Causal Agent Of Gray Mold Research Articles

Blue lighting combined with cold storage temperature can suppress gray mold in strawberry fruit

Cold storage is an optimal way of preventing quality deterioration in fruit crops, and this is exemplified by strawberries. However, Botrytis cinerea, the causal agent of gray mold, is cold-adaptive and can cause losses to cold-stored fruit. This study evaluated the regulatory effects of the spectral quality of light on the fungal growth in vitro, and the development of gray mold on postharvest strawberries at both ambient (21 ℃) and cold (4 ℃) temperatures. None of the light qualities tested (white, blue, green, or red) significantly affected colony growth of B. cinerea compared with the dark conditions in which they were tested at 21 ℃. In fungal cultures kept at 4 ℃, blue light significantly retarded colony expansion compared to other light conditions and darkness. Moreover, blue light and cold conditions can synergistically result in an increased number of septa, hyphal abnormality and intracellular vacuoles. An enhanced accumulation of reactive oxygen species (ROS) was also observed in fungal hypha exposed to blue light under cold conditions. Infection assay on strawberries demonstrated that blue light caused insignificant and significant suppressive effects at 21 ℃ and 4 ℃, respectively. In addition, blue-light caused significant weight loss in strawberries compared with all other treatments. Consequently, blue-light illumination under cold conditions may result in oxidative stress to the B. cinerea cells, thus preventing this cold-adaptive pathogen from causing unexpected deterioration in the stored fruit.

Essential oil from orange peel in the control of Botrytis cinerea and in the postharvest conservation of ‘Benitaka’ table grape

The objective of this work was to evaluate the efficiency of essential oil from orange peel in the refrigerated conservation of the ‘Benitaka’ table grape, as well as to evaluate its in vitro effectiveness on Botrytis cinerea, the causal agent of gray mold. Grapes were harvested from a commercial field in the municipality of Cambira, Paraná, during the 2022 and 2023 seasons. The experimental design was completely randomized, with four treatments and five replications of five bunches per plot. The treatments were: a) control; b) essential oil from orange peel at 4.0 mL of the commercial product (c.p.) L-1; c) dual phase SO2-generating pads containing 1 and 4 g of the active ingredient (a.i.) in the fast and slow phases, respectively; and d) essential oil from orange peel at 4.0 mL c.p. L-1 associated with the dual phase SO2-generating pads containing 1 and 4 g of the a.i. in the fast and slow phases, respectively. A commercial product containing 61.14 g L-1 (6% w/v) of 4-isopropenyl-1-methylcyclohexane, the source of orange essential oil, was applied by spraying it directly onto the bunches. After drying, the grape bunches were stored in a refrigerated chamber at 1.0±1°C and 95% relative humidity. The following variables were assessed 30 and 45 days after the beginning of cold storage: the incidence of gray mold on berries, loss of bunch mass, stem browning, shattered berries, and bleaching. The minimum inhibitory concentration for the development of B. cinerea was determined, and fungal mycelia were observed using scanning electron microscopy to evaluate the in vitro efficacy of orange essential oil. The data were subjected to analysis of variance, and the means were compared using Fisher's difference test at 5% probability. The effectiveness of orange essential oil in suppressing the development of B. cinerea was demonstrated both in vivo and in vitro, making it a safe alternative for the postharvest conservation of 'Benitaka' table grapes.

Antifungal activity of essential oils rich in ketones against Botrytis cinerea: New strategy for biocontrol

