Botrytis Spores Research Articles

Paraburkholderia phytofirmans PsJN delays Botrytis cinerea development on grapevine inflorescences.

Grapevine flowering is an important stage in the epidemiology of Botrytis cinerea, the causal agent of gray mold disease. To prevent infection and to minimize postharvest losses, the control of this necrotrophic fungus is mainly based on chemical fungicides application. However, there is a growing interest in other control alternatives. Among them, the use of beneficial microorganisms appears as an eco-friendly strategy. This study aims to investigate the effect of Paraburkholderia phytofirmans PsJN, root-inoculated or directly sprayed on fruiting cuttings inflorescences to control B. cinerea growth. For this purpose, quantification by real time PCR of Botrytis development, direct effect of PsJN on fungal spore germination and chemotaxis were assayed. Our results showed a significant protective effect of PsJN only by direct spraying on inflorescences. Moreover, we demonstrated an inhibition exerted by PsJN on Botrytis spore germination, effective when there was a direct contact between the two microorganisms. This study showed that PsJN is positively attracted by the pathogenic fungus B. cinerea and forms a biofilm around the fungal hyphae in liquid co-culture. Finally, microscopic observations on fruit cuttings revealed a co-localization of both beneficial and pathogenic microorganisms on grapevine receptacle and stigma that might be correlated with the protective effect induced by PsJN against B. cinerea via a direct antimicrobial effect. Taking together, our findings allowed us to propose PsJN as a biofungicide to control grapevine gray mold disease.

Hormetic Responses of Photosystem II in Tomato to Botrytis cinerea.

Botrytis cinerea, a fungal pathogen that causes gray mold, is damaging more than 200 plant species, and especially tomato. Photosystem II (PSII) responses in tomato (Solanum lycopersicum L.) leaves to Botrytis cinerea spore suspension application were evaluated by chlorophyll fluorescence imaging analysis. Hydrogen peroxide (H2O2) that was detected 30 min after Botrytis application with an increasing trend up to 240 min, is possibly convening tolerance against B. cinerea at short-time exposure, but when increasing at relative longer exposure, is becoming a damaging molecule. In accordance, an enhanced photosystem II (PSII) functionality was observed 30 min after application of B. cinerea, with a higher fraction of absorbed light energy to be directed to photochemistry (ΦPSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in a significant decrease in the dissipated non-regulated energy (ΦNO), indicating a possible decreased singlet oxygen (1O2) formation, thus specifying a modified reactive oxygen species (ROS) homeostasis. Therefore, 30 min after application of Botrytis spore suspension, before any visual symptoms appeared, defense response mechanisms were triggered, with PSII photochemistry to be adjusted by NPQ in a such way that PSII functionality to be enhanced, but being fully inhibited at the application spot and the adjacent area, after longer exposure (240 min). Hence, the response of tomato PSII to B. cinerea, indicates a hormetic temporal response in terms of “stress defense response” and “toxicity”, expanding the features of hormesis to biotic factors also. The enhanced PSII functionality 30 min after Botrytis application can possible be related with the need of an increased sugar production that is associated with a stronger plant defense potential through the induction of defense genes.

Analysis of Tomato Post-Harvest Properties: Fruit Color, Shelf Life, and Fungal Susceptibility.

A wide variety of fresh market and processing tomatoes (Solanum lycopersicum) is grown and consumed worldwide. Post-harvest losses are a major contributing factor to losses in crop productivity and can account for up to 50% of the harvest. To select and breed elite tomato varieties, it is important to characterize fruit quality and evaluate the post-harvest properties of tomato fruits. This includes the analysis of shelf life (the period during which a fruit remains suitable for consumption without qualitative deterioration), color, and pathogen susceptibility. Tomato shelf life depends upon the rate of fruit softening which accompanies fruit ripening and exacerbates damage during transport and handling. Furthermore, the susceptibility of tomatoes to fruit pathogens is also often linked to fruit ripening, especially for necrotrophic fungi such as Botrytis cinerea, also known as gray mold. The methods described here are critical for determining fruit quality and fungal susceptibility during storage. © 2020 The Authors. Basic Protocol 1: Fruit color as a determinant of fruit quality Basic Protocol 2: Shelf life test of tomato fruits Basic Protocol 3: Botrytis cinerea pathogen test of tomato fruits Support Protocol: Preparation of Botrytis spore inoculum.

