Incidence Of Gray Mold Research Articles

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.

Electrical Stimulation Enhances Plant Defense Response in Grapevine through Salicylic Acid-Dependent Defense Pathway.

Concern over environmental pollution generated by chemical fungicides has led to the introduction of alternative pest management strategies to chemical fungicide application. One of those strategies is the induction of plant defense response by an abiotic elicitor. In the present study, field-grown grapevines were subjected to electrical stimulation using a solar panel from two weeks before flowering to harvest in the 2016 and 2020 growing seasons. In both years, electrical stimulation decreased the incidence of gray mold and/or ripe rot on bunches and downy mildew on leaves of the field-grown grapevine. Transcription of a gene encoding β-1,3-glucanase but not class IV chitinase in leaves of potted grapevine seedlings was upregulated 20 days after electrical stimulation, suggesting that electrical stimulation acts as an abiotic elicitor of plant defense response to fungal diseases. The gene expression of PR1 but not PDF1.2 was upregulated in Arabidopsis plants subjected to electrical stimulation. On the other hand, PR1 gene expression was not induced in salicylic acid (SA)-insensitive Arabidopsis mutant npr1-5 subjected to electrical stimulation. Taken together, electrical stimulation is responsible for plant defense response through the SA-dependent defense pathway. These findings would help us develop a novel and innovative practical technique that uses electrical stimulation in integrated pest management.

Endophytic bacteria from strawberry plants control gray mold in fruits via production of antifungal compounds against Botrytis cinerea L.

Botrytis cinerea causes the gray mold disease in a wide range of plant hosts, especially in post-harvest periods. The control of this phytopathogen has been accomplished through the application of fungicides. However, this practice can cause environmental problems and increase fruit production costs. In addition, this fungus species has developed resistance to conventional synthetic fungicides. In this context, plant growth-promoting bacteria have shown potential for application in agricultural production because they are able to stimulate plant growth through different mechanisms, including the biological control of phytopathogens (indirect growth promotion mechanism). The aim of this work was to evaluate in vitro and in fruits the potential for indirect plant growth-promotion of bacteria isolated from strawberry leaves and roots. Dual plate method and inverted plate method were used to verify the ability of controlling in vitro the growth of Botrytis cinerea via the production of diffusible and volatile antifungal compounds, respectively. The effect of six bacterial isolates that showed greater potential for biological control in vitro was evaluated by scanning electron microscopy. Antifungal compounds produced by these bacterial isolates were identified by liquid chromatography coupled with mass spectrometry. Six bacterial strains were tested on strawberry pseudofruits. Five selected strains belong to the genus Bacillus and one to the genus Pantoea sp. Selected strains were able to inhibit more than 80 % of the mycelial growth of B. cinerea by the production of diffusible compounds and 90 % by volatile antifungal compounds production. Scanning electron microscopy showed the intense degradation of fungal hyphae caused by the presence of all bacterial strains. Bioactive compounds (salycilamide, maculosin, herniarin, lauroyl diethanolamide, baptifoline, undecanedioic acid, botrydial, 8 3-butylidene-7-hydroxyphthalide and N-(3-oxo-henoyl)-homoserine lactone) were obtained from liquid culture of these strains and extraction with ethyl acetate. All six isolates tested in vivo reduced the incidence of gray mold in strawberry pseudofruits in postharvest. It is concluded that isolates 26, 29, 65, 69, 132 (Bacillus sp.) and MQT16M1 (Pantoea sp.) have potential application for the biological control of Botrytis cinerea in strawberry via the production of diffusible and volatile antifungal compounds.