Plant secondary metabolites, including essential oils (EOs), are becoming an alternative to traditional methods of controlling phytopathogens. In the present work we evaluated the antifungal activity of EOs from two populations of Aloysia polystachya on the causal agent of gray mold, Botrytis cinerea. The chemical composition of EOs showed carvone and α-thujone as the main components of each EO, determining that they were two different chemotypes. The antifungal effect of both chemotypes against B. cinerea was evaluated in their vapor phase, at different concentrations. The MIC for the carvone-rich chemotype was 71 μL L−1, while the α-thujone-rich chemotype completely inhibited growth at a concentration of 189 μL L−1. Both chemotypes significantly inhibited the germination of fungal conidia. The normal morphology of the hyphae of B. cinerea was compromised in the presence of both chemotypes, showing flattening and emptying of the content, compared to the untreated mycelium. The effect of the chemotypes on the disease caused by the fungus was also evaluated in artificially inoculated tomatoes, with the carvone-rich chemotype being more effective in reducing the characteristic symptoms. None of the chemotypes produced alterations in postharvest quality parameters. Our data allow us to propose the EO of A. polystachya with abundant content of the terpene carvone, as a natural strategy for the control of the pathogen B. cinerea. This research is important to show how the existence of variants within the same botanical species implies differences in their effectiveness as fungicides.

Amphibian skin bacteria display antifungal activity and induce plant defense mechanisms against Botrytis cinerea.

Botrytis cinerea is the causal agent of gray mold, which affects a wide variety of plant species. Chemical agents have been used to prevent the disease caused by this pathogenic fungus. However, their toxicity and reduced efficacy have encouraged the development of new biological control alternatives. Recent studies have shown that bacteria isolated from amphibian skin display antifungal activity against plant pathogens. However, the mechanisms by which these bacteria act to reduce the effects of B. cinerea are still unclear. From a diverse collection of amphibian skin bacteria, three proved effective in inhibiting the development of B. cinerea under in vitro conditions. Additionally, the individual application of each bacterium on the model plant Arabidopsis thaliana, Solanum lycopersicum and post-harvest blueberries significantly reduced the disease caused by B. cinerea. To understand the effect of bacteria on the host plant, we analyzed the transcriptomic profile of A. thaliana in the presence of the bacterium C32I and the fungus B. cinerea, revealing transcriptional regulation of defense-related hormonal pathways. Our study shows that bacteria from the amphibian skin can counteract the activity of B. cinerea by regulating the plant transcriptional responses.

In vitro and in vivo biocontrol studies against Botrytis cinerea, the causal agent of grey mould in Hydrangea macrophylla

ABSTRACT Necroses on aerial parts of Hydrangea macrophylla were regularly observed in plant storage chamber at 2°C in Hortensia France company. A total of 34 Botrytis isolates were collected from Hydrangea plants and their environment. To develop biocontrol methods against Botrytis, eight Trichoderma isolates were collected from Hydrangea or the plant soil substrate in the same cold room. Two Trichoderma isolates (E10SM, E014) from this study and one reference isolate (M03) exhibited a high degree of in vitro parasitism against B. cinerea, by comparison with Trichoderma C04 reference isolate (no parasitism). Culture filtrates of isolates E014 and M03 also showed significant in vitro antibiotic properties against B. cinerea growth. A pathosystem H. macrophylla – B. cinerea was set up in the greenhouse, with the inoculation of leaves using mycelial explants selected as the best infection mode. Using this pathosystem, a biocontrol assay showed a significant effect of M03 isolate towards B. cinerea, using Trichoderma conidia applied to leaves 5 h prior pathogen inoculation. After elicitor addition (B. cinerea grinded mycelia) in Trichoderma cultures, antagonistic potentialities of isolate C04 towards the pathogen was highly enhanced, reaching the inhibition level assessed with isolate M03 grown without elicitor. Optimisation of Trichoderma culture filtrates for antagonistic abilities was investigated, and specific cultural conditions were selected for M03 (12 g L−1 PDB, pH 4.2, 22°C, 22 days) and C04 (2.4 g L−1 PDB, pH 6.2, 13°C, 7 days). Overall, our results suggest great properties of several Trichoderma isolates for future development as biocontrol products.

Perillaldehyde Functions as a Potential Antifungal Agent by Triggering Metacaspase-Independent Apoptosis in Botrytis cinerea.

