Gray Mold Severity Research Articles

Efficacy and Molecular Mechanisms of Nystatin Against Botrytis cinerea on Postharvest Table Grape

The primary cause of postharvest loss in table grape fruit is attributed to gray mold, which is caused by Botrytis cinerea. The present study confirmed the inhibitory effects of nystatin on the growth and development of B. cinerea, which led to a remarkable reduction in the severity of gray mold on table grape fruits. Furthermore, the application of nystatin disrupted the membrane permeability of B. cinerea, causing increased cellular leakage and cell death. In addition, the transcriptome analysis showed that the application of nystatin effectively modulated the transcriptional profile of genes involved in ribosome and mitochondrion biogenesis, as well as oxidoreductase activity, thereby disrupting the homeostasis of cellular organelles. Moreover, the nystatin treatment down-regulated genes associated with membrane trafficking, protein degradation by the ubiquitin–proteasome system, and the autophagy process, ultimately attenuating the pathogenicity of B. cinerea. Collectively, nystatin can be considered a viable agent for managing gray mold on table grape fruit.

Effect of Black Soldier Fly Larvae Frass as Organic Fertilizer on Postharvest Quality and Shelf Life of Open-field-grown Tomato (Solanum lycopersicon L.)

Open-field-grown tomatoes in Saudi Arabia are stressed by poor soil fertility because of the low organic matter content, low nutrient availability, and high pH. Thus, high chemical fertilizer inputs are crucial for commercial production; however, they cause economic loss as well as negatively affect environmental sustainability. The use of efficient organic fertilizers would be useful for developing more cost-effective, environmentally friendly, and sustainable agriculture. The current study evaluated the impact of Black soldier fly (Hermetia illucens L.) frass (BSFF) fertilizer applications as organic fertilizer on postharvest fruit quality and shelf life of open-field-grown F1 hybrid ‘Sinag Tala’ tomatoes compared with those grown under control treatment (received recommended doses of chemical fertilizers for tomato production under open field conditions). The experiment was conducted using a randomized complete block design with four replicates. The results showed that the application of BSFF fertilizer, especially at the higher rate (5 ton/ha; BSFF3), improved the overall quality of tomato fruit. The BSFF fertilizer treatments reduced weight loss, maintained higher firmness, antioxidants [vitamin C, total phenol content (TPC) and total flavinoid (TFC)], total soluble solids (TSS), and titratable acidity (TA) contents, and lowered the TSS/TA ratio of fruits during shelf life compared with those of the control. The decay incidence was only detected after 9 days of shelf life and was significantly lower in all the BSFF fertilizer treatments (range, 8.40%-12.05%) than in the control (15.9%). In addition, BSFF fertilizer treatments reduced both disease incidence and severity of gray mold following pathogen inoculation during shelf life compared with those of the control. These results might be attributable to the higher antioxidants content (vitamin C, TPC, and TFC) and higher polyphenol oxidase activity in BSFF-fertilized tomatoes. In conclusion, BSFF fertilizer could be used as a potential eco-friendly alternative to chemical fertilizers to improve tomato fruit quality during shelf life.

Selection and application of methanol-utilizing bacteria from tomato leaves for biocontrol of gray mold.

Gray mold, caused by Botrytis cinerea, is a significant threat to tomato production. Traditional chemical control methods have become increasingly ineffective because of the development of resistance. This study aimed to isolate methanol-utilizing bacteria from tomato leaves and evaluate their biocontrol potential against gray mold. To obtain bacterial suspensions, tomato leaf samples were collected and washed. We analyzed the microbial communities of these samples using 16S rRNA amplicon sequencing and identified several methylotrophic strains. Among these, 405 isolated strains were cultivated on a solid low-nutrient inorganic salt medium containing methanol, and 7 strains exhibiting considerable antifungal activity against B. cinerea were identified. Greenhouse tests revealed that two strains-SY163 and SY183-significantly reduced the severity of gray mold on tomato leaves. Disease index scores and the area under the disease progress curve values confirmed the efficacy of these strains as biocontrol agents. Statistical analysis indicated the effectiveness of pre- and co-application of these strains with B. cinerea. Phylogenetic analysis identified Serratia rubidaea as the inhibitory strain. The biocontrol activity is likely mediated through the production of antifungal compounds and suppression of B. cinerea sporulation. This study provides the basis for developing a technology of gray mold suppression by controlling the abundance of S. rubidaea in plant microbial communities.