Fabrication of chitosan nanoparticles incorporated with Pistaciaatlantica subsp. kurdica hulls’ essential oil as a potential antifungal preservative against strawberry grey mould

SummaryEssential oil was extracted from Pistacia atlantica subsp. kurdica hulls and encapsulated in chitosan nanoparticles (NPs) by an emulsion‐ionic gelation method. A desirable retention rate (43.3–61.5%) of P. atlantica subsp. kurdica hulls’ essential oil (PAHEO) encapsulated in chitosan NPs was confirmed. In addition, the Fourier transform infrared spectroscopy and X‐ray diffraction analysis results revealed the success of PAHEO encapsulation. The formed NPs illustrated a shrunk and spherical shape with a size range of 187.2–632.5 nm as indicated by scanning electron microscopy and dynamic light scattering. The encapsulated PAHEO had a high antifungal activity against Botrytis cinerea under both the in vitro and in vivo conditions. It also significantly decreased the incidence and disease severity of grey mould on strawberries during storage. The spoilage process was postponed by the 8th days of storage at 4 °C in the strawberry fruit treated by PAHEO‐incorporated chitosan NPs. These findings imply that NP‐encapsulated PAHEO will have promising novel applications in food industries.

Performance of elite castor (Ricinus communis L.) hybrids and varieties under rainfed Alfisols

A field experiment was conducted during the rainy (kharif) seasons of 2018 and 2019 at Zonal Agricultural Research Station, University of Agricultural Sciences, Bangalore to study the per se performance, productivity and profitability of seven elite castor hybrids and varieties. Treatments comprised five hybrids (GCH-8, DCH-177 DCH-519, GCH-7, GCH-4) and two varieties (48-1, DCS-107). Based on the pooled analysis, castor hybrids (GCG-8, DCH-177 and DCH-519) showed significantly higher total dry matter production (TDMP) on account of significant superiority in crop growth rate (CGR), relative growth rate (RGR) and absolute growth rate (AGR). Nevertheless, the performance of genotypes in this study was not a true reflection of their growth attributes. Therefore, castor genotypes did not show consistency for seed yield over the years of their evaluation. It was mainly due to their differential reaction to incidence of gray mold. During 2018 significantly higher grain yield (2369 kg/ha), oil yield (1152 kg/ha), gross return (` 1,23,188/ha), net return (` 99,809/ha) and benefit: cost ratio (3.95) was recorded in GCH-8. Whereas, during 2019, 48-1 recorded significantly higher grain yield (1270 kg/ha), oil yield (602 kg/ha), gross return (` 66,040/ha), net return (` 36,897/ha) and benefit: cost ratio (2.27). Based on the pooled analysis, castor hybrid GCH-8 (1777 kg/ha) recorded significantly higher yield and closelyfollowed by castor variety 48-1 (1476 kg/ha) and DCS-107 (1444 kg/ha).

SO2-generating pads reduce gray mold in clamshell-packaged ‘Rubi’ table grapes grown under a two-cropping per year system

The aim of this work was to evaluate different SO2-generating pads and liners to control gray mold in ventilated clamshell-packaged ‘Rubi’ table grapes grown under a two-cropping per year system. The treatments consisted of SO2-generating pads (slow release or dual release) and plastic liners with different perforations (microperforated; 2.0; 4.0 or 5.0 mm in diameter) and a control, only with the standard microperforated plastic liner. The packaged grapes were stored in a cold chamber at 1.0 ± 1.0 °C and 95% relative humidity. After 45 days, the grapes were removed from cold storage and placed, without liners and SO2-generating pads, for 3 days at room temperature (22.0 ± 1.0 °C). The evaluations occurred at 30 and 45 days after the beginning of cold storage, and the following variables were assessed: incidence of gray mold, mass loss, stem browning and shattered berries. At 3 days of shelf-life, the same variables were assessed, except mass loss. The completely randomized design was used as a statistical model with four replications, and each plot consisted of five bunches individually stored in ventilated clamshell-packaged. The dual release SO2-generating pads are efficient in controlling the gray mold in ‘Rubi’ table grapes regardless of the type of perforation of the plastic liners, with low mass loss and shattered berries, with good conservation of the freshness of the rachis. The disease was efficiently controlled in both annual crops. The slow-release SO2-generating pads, regardless of the type of perforation of the plastic liners, resulted in intermediate efficiency of gray mold control, with good physical quality of the bunches. Thus, the use of dual release SO2-generating pads is recommended to control gray mold in ventilated clamshell-packaged ‘Rubi’ table grapes.

