Cinerea Conidia Research Articles

Sesquiterpenes from Pistacia lentiscus L. as potential antibacterial, antifungal and allelopathic agents

ABSTRACT The present study investigated the antibacterial, antifungal and allelopathic activities of Pistacia lentiscus essential oils (EOs) isolated at the vegetative, flowering and fructification stages. The chemical composition of EOs varied according to both the phenological stages and the used mix plant parts. The main chemical class was sesquiterpene hydrocarbons with the predominance of germacrene D, δ-cadinene and β-caryophyllene. The antibacterial activity was evaluated against five collection strains. At the vegetative stage, P. lentiscus EO was the most effective against Listeria monocytogenes and Echerchia coli as compared to the other stages. P. lentiscus EO also exhibited significant antifungal activity against the phytopathogenic strain Botrytis cinerea. Microscopic observation showed that EO induced swelling and crumbling of B. cinerea conidia. Moreover, P. lentiscus EO at the vegetative stage possessed significant allelopathic activity by inhibiting low concentration the germination and radical elongation of Raphanus sativus and radical elongation of Lepidium sativum.

A novel approach to control Botrytis cinerea fungal infections: uptake and biological activity of antifungals encapsulated in nanoparticle based vectors

Botrytis cinerea, responsible for grey mold diseases, is a pathogen with a broad host range, affecting many important agricultural crops, in pre and post harvesting of fruits and vegetables. Commercial fungicides used to control this pathogen are often subjected to photolysis, volatilization, degradation, leaching, and runoff during application. In this context, the use of a delivery system, based on poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) represents an innovative approach to develop new pesticide formulations to successfully fight B. cinerea infections. In order to study NPs uptake, B. cinerea conidia and mycelium were treated with PLGA NPs loaded with the high fluorescent probe coumarin 6 (Cu6-PLGA NPs) and analyzed under ApoTome fluorescence microscopy. The observations revealed that 50 nm Cu6-PLGA NPs penetrated into B. cinerea conidia and hyphae, as early as 10 min after administration. Pterostilbene, a natural compound, and fluopyram, a synthetic antifungal, were entrapped in PLGA NPs, added to B. cinerea conidia and mycelium, and their antifungal activity was tested. The results revealed that the compounds loaded in NPs exhibited a higher activity against B. cinerea. These results lay the foundations for the use of PLGA NPs as a new strategy in plant pest management.

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

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

Stimulatory Effects of Sublethal Doses of Carbendazim on the Virulence and Sclerotial Production of Botrytis cinerea.

Stimulatory effects of low doses of fungicides on the virulence of phytopathogens have profound implications for applications of fungicides. The present study demonstrated that carbendazim sprayed at 0.001 to 0.03 μg/ml had stimulatory effects on the virulence of mycelia of Botrytis cinerea, and the maximum percent stimulations were 15.5 and 21.4% for isolates HB459 and HB536, respectively. Potato dextrose agar (PDA) amended with carbendazim at 0.01, 0.02, and 0.05 μg/ml inhibited mycelial growth of isolate HB536 by 0.8, 10.0, and 30.6%, respectively. However, after the inhibited mycelia were inoculated on cucumber leaves, virulence increased by 10.1, 12.9, and 10.8%, respectively. With respect to sclerotial production, carbendazim at 0.005 and 0.02 μg/ml in PDA significantly (P < 0.05) increased, while at 0.1 μg/ml significantly (P < 0.05) reduced the sclerotial number and weight of both isolates compared with nontreated controls. Conidia germination percentages slightly yet statistically significantly (P < 0.05) increased after being inoculated on PDA amended with carbendazim at 0.001 and 0.005 μg/ml. Carbendazim at 0.001∼0.02 μg/ml, either sprayed on cucumber leaves or cosuspended with conidia, exerted significantly (P < 0.05) stimulatory effects on the virulence of B. cinerea conidia. Mechanism studies showed that sublethal doses of carbendazim did not increase the expression levels of pathogenicity-related pectin methylesterase gene Bcpme1, endopolygalacturonase gene Bcpg2, cutinase gene CutA, xylanase gene Xyn11A, or NADPH oxidase gene BcnoxA.