Biocontrol efficacy of Botrytis cinerea on postharvest tomato fruit by the endophytic bacterium Bacillus velezensis BE1

Endophytic bacteria offer numerous advantages in the control of postharvest diseases. Bacillus velezensis has been identified as a promising biocontrol agent against postharvest pathogens in various fruits and vegetables. In this study, B. velezensis BE1 was identified by 16S rRNA sequencing and caused 76.9 % inhibition against Botrytis cinerea in dual culture assay. The cell-free culture filtrate (CFCF) of B. velezensis strongly inhibited the growth, spore germination, and germ tube elongation of B. cinerea. Moreover, 11 bioactive compounds were identified in the CFCF using gas chromatography-mass spectrometry, and phthalic acid, dioctyl ester was the predominant component by 72.92 %. Scanning and transmission electron microscopy observations revealed that the CFCF causes irreversible morphological and ultrastructural damage to the fungal hyphae and conidia, including deformed, wrinkled, lysis, collapse, and degradation of cytoplasmic organelles. The incidence and severity of gray mold were significantly suppressed after applying CFCF at 50 % in tomato fruit. The application of CFCF caused an increase in the total phenolics and flavonoids content in tomato fruit compared with the control throughout the experiment. Furthermore, the activities of enzymes associated with defense such as phenylalanine ammonia-lyase, polyphenoloxidase, and peroxidase were significantly higher in the treated tomatoes relative to the untreated group. These results indicate that B. velezensis BE1 has significant potential as an effective biocontrol agent against the pathogen B. cinerea, offering a valuable approach for controlling gray mold in postharvest fruit.

Theanine enhances resistance to Botrytis cinerea in postharvest strawberry fruit via modulating cell-wall and phenylpropanoid metabolisms

Theanine (N-ethyl-γ-glutamine), as a unique non-protein amino acid, plays vital roles in abiotic stress resistance, while its roles in biotic stress resistance are still unclear. Gray mold caused by Botrytis cinerea is a major disease in strawberries. Effects of theanine on the development of gray mold, cell-wall and phenylpropanoid metabolisms in strawberries were investigated in this study. Results showed that 5 mmol L−1 theanine treatment reduced disease incidence and severity of gray mold in strawberries with antifungal activity in vitro. Meanwhile, theanine treatment enhanced the accumulation of phenolic compounds and lignin, especially ellagic acid, cyanidin, and quercetin, which was associated with increased phenylpropanoid pathway related enzyme activities. Moreover, theanine induced callose deposition and suppressed cell- wall disassembling enzymes, accompanied by higher levels of water insoluble pectin, hemicellulose and cellulose. Therefore, theanine treatment could alleviate decay of B. cinerea-inoculated strawberries by regulating phenylpropanoid and cell-wall metabolisms, maintaining higher levels of phenolic compounds and cell-wall components, thereby contributing to disease resistance and cell-wall structure integrity.

24-Epibrassinolide improves quality and resistance against Botrytis cinerea of harvest table grapes through modulating reactive oxygen species homeostasis