Nanoencapsulation of hyssop essential oil in chitosan-pea protein isolate nano-complex

Nanoencapsulation of bioactive compounds is an emerging field in food and pharmaceutical industries. In present work, essential oil was extracted from aerial parts of hyssop and encapsulated in chitosan-pea protein isolate nano-complex using a nanoprecipitation method. A central composite design (CCD) was employed to optimize the formation of nano-complex for maximizing the retention rate of hyssop essential oil (HEO) loaded in the nano-matrix and minimizing the average particle size simultaneously. The optimum nano-matrix formation were of chitosan/pea protein isolate ratio of 2.12 (w/w) and essential oil/chitosan-pea protein isolate ratio of 1.88 (w/v). Under these conditions, the retention rate of HEO and the average particle size were 81.2% and 216.4 nm, respectively. Furthermore, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses indicated the success of HEO encapsulation. The formed nanoparticles illustrated a spherical shape and regular distribution as indicated by scanning electron microscopy (SEM). The antioxidant activity of HEO-loaded chitosan-pea protein isolate nano-complex was higher than free HEO. Similarly, the encapsulated HEO had a high antifungal activity against Botrytis cinerea under both in vitro and in vivo conditions. The encapsulated HEO at 2 mg/mL concentration significantly decreased both the incidence and disease severity of gray mold on strawberries during storage at 4 °C. These findings imply that HEO-loaded chitosan-pea protein isolate nano-complex is a promising case to be used for novel applications in pharmaceutical and food industries.

On-Farm Trials Reveal Significant but Uncertain Control of Botrytis cinerea by Aureobasidium pullulans and Potassium Bicarbonate in Organic Grapevines.

Botrytis cinerea, a fungal pathogen that causes gray mold on grapes, can decrease yield, substantially reduce wine quality, and therefore cause significant economic losses. In a context of increasing awareness of environmental and human health, biopesticides are a potential alternative to synthetic chemical treatments to produce grapes and wine in compliance with high food standards. However, the effectiveness of biopesticides is not well known and more research is needed to help winegrowers assess their ability to control wine diseases. Our study aims to assess the efficacy of two commercial biopesticides, based on potassium bicarbonate and Aureobasidium pullulans, in reducing the incidence of gray mold (i.e., the proportion of grape bunches that are diseased). We use data from an on-farm trial network managed over 3 years (from 2014 to 2016) in a major wine producing region located in Southwestern France, and fit Bayesian generalized linear multilevel models able to take the variability of treatment effect across trials into account. The fitted models were then used to estimate the efficacy on incidence as a function of the severity (i.e., the proportion of diseased grape berries in a bunch) in an untreated plot in order to determine if the effectiveness of the treatments depends on the disease pressure. At average disease severity (i.e., 3%), the efficacy on disease incidence at the network level was equal to 20% [95% CI = (−0.1; 37.3)] and 13% [95% CI = (0.2; 24.7)] for potassium bicarbonate and A. pullulans, respectively. For both biopesticides, the efficacy on incidence for a new site-year is highly uncertain, but potassium bicarbonate had a lower uncertainty and a lower application cost compared to A. pullulans. Our results confirm that potassium bicarbonate is an interesting biopesticide under farming conditions in organic vineyards in southwestern France, but the amount of uncertainty points to the need for further research.

