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Antifungal compounds in Geraldton waxflower tissue
Abstract
Geraldton waxflower is the most economically important native Australian cut flower export. Infection of waxflower by Botrytis cinerea can lead to unacceptable levels of flower abscission after harvest. An investigation was conducted into the nature and identities of constitutive antifungal compounds in flowers and leaves. Antifungal activity against B. cinerea ( pathogen) and Cladosporium cladosporioides (bioassay organism) was observed in leaf and flower extracts. Leaf tissue contained less antifungal activity than flower tissue. Four antifungal compounds were common to the three different waxflower cultivars studied. Two antifungal compounds were identified as the sesquiterpene, globulol, and the monoterpene, grandinol. At least two unidentified phenolic compounds also demonstrated strong antifungal activity. Notwithstanding general similarities in antifungal profiles, it was evident from TLC bioassays that variations exist in some antifungal compounds between different waxflower cultivars.
... de Vries, were recovered from naturally infected strawberry cv. Elsanta fruit (Terry et al., 2003). They were cultured in 9 cm diameter Petri plates on ½ strength PDA (potato dextrose agar; 19.5 g l -1 distilled water) (Oxoid Ltd., Berkshire, UK) at 22 ±1 and 20 ±1°C, respectively. ...
... TLC plates were developed in either one or two dimensions (1-D, 2-D) at approximately 22°C in a TLC tank (20 x 20 x 10 cm) lined with filter paper to create a solvent saturated atmosphere. 1-D TLCs were developed either in 100 ml of running solvents comprised of hexane: ethyl acetate: methanol (A = 60:40:1; B = 60:40:10; C = 60:40:20; D = 60:40:30 v/v/v) (Terry et al., 2003) or in the organic phase of ethyl acetate: benzene: ethanol (4:1:1, v/v/v; Mussell and Staples, 1971). 2- D TLCs (Wedge and Nagle, 2000) were developed in solvent system A (1-D) and then solvent system D (2-D). ...
... After examination, ammonia was removed from plates by air drying for 1h. Replicate plates were sprayed with 10% w/v phosphomolybdic acid (PMA) in ethanol, and heated to about 100°C for 2 min (Terry et al., 2003). PMA is a general visualisation reagent for oxidizable compounds. ...
Antifungal activity against the pathogen, Botrytis cinerea, and a bioassay organism, Cladosporium cladosporioides, declined with advancing strawberry fruit maturity as shown by thin layer chromatography (TLC) bioassays. Preformed antifungal activity was also present in flower tissue. The fall in fruit antifungal compounds was correlated with a decline in natural disease resistance (NDR) against B. cinerea in planta. Crude extracts of green stage I fruit (7 days after anthesis) contained at least two preformed antifungal compounds (Rf=0.44 and 0.37) that were not present in white and red stage fruit. These compounds were shown with TLC reagent sprays to be neither phenolics nor alkaloids. Positive reactions to Ehrlich’s reagent suggested that Rf=0.37 was a terpene. Most antifungal activity was found in the achenes of green stage I fruit. However, antifungal activity was found in all tissue types (viz. pith, cortex, epidermis) of green stage I fruit. TLC bioassays revealed that all fruit stages yielded antifungal activity at the origin (Rf=0.00). The approximate area of fungal inhibition at the origin in green stage 1 fruit extracts was 1.87- and 1.73-fold greater than in white and red stages, respectively. TLC reagent sprays showed that the antifungal compound(s) at origin included phenolics. This observation is consistent with previous reports that phenolic compounds in strawberry fruit are inhibitory to B. cinerea.
... Once the compounds have been separated, the plates are dried and spores/ conidia can then be sprayed on the surface. Compounds with antifungal activity can be identified as the area with reduced mycelial growth (Adikaram and Ratnayake Bandara, 1998; Terry et al., 2003 Terry et al., , 2004). The identity of these antifungal compounds can be determined by developing spots of known standards. ...
... Once the compounds have been separated, the plates are dried and spores/conidia can be sprayed on the surface. Compounds with antifungal activity can be identifi ed as the area with reduced mycelia growth (Adikaram and Ratnayake Bandara, 1998;Terry et al., 2003Terry et al., , 2004. The identity of these antifungal compounds can be determined by developing spots of known standards. ...