Calcium Application Method Impacts Botrytis Blight Severity on Petunia Flowers

Two application methods of calcium (Ca), fertigation and spray, were investigated regarding their effects on Botrytis blight on petunia (Petunia ×hybrida) flowers. Plants were grown for 6 weeks with three nutrient solutions consisting of 0, 100, or 200 mg·L−1 Ca and weekly calcium chloride (CaCl2) sprays of 0, 750, or 1500 mg·L−1 Ca for a total of nine treatment combinations. Flowers were harvested, inoculated with Botrytis spores, placed in humidity chambers, and evaluated for Botrytis blight severity. Disease severity decreased by 57% and 70% when flowers were treated with Ca spray applications of 750 and 1500 mg·L−1 Ca, respectively; however, no change in disease severity occurred across the Ca fertigation applications. Ca concentration in the flower petal tissue increased with the Ca spray applications: the flower petal Ca concentration increased from 0.26% to 0.65% of tissue dry mass (DM) as the Ca spray application rate increased from 0 to 1500 mg·L−1. However, no change was observed across the Ca fertigation treatments. Leaf tissue Ca concentration increased from 2.1% to 3.2% DM as the fertigation solution increased from 0 to 200 mg·L−1 Ca, whereas spray application had no significant effects of leaf tissue Ca concentration. The results demonstrate that spray application is a more effective technique than fertigation application to provide higher Ca tissue concentrations in flowers, and that the Ca concentration in flower petal tissue is an important consideration when evaluating tissue susceptibility to Botrytis blight. Because of the high rate of fungicide resistance to Botrytis cinerea found in commercial greenhouses, spray applications of CaCl2 are an important disease management tool for commercial growers.

First Report of Botrytis mali Causing Gray Mold on Strawberry in California

Gray mold of strawberry is caused by Botryotinia ricini, Botrytis caroliniana, Botrytis cinerea, Botrytis fragariae, and Botrytis mali, but only B. cinerea has been reported in California (Amiri et al. 2016; Dowling et al. 2017). In 2016, spores of Botrytis spp. were collected from strawberry fruit symptomatic of gray mold from 40 fields distributed throughout California’s strawberry production acreage. A PCR-based assay of variability within the NEP2 gene was used to differentiate a proportion of these isolates between B. cinerea, B. fragariae, and B. mali (Dowling et al. 2017). Out of 80 isolates, one isolate collected from Coachella Valley was B. mali. In vitro colony morphology was slightly different from B. cinerea with more pronounced aerial mycelium. Conidia measured 10.5 to 13.5 x 8.7 to 10.2 µm (average 10.5 x 8.8 µm). This isolate was also characterized as resistant to fludioxonil, reduced sensitivity to polyoxin D, and sensitive to boscalid, cyprodinil, fenhexamid, iprodione, isofetamid, penthi...

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.

Natural Products to Control Postharvest Gray Mold of Tomato Fruit- Possible Mechanisms

Grey mold is the one of most important postharvest disease of tomato fruit worldwide. Treatments with edible, natural products are needed to reduce losses and contribute to food sustainability. Based on the hypothesis that inhibition of Botrytis spore germination will significantly reduce postharvest losses, botanicals were tested for their effects on conidia. Ten Botrytis isolates from rotting tomato fruit collected at seventeen different sites in Hawaii were identified morphologically and confirmed by DNA sequence analysis. Effects of plant extracts on spore germination were assessed at several dilutions. Leaves of candidate biocontrol plants were frozen at -20°C and plant fluids were sterilized by passing through a 0.22 μm millipore. The effect of plant extracts on germination of Botrytis spores (106/ml) in sterile malt extract broth was evaluated in multi-well microplates using preparations ranging from 10 to 40%. Changes in absorbance measured at 6, 12, and 24 hours after inoculation were analyzed with Gen5 software. Capsicum chinense cultivars Datil and C. annuum Carnival completely inhibited fungal germination at all evaluation times. Extracts from Capsicum species were superior to all other extracts tested. Treatments with 40% extracts increased the generation of intercellular reactive oxygen species in the fungal conidia. Plasma membrane damage was shown with fluorescence microscopy when extract-treated conidia were stained with propidium iodide. Loss of integrity in the spore plasma membrane appears to account for the inhibition of Botrytis spore germination. Extracts from the two pepper cultivars, Datil and Carnival, showed promise as pre-harvest sprays in the greenhouse and as edible coatings on tomato fruit postharvest to reduce grey mold.

