Detection and Molecular Characterization of Resistance to the Dicarboximide and Benzamide Fungicides in Botrytis cinerea From Tomato in Hubei Province, China

Fungicide resistance in Colletotrichum fructicola and Colletotrichum siamense causing peach anthracnose in China

Peach is one of the popular and economically important fruit crops in China. Peach cultivation is hampered due to attacks of anthracnose disease, causing significant economic losses. Colletotrichum fructicola and Colletotrichum siamense belong to the Colletotrichum gloeosporioides species complex and are considered major pathogens of peach anthracnose. Application of different groups of fungicides is a routine approach for controlling this disease. However, fungicide resistance is a significant drawback in managing peach anthracnose nowadays. In this study, 39 isolates of C. fructicola and 41 isolates of C. siamense were collected from different locations in various provinces in China. The sensitivity of C. fructicola and C. siamense to some commonly used fungicides, i.e., carbendazim, iprodione, fluopyram, and propiconazole, was determined. All the isolates of C. fructicola collected from Guangdong province showed high resistance to carbendazim, whereas isolates collected from Guizhou province were sensitive. In C. siamense, isolates collected from Hebei province showed moderate resistance, while those from Shandong province were sensitive to carbendazim. On the other hand, all the isolates of C. fructicola and C. siamense showed high resistance to the dicarboximide (DCF) fungicide iprodione and succinate dehydrogenase inhibitor (SDHI) fungicide fluopyram. However, they are all sensitive to the demethylation inhibitor (DMI) fungicide propiconazole. Positive cross-resistance was observed between carbendazim and benomyl as they are members of the same methyl benzimidazole carbamate (MBC) group. While no correlation of sensitivity was observed between different groups of fungicides. No significant differences were found in each fitness parameter between carbendazim-resistant and sensitive isolates in both species. Molecular characterization of the β-tubulin 2 (TUB2) gene revealed that in C. fructicola, the E198A point mutation was the determinant for the high resistance to carbendazim, while the F200Y point mutation was linked with the moderate resistance to carbendazim in C. siamense. Based on the results of this study, DMI fungicides, e.g., propiconazole or prochloraz could be used to control peach anthracnose, especially at locations where the pathogens have already developed the resistance to carbendazim and other fungicides.

Plant immune inducer ZNC promotes rutin accumulation and enhances resistance to Botrytis cinerea in tomato

Gray mold is a destructive disease caused by Botrytis cinerea, a pervasive plant pathogen, which poses a threat to both tomato growth and postharvest storage. The utilization of induced resistance presents a potential strategy for combating plant pathogenic attacks. ZNC (zhinengcong), an extract derived from the endophytic fungus Paecilomyces variotii, has been discovered to play a vital role in preventing diverse forms of bacterial infections. Nevertheless, the precise mechanism behind its ability to enhance tomato resistance to fungi remains unclear. In this study, we found that the exogenous spraying of ZNC could significantly improve the resistance of tomato plants to B. cinerea. The results of both the metabolomic analysis and high-performance liquid chromatography (HPLC) demonstrated that tomato plants responded to ZNC treatment by accumulating high levels of rutin. Additional transcriptome analysis uncovered that rutin enhances tomato resistance possible by initiating the generation of reactive oxygen species (ROS) and phosphorylation of mitogen-activated protein kinases (MPKs) related genes expression during the initial phase of invasion by B. cinerea. In addition, we also found that rutin might activate plant immunity by eliciting ethylene (ET) and jasmonic acid (JA)-mediated pathways. Therefore, plant immune inducer ZNC and rutin has bright application prospects and high utilization value to control gray mold.