Botrytis cinerea, the causal agent of gray mold, is an important plant pathogen causing preharvest and postharvest diseases. Due to the extensive use of commercial fungicides, fungicide-resistant strains have emerged. Natural compounds with antifungal properties are widely present in various kinds of organisms. Perillaldehyde (PA), derived from the plant species Perilla frutescens, is generally recognized as a potent antimicrobial substance and to be safe to humans and the environment. In this study, we demonstrated that PA could significantly inhibit the mycelial growth of B. cinerea and reduced its pathogenicity on tomato leaves. We also found that PA had a significant protective effect on tomato, grape, and strawberry. The antifungal mechanism of PA was investigated by measuring the reactive oxygen species (ROS) accumulation, the intracellular Ca2+ level, the mitochondrial membrane potential, DNA fragmentation, and phosphatidylserine exposure. Further analyses revealed that PA promoted protein ubiquitination and induced autophagic activities and then triggered protein degradation. When the two metacaspase genes, BcMca1 and BcMca2, were knocked out from B. cinerea, all mutants did not exhibit reduced sensitivity to PA. These findings demonstrated that PA could induce metacaspase-independent apoptosis in B. cinerea. Based on our results, we proposed that PA could be used as an effective control agent for gray mold management. IMPORTANCE Botrytis cinerea causes gray mold disease, is considered one of the most important dangerous pathogens worldwide, and leads to severe economic losses worldwide. Due to the lack of resistant varieties of B. cinerea, gray mold control has mainly relied on application of synthetic fungicides. However, long-term and extensive use of synthetic fungicides has increased fungicide resistance in B. cinerea and is harmful to humans and the environment. In this study, we found that perillaldehyde has a significant protective effect on tomato, grape, and strawberry. We further characterized the antifungal mechanism of PA on B. cinerea. Our results indicated that PA induced apoptosis that was independent of metacaspase function.

Vapours from plant essential oils to manage tomato grey mould caused by Botrytiscinerea

Tomato grey mould has been a great concern during tomato production. The in vitro antifungal activity of vapours emitted from four plant essential oils (EOs) (cinnamon oil, fennel oil, origanum oil, and thyme oil) were evaluated during in vitro conidial germination and mycelial growth of Botrytis cinerea, the causal agent of grey mould. Cinnamon oil vapour was the most effective in suppressing conidial germination, whereas the four EOs showed similar activities regarding inhibiting mycelial growth in dose-dependent manners. The in planta protection effect of the four EO vapours was also investigated by measuring necrotic lesions on tomato leaves inoculated by B. cinerea. Grey mould lesions on the inoculated leaves were reduced by the vapours from cinnamon oil, origanum oil and thyme oil at different levels, but fennel oil did not limit the spread of the necrotic lesions. Decreases in cuticle defect, lipid peroxidation, and hydrogen peroxide production in the B. cinerea-inoculated leaves were correlated with reduced lesions by the cinnamon oil vapours. The reduced lesions by the cinnamon oil vapour were well matched with arrested fungal proliferation on the inoculated leaves. The cinnamon oil vapour regulated tomato defence-related gene expression in the leaves with or without fungal inoculation. These results suggest that the plant essential oil vapours, notably cinnamon oil vapour, can provide eco-friendly alternatives to manage grey mould during tomato production.

Agroecological Management of the Grey Mould Fungus Botrytis cinerea by Plant Growth-Promoting Bacteria.

Botrytis cinerea is the causal agent of grey mould and one of the most important plant pathogens in the world because of the damage it causes to fruits and vegetables. Although the application of botrycides is one of the most common plant protection strategies used in the world, the application of plant-beneficial bacteria might replace botrycides facilitating agroecological production practices. Based on this, we reviewed the different stages of B. cinerea infection in plants and the biocontrol mechanisms exerted by plant-beneficial bacteria, including the well-known plant growth-promoting bacteria (PGPB). Some PGPB mechanisms to control grey mould disease include antibiosis, space occupation, nutrient uptake, ethylene modulation, and the induction of plant defence mechanisms. In addition, recent studies on the action of anti-Botrytis compounds produced by PGPB and how they damage the conidial and mycelial structures of the pathogen are reviewed. Likewise, the advantages of individual inoculations of PGPB versus those that require the joint action of antagonist agents (microbial consortia) are discussed. Finally, it should be emphasised that PGPB are an excellent option to prevent grey mould in different crops and their use should be expanded for environmentally friendly agricultural practices.