Computer fluid dynamics prediction of climate and fungal spore transfer in a rose greenhouse

Fungal pathogens and especially grey mould are among the most virulent bio-aggressors of protected crops. A warm, moist greenhouse climate encourages the outbreak of explosive epidemics, of Botrytis cinerea in particular . The aim of this study was to simulate Botrytis spore concentration and deposition patterns in a greenhouse and model the inside climate conditions. The general flow equations were solved using the Fluent® CFD code with a simulation of the coupling between aerial transport and crop activity based on earlier research. A specific Eulerian particle transfer module was added to account for spore transfer with a new species: the Botrytis spore concentration. To describe the spore transport equation, the governing equations were modified, adding a vertical terminal velocity term accounting for the effect of gravity on the spores and sink terms accounting for spore interception by impaction or deposition. The necessary parameters for the model, together with spore concentration and climate boundary conditions, were determined in an experimental study of a rose greenhouse with roof and lateral vents equipped with insect-proof nets. These experimental devices have already been exploited for validating a ventilation model and a Botrytis spore balance. In addition to these previous studies, the present paper was essentially designed to determine greenhouse climate and spore concentration and deposition patterns. The accuracy of the inside–outside air temperature difference simulation is good but deteriorates for inside–outside air humidity. Spore transfer is also accurately simulated, with a mean error of only 0.2 sp m −3 for daytime and 0.53 sp m −3 for night time. The observed values of spore deposition show a similar order of magnitude to the simulations. However, validation was hindered by difficulties encountered in measuring spore deposition, even on an average daily time scale. Analysis of the heterogeneity of the simulated distribution of spore deposition and concentration revealed that, when the Botrytis spores came from outside, their concentrations in the air are filtered by the insect proof nets on the vent openings and then by the crop canopy – the rose stems, buds and leaves. Consequently, if, as in this case, no inoculums is produced inside the greenhouse, we note a considerable decrease in inside airborne spore concentration due to these various filters and considerable spore deposition on the crop cover near the vent openings where the air enters. This approach can provide information's on the patterns of inoculums deposition and climate conditions explaining the risks of future fungal development.

The use of aerobiological methods for forecasting Botrytis spore concentrations in a vineyard

Grey mould, caused by Botrytis cinerea, is one of the most common diseases in Galician vineyards. Knowledge of local airborne spore concentrations is of great value for developing models to predict fungal propagule concentrations, thus enabling phytosanitary treatments to be applied when a real risk of infection is detected. In order to develop an accurate model for forecasting airborne B. cinerea spore concentrations, a phenological and aerobiological survey was carried out in a vineyard located in Galicia (north-west Spain), from 2004 to 2008. Phenological observations were made on 20 vines of each of three grape varieties (Treixadura, Godello and Loureira) using the BBCH standardised phenological scale. A Hirst-type volumetric spore-trap was used for the aerobiological monitoring. The study sought to chart Botrytis spore concentrations as function of grapevine phenological stage. The highest spore concentrations over the grapevine cycle as a whole were recorded in 2008 (37299 spores), and the lowest in 2005 (1700 spores). In the five study years, the highest concentrations were registered during stage 8 (berry ripening), stage 7 (fruit development) and stage 5 (inflorescence emergence). The weather-related parameters displaying the most significant correlation with spore concentrations were dew point and relative humidity. ARIMA (Autoregressive Integrated Model of Running Mean) time-series models was used to forecast daily spore concentrations, considering B. cinerea spore concentrations and weather data as predictor variables.

EFFECTS OF GROWTH CONDITIONS ON POSTHARVEST BOTRYTIS INFECTION IN GERBERA – A NURSERY COMPARISON

Botrytis cinerea is one of the main postharvest problems in gerbera cut flowers. There are clear differences among growers in the percentage of flowers showing symptoms of Botrytis infection after harvest. Because the factors causing these differences are uncertain, cultivation parameters of twelve different growers were followed and a nursery comparison was carried out. Gerbera flowers ‘Dino’ were sampled twelve times; six times in autumn 2006 and six times in spring of 2007. At the nurseries climate (air temperature, relative humidity, light intensity and CO2 concentration) was logged, and plant density, plant age and other characteristics were monitored. Before each harvest Botrytis spores were trapped in the greenhouses and counted. After sampling, flowers were treated according to a standard transport simulation. Thereafter Botrytis infection was monitored, and statistical analyses were performed on the effect of the pre-harvest conditions on Botrytis infection in the postharvest stage. Clear influence of the spore level in the greenhouse was observed. When a sufficient number of spores were present in the greenhouse environment, the humidity level and the intensity and duration of irradiation had the strongest influence on infection. In general, factors those lead to a dry microclimate such as the use of ventilators, the use of supplemental lighting and a low plant density were related with a lower number of lesions on gerbera petals in the postharvest phase.