Chitosan-Decorated Copper Oxide Nanocomposite: Investigation of Its Antifungal Activity against Tomato Gray Mold Caused by Botrytis cinerea

Owing to the remarkable antimicrobial potential of these materials, research into the possible use of nanomaterials as alternatives to fungicides in sustainable agriculture is increasingly progressing. Here, we investigated the potential antifungal properties of chitosan-decorated copper oxide nanocomposite (CH@CuO NPs) to control gray mold diseases of tomato caused by Botrytis cinerea throughout in vitro and in vivo trials. The nanocomposite CH@CuO NPs were chemically prepared, and size and shape were determined using Transmission Electron Microscope (TEM). The chemical functional groups responsible for the interaction of the CH NPs with the CuO NPs were detected using the Fourier Transform Infrared (FTIR) spectrophotometry. The TEM images confirmed that CH NPs have a thin and semitransparent network shape, while CuO NPs were spherically shaped. Furthermore, the nanocomposite CH@CuO NPs ex-habited an irregular shape. The size of CH NPs, CuO NPs and CH@CuO NPs as measured through TEM, were approximately 18.28 ± 2.4 nm, 19.34 ± 2.1 nm, and 32.74 ± 2.3 nm, respectively. The antifungal activity of CH@CuO NPs was tested at three concentrations of 50, 100 and 250 mg/L and the fungicide Teldor 50% SC was applied at recommended dose 1.5 mL/L. In vitro experiments revealed that CH@CuO NPs at different concentrations significantly inhibited the reproductive growth process of B. cinerea by suppressing the development of hyphae, spore germination and formation of sclerotia. Interestingly, a significant control efficacy of CH@CuO NPs against tomato gray mold was observed particularly at concentrations 100 and 250 mg/L on both detached leaves (100%) as well as the whole tomato plants (100%) when compared to the conventional chemical fungicide Teldor 50% SC (97%). In addition, the tested concentration 100 mg/L improved to be sufficient to guarantee a complete reduction in the disease's severity (100%) to tomato fruits from gray mold without any morphological toxicity. In comparison, tomato plants treated with the recommended dose 1.5 mL/L of Teldor 50% SC ensured disease reduction up to 80%. Conclusively, this research enhances the concept of agro-nanotechnology by presenting how a nano materials-based fungicide could be used to protect tomato plants from gray mold under greenhouse conditions and during the postharvest stage.

Benzimidazole-Resistant Isolates with E198A/V/K Mutations in the β-Tubulin Gene Possess Different Fitness and Competitive Ability in Botrytis cinerea

Previous studies in Botrytis cinerea showed that resistance to methyl benzimidazole carbamates (MBCs) was mainly related to E198A/V/K and F200Y mutations of the β-tubulin gene, and E198V was the dominant mutation in the resistant subpopulation in Hubei Province of China, indicating that resistant mutations might influence fitness. However, little is known about the effect of each E198A/V/K mutation on fitness. In this study, the fitness and competitive ability of isolates with E198A/V/K mutations were investigated. Results showed that E198A/V/K isolates and wild-type isolates shared similar fitness components in terms of virulence, sporulation, conidial germination, oxidative sensitivity, and sclerotial production and viability. However, slower mycelial growth at 4°C, higher sensitivity to 4% NaCl, and increased sclerotial production percentage at 4°C were observed in the isolates with E198V, E198K, and E198A mutations, respectively. Competitive analysis showed that the wild-type subpopulation became dominant after three disease cycles in the absence of fungicide selection pressure, whereas the resistant subpopulation seized the space of the sensitive subpopulation upon MBC application. Unexpectedly, the frequency of E198V isolates decreased dramatically after the first disease cycle with or without fungicide selection pressure. These results suggest that MBC-resistant isolates suffer little fitness penalty but possess competitive disadvantages in the absence of fungicide selection pressure. Under fungicide selection pressure, E198V isolates could not compete with E198A/K isolates. According to the current results, there is a great possibility that the E198V mutation will lose dominance in the future in China.

Rapid visual detection of benzimidazole resistance in Botrytis cinerea by recombinase polymerase amplification combined with a lateral flow dipstick

BACKGROUND

Benzimidazole resistance in Botrytis cinerea is related to point mutations in the target β-tubulin gene (TUB2). Three mutations (E198A, E198K, E198V) at codon 198 account for most of the resistant strains. A rapid on-site diagnostic assay would be useful to detect the presence and monitor further spread of this resistance mechanism.