Bacillus subtilis KLBC BS6 induces resistance and defence-related response against Botrytis cinerea in blueberry fruit

The potential biocontrol strain Bacillus subtilis KLBC BS6 was isolated from blueberry rhizosphere soil, and its efficacy for controlling grey mould caused by Botrytis cinerea in postharvest blueberry fruit and the underlying possible disease resistance mechanisms were investigated. Treatment with B. subtilis KLBC BS6 was expected to inhibit the mycelial growth and conidial germination of B.cinerea in vitro. The incidence of grey mould in blueberry fruit treated with B. subtilis KLBC BS6 (and inoculated with B. cinerea) was decreased compared with that in the control fruit after 4 days of incubation, regardless of the preventive or curative nature of the treatment. Moreover, preventive treatment was more effective than the curative one in controlling of grey mould-induced decay. In B. subtilis KLBC BS6-treated blueberry fruit, the activities of disease resistance-related enzymes (chitinase, phenylalanine ammonia lyase, peroxidase, and polyphenol oxidase) were significantly enhanced. Furthermore, compared to the control fruit, the B. subtilis KLBC BS6-treated blueberry fruit exhibited unimpaired internal fruit quality and maintained high titratable acidity and ascorbic acid content. Thus, B. subtilis KLBC BS6 is a suitable biocontrol agent for prolonging the postharvest shelf-life of blueberry fruit and other horticultural products.

Chitosan/silica nanocomposite-based formulation alleviated gray mold through stimulation of the antioxidant system in table grapes

The main purpose of this study was to explore the ability of a novel silica/polysaccharide polymer-based formulation, namely, chitosan/silica nanocomposites (CSNs), to directly affect Botrytis cinerea in vitro and in inoculated berries, and indirectly to induce natural host resistance via enzymatic and nonenzymatic antioxidants against gray mold of table grapes. The results indicated a positive correlation in in vitro tests in terms of radial growth, spore germination and germ tube elongation, where those parameters were completely inhibited by CSN at 1%. SEM and TEM investigations showed that morphological and internal structural damage was observed in B. cinerea-hyphae/spores treated with CSN. Additionally, most of the treated spores were affected, and cellular vacuolization and cytoplasmic disorganization were observed. The results revealed that CSN reduced gray mold incidence and severity on inoculated berries directly and indirectly. In direct activity, CSN (1%) reduced mold incidence and severity by 100% compared to the control. In indirect activity, mold incidence and severity was reduced by 51% and 64%, respectively. CSN significantly increased superoxide dismutase, ascorbate peroxidase, peroxidase, total phenol and flavonoid at 48 h post-treatment by 1.2-, 1.6-, 1.3-, 1.3- and 1.6-fold, respectively, in grape-treated tissues. It could be concluded that CSN, as a promising alternative control method against gray mold of table grapes, can directly affect the pathogen and indirectly enhance the natural host resistance of the antioxidant system.

Control of postharvest gray mold of ‘BRS Nubia’ table grape under cold storage

The demand for high-quality nutritional products has increased fruit consumption, as grapes, for this reason postharvest techniques are required to prevent losses, to preserve quality, to extend shelf life, and to attend to consumer needs. In this way, the objective of this study was to evaluate strategies to control gray mold caused by Botrytis cinerea in ‘BRS Nubia’ grapes during cold storage and shelf life periods. Grape bunches were harvested from a commercial vineyard in Marialva, Parana, Brazil. Grapes were subjected to the following treatments: cold storage at 2 ºC (control), cold storage at 2 ºC with SO2-generating pads, cold storage at 2 ºC and inoculated with B. cinerea suspension, and cold storage at 2 ºC with SO2-generating pads and inoculated with B. cinerea suspension. The experiment was conducted in a complete randomized design with five replications per treatment using four bunches per experimental unit. A factorial arrangement (absence/presence of SO2 pads × absence/presence of Botrytis inoculation) was applied. At the end of 30 days of cold storage and 7 days of shelf life (22 ºC), gray mold incidence, shattered berries, and physicochemical parameters were evaluated. The gray mold incidence on ‘BRS Nubia’ grapes decreased when SO2-generating pads were used during cold storage. Berry weight loss was greater in the treatments without SO2-generating pads after 30 days of cold storage followed by 7 days of shelf life. Berry firmness, soluble solids content (SS), total acidity (TA), SS/TA ratio, and anthocyanins concentration were not negatively affected by SO2-generating pad treatments. However, a slight increase in the shattered berries percentage was recorded for the SO2-generating pad treatments. No significant quality loss of ‘BRS Nubia’ grape was evident after 30 days of cold storage followed by 7 days of exposure at room temperature. In this context, SO2-generating pads can be used to control the gray mold incidence on ‘BRS Nubia’ table grapes during cold storage.