24-epibrassinolide (EBR) application has been proven to be effective in the control of gray mold (Botrytis cinerea) and preservation in table grape, however, the possible underlying mechanism of EBR on maintaining the postharvest quality and controlling gray mold of table grape are incompletely understood. In this study, the application of EBR at veraison (T1) and postharvest (T2) could effectively alleviate the quality deterioration of table grapes during storage, as observed by higher fruit firmness, rachis chlorophyll content, titratable acidity, and total soluble solid, and lower shattering rate, decay incidence, weight loss rate, browning index and relative electrolyte leakage of rachis, and respiration rate. Moreover, EBR application inhibited the excess accumulation of superoxide anion, hydrogen peroxide (H2O2), malondialdehyde, and the expression of hydrogen peroxide sensor (HPCA) genes (VvHPCA1, VvHPCA2, and VvHPXA3). In addition, T1 and T2 treatments resulted in higher activities of superoxide dismutase, peroxidase, catalase, and superoxide anion, as well as the expression level of their corresponding gene expression. A considerable increase in key enzyme activities, antioxidant content, and gene expression in the ascorbate-glutathione (ASA-GSH) cycle was also observed in grape fruit treated with EBR. Importantly, the multivariate statistical analysis revealed that T2 treatment had a more remarkable effect on preserving the quality of postharvest grapes. In addition, under artificial infections, EBR treatment significantly reduced gray mold severity in table grapes and reduced malondialdehyde and superoxide anion generation while exhibiting no antifungal activity in vitro. Simultaneously, defensive enzyme activities, including peroxidase, polyphenol oxidase, chitinase, and β-1,3-glucanase, were remarkably increased in fruit treated with EBR. Therefore, our findings suggest that exogenous application of EBR maintains the quality of postharvest grapes and improves the resistance of table grapes to gray mold during postharvest storage by regulating oxidative stress and the activity of antioxidant enzymes and defensive enzymes.

Integration of mathematical modeling and target-based application of biocontrol agents for the control of Botrytis cinerea in vineyards.

Biocontrol agents (BCAs) are alternatives to synthetic fungicides with low risk to the environment and human health. Although several studies on the biocontrol of gray mold in vineyards have been performed, it is necessary to improve the usage of BCAs in fields conditions. Therefore, in the present study, BCAs were used both in calendar-based [based on four growth stages (GSs), i.e., flowering, pre-bunch closure, veraison, and before harvest] and predictive model-based strategies (only when Botrytis cinerea infection risk was predicted by the model). The BCAs applied during the seasons were selected considering the grapevine GSs. Treatments performed with BCAs were compared with synthetic fungicide treatments and an untreated control. The trials were conducted in three experimental vineyards with four epidemics. To evaluate the level of gray mold control of each treatment, disease severity was assessed at harvest and the presence of latent infection was evaluated. The integrative use of the predictive model and BCAs provided satisfactory levels of gray mold control, with gray mold severity levels significantly lower (P < 0.001) than those of the untreated control, which had severity values (< 7%) similar to those observed with synthetic fungicides following both calendar and model-based strategies. The integrative use of the predictive model and BCAs represents a valid alternative to conventional methods of gray mold control in vineyards, with more than 75% reduction in fungicide usage. © 2024 Society of Chemical Industry.

Postharvest application of natamycin to control gray mold in table grapes

Gray mold caused by Botrytis cinerea is the most economically important postharvest disease of table grapes in California. In this study, the efficacy of the new biofungicide natamycin in controlling gray mold and its effects on fruit quality of table grapes were evaluated on two varieties. Four rates of natamycin treatment, ‘full’ (a.i. 920 mg L−1), ‘half’ (a.i. 460 mg L−1), ‘quarter’ (a. i. 230 mg L−1), and ‘eighth’ (a.i. 115 mg L−1) of the label rate, administered through dipping or spraying, were tested on grape berries that were with or without inoculation with B. cinerea prior to the treatment at 20 °C for 4 d or at 1 °C for 4 w. Natamycin significantly reduced percentage and severity of gray mold on the grape berries inoculated with B. cinerea, regardless of application methods, grape varieties, and incubation temperatures. Natamycin at all four rates also significantly reduced the percentage of grape berries showing fruit rots resulting from naturally occurring infections after the storage at 1 °C for 4 w, in comparison with the non-treated control, and remained effective when the fruit were evaluated after four-week cold storage followed by additional two days at 20 °C. Natamycin, however, had little effect on the spread of gray mold (nesting) within the grape cluster via fruit contact by mycelium of B. cinerea. Natamycin did not have any negative effects on the fruit quality parameters such as the appearance of grape rachis, firmness of berries, soluble solids, and titratable acidity. Our findings indicated that natamycin can be an effective postharvest treatment for managing gray mold on table grapes during storage.