RESULTS

A recombinase polymerase amplification combined with lateral flow detection (RPA-LFD) method was established for the rapid detection of methyl benzimidazole carbamate (MBC) resistance in B. cinerea. Based on the three mutations at TUB2 codon 198, three sets of RPA-LFD primers were designed, and each of these primer sets was able to specifically amplify the DNA containing its corresponding mutation; no amplification was detected with other mutated or wild-type DNA. The assay was optimized for specificity and sensitivity and was shown to detect the presence of 2 × 10² copies μl^-1 of target DNA per reaction within 10 min. DNA from eight other common fungal species of small fruit did not yield a signal. The system worked well over a wide range of temperatures from 25 to 45°C. Crude DNA obtained from boiled mycelium and conidia of symptomatic fruit could be used as templates, which simplified the assay process.

CONCLUSION

This study developed a novel assay based on RPA-LFD for the rapid and equipment-free detection of MBC-resistant isolates. In combination with a simple DNA extraction method, the assay could detect B. cinerea MBC-resistant isolates even without specialized equipment within 30 min. Considering its specificity, stability and simplicity, the RPA-LFD assay could be a promising tool for rapid on-site diagnosis of fungicide-resistant isolates. © 2021 Society of Chemical Industry.

Sensitivity of Colletotrichum nymphaeae to Six Fungicides and Characterization of Fludioxonil-Resistant Isolates in China

Colletotrichum nymphaeae is the dominant species causing anthracnose disease of peach in China. In this study, 140 isolates of C. nymphaeae were assessed for their sensitivity to six fungicides. It was found that C. nymphaeae was highly resistant to carbendazim, procymidone, and boscalid but sensitive to pyraclostrobin and prochloraz. For fludioxonil, the fungus exhibited differential sensitivities (i.e., approximately 14% of isolates were resistant to fludioxonil and the resistance was stable). Fludioxonil-resistant isolates had a mean EC₅₀ value of 2.2380 µg/ml, whereas the mean EC₅₀ value was 0.0194 µg/ml in fludioxonil-sensitive isolates. The mean EC₅₀ values of C. nymphaeae for pyraclostrobin and prochloraz were 0.0083 µg/ml and 0.002 µg/ml, respectively. No cross-resistance was observed between fungicides from different groups. Mycelial growth rate, control efficacy, and osmotic stress responses were significantly different (P < 0.05) between fludioxonil-sensitive (Flu^S) and -resistant (Flu^R) isolates, but no significant difference was observed (P > 0.05) in virulence and sporulation between Flu^S and Flu^R isolates. No mutation was detected in coding regions of the CnOs-1, Cal, Hk1, Hog1, TPI, and Mrr1 genes. Interestingly, with fludioxonil treatment, the expression of ABC transporter gene atrB was significantly overexpressed in some resistant isolates. However, overexpression of the atrB gene was not detected in one moderately and one highly resistant isolate, indicating that other unknown mechanisms may be involved. Current findings uncovered several effective chemicals and provided the foundation for designing management strategies to practically control peach anthracnose with the most effective demethylation inhibitor fungicides and quinone outside inhibitor fungicides.