Botrytis cinerea spore balance of a greenhouse rose crop

Fungal pathogens are among the most virulent bioagressors of protected crops. For sustainable plant production and to protect the crop against these airborne organisms one must determine their origin, i.e. whether they come from outside the greenhouse or are produced inside it. We considered Botrytis cinerea spore concentration as a particular physical species which is transported by air in the same way as heat, CO 2, water vapour or any tracer gas. We constructed a mass balance of the viable Botrytis spores on the whole-greenhouse volume to assess the inside production of spores and their exchanges. The different elements in the spore balance are considered and are determined experimentally: • spore transfer into or out of the greenhouse is deduced from the difference between the inside and outside spore concentrations, measured by spore traps, multiplied by the whole-greenhouse ventilation rate; • spore deposition on soil and crop and spore impaction on the plants is deduced from observations made using Petri dishes; • inside spore production is the differential term deduced from the whole-greenhouse volume balance. The first measurements and calculations have shown that the presence of insect-proof nets across the greenhouse openings strongly influences the spore balance, as the nets intercept the B. cinerea spores proportionally to the nets’ solidity. Based on wind tunnel experiments, the interception capacity of the nets was quantified and the whole model completed in consequence. These results show the diurnal Botrytis spore balance over 3–4-week periods in the autumn and spring season for a young rose plantation. In agreement with visual observations of B. cinerea sporulation within the greenhouse, it is shown that the origin of the inocula is predominantly internal (2/3 in quantity). However, due to outside climate and greenhouse opening, it can vary widely from one period to another, with a tendency to become predominantly internal as the crop ages.

Improvement of the Fungal Biocontrol Agent Trichoderma atroviride To Enhance both Antagonism and Induction of Plant Systemic Disease Resistance

Biocontrol agents generally do not perform well enough under field conditions to compete with chemical fungicides. We determined whether transgenic strain SJ3-4 of Trichoderma atroviride, which expresses the Aspergillus niger glucose oxidase-encoding gene, goxA, under a homologous chitinase (nag1) promoter had increased capabilities as a fungal biocontrol agent. The transgenic strain differed only slightly from the wild-type in sporulation or the growth rate. goxA expression occurred immediately after contact with the plant pathogen, and the glucose oxidase formed was secreted. SJ3-4 had significantly less N-acetylglucosaminidase and endochitinase activities than its nontransformed parent. Glucose oxidase-containing culture filtrates exhibited threefold-greater inhibition of germination of spores of Botrytis cinerea. The transgenic strain also more quickly overgrew and lysed the plant pathogens Rhizoctonia solani and Pythium ultimum. In planta, SJ3-4 had no detectable improved effect against low inoculum levels of these pathogens. Beans planted in heavily infested soil and treated with conidia of the transgenic Trichoderma strain germinated, but beans treated with wild-type spores did not germinate. SJ3-4 also was more effective in inducing systemic resistance in plants. Beans with SJ3-4 root protection were highly resistant to leaf lesions caused by the foliar pathogen B. cinerea. This work demonstrates that heterologous genes driven by pathogen-inducible promoters can increase the biocontrol and systemic resistance-inducing properties of fungal biocontrol agents, such as Trichoderma spp., and that these microbes can be used as vectors to provide plants with useful molecules (e.g., glucose oxidase) that can increase their resistance to pathogens.