Digital Twins analysis as a tool to find new descriptors for grapevine bunch morphology categorisation and grey mould infection risk evaluation

Botrytis cinerea is one of the most destructive diseases for Vitis vinifera, and grape bunch morphology plays a crucial role in grey mould infection. However, the common visual evaluation technique for assessing bunch compactness suffers from a lack of sensitivity and objectivity. This study proposes a standardised digital twin shape analysis to evaluate the morphology of grape bunches. Seventeen Pinot Gris and six Pinot Noir clones were considered. The grey mould severity was evaluated in the field. Fully ripened bunches (138) were gathered and then photographed at different angles. Digital twin reconstruction was carried out using the photogrammetry technique. Several measures and indices were extracted from each digital twin. Principal component analysis and multiple linear regression models were applied to identify the descriptors most related to grey mould symptoms. The results revealed that the most significant factors include the berries density, the estimated empty volume, and the bunch width. These results show that digital twins are a suitable tool for estimating grey mould infection risks. Two linear models, divided into 2D and 3D descriptor models, were proposed. The R-squared value and the root mean square error were compared between the models. For Pinot Gris, from the 2D to the 3D models, the R-squared value rose from 0.656 to 0.838, while the error decreased from 1.713 to 1.175. In Pinot Noir, the 2D model did not provide sufficient robustness, while the 3D model had an R-squared value of 0.936 and an error of 0.290.

Antifungal effect of volatile organic compounds (VOCs) release from Antarctic bacteria under postharvest conditions

The generation of biological control agents for postharvest fungal control has prompted the search for different natural sources due to studies indicating adverse effects that may be related to the use of conventional fungicides (e.g., SO2). Some bacteria that have the ability to generate volatile organic compounds (VOCs) with antifungal activity stand out in this regard. Thus, the Antarctic bacterium Pseudomonas sp. AN3A02, which can grow in very cold environments with low nutrient availability, has shown a fungistatic effect on Botrytis cinerea in dual culture. In this study, in vitro assays were performed to evaluate its effect and activity on strains of B. cinerea isolated from blueberries using dual-plate assays. An antifungal assay (in vivo) was performed by artificial wounding on blueberries inoculated with B. cinerea (1 ×106 conidia/mL) and stored at 0 °C for 20 d plus 3 d at 20 °C. The results obtained showed that in the presence of the bacteria, the severity of gray mold on blueberries was reduced by 71.38 %. In addition, this bacterium released a diversity of VOCs, including alcohols (1-octanol, 10.3 %), aldehydes (paraldehyde, 2.1 %), esters (ethyl butyrate, 4 %; isoamyl acetate, 2 %), ketones (2-nonanone, 1.4 %), terpenes (linalool, 1.9 %; D-limonene, 0.7 %), phenolic derivatives (2,4-di-tert-butylphenol, 2.5 %) and other groups, which were identified by GC–MS. The release of VOCs affects and modifies the hyphae and germ tube of B. cinerea, influencing its growth. Therefore, a new and environmentally friendly alternative for postharvest pathogen control could be generated based on this Antarctic microorganism.

Effect of phyllosphere and spike mycoflora on castor gray mold incited by Amphobotrys ricini

Gray mold of castor incited by Amphobotrys ricini is an economically important disease causing heavy lossesduring capsule formation stage under high humid conditions. The phyllosphere and spike mycoflora were isolated from castor and tested for their bioefficacy against gray mold under laboratory and greenhouse conditions. The mycoflora isolated were identified based on morphological characters as species of Acremonium, Aspergillus, Choanephora, Cladosporium, Fusarium, Macrophomina and Penicillium. Among the mycoflora tested in vitro, highest inhibition of the test pathogen was recorded with Acremonium species. Greenhouse evaluation of phyllosphere and spike mycoflora by detached spike method has shown that inoculation of detached spikes with Penicillium spp. 24 hours prior to pathogen inoculation has significantly reduced gray mold severity compared to control.