Transcriptomic Analysis of Resistant and Wild-Type Botrytis cinerea Isolates Revealed Fludioxonil-Resistance Mechanisms.

Botrytis cinerea, the causal agent of gray mold, is one of the most destructive pathogens of cherry tomatoes, causing fruit decay and economic loss. Fludioxonil is an effective fungicide widely used for crop protection and is effective against tomato gray mold. The emergence of fungicide-resistant strains has made the control of B. cinerea more difficult. While the genome of B. cinerea is available, there are few reports regarding the large-scale functional annotation of the genome using expressed genes derived from transcriptomes, and the mechanism(s) underlying such fludioxonil resistance remain unclear. The present study prepared RNA-sequencing (RNA-seq) libraries for three B. cinerea strains (two highly resistant (LR and FR) versus one highly sensitive (S) to fludioxonil), with and without fludioxonil treatment, to identify fludioxonil responsive genes that associated to fungicide resistance. Functional enrichment analysis identified nine resistance related DEGs in the fludioxonil-induced LR and FR transcriptome that were simultaneously up-regulated, and seven resistance related DEGs down-regulated. These included adenosine triphosphate (ATP)-binding cassette (ABC) transporter-encoding genes, major facilitator superfamily (MFS) transporter-encoding genes, and the high-osmolarity glycerol (HOG) pathway homologues or related genes. The expression patterns of twelve out of the sixteen fludioxonil-responsive genes, obtained from the RNA-sequence data sets, were validated using quantitative real-time PCR (qRT-PCR). Based on RNA-sequence analysis, it was found that hybrid histidine kinase, fungal HHKs, such as BOS1, BcHHK2, and BcHHK17, probably involved in the fludioxonil resistance of B. cinerea, in addition, a number of ABC and MFS transporter genes that were not reported before, such as BcATRO, BMR1, BMR3, BcNMT1, BcAMF1, BcTOP1, BcVBA2, and BcYHK8, were differentially expressed in the fludioxonil-resistant strains, indicating that overexpression of these efflux transporters located in the plasma membranes may associate with the fludioxonil resistance mechanism of B. cinerea. All together, these lines of evidence allowed us to draw a general portrait of the anti-fludioxonil mechanisms for B. cinerea, and the assembled and annotated transcriptome data provide valuable genomic resources for further study of the molecular mechanisms of B. cinerea resistance to fludioxonil.

Biocontrol and Biostimulant Effect of a Fungal-Derived Extract in Commercial Varieties of Strawberry (Fragaria x ananassa Duch.)

Objective: Strawberry postharvest fruits and plants are mainly affected by the fungus Botrytis cinerea (B. cinerea), which causes grey mould rot. Biological control agents and biostimulants can effectively control this fungus and promote plant growth. This study aimed to evaluate the capacity of a novel fungal-derived extract called culture filtrate (CF) to biocontrol grey mould rot in postharvest strawberries and plants while promoting plant growth. Methods: The CF extract was obtained from the liquid culture of a strawberry pathogenic fungus, gauze-filtered and inactivated by autoclave. The Fragaria x ananassa cultivars Camino Real, Benicia, and Merced were used. For the postharvest assay, fruit natural decay was evaluated by simulating real storage conditions. For the phytopathological assays, first-generation plants inoculated with B. cinerea were evaluated 26 days post infection. The effect of CF on plant growth and biomass promotion was evaluated 60 days post treatment (DPT). Results: The treatment with CF yielded healthier fruits of the three varieties, which presented minor severity of grey mould symptoms compared to the controls treated with water or potato dextrose broth (PDB) by 7 DPT. For instance, 40% of Camino Real, 80% of Benicia, and 20% of Merced fruits presented an incipient lesion (severity 1), whereas no fruits treated with water or PDB showed this minor level of infection. On the contrary, around 50% and 70% of the control fruits presented the highest level of severity. Moreover, CF pre-treatment of Benicia “mother plants” protected first-generation untreated plants. Likewise, the best biostimulant effect was observed for Benicia plants, which presented an increased number of leaves and runner production 60 DPT. Conclusion: The fungal-derived extract CF constitutes a promising alternative to be used as a biological control agent of B. cinerea in strawberry. CF efficiently controlled the causal agent of grey mould in harvested strawberries and first-generation untreated plants. Yet, showed a minor effect as a plant growth promoter. Thus, the current study opens up the possibility to develop "phytovaccines" using extracts of almost any fungus, including pathogenic ones, as long as they are previously inactivated.