Salt Solution Treatments Trigger Antioxidant Defense Response against Gray Mold Disease in Table Grapes.

To obtain a clear understanding of the mode of action of potassium bicarbonate (PB), sodium silicate (SSi) and calcium chelate (CCh) solutions (1%) in inducing resistance to gray mold disease in table grapes, enzymatic and nonenzymatic investigations were carried out. In particular, changes in the activity of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), total phenolic content and total flavonoid content were studied. As indirect action, PB, SSi and CCh reduced the incidence of gray mold by 43%, 50% and 41%, respectively. The highest activity of SOD was detected at 48 h in SSi-treated tissue, PB-treated tissue and CCh-treated tissue, and it was 1.7-, 1.4- and 1.2-fold higher, respectively, compared to the control. The APX activity was significantly higher in SSi-treated tissue than in the control at 24, 48 and 72 h and showed an increase in activity 2-fold for all times. Additionally, PB, SSi and CCh increased the activity of POD by 1.4-, 1.2- and 2.7-fold at 48 h posttreatment, respectively. The results showed that CCh was the most pronounced salt to increase both total phenol and flavonoid contents by 1.3 and 2.1, respectively. Additionally, the three tested salts induced an increase in total phenols and total flavonoids at 48 h posttreatment. The obtained result is one more movement towards an overall understanding of the mechanism by which salt solutions act as antimicrobial agents against gray mold of table grapes.

Selection and application of antifungal VOCs-producing yeasts as biocontrol agents of grey mould in fruits

Rotting caused by grey mould (Botrytis cinerea) is a concerning disease for numerous crops both pre- and postharvest stages. Application of antagonistic yeasts is a promising strategy for controlling grey mould incidence which could mitigate undesirable consequences of using synthetic fungicides. In this work, a screening for detection of yeasts isolated from figs producers of antifungal volatile organic compounds (VOCs) were performed by confrontation in double dishes systems. Eleven out of 34 yeasts confronted reduced B. cinerea growth parameter in vitro. This reduction was correlated (p ≤ 0.050) with the production of 10 volatile compounds: two acids (acetic acid and octanoic acid), 7 esters (Ethyl propionate, n-Propyl acetate, Isobutyl acetate, 2-methylbutyl acetate, furfuryl acetate, phenylmethyl acetate, 2-phenylethyl acetate) and one ketone (Heptan-2-one). In bases on in vitro assay, Hanseniaspora uvarum 793 was applied to in vivo assays with strawberries and cherries. The reduction of incidence of B. cinerea in strawberries at 7 °C and 25 °C was 54.9 and 72.1% after 6 and 3 days, respectively. The reduction of incidence of B. cinerea in cherries at 7 °C and 25 °C was 48.9 and 45.6% after 5 and 4 days, respectively. These results showed that VOCs produced by Hanseniaspora uvarum 793 are effective in the control of incidence of Botrytis cinerea in fruits, being a potential alternative to chemical fungicide.