An Analysis of Postharvest Fungal Pathogens Reveals Temporal-Spatial and Host-Pathogen Associations with Fungicide Resistance-Related Mutations

Fungicides are the primary tools to control a wide range of postharvest fungal pathogens. Fungicide resistance is a widespread problem that has reduced the efficacy of fungicides. Resistance to FRAC-1 (Fungicide Resistance Action Committee-1) chemistries is associated with mutations in amino acid position 198 in the β-tubulin gene. In our study, we conducted a meta-analysis of β-tubulin sequences to infer temporal, spatial, plant host, and pathogen genus patterns of fungicide resistance in postharvest fungal pathogens. In total, data were acquired from 2,647 specimens from 12 genera of fungal phytopathogens residing in 53 countries on >200 hosts collected between 1926 and 2020. The specimens containing a position 198 mutation were globally distributed in a variety of pathosystems. Analyses showed that there are associations among the mutation and the year an isolate was collected, the pathogen genus, the pathogen host, and the collection region. Interestingly, fungicide-resistant β-tubulin genotypes have been in a decline since their peak between 2005 and 2009. FRAC-1 fungicide usage data followed a similar pattern in that applications have been in a decline since their peak between 1997 and 2003. The data show that, with the reduction of selection pressure, FRAC-1 fungicide resistance in fungal populations will decline within 5 to 10 years. Based on this line of evidence, we contend that a β-tubulin position 198 mutation has uncharacterized fitness cost(s) on fungi in nature. The compiled dataset can inform end users on the regions and hosts that are most prone to contain resistant pathogens and assist decisions concerning fungicide resistance management strategies.

Sensitivity of Colletotrichum fructicola and Colletotrichum siamense of Peach in China to Multiple Classes of Fungicides and Characterization of Pyraclostrobin-Resistant Isolates

Anthracnose, mainly caused by Colletotrichum gloeosporioides species complex including Colletotrichum fructicola and Colletotrichum siamense, is a devastating disease of peach. Chemical control has been widely used for years, but management failures have increased with the commonly used fungicides. Therefore, screening of sensitivity of Colletotrichum spp. to fungicides with different modes of action is needed to make proper management strategies for peach anthracnose. In this study, the sensitivity of 80 isolates of C. fructicola and C. siamense was screened for pyraclostrobin, procymidone, prochloraz, and fludioxonil based on mycelial growth inhibition at discriminatory doses. Results showed that C. fructicola and C. siamense isolates were highly resistant to procymidone and fludioxonil with 100% resistance frequencies to both fungicides, but sensitive to prochloraz, i.e., no resistant isolates were found. For pyraclostrobin, 74% of C. fructicola isolates showed high resistance, 26% showed low resistance, and all of the C. siamense isolates showed low resistance. No positive cross-resistance was observed between pyraclostrobin and azoxystrobin even when they are members of the same quinone outside inhibitor (QoI) fungicide group or between pyraclostrobin and non-QoIs. Resistant isolates to QoI fungicides were evaluated for the fitness penalty. Results showed that no significant differences except for the mycelial growth rates that were detected between high- and low-resistance isolates of C. fructicola. Molecular characterization of the Cyt b gene revealed that the G143A point mutation was the determinant of the high resistance in C. fructicola. This study demonstrated the resistance status of C. fructicola and C. siamense to different fungicides and briefly discussed implications of that resistance. Demethylation inhibitor fungicides were found to be the best option among the different chemicals studied here, to control peach anthracnose in China.

The Bioactivity and Efficacy of Benzovindiflupyr Against Corynespora cassiicola, the Causal Agent of Cucumber Corynespora Leaf Spot

Corynespora cassiicola, which causes Corynespora leaf spot, results in considerable yield loss of cucumber grown in greenhouses. Frequent reports of reduced efficacy and control failure of fungicides warrant new, efficient alternative chemistries. In this study, the sensitivity of C. cassiicola to benzovindiflupyr was evaluated using a collection of 81 isolates collected from Shandong, China. The mean EC₅₀ values for mycelial growth, spore germination, and germ tube elongation of C. cassiicola were 0.69 ± 0.44, 0.12 ± 0.063, and 0.13 ± 0.076 µg ml^-1, respectively. Benzovindiflupyr treatment led to a reduced respiration rate and ATP production of C. cassiicola and decreased spore pathogenicity by 21.9% on average. Additionally, detached cucumber leaves sprayed with fungicides before or after inoculation were used to assess the efficacy of benzovindiflupyr against C. cassiicola. Benzovindiflupyr (150 µg ml^-1) exhibited preventive and curative efficacies of 86.9 and 77.1%, respectively. Benzovindiflupyr at 150 g a.i. ha^-1 provided over 70% efficacy in field trials performed in 2018 and 2019, which was significantly higher than that of the reference fungicides fluopyram and fluxapyroxad at the same dose. Furthermore, the yield of commercial cucumber increased as disease incidence decreased. Our findings pave the way for the introduction of benzovindiflupyr in the integrated management of Corynespora leaf spot.