Characterization of the Mechanism of Action of Serratia rubidaea Mar61-01 against Botrytis cinerea in Strawberries.

Several bacterial strains belonging to Serratia spp. possess biocontrol capability, both against phytopathogens and human pathogenic species, thanks to the production of secondary metabolites, including as a red-pink, non-diffusible pigment, 2-methyl-3-pentyl-6-methoxyprodiginine (prodigiosin). Botrytis cinerea is the causal agent of gray mold, which is an economically relevant disease of many crops worldwide. Gray mold is normally controlled by chemical fungicides, but the environmental and health concerns about the overuse of pesticides call for environmentally friendly approaches, such as the use of biocontrol agents. In this study, the efficacy of a specific strain of Serratia rubidaea (Mar61-01) and its metabolite prodigiosin were assessed against B. cinerea under in vitro and in vivo conditions. This strain was effective against B. cinerea, and the effect of prodigiosin was confirmed under in vitro and in vivo conditions. The strain suppressed mycelial growth of B. cinerea (71.72%) in the dual-culture method. The volatile compounds produced by the strain inhibited mycelial growth and conidia germination of B. cinerea by 65.01% and 71.63%, respectively. Efficacy of prodigiosin produced by S. rubidaea Mar61-01 on mycelial biomass of B. cinerea was 94.15% at the highest concentration tested (420 µg/mL). The effect of prodigiosin on plant enzymes associated with induction of resistance was also studied, indicating that the activity of polyphenol oxidase (PPO), superoxide dismutase (SOD) and phenylalanine ammonia lyase (PAL) were increased when prodigiosin was added to the B. cinerea inoculum on strawberry fruits, while catalase (CAT) and peroxidase (POD) did not change. In addition, the volatile organic compounds (VOCs) produced by S. rubidaea Mar61-01 reduced mycelial growth and inhibited conidial germination of B. cinerea in vitro. The findings confirmed the relevant role of prodigiosin produced by S. rubidaea Mar61-01 in the biocontrol of B. cinerea of strawberries, but also indicate that there are multiple mechanisms of action, where the VOCs produced by the bacterium and the plant-defense reaction may contribute to the control of the phytopathogen. Serratia rubidaea Mar61-01 could be a suitable strain, both to enlarge our knowledge about the potential of Serratia as a biocontrol agent of B. cinerea and to develop new biofungicides to protect strawberries in post-harvest biocontrol.

Biochemical and genetic characterization of Botrytis cinerea laboratory mutants resistant to propamidine.

Botrytis cinerea, the causal agent of gray mold, is one of the top 10 fungal pathogens in the world. Propamidine, an aromatic diamidine compound, exhibited both protective and therapeutic effects against B. cinerea. However, the resistance risk and mechanism of B. cinerea to propamidine are unclear. Twelve high and stable resistant mutants were obtained from B. cinerea B05.10 by fungicide induction. Compared with the parental strain, the biological fitness of the mutants, including growth rate, spore germination, pathogenicity, and oxalic acid decreased significantly. There was no cross-resistance among propamidine and other commonly used fungicides, while the efficacy of propamidine against the resistance mutants declined. In addition, the cell membrane permeability, substance metabolism, and defense enzyme activities of the resistant mutants were significantly increased compared with the wild strain. Whole-genome sequencing of all resistant mutants found that there were 32 SNPs and nine InDels. Importantly, nine common single-point mutant genes in the exon region were found in all 12 resistant mutants, and these genes were related to multiple pathways in vivo, indicating that many factors contributed to the formation of propamidine resistance. These data suggested the resistance risk of B. cinerea to propamidine was low to moderate and the mechanism of propamidine was different from that of the existing fungicides. These results will increase understanding of the resistance mechanism of propamidine and provide a critical basis for the rational design of pesticide molecules based on targets. © 2022 Society of Chemical Industry.