Diagrammatic scale to evaluate the severity of gray mold (Botrytis cinerea) in pomegranate

The aim of this study was to design and validate a diagrammatic scale to estimate the severity of gray mold induced by Botrytis cinerea in pomegranate cultivation. A total of 120 healthy and diseased fruits with varying degrees of affliction were collected from orchards with active production located in the municipalities of Chilcuahutla and Taxquillo in the state of Hidalgo, Mexico (20° 18’ 11’’ N, 99° 14’ 23’’ W, 20° 32’ 01’’ N, 99° 20’ 03’’ W, respectively). From these, 60 were selected to determine the severity percentage, according to a 6-class scale (Class 0 = 0%, Class 1 = &gt;0% - 5% - 10%, Class 2 = &gt;10% - 25% - 50%, Class 3 = &gt;50% - 75% - 85%, Class 4 = &gt;85% - 90% - 95%, and Class 5 = &gt;95% - 100%), using the 2LOG software. With the obtained data, representative images were selected to build the diagrammatic scale using Adobe Photoshop. The accuracy (r2 ), precision (β0 ), and reproducibility (β1 ) were verified by simple linear regression applied to the data obtained by 12 evaluators with and without experience in the observation of plant diseases. As a result, values of r2 of 0.42 and 0.85 were obtained, without and with the use of the scale, respectively, which confirmed that this tool is suitable to evaluate the severity of the disease accurately and reproducibly.

Biological control of strawberry diseases by Aureobasidium pullulans and sugar beet extract under field conditions

Grey mould (caused by Botrytis cinerea) is the most important pathogen underlying high fungicide dependence in strawberry fields. Reliable biocontrol agents (BCAs) with improved efficiency are needed to replace fungicides. The yeast-like beneficial fungus Aureobasidium pullulans (AP-SLU6) has previously exhibited great potential to combat grey mould in greenhouse environments. Here we report results from a two-year full-factorial field trial in a conventional strawberry field, in which we tested two different concentrations of A. pullulans (107 CFU/ml and 106 CFU/ml) and sugar beet extract (SBE). The results showed that all the field treatments reduced grey mould severity postharvest and increased shelf life of the harvested fruit in both years. The best effect was achieved using the highest conidial concentration of A. pullulans, which also resulted in 53% higher fruit production compared to the control treatment at the end of the season, indicating a plant-growth promoting effect of the BCA. These results reveal that spray applications of these novel BCAs contribute to reliable biocontrol of grey mould, leading to improvement of the shelf life of strawberry sales boxes. These findings suggest that A. pullulans and SBE can contribute to a shift from chemical fungicides to sustainable methods without compromising cropping security.

Efficacy of preharvest application of biocontrol agents against gray mold in grapevine.

The use of biocontrol agents (BCAs) represents a promising alternative to conventional methods for the management of gray mold in vineyards during the berry ripening stage. The main advantages of BCAs are the short preharvest interval and lack of chemical fungicide residues in wine. In this study, eight commercial BCAs (based on different Bacillus or Trichoderma species and strains, Aureobasidium pullulans, Metschnikowia fructicola, and Pythium oligandrum) and a reference fungicide (boscalid) were applied to a vineyard during berry ripening over three seasons to evaluate the dynamics over time in terms of their relative efficacies in gray mold control. At 1-13 days after application of BCAs to the berry surfaces in field conditions, the berries were collected and artificially inoculated with conidia of Botrytis cinerea under controlled laboratory conditions, and gray mold severity was observed after 7 days of incubation. Significant differences were observed in gray mold severity among years, according to the number of days the BCAs grew on the berry surface before B. cinerea inoculation, and the season by day interaction (altogether accounting for >80% of the experimental variance). The variability in BCA efficacy was closely related to the environmental conditions at the time of application and in the following days. Overall, the BCA efficacy increased with the degree days accumulated between BCA application in the vineyard and B. cinerea inoculation in the dry (no rain) periods (r = 0.914, P = 0.001). Rainfall and the associated drop in temperature caused a relevant reduction of BCA efficacy. These results demonstrate that BCAs are an effective alternative to conventional chemicals for the preharvest control of gray mold in vineyards. However, environmental conditions can considerably affect the BCA efficacy.

Intermittent changes in temperature and humidity repress gray mold in tomato.