Streptomyces botrytidirepellens sp. nov., a novel actinomycete with antifungal activity against Botrytis cinerea

The fungal pathogen Botrytis cinerea is the causal agent of devastating gray mold diseases in many economically important fruits, vegetables, and flowers, leading to serious economic losses worldwide. In this study, a novel actinomycete NEAU-LD23^T exhibiting antifungal activity against B. cinerea was isolated, and its taxonomic position was evaluated using a polyphasic approach. Based on the genotypic, phenotypic and chemotaxonomic data, it is concluded that the strain represents a novel species within the genus Streptomyces, for which the name Streptomyces botrytidirepellens sp. nov. is proposed. The type strain is NEAU-LD23^T (=CCTCC AA 2019029^T=DSM 109824^T). In addition, strain NEAU-LD23^T showed a strong antagonistic effect against B. cinerea (82.6±2.5%) and varying degrees of inhibition on nine other phytopathogenic fungi. Both cell-free filtrate and methanol extract of mycelia of strain NEAU-LD23^T significantly inhibited mycelial growth of B. cinerea. To preliminarily explore the antifungal mechanisms, the genome of strain NEAU-LD23^T was sequenced and analyzed. AntiSMASH analysis led to the identification of several gene clusters responsible for the biosynthesis of bioactive secondary metabolites with antifungal activity, including 9-methylstreptimidone, echosides, anisomycin, coelichelin and desferrioxamine B. Overall, this research provided us an excellent strain with considerable potential to use for biological control of tomato gray mold.

Advances in Understanding Fungicide Resistance in Botrytis cinerea in China

Gray mold, caused by Botrytis cinerea, is a devastating disease that causes significant yield losses in various economically important plants. Fungicide application is one of the main strategies for management of gray mold; however, B. cinerea has developed resistance to various groups of fungicide. In China, benzimidazole-, dicarboximide-, and quinone outside inhibitor-resistant populations of B. cinerea have become dominant. Substitute mutations in fungicide target genes are responsible for resistance in B. cinerea. Based on known resistance mechanisms, molecular methods including loop-mediated isothermal amplification have been developed for rapid detection of resistant isolates of B. cinerea. Because B. cinerea is able to quickly develop resistance to various fungicides, various integrated strategies have been implemented in the last decade, including biological and agricultural practices, to manage fungicide resistance in B. cinerea.

Solution Structure, Dynamics, and New Antifungal Aspects of the Cysteine-Rich Miniprotein PAFC

The genome of Penicillium chrysogenum Q176 contains a gene coding for the 88-amino-acid (aa)-long glycine- and cysteine-rich P. chrysogenum antifungal protein C (PAFC). After maturation, the secreted antifungal miniprotein (MP) comprises 64 aa and shares 80% aa identity with the bubble protein (BP) from Penicillium brevicompactum, which has a published X-ray structure. Our team expressed isotope (15N, 13C)-labeled, recombinant PAFC in high yields, which allowed us to determine the solution structure and molecular dynamics by nuclear magnetic resonance (NMR) experiments. The primary structure of PAFC is dominated by 14 glycines, and therefore, whether the four disulfide bonds can stabilize the fold is challenging. Indeed, unlike the few published solution structures of other antifungal MPs from filamentous ascomycetes, the NMR data indicate that PAFC has shorter secondary structure elements and lacks the typical β-barrel structure, though it has a positively charged cavity and a hydrophobic core around the disulfide bonds. Some parts within the two putative γ-core motifs exhibited enhanced dynamics according to a new disorder index presentation of 15N-NMR relaxation data. Furthermore, we also provided a more detailed insight into the antifungal spectrum of PAFC, with specific emphasis on fungal plant pathogens. Our results suggest that PAFC could be an effective candidate for the development of new antifungal strategies in agriculture.