Botrytis cinerea as the causal agent of grey mould on floral tissue of mango in Japan

In March 2016, grey mould disease was observed on mango (Mangifera indica) in Okinawa Prefecture, Japan. During the flowering period, the disease caused a brown coloration of the petals and peduncles accompanied by white aerial mycelium. As the disease symptoms progressed, the rot of panicle parts was accompanied by grey mould, resulting in fruit set failure. A fungus was isolated from the discoloured inflorescence into pure culture. Based on morphology and analyses of glyceraldehyde-3-phosphate dehydrogenase (g3pdh), heat-shock protein 60 (hsp60) and DNA-dependent RNA polymerase subunit II (rpb2) DNA sequences the fungus was identified as Botrytis cinerea. In an inoculation test, the isolate reproduced the symptoms observed on mango petals and peduncles and was reisolated from the flowers. This is the first report of B. cinerea as the causal agent of grey mould (haiirokabi-byo in Japanese) on floral tissue of mango in Japan.

Genetic and pathogenic variation of Botrytis cinerea, the causal agent of grey mould on Panax ginseng in China

Grey mould, caused by Botrytis cinerea, is an increasingly destructive disease of ginseng (Panax ginseng) in China. However, the extent of variation in the morphological characteristics of fungal colonies, genetic background and pathogenicity of different strains of this pathogen remains unknown. In this study, we isolated and identified 102 isolates of B. cinerea from ginseng. Among these, the sclerotial phenotype was dominant, followed by the mycelial and conidial phenotypes, with the proportion of each phenotype in the pathogen population showing no obvious variance across three provinces. Isolates were separated into three groups with differing pathogenicity, based on the diameter of the lesions they caused in pathogenicity tests; moderate-pathogenicity isolates were dominant, followed by strong- and weak-pathogenicity isolates. Variation was observed in the pathogenicity of isolates from three provinces. The Nei’s genetic diversity index and the Shannon’s information index of isolates from Jilin province was highest, followed by those from Liaoning, while isolates from Heilongjiang displayed the lowest genetic diversity. Furthermore, most of the genetic variance was found within the geographically defined B. cinerea populations; the low-genetic variance among populations was probably counteracted by gene flow. Results from this study provide a base understanding of genetic and pathogenic variation in B. cinerea populations from the main ginseng-growing regions of China, which will be helpful for further research and control of grey mould of ginseng.

Degradation of oxalic acid produced by Botrytis elliptica infection in two ploidy levels of Lilium rosthornii Diels.

Oxalic acid (OA) is a crucial pathogenic factor for Sclerotinia spp. fungi, which is closely related to Botrytis spp. fungi. Whether OA is a pathogenic factor for the causal agent of grey mould in lily, Botrytis elliptica, and the response of lily to OA are poorly understood. To address these questions, lesion tissues and deposition of calcium oxalate (CaOX) and callose were observed in diploid and tetraploid leaves of L. rosthornii after inoculation with B. elliptica. Oxalate oxidase (OXO) activity and the transcript levels of some genes related to OA degradation (LrGLP1, LrGLP2 and LrWRKY4), reactive oxygen species (ROS) production/scavenging systems (LrRBOHD, LrGST, LrPOD and LrAPX1) and pathogen-related protein (PR) synthesis (LrCHI, LrBGL and LrPR10) were compared. After diploid and tetraploid leaves inoculation, lesion tissue and callose and CaOX were separately observed around in guard cells and stomata rather than the epidermis in the infected area. OXO activity was triggered at 2 h post-inoculation (hpi) in both ploidy leaves, and it was higher in the latter from 12-48 hpi. Expression of LrGLP1, LrGLP2, LrRBOHD, LrGST, LrPOD, LrCHI, LrBGL and LrPR10 was higher in tetraploids than in diploids from 24(12)-36(48) hpi. In conclusion, for B. elliptica, OA mainly chelates Ca2+ from the stomata cell wall. The strong capability to degrade OA and higher expression levels of some genes related to ROS accumulation/scavenging and PR synthesis may partially explain the relatively higher grey mould resistance of tetraploid L. rosthornii.