A novel endophytic strain of Lactobacillus plantarum CM-3 with antagonistic activity against Botrytis cinerea on strawberry fruit

The fungal pathogen Botrytis cinerea causes grey mold, a severely damaging disease of strawberry. Lactic acid bacteria (LAB) are known for their biopreservative activity. Meanwhile, LAB dominate in plant organs over time, and are of pivotal importance for plant defense. The goal of the present study was to isolate endophytic LAB and to evaluate for their biocontrol activities against B. cinerea. Of the tested endophytic bacteria isolates, Lactobacillus plantarum CM-3 demonstrated the highest potential for in vitro and in vivo control of B. cinerea. The in vitro results showed that L. plantarum CM-3 reduced the mycelial growth of B. cinerea on Potato Dextrose Agar (PDA) between 55.27% and 79.80%. Spore germination of the pathogen was greatly inhibited in the presence of living cell suspensions. In in vivo biocontrol assays, the decay incidence and lesion diameter of grey mold decay of strawberries treated by L. plantarum CM-3 cells were significantly (P < 0.05) reduced compared with the control fruit. At concentrations of 1 × 108 and 1 × 109 CFU mL−1, the incidence of gray mold was reduced by 48.23% and 75.00% respectively, compared to the control, after storage at 20 °C for 6 d. Moreover, rapid colonization of L. plantarum CM-3 in wounds was observed both in the presence or absence of B. cinerea at 20 °C during the storage period. The concentrations of the antagonist had significant effects on biocontrol effectiveness both in vitro and in vivo. However, cell-free filtrates of the strain failed to provide any protection against B. cinerea. Findings of the present study suggested that L. plantarum CM-3 could be a promising biocontrol agent for application during the post-harvest storage and marketing of horticultural products. This study reports the first assessment of endophytic LAB isolated from strawberry fruit and selection of isolates for the biocontrol of B. cinerea.

Effect of heat shock and potassium sorbate treatments on gray mold and postharvest quality of ‘XuXiang’ kiwifruit

We determined whether heat and chemical treatments could reduce the decay of kiwifruit caused by Botrytis cinerea during postharvest storage. Kiwifruits were treated with 5 g/L (w/v) potassium sorbate (PS), with a 48 °C hot water treatment (HT), and with a combined treatment (HT + PS). Mycelial growth of B. cinerea and the postharvest quality of ‘XuXiang’ kiwifruits were evaluated. HT + PS significantly inhibited mycelial growth, germ tube growth, and spore germination of B. cinerea. This treatment also reduced the incidence of gray mold in kiwifruit postharvest, and enhanced activities of defense-related enzymes in kiwifruit tissues. Compared with the control, all treatments resulted in lower malondialdehyde (MDA) contents and higher total phenolic contents in kiwifruits. HT + PS also increased the activities of chitinase and β-1,3-glucanase and the transcript levels of their encoding genes. HT + PS can improve kiwifruit quality and reduce decay during postharvest storage.

First Report of Gray Mold on Jinxianlian (Anoectochilus roxburghii) Caused by Botrytis cinerea in China