Cupressus sempervirens essential oils and their major compounds successfully control postharvest grey mould disease of tomato

Medicinal plants generally produce many secondary metabolites which constitute an important source of many bioactive molecules. Among them Cupressus sempervirens is recognized by its richness in essential oil with antimicrobial properties. The aim of this study is to use C. sempervirens essential oil or its bioactive components as an alternative to synthetic fungicides currently used to control Botrytis cinerea. Essential oils of C. sempervirens were extracted at vegetative, flowering and fructification stages and a total of 54 compounds were identified by chromatography-mass spectrometry. Essential oils composition varied with the phenological stage and the main chemical classes were sesquiterpene hydrocarbons (59.59%–64.5%) with the most representative compounds being germacrene D (18.38%–24.82%) and those of the monoterpene hydrocarbons class (16.63%–26.5%) with α-pinene as the most representative compound (14.75%–22.92%). The in vitro antifungal tests against B. cinerea showed that the three studied essential oils inhibit mycelia growth with the highest activity observed at flowering stage. The antifungal activity of some pure compounds (α-pinene, α-cedrol and β-caryophyllene) alone or combined according to their proportions in the natural essential oil showed that α-pinene combined with β-caryophyllene provided the highest antifungal activity at a concentration as low as 0.12 mg/mL as compared to that of the chemical fungicide used as a positive control. Microscopic observation showed that essential oil at flowering stage induced swelling and crumbling of B. cinerea conidia. The pulverization of C. sempervirens essential oils on tomato fruits at 1 mg/mL inhibited 54% of B. cinerea infection which constitute a promising safe product for the biocontrol of the post-harvest disease Botrytis cinerea during storage and transport of tomato.

Epidemiology of Botrytis cinerea on Grape: Wound Infection by Dry, Airborne Conidia

This study describes the infection of fresh wounds on berries exposed to freshly deposited airborne Botrytis cinerea conidia, and on berries carrying previously deposited conidia and germlings (latent infections). Grapes at bunch closure and at the mature (harvest) stage, as well as mature, cold-stored grapes, were used. The grapes were dusted with dry conidia in a settling tower. The inocula were subjected to conditions commonly encountered by the pathogen in grape bunches: dry conidia on dry berries under dry conditions, dry conidia on dry berries under high relative humidity, and dry conidia exposed to a film of water on the berry surface. The mean number of wounds that yielded B. cinerea decay 14 days after inoculation was calculated. Fluorescence microscopy revealed that conidia occurred evenly as single cells on the grape berry surface and seldom landed at the wound periphery. They remained dormant on dry berries, but germinated freely on the unbroken skin and at the wound periphery on moist and wet berries. In the case of berries inoculated at bunch closure and harvest stages, wounds were not infected by conidia deposited on berries four days prior to wounding. This finding indicated that, following adhesion and the first stages of growth, the pathogen did not survive for extended periods on surfaces of immature and mature grape berries. Freshly deposited dry conidia were needed to infect the wounds. The freshly deposited conidia furthermore needed free water, and not high humidity or wound exudates, to infect the fresh wounds. Proportions of wounds infected were extremely low. According to these findings, this mode of infection should not contribute to a gradual build-up of secondary inoculum and to B. cinerea epiphytotics in the vineyard. The previously and freshly deposited conidia both infected wounds made on cold-stored mature berries. Of the two inocula, freshly deposited conidia were more successful in causing wound infection. Therefore, in the event of wounding, postharvest decay would be caused primarily by conidia occurring on the grape berry surface, and not by mycelia in the berry skin.

Antimicrobial efficacy of liposomes containing d-limonene and its effect on the storage life of blueberries

The purpose of this study was to investigate the antimicrobial activity of unilamellar nano vesicles (liposome) containing d-limonene against selected fruit rotting fungi (Botrytis cinerea and Penicillium chrysogenum) and food borne illness causing bacteria (Escherichia coli and Listeria monocytogenes). Furthermore, the research evaluated the extended shelf life and enhanced food safety of blueberries treated with d-limonene and liposomes. Liposomal nanoparticles were created by thin lipid film hydration followed by sonication. Mean liposome radius was 100.2±3.1nm. The antibacterial activity against E. coli showed 0.99 and 1.6 log10 reductions in CFUmL−1 at 10μM and 50μM, respectively, within 48h. The log10 reduction was 1.6 at 10μM and 3.4 at 50μM for L. monocytogenes.Germination of B. cinerea conidia was completely suppressed over 48h by a 50μM concentration of limonene. Liposomes exhibited 2.2 and 2.8 log10 reductions for P. chrysogenum, whereas 3.7 and 4.6 log10 reductions were observed for B. cinerea with 10μM and 50μM limonene, respectively. The in vivo study of liposome coatings on blueberries also revealed protection against microbial growth even after nine weeks of storage at 4°C with liposomes reducing blueberry spoilage by more than 60% at the end of nine weeks. The results of this study can benefit the produce industry through both enhancement of food safety and extending the shelf life of blueberries, further highlighting the commercial applications of liposomes.