Acinetobacter calcoaceticus SJ19 and Bacillus safensis SJ4, two Algerian rhizobacteria protecting tomato plants against Botrytis cinerea and promoting their growth

BackgroundBotrytis cinerea, the causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato. In many countries, including Algeria, the management of grey mould is a challenging problem, even with chemical control. This necessitates the search for other strategies. The objective of this study was to evaluate the biocontrol potential of two rhizospheric bacterial isolates for the protection of tomato against B. cinerea.ResultsOn tomato plants, the two bacterial isolates consistently provided high levels of protection (on average 72.1% for SJ19 and 52.3% for SJ4). Their applications as a 1:1 mixture reinforced their effect (87.8% protection), indicating their compatibility and a potential use as a consortium. In vitro, the isolates significantly inhibited the mycelial growth of B. cinerea strains, both through direct confrontation in dual-culture assays (12–69% inhibition) and through the production of volatile compounds (36–46% inhibition). The two isolates, applied as seed treatment and as drench on seedlings, also showed strong growth-promoting effects on tomatoes. They substantially increased the length and fresh weight of shoots and roots, as well as stem diameter, leaf number and chlorophyll content, compared to untreated plants.ConclusionThe two bacteria tested in this study showed a high potential for use as biostimulants and as biofungicides against tomato grey mould.

Root treatment with a vitamin K3 derivative: a promising alternative to synthetic fungicides against Botrytis cinerea in tomato plants.

Botrytis cinerea, the causal agent of gray mold has a great economic impact on several important crops. This necrotrophic fungus causes disease symptoms during vegetative growth and also into postharvest stages. The current method to combat this disease is fungicide application, with high economic costs and environmentally unsustainable impacts. Moreover, there is an increasing general public health concern about these strategies of crop protection. We studied the protection of tomato plants against B. cinerea by previous root treatment with menadione sodium bisulfite (MSB), a known plant defense activator. Root treatment 48 h before inoculation with MSB 0.6 mmol L-1 reduced leaf lesion diameter by 30% and notably cell deaths, compared to control plants 72 h after inoculation. We studied the expression level of several pathogenesis-related (PR) genes from different defense transduction pathways, and found that MSB primes higher PR1 expression against B. cinerea. However, this stronger induced resistance was impaired in transgenic salicylic acid-deficient NahG line. Additionally, in the absence of pathogen challenge, MSB increased tomato plant growth by 28% after 10 days. Our data provide evidence that MSB protects tomato plants against B. cinerea by priming defense responses through the salicylic acid (SA)-dependent signaling pathway and reducing oxidative stress. This work confirms the efficacy of MSB as plant defense activator against B. cinerea and presents a novel alternative to combat gray mold in important crops.

Antifungal compound, methyl hippurate from Bacillus velezensis CE 100 and its inhibitory effect on growth of Botrytis cinerea.