Variation in fungal spore concentrations of selected taxa associated

The aim of the study was to determine seasonal variation in concentrations of selected fungal spore types due to meteorological parameters. The presence of spores of thirteen taxa: Cladosporium, Torula, Alternaria, Botrytis, Epicoccum, Stemphylium, Ganoderma, Erysiphales, Entomophthora, Drechslera type, Didymella, Polythrincium and Pithomyces was recorded in Cracow using a Burkard trap. The majority of selected taxa belong to the anamorphic fungi group, the others to Ascomycetes, Basidiomycetes and Zygomycetes. Fungal spores were present in the air in large numbers throughout the summer with the highest levels being reached in June, July and August although their highest concentrations differed with time. For most of the studied spore types: Botrytis, Ganoderma, Alternaria, Epicoccum, Torula, Drechslera type, Polythrincium, Stemphylium and Pithomyces the peak period was recorded in August. Didymella and Entomophthora spores reached their highest concentrations in July while concentrations of Erysiphales and Cladosporium spores were highest in June. Multiple regression analysis was performed for two seasonal periods: pre-peak and post-peak. In the pre-peak period concentrations of 10 spore types: Cladosporium, Botrytis, Epicoccum, Stemphylium, Drechslera type, Pithomyces, Didymella, Erysiphales, Ganoderma and Entomophthora were strongest influenced by minimum temperature while Alternaria, Polythrincium and Torula by maximum temperature (significance level of I±=0.05). During the post-peak period the most important factor affecting variation in concentrations of Botrytis, Polythrincium, Didymella, Erysiphales, Ganoderma and Entomophthora spores was the minimum temperature. For Alternaria, Cladosporium, Epicoccum and Torula the maximum temperature appeared to be the most influential, whereas for Drechslera type, Stemphylium and Pithomyces it was sunshine. All correlations between spore concentration, minimum and maximum temperature and sunshine were significant (significance level of I±=0.05), and positive although the percentage of explained variation (R2) was low.

Differentiation of allergenic fungal spores by image analysis, with application to aerobiological counts

The ability of an image analysis routine to differentiate between spores of eleven allergenic fungal genera was tested using analysis based on seven basic and up to 17 more complex features, extracted from digitised images. Fungal spores of Alternaria, Cladosporium, Fusarium, Aspergillus, Penicillium, Botrytis, Epicoccum, Exserohilum, Ustilago, Coprinus and Psilocybe were examined in a series of experiments designed to differentiate between spores at the genus and species level. Linear and Quadratic Discriminant Analysis of feature measurements, recorded for 100 to 1600 spores per taxon, differentiated between genera and species with a high level of accuracy. Genus comparisons using only seven basic features resulted in 98% accuracy for the recognition of conidia belonging to Cladosporium, Fusarium and Epicoccum. Differentiation between conidia of Aspergillus and Penicillium was the least reliable, with 56% of Aspergillus conidia correctly identified and 41% misidentified as Penicillium. At the species level, conidia of Cladosporium macrocarpum, Fusarium moniliforme (microconidia), F. oxysporum (microconidia), F. solani (macroconidia), Alternaria helianthi and A. brassicae were consistently identified with 86--100% accuracy. Reduced levels of accuracy in the identification of spores by image analysis reflected similarities between species in their spore morphology. The application of image analysis to aerobiological counting methods is discussed in relation to the results obtained.

Phytotoxocity of vapour phase hydrogen peroxide to Thompson Seedless grapes and Botrytis cinerea spores

The tolerance of Botrytis cinerea Pers. spores and Thompson Seedless grapes ( Vitis vinifera L.) to vapour phase hydrogen peroxide (H 2O 2 vapour) at various concentrations and temperatures was determined. The germination rate of botrytis spores decreased logarithmically with exposure time to H 2O 2 vapour. Treatments of 0.27 and 0.55 mg l −1 H 2O 2 vapour at 20 or 30 °C, respectively, required 10.5 and 5.7 min to kill 99% of the spores. Grapes did not develop visible injury until they were exposed to 0.55 mg l −1 H 2O 2 vapour for 6 h at 40 °C. Injury developed as a yellow-brown discoloration of the fruit and stems. Discoloration increased with time of exposure and concentration of H 2O 2 vapour. High treatment temperatures also increased the rate of discoloration. Prolonged exposure to H 2O 2 vapour caused increased water loss and loss of firmness of the grapes. Grapes were able to tolerate exposures of 0.27 mg l −1 H 2O 2 vapour at 40 °C for 24 h with no visible injury. The difference in the tolerance of botrytis spores and grapes to H 2O 2 vapour may allow its use to control botrytis bunch rot in stored table grapes.

Vapor Phase Hydrogen Peroxide Inhibits Postharvest Decay of Table Grapes

The potential use of vapor phase hydrogen peroxide (VPHP) to prevent decay caused by Botrytis cinerea Pers. ex Fr. in table grapes (Vitis vinifera L.) was investigated. `Thompson Seedless' and `Red Globe' grapes, inoculated with Botrytis cinerea spores, were placed in polyethylene bags and flushed for 10 minutes with VPHP generated from a 30% to 35% solution of liquid hydrogen peroxide at 40C. Immediately after treatment, bags were sealed and held at 10C. Vapor phase hydrogen peroxide significantly reduced the number of terminable Botrytis spores on grapes. The number of terminable spores on `Thompson Seedless' and `Red Globe' grapes had been reduced 81% and 62%, respectively, 24 hours following treatment. The incidence of decay on inoculated `Thompson Seedless' and `Red Globe' grapes was reduced 33% and 16%, respectively, after 8 days of storage at 10C compared with control fruit. Vapor phase hydrogen peroxide reduced the decay of noninoculated `Thompson Seedless' and `Red Globe' grapes 73% and 28%, respectively, after 12 days of storage at 10C. Treatment with VPHP did not affect grape color or soluble solids content.