Studies of Botrytis cinerea causing botrytis gray mold disease in chickpea (Cicer arietinum L.)

Context: To investigate the morphological and pathological information on causal organism Botrytis cinerea for better understanding of the infection process and controlling outbreaks of the most damaging disease, Botrytis Gray Mold (BGM),of chickpea.Objectives: To study the cultural and morphological characteristics and growth requirements of Botrytis cinerea Pers. ex. Fr. This study was also aimed to know about the cytological and genetic behavior of B. cinerea in relation to its pathogenicity and the infection process on chickpea.Materials and Methods: A total of 83 isolates of Botrytis cinerea Pers. ex. Fr. collected from the major chickpea growing areas of Bangladesh were studied under 5 and 2 different groups based on their cultural and morphological characteristics, respectively. Four different types of isolates were observed and characterized considering the arrangement of sclerotia by growing them on PDA. Cultural characteristics such as colony color, shape, margin and texture of B. cinerea isolates were observed on the prepared PDA medium. Morphological characteristics in terms of sclerotia color, shape and size, ability of sclerotia production and their arrangement were observed on PDA medium after three days of incubation at 20°C. The prepared samples were placed in a platinum coater providing 10 mA current flow and then placed into the Scanning Electron Microscope (SEM) for obtaining the image. The conidial observation was taken using aqua suspension under the fluorescence microscope at 19V/100W. SEM observation was made to study the infection process of B. cinerea. Data on quantitative and qualitative cultural characteristics were put into analytical software 'SPSS 11.5 for Windows' and nonhierarchical clustering was performed.Results: The mean sizes of five isolates of B. cinerea were 8.02-12.3x 5.1-9.0 ?m (volume 158.12-445.38 ?m3). The pathogen B. cinerea grew well on malt-extract agar (MEA) and chickpea dextrose agar (CDA) medium. The highest (81.26 mm) average mycelial radial growth was obtained on MEA followed by CDA (81.11 mm). Maximum disease in the shortest incubation period was produced with the inoculum concentration of 2.5×104. More pathogenicity and higher disease score was performed by the isolates containing higher mean number of nucleus per conidia than the isolates containing lower values. Optimum temperature and incubation time for conidial germination was observed at 20°C and 24 h, respectively. More than 90% relative humidity was needed for the germination of B. cinerea conidia. B. cinerea survived in all plant parts up to next cropping season. Sclerotia of B. cinerea were also found to survive in the soil up to 9 months. All the 5 isolates of B. cinerea remained viable after 3 years of storage in sterile water at -80°C and in sand at 4°C with same pathogenicity.Conclusion: The cyto-pathological observations including cultural and morphological information of the causal pathogen B. cinerea might be useful in controlling the outbreaks of the disease BGM and ultimately reducing the yield loss of the valuable crop chickpea.J. bio-sci. 22: 69-76, 2014

Interface of the environment and occurrence of Botrytis cinerea in pre-symptomatic tomato crops

Botrytis cinerea (Grey mould) is a necrotrophic fungus infecting over 230 plant species worldwide. It can cause major pre- and post-harvest diseases of many agronomic and horticultural crops. Botrytis cinerea causes annual economic losses of 10–100 billion US dollars worldwide and instability in the food supply (Jin and Wu, 2015). Grey mould losses, either at the farm gate or later in the food chain, could be reduced with improved knowledge of inoculum availability during production. In this paper, we report on the ability to monitor Botrytis spore concentration in glasshouse tomato production ahead of symptom development on plants. Using a light weight and portable air sampler (microtitre immunospore trap) it was possible to quantify inoculum availability within hours. Also, this study investigated the spatial aspect of the pathogen with an increase of B. cinerea concentration in bio-aerosols collected in the lower part of the glasshouse (0.5 m) and adjacent to the trained stems of the tomato plants. No obvious relationship was observed between B. cinerea concentration and the internal glasshouse environmental parameters of temperature and relative humidity. However the occurrence of higher outside wind speeds did increase the prevalence of B. cinerea conidia in the cropping environment of a vented glasshouse. Knowledge of inoculum availability at time periods when the environmental risk of pathogen infection is high should improve the targeted use and effectiveness of control inputs.