Environmental temperature and humidity play a vital role in plant-pathogen interactions, which profoundly affect the occurrence of crop diseases. However, the specific methods and mechanisms through which intermittent changes in temperature and humidity mitigate plant diseases remain unclear. In this study, six temperature and humidity combinations were set, the disease severity of tomatoes, biomass of Botrytis cinerea were analyzed, and the infection process of pathogens was observed using an optical microscope. Furthermore, dual RNA-seq analysis was performed to explore the interactions between plants and pathogens. Results showed that the 24hpi-12h day (regulation was performed at 24hpi (hours post-inoculation) for 12h after inoculation during the day) treatment reduced the gray mold severity and biomass of B. cinerea in plants by the greatest amount and effectively inhibited the growth of mycelia. The 24hpi-12h day treatment induced the up-regulation of light reactions, photorespiration, and Calvin cycle-related genes in tomatoes, whereas fungal genes related to the biosynthesis of sesquiterpene botrydial and polyketide botcinic acid were downregulated. Overall, we identified the optimal combination of temperature and humidity changes to inhibit the development of tomato gray mold, and preliminarily explored the interactions between tomato and B. cinerea under temperature and humidity changes. This work has practical importance and provides a theoretical basis for the ecological control of plant diseases.

Molecular dissection of rose and Botrytis cinerea pathosystems affected by ethylene

Botrytis cinerea (B. cinerea) is a necrotrophic pathogen that causes significant growth and postharvest commercial losses in cut roses. Postharvest disease severity is affected by ethylene levels during transport and storage conditions. In this study, we identified the relationship between ethylene, fungal growth, and ethylene inhibitors during B. cinerea infection in cut ‘Pink Beauty’ roses. The results suggest that cut rose susceptibility to gray mold disease is associated with the developmental stage of flowers, especially the level of senescence, which is stimulated by ethylene biosynthesis in petals. The mRNA levels of ethylene biosynthesis genes in petals were related to the severity of gray mold; however, their expression levels decreased when the cut roses were completely macerated by B. cinerea. B. cinerea infections in cut flowers activated ethylene biosynthesis and signaling pathways, leading to the activation of RhERFs in the petals. Ethylene regulated the development of B. cinerea infections in the cut flowers directly by binding to the receptors or indirectly by promoting the ethylene response in the host tissues. The suppression of ethylene responses in petals and inhibition of the fungal histidine kinase receptor of B. cinerea by 1-methylcylopropene (1-MCP) made cut rose flowers resistant to such necrotrophic pathogens. We also established a working model for ethylene binding and plant and fungus actions in the rose-B. cinerea pathosystem. Understanding the relationship between ethylene and gray mold disease in cut roses and the interaction between ethylene inhibitors and B. cinerea will help improve postharvest treatments for reducing B. cinerea damage in cut flowers.

Exogenous Melatonin Treatment Induces Disease Resistance against Botrytis cinerea on Post-Harvest Grapes by Activating Defence Responses.

Botrytis cinerea seriously affects the value of post-harvest grapes. Melatonin can act as an exogenous regulator in the resistance of exogenous pathogens due to its antioxidant activity. An artificial inoculation trial was conducted to research the induced resistance mechanism of melatonin treatment using the table grape “Muscat Hamburg” (Vitis vinifera L. cv). Grapes were immersed with 0.02, 0.2, and 2 mmol/L melatonin, followed by B. cinerea suspension injections after 48 h. The results showed that the mycelial growth and spore germination of B. cinerea was not significantly inhibited by melatonin at different concentrations (0.02–2 mmol/L). However, post-harvest melatonin treatment inhibited the increase of disease incidence and severity of grey mould, induced the synthesis and accumulation of total phenols and flavonoids, reduced malondialdehyde generation, and inhibited an increase in cell membrane permeability. Meanwhile, defensive enzyme activities, including superoxide dismutase (SOD), peroxidize (POD), catalase (CAT), phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), chitinase (CHI), and β-1,3-glucanase, were significantly increased in fruits treated with exogenous melatonin. These results suggested that exogenous melatonin treatment could activate defence responses to combat the infection of B. cinerea in post-harvest grapes.

