.6μg/mL) and Fusarium solani (EC50 = 5.1μg/mL), respectively. Preliminary studies on the mechanism of action indicated that the imidazo[1,2-a]quinoxaline skeleton likely exerted its antifungal effects by disrupting hyphal differentiation, spore germination, and germ tube growth. Moreover, the cell experiment results indicated that these target compounds possessed good safety to BV2 cells. Overall, compounds 5c and 5f can be considered candidate compounds against specific fungi for further detailed research. This study can provide a theoretical basis for the application of imidazo[1,2-a]quinoxaline scaffolds as novel fungicides in agriculture.

Effect of edible coating incorporating sodium carboxymethyl cellulose/cellulose nanofibers and self-produced mandarin oil on strawberries

Edible coatings were prepared using a mixture of 1.0 % (w/v) sodium carboxymethyl cellulose (CMC), 0.5 % (w/v) cellulose nanofibers (CNF), and varying concentrations of mandarin oil (MO) at 0.05, 0.1, 0.2, 0.3, or 0.4 % (w/v). The research investigated the physicochemical characteristics and antifungal activities of the films on Botrytis cinerea (B. cinerea). CMC/CNF/MO coatings were used to preserve the strawberries (Amaou). The changes in quality and antifungal activity on the strawberries were assessed during storage at 5 °C and 85 ± 5 % relative humidity (RH). Results showed the major components of MO include β-pinene, limonene, and methyl palmitate. The addition of MO into coatings indicated a significant effect on the properties of coating solutions as well as the film characteristics as shown in b* and roughness values increased strongly. The coatings contained MO also represented a marked effect on fruit weight loss and antifungal activity against B. cinerea strain both in vitro and in vivo. The addition of MO at a concentration of 0.05 % illustrated the significant effect in controlling weight loss and antifungal activity on strawberries.

Iron and copper on Botrytis cinerea: new inputs in the cellular characterization of their inhibitory effect.

Certain metals play key roles in infection by the gray mold fungus, Botrytis cinerea. Among them, copper and iron are necessary for redox and catalytic activity of enzymes and metalloproteins, but at high concentrations they are toxic. Understanding the mechanism requires more cell characterization studies for developing new, targeted metal-based fungicides to control fungal diseases on food crops. This study aims to characterize the inhibitory effect of copper and iron on B. cinerea by evaluating mycelial growth, sensitivity to cell wall perturbing agents (congo red and calcofluor white), membrane integrity, adhesion, conidial germination, and virulence. Tests of copper over the range of 2 to 8 mM and iron at 2 to 20 mM revealed that the concentration capable of reducing mycelial growth by 50% (IC50) was 2.87 mM and 9.08 mM for copper and iron, respectively. When mixed at equimolar amounts there was a significant inhibitory effect mostly attributable to copper. The effect of Cu50, Fe50, and Cu50-Fe50 was also studied on the mycelial growth of three wild B. cinerea strains, which were more sensitive to metallic inhibitors. A significant inhibition of conidial germination was correlated with adhesion capacity, indicating potential usefulness in controlling disease at early stages of crop growth. Comparisons of the effects of disruptive agents on the cell wall showed that Cu, Fe, and Cu-Fe did not exert their antifungal effect on the cell wall of B. cinerea. However, a relevant effect was observed on plasma membrane integrity. The pathogenicity test confirmed that virulence was correlated with the individual presence of Cu and Fe. Our results represent an important contribution that could be used to formulate and test metal-based fungicides targeted at early prevention or control of B. cinerea.

Bioactivity-Guided Subtraction of MIQOX for Easily Available Isoquinoline Hydrazides as Novel Antifungal Candidates.

The discovery of novel and easily available leads provides a convincing solution to agrochemical innovation. A bioassay-guided scaffold subtraction of the previous "Chem-Bio Model" isoquinoline-3-oxazoline MIQOX was conducted for identifying the easily available isoquinoline-3-hydrazide as a novel antifungal scaffold. The special and practical potential of this model was demonstrated by a phenotypic antifungal bioassay, molecular docking, and cross-resistance evaluation. A panel of antifungal leads (LW2, LW3, and LW11) was acquired, showing much better antifungal performance than the positive controls. Specifically, compound LW3 exhibited a broad antifungal spectrum holding EC50 values as low as 0.54, 0.09, 1.52, and 2.65 mg/L against B. cinerea, R. solani, S. sclerotiorum , and F. graminearum, respectively. It demonstrated a curative efficacy better than that of boscalid in controlling the plant disease caused by B. cinerea. The candidate LW3 did not show cross-resistance to the extensively used succinate dehydrogenase inhibitor (SDHI) fungicides and can efficiently inhibit resistant B. cinerea strains. The molecular docking of compound LW3 is quite different from that of the positive controls boscalid and fluopyram. This progress highlights the practicality of isoquinoline hydrazide as a novel model in fungicide innovation.