Inhibition of Botrytis cinerea by Epirodin: A Secondary Metabolite from New Zealand Isolates of Epicoccum nigrum

AbstractMany isolates of the saprophytic fungus Epicoccum nigrum produce yellow compounds that diffuse readily into culture media. Historically, two such compounds have been identified; flavipin and epirodin both reported to have antimicrobial properties. Preliminary studies on 280 New Zealand isolates of E. nigrum confirmed that all but two produced a yellow, intensely pigmented substance in sufficient amounts to inhibit the germination of Botrytis cinerea conidia. The compound produced by the inhibitory isolates is epirodin, a polyene antibiotic. Five representative E. nigrum isolates were selected for further investigation. Two of these produced relatively large amounts of epirodin and, in a diffusible metabolite assay, reduced germination of B. cinerea conidia by up to 94%. Another isolate produced a trace amount of epirodin and had no effect on the germination of B. cinerea conidia or on germ tube morphology. The two remaining isolates produced intermediate amounts of epirodin and were only moderately inhibitory to the germination of B. cinerea conidia and to germ tube morphology. In slide dual‐culture experiments, epirodin appeared to concentrate in conidia and mycelia of B. cinerea. In acid conditions, as on dual‐culture slides of E. nigrum and B. cinerea, the yellow‐coloured epirodin underwent a hypsochromic shift, changing colour to become red. The relationship between epirodin production and the suppression of Botrytis growth and development was further investigated using necrotic kiwifruit leaf discs. The E. nigrum isolate that produced the greatest amount of epirodin almost completely inhibited the growth and development of B. cinerea on the leaf discs. In contrast, the efficacy of E. nigrum isolates which produced less epirodin ranged from 78% to just 23%. This is the first report of epirodin production by New Zealand isolates of E. nigrum, and we conclude that isolates that produce high concentrations of epirodin may have potential for plant disease control.

Relationship of Airborne Botrytis cinerea Conidium Concentration to Tomato Flower and Stem Infections: A Threshold for De-leafing Operations.

Gray mold, caused by Botrytis cinerea, is an important threat for tomato greenhouse producers. The influence of airborne conidia concentration (ACC) on both flower and stem-wound infections was studied in a greenhouse maintained at a temperature of 15, 20, or 25°C using diseased tomato leaves as the unique source of dry inoculum. Spore samplers were used to monitor ACC, and a previously developed real-time qPCR assay was used to quantify airborne B. cinerea conidia. The proportion of infected flowers remained low at ACC < 10 conidia/m3; above this concentration, flower infection increased with increasing ACC. The influence of ACC on proportion of infected flowers was well described by a sigmoid model (R2 = 0.90 to 0.92). The mean proportion of infected stem wounds over the three trials was 0.021; no infected wounds were observed at ACC < 100 conidia/m3. Based on logistic regression, the probability that a stem becomes infected increased rapidly with mean probabilities of 0.24 and 0.87 at ACCs of 315 and 3,161 conidia/m3, respectively. The results suggest that the amount of airborne B. cinerea inoculum in the greenhouse is often above the action threshold for flower infection and that monitoring airborne B. cinerea inoculum could help in timing de-leafing operations.

Proteomic profiling of Botrytis cinerea conidial germination.

Botrytis cinerea is one of the most relevant plant pathogenic fungi. The first step during its infection process is the germination of the conidia. Here, we report on the first proteome analysis during the germination of B. cinerea conidia, where 204 spots showed significant differences in their accumulation between ungerminated and germinated conidia by two-dimensional polyacrylamide gel electrophoresis and qPCR. The identified proteins were grouped by gene ontology revealing that the infective tools are mainly preformed inside the ungerminated conidia allowing a quick fungal development at the early stages of conidial germination. From 118 identified spots, several virulence factors have been identified while proteins, such as mannitol-1-phosphate dehydrogenase, 6,7-dimethyl-8-ribityllumazine synthase or uracil phosphoribosyltransferase, have been disclosed as a new potential virulence factors in botrytis whose role in pathogenicity needs to be studied to gain new insights about the role of these proteins as therapeutic targets and virulence factors.