Anoectochilus roxburghii is one of the important herbal medicines in China. As a national rare and endangered plant, A. roxburghii is presently cultivated in bottles through greenhouse productions. The cultivation of A. roxburghii in Zhejiang Province accounts for a large proportion in China. Gray mold was found to severely affect the production of A. roxburghii. In 2018, the incidence of gray mold indicated by water-soaked gray mold symptoms with white to gray mycelia and conidiogenous apparatus on infected stems and leaves was observed for 6% of seedling bottles. When the conditions are suitable, gray mold spreads to the whole leaf and then gradually turns into grayish black and produces brown dead plaque, which causes the plant to wrinkle in severe cases. Thirty-one diseased leaves collected from different greenhouses in Jinhua City were picked with a needle on 2% potato dextrose agar (PDA) and cultured in the dark at 23°C. The colonies on the PDA were initially grayish white, followed by brownish black, and produced one-celled, round conidia (8.78 ± 0.4 × 12.60 ± 0.3 μm). These morphological features are consistent with Botrytis cinerea. In order to confirm the identification based on morphological features, DNA-dependent RNA polymerase subunit II (RPB2), heat-shock protein 60 (HSP60), and glyceraldehyde-3-phosphate (G3PDH) were amplified from the DNA extracted from the mycelium produced on PDA (Berbee et al. 1999; Liu et al. 1999; Smith 1989). The sequences were deposited in NCBI under accession numbers RPB2 (MN464111, MN464112, MN464113), HSP60 (MN464108, MN464109, MN464110), and G3PDH (MN464105, MN464106, MN464107). BLAST analysis of the RPB2 (1,106 bp) segment showed 100% identity to the RPB2 sequence of B. cinerea isolate S4GBR40 (GenBank accession no. MK3880531). The HSP60 (956 bp) segment showed 100% identity to the HSP60 sequence of B. cinerea isolate F2-17 (GenBank accession no. MK256903). And the G3PDH (994 bp) gene segment showed 100% identity to B. cinerea isolate GZFQ-1 (GenBank accession no. MH479930). Phylogenetic analysis based on RPB2, HSP60, and G3PDH showed that the pathogen was B. cinerea. Uninfected A. roxburghii healthy plants were sprayed with 2 × 10⁶ conidia/ml in distilled water as inoculum, and plants inoculated with only distilled water were adopted as the blank control. For each isolate, 16 intact plants were inoculated. Plants were then kept at 25°C and 95% relative humidity in a 12-h light/dark incubation. After 10 days, all three tested isolates caused gray mold symptoms on A. roxburghii, whereas no symptoms appeared in the controls. Cultures reisolated from lesions and cultured on PDA exhibited the same morphological characteristics as B. cinerea (Carmichael et al. 2019), confirming Koch’s postulates. The inoculations were performed twice. To the best of our knowledge, this is the first report of the gray mold in A. roxburghii, which is the main factor limiting its productions. Measures must be taken to manage the disease in a timely manner.

Priming of Defense Systems and Upregulation of MYC2 and JAZ1 Genes after Botrytis cinerea Inoculation in Methyl Jasmonate-Treated Strawberry Fruits.

Several attempts have been made to study the effects of methyl jasmonate (MeJA) on plants in the past years. However, the comparative effects of the number and phenological time of MeJA applications on the activation of defense systems is currently unknown in strawberries. In the present research, we performed three field treatments during strawberry (Fragaria × ananassa ‘Camarosa’) fruit development and ripening which consisted of differential MeJA applications at flowering (M3), and the large green (M2 and M3) and red ripe (M1, M2, and M3) fruit stages. We also checked changes in gene expression related to plant defense against Botrytis cinerea inoculation post-harvest. In M3 treatment, we observed an upregulation of the anthocyanin and lignin contents and the defense-related genes, encoding for chitinases, β-1,3-glucanases and polygalacturonase-inhibiting proteins, after harvest (0 hpi), along with the jasmonate signaling-related genes FaMYC2 and FaJAZ1 at 48 h after B. cinerea inoculation (48 hpi) during postharvest storage. Although we did not find differences in gray mold incidence between the MeJA treatments and control, these results suggest that preharvest MeJA treatment from the flowering stage onwards (M3) primes defense responses mediated by the upregulation of different defense-related genes and retains the upregulation of MYC2 and JAZ1 at 48 hpi.

Sulphur Dioxide Pads Can Reduce Gray Mold While Maintaining the Quality of Clamshell-Packaged ‘BRS Nubia’ Seeded Table Grapes Grown under Protected Cultivation