Since it is widely recognized that the benefi cial infl uence of fruit on human health is linked with the presence of specifi c phytochemicals, the determination of the nature of these com-pounds in different commodities and the infl uence of preharvest, postharvest and pro-cessing treatments has been a main area of research (Espín et al., 2007; Frankel, 2007). Antioxidants can be measured as individual compounds or as a total capacity, yet some methods which quantify total antioxidant activ-ity are thought to take into account compounds not classed as antioxidants, for instance, reduc-ing sugars (Huang et al., 2005). This chapter summarizes the wide variety of extraction and characterization techniques which are used to quantify individual or total antioxidants, as well as other bioactive compounds. 18.2 Sample Preparation Fruit and vegetables contain a complex pro-fi le of bioactive compounds, of which most are labile to heat, air and/or light (Brat, 2008). To extract bioactive compounds effectively from fresh tissue, samples are usually cut into small pieces and then snap-frozen immediately in liquid nitrogen since chopped material is much more unstable. Failure to prepare sam-ples in this way can result in enzymatic browning, as well as undesirable molecular, biochemical and physiological changes. Sam-ples are often freeze-dried before extraction takes place to remove water. Lyophilization aids sample grinding, which benefi ts extrac-tion by increasing solvent penetration due to greater sample surface area. Puupponen-Pimiä et al. (2003) have investigated the effects of freezer storage on fresh vegetables. After being frozen quickly to –40°C (method not stated), frozen vegetables were then stored at –20°C for 6, 12 and 18 months. The authors found that different bioactives were affected by long-term freezer storage in dif-ferent vegetable groups. A decrease in α-and β-carotene was observed in processed carrots yet not in peas between 6 and 12 months at –20°C. Similarly, over twofold reductions of quercetin and kaempferol content were observed in caulifl ower and broccoli over the same period. It is therefore important, espe-cially when comparing different fruit and veg-etable groups, that analyses are undertaken as soon as possible after sample preparation and ideally that samples are kept at or below –40°C. Differences among the literature may indeed be due to sample preparation and subsequent storage.
The leaf essential oil of Dendropanax gonatopodus from Monteverde, Costa Rica, has been obtained by hydrodistillation and the chemical composition determined by GC-MS. The major components in the leaf oil were (E)-2-hexenal (16.9%), terpinolene (14.8%), δ-cadinene (13.5%), (E)-caryophyllene (9.9%), and α-copaene (7.3%). Minor amounts of the aromadendrane sesquiterpenoids aromadendrene (0.3%), alloaromadendrene (0.3%), spathulenol (0.6%) and globulol (0.6%) were also detected. An ab initio investigation of the aromadendrane sesquiterpenoids has been carried out using both density functional (B3LYP/6-31G*) and post Hartree-Fock (MP2/6-31G**) methods. The calculated relative energies of the aromadendranes belie their relative concentrations generally observed in essential oil compositions.
Origins and economic importanceGeneral fruit anatomyFruit developmentFruit ripeningPost-harvest handlingSelective gaseous atmosphere storagePost-harvest diseaseGenetic transformationConclusion
Ethanol-dichloromethane crude extract from peel of pear (Pyrus bretschneideri Rehd. cv. Pingguoli) was separated by thin layer chromatographic plates and bioassayed with conidia of Alternaria alternata. The inhibition zones differed significantly in retention factor (Rf) at expanding stage, harvest time and after 100 days of cold storage. The compounds in the inhibition zones were isolated and identified with gas chromatography and mass spectroscopy. Palmitate methyl, oleic acid methyl, linolenic acid methyl and squalene were present at all stages. The concentration of these chemicals was the highest in expanding stage fruit peel and decreased rapidly with fruit development. It is suggested that these compounds may be the main antifungal compounds in the growing fruit. The phthalate alkyl esters occurred at relatively higher concentrations in pear peel at harvest and after 100 days of cold storage. Six phthalate alkyl esters were identified from peel of pear fruit after 100 days of cold storage. It is also supposed that these esters may be the antifungal compounds in postharvest pear.