Genetic and phenotypic characterization of Botrytis calthae

Botrytis calthae is a necrotrophic plant pathogen, closely related to the ubiquitous broad host range fungus Botrytis cinerea, but highly host specific. Botrytis isolates from lesions of Caltha palustris grown at different locations were classified with genetic markers as either B. calthae or Botrytis pseudocinerea, or less frequently as B. cinerea. A PCR‐based identification of B. calthae was developed. Seven haplotypes of B. calthae could be distinguished. Compared to B. cinerea, mycelium growth of B. calthae was similar, but conidiation less abundant, and sclerotia formation was only partially repressed by light. Conidia of B. calthae germinated more slowly, and showed a highly acidic optimum (pH 2·5) compared to B. cinerea conidia (pH 5·3). All B. calthae isolates were sensitive to common anti‐Botrytis fungicides, but showed partial resistance to the succinate dehydrogenase inhibitors boscalid, fluopyram and carboxin. Infection experiments revealed a weak capability of B. calthae to induce necrotic lesions on plants that are hosts for B. cinerea. On C. palustris leaves, B. calthae induced similar lesions to B. cinerea. These data provide a basis for comparative molecular investigation of the physiology and host specificity of B. calthae and closely related Botrytis species.

Potential secondary inoculum sources ofBotrytis cinereaand their influence on bunch rot development in dry Mediterranean climate vineyards

Epidemiological studies have described the life cycle of B. cinerea in vineyards. However, there is a lack of information on the several infection pathways and the quantitative relationships between secondary inoculum and bunch rot at harvest. Over two seasons, different spray programmes were used to determine key phenological stages for bunch rot development. Secondary inoculum sources within the bunch were also studied. The relative importance of flowering was evidenced in the given conditions, as treatments that included two fungicide applications at flowering were the most effective. In 2010, under conducive meteorological conditions for B. cinerea development after veraison, an extra application provided significantly higher control. Infections of necrotic tissues inside the bunch and latent infections developed mainly during flowering, while very low quantities of B. cinerea conidia were recovered from the fruit surface at veraison. Regression analysis correlated the incidence of latent infections and B. cinerea incidence on calyptras and aborted fruits at veraison with incidence of Botrytis bunch rot at harvest, presenting R2 = 0.95 for the overall regression model. This work points out key phenological stages during the season for bunch rot and B. cinerea secondary inoculum development and relates quantitatively inoculum sources at veraison to bunch rot at harvest. Recommendations for field applications of antibotrytic products are also suggested.

Optimisation of techniques for quantification ofBotrytis cinereain grape berries and receptacles by quantitative polymerase chain reaction

Background and Aims Bunch rot symptoms can appear weeks after the infection of grape flowers by Botrytis cinerea. Quantitative polymerase chain reaction (qPCR) detects changes in the DNA mass of a target organism and is a potential tool for studying quiescent infections. The aim was to optimise a duplex qPCR to quantify B. cinerea DNA in the background of endogenous Vitis vinifera DNA. Methods and Results Three DNA extraction techniques and three probe sets were compared. The optimised qPCR using the Bc3 probe set was 1000-fold more sensitive than other probe sets, with a threshold cycle value of <33 for as little as 1 picogram of B. cinerea DNA. The duplex assay successfully detected an increasing amount of B. cinerea DNA when mixed with V. vinifera DNA or of B. cinerea conidia when added to grape receptacles. Conclusions Duplex assays quantifying B. cinerea DNA in the background of endogenous grape DNA were efficient and sensitive, with calculation of a pathogen coefficient allowing comparison of results among assays. Significance of the Study The results demonstrate the potential to monitor symptomless, quiescent infections and to investigate the consequence of an intervention (e.g. a fungicide treatment) before disease symptoms are visible.