Effects of Origanum vulgare essential oil and its two main components, carvacrol and thymol, on the plant pathogen Botrytis cinerea

Background

Botrytis cinerea causes serious gray mold disease in many plants. This pathogen has developed resistance to many fungicides. Thus, it has become necessary to look for new safe yet effective compounds against B. cinerea.

Methods

Essential oils (EOs) from 17 plant species were assayed against B. cinerea, of which Origanum vulgare essential oil (OVEO) showed strong antifungal activity, and accordingly its main components were detected by GC/MS. Further study was conducted on the effects of OVEO, carvacrol and thymol in vitro on mycelium growth and spore germination, mycelium morphology, leakages of cytoplasmic contents, mitochondrial injury and accumulation of reactive oxygen species (ROS) of B. cinerea. The control efficacies of OVEO, carvacrol and thymol on tomato gray mold were evaluated in vivo.

Results

Of all the 17 plant EOs tested, Cinnamomum cassia, Litsea cubeba var. formosana and O. vulgare EOs had the best inhibitory effect on B. cinerea, with 0.5 mg/mL completely inhibiting the mycelium growth of B. cinerea. Twenty-one different compounds of OVEO were identified by gas chromatography–mass spectrometry, and the main chemical components were carvacrol (89.98%), β-caryophyllene (3.34%), thymol (2.39%), α-humulene (1.38%) and 1-methyl-2-propan-2-ylbenzene isopropyl benzene (1.36%). In vitro experiment showed EC₅₀ values of OVEO, carvacrol and thymol were 140.04, 9.09 and 21.32 μg/mL, respectively. Carvacrol and thymol completely inhibited the spore germination of B. cinerea at the concentration of 300 μg/mL while the inhibition rate of OVEO was 80.03%. EC₅₀ of carvacrol and thymol have significantly (P < 0.05) reduced the fresh and dry weight of mycelia. The collapse and damage on B. cinerea mycelia treated with 40 μg/mL of carvacrol and thymol was examined by scanning electron microscope (SEM). Through extracellular conductivity test and fluorescence microscope observation, it was found that carvacrol and thymol led to increase the permeability of target cells, the destruction of mitochondrial membrane and ROS accumulation. In vivo conditions, 1000 μg/mL carvacrol had the best protective and therapeutic effects on tomato gray mold (77.98% and 28.04%, respectively), and the protective effect was significantly higher than that of 400 μg/mL pyrimethanil (43.15%). While the therapeutic and protective effects of 1,000 μg/mL OVEO and thymol were comparable to chemical control.

Conclusions

OVEO showed moderate antifungal activity, whereas its main components carvacrol and thymol have great application potential as natural fungicides or lead compounds for commercial fungicides in preventing and controlling plant diseases caused by B. cinerea.

Cytological and Gene Profile Expression Analysis Reveals Modification in Metabolic Pathways and Catalytic Activities Induce Resistance in Botrytis cinerea Against Iprodione Isolated From Tomato