Botrytis cinerea, the causal agent of gray mold is one of the major devastating fungal pathogens that occurs in strawberry cultivation and leads to massive losses. Due to the rapid emergence of resistant strains in recent years, an ecofriendly disease management strategy needs to be developed to control this aggressive pathogen. Bacillus velezensis CE 100 exhibited strong antagonistic activity with 53.05% against B. cinerea by dual culture method. In the present study, 50% of culture filtrate supplemented into PDA medium absolutely inhibited mycelial growth of B. cinerea whereas the highest concentration (960mg/L) of different crude extracts including ethyl acetate, chloroform, and n-butanol crude extracts of B. velezensis CE 100, strongly inhibited mycelial growth of B. cinerea with the highest inhibition of 79.26%, 70.21% and 69.59% respectively, resulting in severe damage to hyphal structures with bulging and swellings. Hence, the antifungal compound responsible was progressively separated from ethyl acetate crude extract using medium pressure liquid chromatography. The purified compound was identified as methyl hippurate by nuclear magnetic resonance and mass spectrometry. The inhibitory effect of methyl hippurate on both spore germination and mycelial growth of B. cinerea was revealed by its dose-dependent pattern. The spore germination rate was completely restricted at a concentration of 3mg/mL of methyl hippurate whereas no mycelial growth was observed in agar medium supplemented with 4mg/mL and 6mg/mL of methyl hippurate by poisoned food method. Microscopic imaging revealed that the morphologies of spores were severely altered by long-time exposure to methyl hippurate at concentrations of 1mg/mL, 2mg/mL and 3mg/mL and hyphae of B. cinerea were severely deformed by exposure to methyl hippurate at concentrations of 2mg/mL, 4mg/mL and 6mg/mL. No significant inhibition on tomato seed germination was observed in treatments with methyl hippurate (2mg/mL) for both 6h and 12h soaking period as compared to the controls. Based on these results, B. velezensis CE 100 could be considered a potential agent for development of environmentally friendly disease control strategies as a consequence of the synergetic interactions of diverse crude metabolites and methyl hippurate.

Alginate oligosaccharide improves resistance to postharvest decay and quality in kiwifruit (Actinidia deliciosa cv. Bruno)

Kiwifruit is an extremely perishable fruit; postharvest disease and senescence during storage can reduce the fruit quality, resulting in economic loss. Considerable research effort has focused on identifying safe and cost-effective ways to preserve fresh kiwifruit. To this end, the present study investigated the effects of alginate oligosaccharide (AOS) soaking treatment on postharvest quality and disease in the ‘Bruno’ variety of kiwifruit. The involved physiological mechanisms were further explored. The results showed that AOS did not inhibit the growth of Botrytis cinerea in vitro, the causal agent of gray mold in kiwifruit, but reduced the incidence of gray mold and diameter of lesions of kiwifruit during storage. Kiwifruit treated with 50 mg · L−1 AOS showed a higher degree of firmness and lower soluble solid content than control fruit treated with distilled water. Moreover, AOS treatment inhibited the activity of polygalacturonase and pectinesterase, while enhancing the activity of polyphenoloxidase, l-phenylalanine ammonia lyase and β-1,3-glucanase related to pathogen defense, and also improved total antioxidant capacity determined by the DPPH, FRAP, and ABTS methods in kiwifruit. These results indicate that 50 mg · L−1 AOS can confer disease resistance in kiwifruit during storage.

Actinomycete as biocontrol agents against tomato gray mold disease caused by Botrytis cinerea

The present work aims to isolate actinomycete bacteria with antagonistic abilities towards Botrytis cinerea, the causal agent of gray mold, from a soil sample collected from the rhizosphere of a healthy tomato grove. In vitro confrontation led to the isolation of 104 actinomycete isolates; fifteen isolates have shown the most significant mortality rate of the mycelial growth of B. cinerea (>50%). Based on the results of this screening, representative strains were selected to verify their in vivo antagonistic activity on tomato fruits; the reduction of B. cinerea has a percentage ranging from 52.38% to 96.19%. Furthermore, the actinomycete isolates were evaluated for their plant growth-promoting (PGP) properties and their ability to produce biocontrol-related extracellular enzymes viz., amylase, protease, cellulase, chitinase, esterases, and lecithinase. Indeed, Ac70 showed high β-1,3-glucanase activity and siderophore production (17U/ml and 43% respectively), and the highest chitinase activity (39μmol/ml) was observed for Ac24. These results indicated that these actinomycetes might potentially control gray mold caused by B. cinerea on tomato fruits. Investigations on enhancing the efficacy and survival of the biocontrol agent in planta and finding out the best formulation are recommended for future research.