Trichoderma harzianum to control botrytis cinerea and High-dynamized dilutions of Silicia terra to promote plant growth on the strawberry culture: methods for sustainable farming practices

Agroecological interventions for pest and disease management include several strategies to enhance homeostasis of the crop. Biological agents and homeopathic remedies are innovative and efficient agriculture technologies in the production of pesticide-free food. The objective of this work was to evaluate the effects of the biological control Trichoderma spp. and high-dynamized dilutions of Silicea terra to manage grey mould (Botrytis cinerea) and to promote growth in strawberry plants cv. San Andreas. The experiment was carried out in a greenhouse at EPAGRI experimental station, Lages-SC, 2017. The experimental design consisted of six treatments and five repetitions which were completely randomised. Each plot consisted of a strawberry plant cultivated in a 3.6 L plastic pot. Leaf area, number of leaves, root and leaf weights were assessed. The incidence and severity of grey mould on fruits was also evaluated. The statistical analysis was done by environment R®. Plants treated with Trichoderma spp. (WP formulation) resulted in a lower fruit incidence of B. cinerea fruits in all evaluated periods. Plants treated with Silicea12CH showed wider leaf area, produced more leaves during the cycle and had greater root weight.

Bacillus pumilus PTB180 and Bacillus subtilis PTB185: Production of lipopeptides, antifungal activity, and biocontrol ability against Botrytis cinerea

Bacillus pumilus strain PTB180 and Bacillus subtilis strain PTB185 were recently reported for their strong in vitro antagonistic activity against several plant pathogens including Fusarium oxysporum, Rhizoctonia solani, Sclerotinia sclerotiorum, Phytophthora capsici, and Pythium ultimum. In this study, strains PTB180 and PTB185 were investigated for the production of lipopetides (LPs), antifungal activity, and biocontrol capabilities against Botrytis cinerea. Strain PTB185 was shown to secrete LPs of the surfactin, iturin, and fengycin families while strain PTB180 was shown to secrete exclusively surfactins. Dual-culture overlay assays indicated that both strains produced antifungal compound(s) that strongly inhibit(s) B. cinerea mycelial growth and conidial germination. The strains were shown to survive for at least 21 days with a survival rate varying from 43% to 61% in the tomato phyllosphere. Survival rate of both PTB180 and PTB185 was approximately 50% when they were applied as a mix (1:1) with almost no variation in the proportion of each strain over time. Preventive foliar applications of the strains alone or as a mix (1:1) reduced significantly (P ≤ 0.01) the incidence and severity of gray mold on tomato plants grown in greenhouse as compared to the control. Incidence and severity of gray mold of tomato plants treated with PTB180, PTB185, or mix of both strains (1:1) were not significantly different. Although PTB180 and PTB185 have a different LPs signature, they showed (1) comparable in vitro antagonistic activity against B. cinerea, (2) comparable survival in the phyllosphere of tomato plants, and (3) comparable biocontrol activity against B. cinerea on tomato plants.

An innovative green synthesis approach of chitosan nanoparticles and their inhibitory activity against phytopathogenic Botrytis cinerea on strawberry leaves

Green synthesis is a newly emerging field of nanobiotechnology that offers economic and environmental advantages over traditional chemical and physical protocols. Nontoxic, eco-friendly, and biosafe materials are used to implement sustainable processes. The current work proposes a new biological-based strategy for the biosynthesis of chitosan nanoparticles (CNPs) using Pelargonium graveolens leaves extract. The bioconversion process of CNPs was maximized using the response surface methodology. The best combination of the tested parameters that maximized the biosynthesis process was the incubation of plant extract with 1.08% chitosan at 50.38 °C for 57.53 min., yielding 9.82 ± 3 mg CNPs/mL. Investigation of CNPs by SEM, TEM, EDXS, zeta potential, FTIR, XRD, TGA, and DSC proved the bioconversion process's success. Furthermore, the antifungal activity of the biosynthesized CNPs was screened against a severe isolate of the phytopathogenic Botrytis cinerea. CNPs exerted efficient activity against the fungal growth. On strawberry leaves, 25 mg CNPs/mL reduced the symptoms of gray mold severity down to 3%. The higher concentration of CNPs (50 mg/mL) was found to have a reverse effect on the infected area compared with those of lower concentrations (12.5 and 25 mg CNPs/mL). Therefore, additional work is encouraged to reduce the harmful side effects of elevated CNPs concentrations.