Grey mold is one of the most serious and catastrophic diseases, causing significant yield losses in fruits and vegetables worldwide. Iprodione is a broad spectrum agrochemical used as a foliar application as well as a seed protectant against many fungal and nematode diseases of fruits and vegetables from the last thirty years. The extensive use of agrochemicals produces resistance in plant pathogens and is the most devastating issue in food and agriculture. However, the molecular mechanism (whole transcriptomic analysis) of a resistant mutant of B. cinerea against iprodione is still unknown. In the present study, mycelial growth, sporulation, virulence, osmotic potential, cell membrane permeability, enzymatic activity, and whole transcriptomic analysis of UV (ultraviolet) mutagenic mutant and its wild type were performed to compare the fitness. The EC₅₀ (half maximal effective concentration that inhibits the growth of mycelium) value of iprodione for 112 isolates of B. cinerea ranged from 0.07 to 0.87 µg/mL with an average (0.47 µg/mL) collected from tomato field of Guangxi Province China. Results also revealed that, among iprodione sensitive strains, only B67 strain induced two mutants, M0 and M1 after UV application. The EC₅₀ of these induced mutants were 1025.74 μg/mL and 674.48 μg/mL, respectively, as compared to its wild type 1.12 μg/mL. Furthermore, mutant M0 showed higher mycelial growth sclerotia formation, virulence, and enzymatic activity than wild type W0 and M1 on potato dextrose agar (PDA) medium. The bctubA gene in the mutant M0 replaced TTC and GAT codon at position 593 and 599 by TTA and GAA, resulting in replacement of phenyl alanine into leucine (transversion C/A) and aspartic acid into glutamic acid (transversion T/C) respectively. In contrast, in bctubB gene, GAT codon at position 646 is replaced by AAT and aspartic acid converted into asparagine (transition G/A). RNA sequencing of the mutant and its wild type was performed without (M0, W0) and with iprodione treatment (M-ipro, W-ipro). The differential gene expression (DEG) identified 720 unigenes in mutant M-ipro than W-ipro after iprodione treatment (FDR ≤ 0.05 and log2FC ≥ 1). Seven DEGs were randomly selected for quantitative real time polymerase chain reaction to validate the RNA sequencing genes expression (log fold 2 value). The gene ontology (GO) enrichment and Kyoto encyclopedia genes and genomes (KEGG) pathway functional analyses indicated that DEG’s mainly associated with lysophopholipase, carbohydrate metabolism, amino acid metabolism, catalytic activity, multifunctional genes (MFO), glutathione-S transferase (GST), drug sensitivity, and cytochrome P450 related genes are upregulated in mutant type (M0, M-ipro) as compared to its wild type (W0, W-ipro), may be related to induce resistant in mutants of B. cinerea against iprodione.

Biological Control of Tomato Gray Mold Caused by Botrytis Cinerea with the Entomopathogenic Fungus Metarhizium Anisopliae

Gray mold disease caused by Botrytis cinerea is a devastating disease that leads to serious financial loss. In this study, the entomopathogenic fungus Metarhizium anisopliae that acts against the gray mold pathogen B. cinerea was evaluated. M. anisopliae produced a significant inhibition zone in front of the B. cinerea colony in the dual culture test. In addition, volatile organic compounds generated by M. anisopliae were shown to have an inhibitory effect on B. cinerea mycelia growth and reduced 41% of gray mold severity of postharvest tomatoes. The 10% concentration of the culture filtrate of M. anisopliae inhibited 88.62% of colony radial growth as well as 63.85% of sclerotia germination and all conidia germination of B. cinerea. Furthermore, the culture filtrate of M. anisopliae retained its inhibitory effect against the radial growth of B. cinerea even after heating for 15 min at 100 °C. Feasible mechanisms of M. anisopliae involved in the control of B. cinerea were explored, and it was demonstrated that the plasma membrane of B. cinerea conidia was damaged by the product of metabolism of M. anisopliae. In addition, after treating with culture filtrate of M. anisopliae, the B. cinerea phenotype was shown to be abnormal, and cell organelles of B. cinerea mycelia were damaged significantly. A significant control efficacy of M. anisopliae against tomato gray mold was detected on both the detached leaf assay (84.24%) as well as the whole plant (72.38%). In addition, a 78% reduction in tomato fruit mold was detected at a 10% treated concentration of M. anisopliae. These findings suggest that M. anisopliae possesses potential as a biocontrol agent against tomato gray mold in the greenhouse and during the postharvest stage.