EFFECTS OF CARBON DIOXIDE ENRICHED ATMOSPHERES ON THE POSTHARVEST CONTROL OF BOTRYTIS ROT OF 'DUETT' CUT ROSES

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Postharvest Technology in the Global Market EFFECTS OF CARBON DIOXIDE ENRICHED ATMOSPHERES ON THE POSTHARVEST CONTROL OF BOTRYTIS ROT OF 'DUETT' CUT ROSES

Changes in Botrytis cinerea Conidia Caused by Berberis vulgaris Extract

Testing plant extracts for controlling fungal diseases is a main biocontrol method. More interesting is to see what happens to the fungus treated with the plant extract. Therefore, the aim of the study was to evaluate the antifungal activity of Berberis vulgaris extract on Botrytis cinerea and to examine the ultrastructural changes in B. cinerea conidia caused by the minimum inhibitory concentration (MIC), using SEM and TEM. The antifungal activity of B. vulgaris bark extract was investigated using agar dilution method, and compared to that of berberine. Fluconazole was used as the positive antimycotic control. It was found that (1) B. vulgaris bark extract had significant antifungal activity against B. cinerea, and its effect was stronger than that of pure berberine. It was also noted that (2)B. vulgaris MIC caused severe structural changes of the conidia, comparable with berberine MIC effect; therefore (3) B. vulgaris bark extract might be recommended to be tested as a biocontrol agent against B. cinerea.

Histology of waxflower (Chamelaucium spp.) flower infection by Botrytis cinerea

Botrytis cinerea infects waxflower (Chamelaucium spp.) flowers and can induce them to abscise from their petioles before disease becomes evident. Botrytis cinerea infection of flowers was studied on two waxflower cultivars by light and electron microscopy. Pot‐grown waxflower flowers were harvested, inoculated with aqueous suspensions of B. cinerea conidia, incubated at 20–22°C and &gt;95% RH and examined within 96 h post‐inoculation (hpi). Conidial germination on petals started 4 hpi, penetration via germ tube tips was 6 hpi and protoappressoria were formed 8 hpi. Germination on petals approximately doubled every 4–6 h to 18 hpi. Conidial germination was ca. 50% at 22–24 hpi. Botrytis cinerea infected most waxflower flower organs, including petals, anthers and filaments, stigma and hypanthium, within 24 hpi. Hyaline and lobate appressoria were observed 36 hpi. Infection cushions on stamen bases were formed 36 hpi by saprophytic hyphae that originated from anthers. This infection process can give rise to tan‐coloured symptoms typical of botrytis disease that radiate from this part of the flower. Subcuticular hyphae were present at high density near stamen bases and evidently resulted from multiple penetrations from single infection cushions. The subcuticular hyphae grew within the hypanthium and towards the centre of the floral tube. When flower abscission occurred, floral tube tissues close to the abscission zone remained uninfected. This observation infers possible transmission of a signal (e.g. ethylene) upon B. cinerea infection. Thus, B. cinerea causes flower abscission apparently as a defence response.

Postharvest UV-C irradiation on cut Freesia hybrida L. inflorescences suppresses petal specking caused by Botrytis cinerea

Postharvest petal specking caused by Botrytis cinerea is a major concern for freesia growers and sellers in Holland and the UK. Germicidal and inducible host defence effects of UV-C irradiation were evaluated. UV-C irradiation of freesia inflorescences after artificial inoculation with B. cinerea (i.e. the germicidal effect) was more effective in reducing petal specking, compared to UV-C treatment before artificial inoculation (i.e. the defence induction effect). Cut freesia inflorescences exposed to 1 kJ m −2 UV-C after artificial inoculation with 10 4 B. cinerea conidia mL −1 displayed reduced disease severity scores, lesion numbers and lesion diameters by 74, 68 and 14%, respectively, compared to non-irradiated control inflorescences. In contrast, UV-C irradiation with 1 kJ m −2 before artificial inoculation reduced lesion numbers and lesion diameters by 13 and 24%, compared to the non-irradiated controls. Higher UV-C doses of 2.5 or 5 kJ m −2 reduced disease severity scores, lesion numbers and lesion diameters when applied after artificial inoculation, but enhanced disease when applied before artificial inoculation. Vase life of cut freesia inflorescences irradiated with 0.5, 1 or 2.5 kJ m −2 UV-C was maintained equal to non-irradiated controls. However, 5 kJ m −2 resulted in phytotoxicity evident as petal discoloration and reduced vase life compared to non-irradiated inflorescences.

Antifungal Activities of Chelidonium majus Extract on Botrytis cinerea in vitro and Ultrastructural Changes in its Conidia

AbstractThe extract from the aboveground parts of Chelidonium majus reduced the mycelial growth of Botrytis cinerea on Czapek agar medium. In minimum fungicidal concentration (60 μl/ml), the extract induced irreversible ultrastructural changes in B. cinerea conidia.