Influence of Resveratrol on Germination of Conidia and Mycelial Growth of Botrytis cinerea and Phomopsis viticola

Abstract After inoculation of agar substrates containing resveratorl (an inducible stilbene characteristic for Vitaceae) with low concentrations (500/cm2) of Botrytis spores, developing germ tubes showed malformations and growth stopped. High, density inoculations (10,000/cm2) resulted in apparently normal growth, but stress conditions were indicated by the formation of a large number of sclerotia after 14 days. By contrast, growth of Botrytis and Phomopsis colonies starting from pieces of mycelium was slowed down by resveratrol concentrations 50 ppm and stopped by higher concentrations. More than 500 ppm (suspensions) induced rhythmical growth; at the front of the mycelium a clear zone appeared, which was free fromstilbene crystals but exhibited a brownish pigmentation. In liquid cultures pigmentation but no growth inhibition was observed. It is assumed that resveratrol is oxidized by fungal laccases whose isoenzyme bands can be stained with resveratrol after isoelectric focusing. The different effects of this substrate on fungal growth in liquid and on solid media is explained by the localized action of laccases on solid substances where the radius of diffusion is limited.

Bovine nasal granuloma in Victoria -- a search for the causative allergens.

Cows with nasal granuloma showed skin sensitivity to a range of environmental allergens while clinically normal control animals showed little sensitivity. The allergens producing the greatest number of positive reactions included the pollens of dock, capeweed, clover, paspalum, sorrel, rye grass, pepper tree and wattle, the spores of penicillium, cladosporium, botrytis and rye grass rust and extracts of sheep's wool and mite. It is likely that different allergens are important in different animals and in different regions and their importance in the aetiology of nasal granuloma probably depends on their presence in the inhaled air in high concentration for long periods.

Structures and pesticidal activities of derivatives of dinitrophenols. XII. In vitro activity of C3 to C13 alpha-branched alkyldinitrophenols and their esters and ethers against the spores of Venturia inaequalis and other fungi.

AbstractThe activity in vitro of 2‐(C3 to C13 α‐branched alkyl)‐4,6‐dinitrophenols and 4‐(C4 to C13 α‐branched alkyl)‐2,6‐dinitrophenols and of their various esters and ethers was determined against the spores of Venturia inaequalis (Cooke) Wint., Botrytis cinerea Pers., Fusarium bulbigenum, Cooke & Massee, var. lycopersici (Brushi) Wollenw. and Cercospora melonis Cooke. Several alkyldinitrophenols were highly active against Venturia and the 2‐alkylphenols were generally more active than the 4‐alkylphenols. The alkyldinitrophenols were not effective against the spores of Botrytis, Fusarium and Cercospora..Esterification of several lower alkyldinitrophenols to methyl carbonates gave compounds with enhanced activity, but methyl carbonates of C7 to C11 alkyl dinitrophenols showed considerably reduced activity. Esterification to ethyl‐ or other alkyl‐carbonates gave compounds with considerably reduced activity against Venturia. Esterification of 2‐isopropyl‐ and 2‐t‐butyl‐4,6‐dinitrophenols to crotonates gave compounds with enhanced activity against Venturia, but crotonates of other phenols showed reduced activity. The acrylates of several C6 to C8 alkyl dinitrophenols proved highly active. Ethers of active phenols showed considerably reduced activity.

On Autotropism in Botrytis: Measurement Technique and Control by CO2

The mutual orientation of the germination of nearby pairs of Botrytis spores growing in a simple, dilute medium was studied. If the medium is equilibrated with room air, they show a very strong tendency to germinate both toward each other and in a cis arrangement, i.e., toward the same side of the line joining their centers. If the medium is equilibrated with air enriched with 0.3% or 3% CO(2), (i.e., 10 or 100 times the normal CO(2) concentration) then the cells show an equally strong tendency to germinate away from each other. The interaction shows little dependence upon pH.