The purpose of this research is to test the efficacy of different types of SO2-generating pads on the incidence of gray mold, and on the physicochemical properties of quality of ‘BRS Nubia’ seeded table grapes grown under protected cultivation. Four types of SO2-generating pads, 5 or 8 g of sodium metabisulfite dual release pads, and 4 or 7 g of sodium metabisulfite slow release pads, were used. Grapes bunches were harvested from a vineyard covered with plastic mash and stored in a cold room at 1 ± 1 °C for 45 days followed by 6 days of shelf life at 22 ± 1 °C at a high relative humidity (&gt;95%). The results showed that SO2-generating pads with a dual release of 5 or 8 g completely inhibited the development of gray mold at all evaluation times. Also, a high reduction of the disease incidence was achieved by using a slow release of 4 g. The study confirmed that SO2-generating pads did not alter the physicochemical properties of ‘BRS Nubia’ seeded table grapes including mass loss, berry firmness, color index, total anthocyanin concentration, total soluble solids (TSS), titratable acidity (TA), and the TSS/TA ratio. Slow release pads at 4 and 7 g reduced the percentage of shattered berries by 56 and 48% as compared to control only after 6 days of shelf life. Also, all types of SO2-generating pads reduced the stem browning score at the end of cold storage. The 5 or 8 g dual release pads and 4 g slow release pads can be considered for effective controlling of gray mold for ‘BRS Nubia’ table grapes grown under protected cultivation while maintaining grape quality.

Biological control of gray mold and Myrothecium leaf spot in begonias

The objective of this study was to evaluate the antagonism of Clonostachys rosea LQC62 and Trichoderma asperellum LQC96 against Botrytis cinerea and Myrothecium roridum, and to evaluate the application of these antagonists in the management of the diseases caused by these pathogens in commercial cultivation. Under controlled in vitro conditions, the production of soluble and volatile compounds was evaluated along with parasitism in paired cultures, competition by colonization in begonia leaf discs, and the effect of the application of the antagonists in the control of gray mold and Myrothecium leaf spot in the commercial cultivation of begonia. Both LQC62 and LQC96 produced soluble compounds in a culture medium that were capable of inhibiting the development of B. cinerea, which was not observed for M. roridum. Both antagonists produced volatile compounds that led to a reduction in the development of the pathogens. There was an overlap of the colonies of the antagonists with those of the pathogens, indicating hyper-parasitic activity. The antagonists colonized the begonia leaf discs, and the application of these antagonists prior to inoculation promoted a reduction in the sporulation of the pathogens of up to 100%. Weekly foliar sprays of LQC62 reduced the incidence of gray mold and of Myrothecium leaf spot in commercial cultivation.

Efficacy of Natamycin Against Gray Mold of Stored Mandarin Fruit Caused by Isolates of Botrytis cinerea With Multiple Fungicide Resistance.

Gray mold caused by Botrytis cinerea is an emerging postharvest disease of mandarin fruit in California. Management of postharvest diseases of mandarins relies on postharvest fungicides; however, multiple resistance to fungicides of different modes of action is common in B. cinerea populations from mandarin, leading to their failure to control decay. Natamycin is commonly used in the food industry as an additive, and it has been registered as a biofungicide for postharvest use on citrus and some other fruits. Sensitivity to natamycin of 64 isolates of B. cinerea from decayed mandarin fruit with known resistance phenotypes to other citrus postharvest fungicides (azoxystrobin, fludioxonil, pyrimethanil, and thiabendazole) was tested. Effective concentrations of natamycin to cause a 50% reduction relative to the control for conidial germination were from 0.324 to 0.567 µg/ml (mean of 0.444 µg/ml), and those for mycelial growth were 1.021 to 2.007 µg/ml (mean of 1.578 µg/ml). Minimum inhibitory concentrations where no fungal growth was present were 0.7 to 1.0 µg/ml for conidial germination and 5.0 to 10.0 µg/ml for mycelial growth. No cross-resistance between natamycin and other citrus postharvest fungicides was detected. Decay control efficacy tests with natamycin were conducted on mandarin fruit inoculated with B. cinerea isolates exhibiting five different fungicide resistance phenotypes, and natamycin significantly reduced incidence and lesion size of gray mold on fruit, regardless of fungicide resistance phenotypes. Natamycin has the potential to be an effective tool for integration into postharvest fungicide programs to control gray mold and manage B. cinerea isolates resistant to fungicides with other modes of action.