Fusarium rot caused by Fusarium oxysporum f. sp. melonis, causes significant postharvest losses in rockmelon crops. Although latent infection is often present in the field, symptoms
of the disease may not appear until fruit maturity. The susceptibility of different-aged rockmelon fruit cv. “Colorado” was
determined by inoculating fruit at different stages of development with a spore suspension of F. oxysporum f. sp. melonis. Disease symptoms appeared first and were more severe in older fruit compared to younger fruit. Disease symptoms on fruit
35 DAA (Days After Anthesis) and 42 DAA appeared within 3days of inoculation and rapidly covered the fruit within 5days.
In contrast, disease symptoms on fruit 7 DAA appeared 6days after inoculation and grew slowly. Extraction of antifungal compounds
without involving acid hydrolysis from 7 DAA fruit rind did not show antifungal activity on TLC plates. However, hydrolysis
of the ethyl acetate fraction resulted in a strong fungal inhibitory zone on agar plates against colonies of F. oxysporum f. sp. melonis. Separation of the hydrolysed crude extracts on TLC plates indicated the presence of two distinct antifungal zones with Rf 0.36 and 0.13 in young fruit 7, 14 and 21 DAA. The area of fungal inhibition of compound Rf 0.36 was greater than that of Rf 0.13 on the TLC plate. Extracts from mature fruit of 35 and 42 DAA did not have detectable levels of antifungal compounds.
The decrease in the susceptibility of rockmelon fruit during maturity may be correlated to a decrease in the antifungal compounds
in the fruit with maturity.
KeywordsInduced resistance-Latent infection-Phytoalexin-Phytoanticipin-Systemic acquired resistance-Thin layer chromatography
Increasing loss of conventional fungicides due to pathogen resistance and general unacceptability in terms of public and environmental risk have favoured the introduction of integrated pest management (IPM) programmes. Induction of natural disease resistance (NDR) in harvested horticultural crops using physical, biological and/or chemical elicitors has received increasing attention over recent years, it being considered a preferred strategy for disease management. This article reviews the enhancement of constitutive and inducible antifungal compounds and suppression of postharvest diseases through using elicitors. The effect of timing of pre- and/or postharvest elicitor treatment and environment on the degree of elicitation and the potential for inducing local acquired resistance, systemic acquired resistance and/or induced systemic resistance to reduce postharvest disease is discussed. The review highlights that more applied and basic research is required to understand the role that induced NDR can play in achieving practical suppression of postharvest diseases as part of an IPM approach.
Cut waxflower (Chamelaucium spp. and hybrids) stems bear numerous small attractive flowers. However, unsightly flower abscission often occurs during their postharvest handling. A range of possible causes of this symptom were initially investigated, including exogenous ethylene, water deficit stress, physical injury, and pathogen infection. Ultimately, the flowers proved to be particularly susceptible to Botrytis cinerea. This cause was not initially obvious because ethylene mediated abscission was elicited by Botrytis infection before disease became evident. Airborne conidia of Botrytis are typically dispersed in the field before harvest. They require cool temperatures and, ideally, free water to germinate. Such conditions are common during handling after harvest. Botrytis can infect all organs of waxflower flowers. Under ideal incubation conditions, flower abscission occurs within 2-4 days. Flower fall occurs at least 1 day before tan coloured lesions appear. A further 1-2 days are required before superficial mycelia and conidiophores form and sporulation occurs. Heavily infected flowers become water-soaked and turn dark brown. Postharvest flower abscission in waxflower can be prevented by treatment with anti-ethylene agents, including silver thiosulphate and, to a lesser degree, 1-methylcyclopropene. However, through better understanding the host-pathogen interaction, opportunities exist to directly address the cause of the problem as opposed to the initial symptom. Fungicides are effective in suppressing Botrytis-elicited flower fall, but their use is falling from favour. In this general context, the waxflower-Botrytis pathosystem constitutes a potentially useful 'model system' for further investigation of pathogen elicited flower abscission at physiological, cellular, biochemical, and molecular levels.
B38 bacterial strain, isolated from Tunisian soil showed a strong antimicrobial activity. Based on biochemical characterization and 16S rDNA sequence analysis, B38 strain was identified as Bacillus subtilis. Cell culture supernatant showed antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus species and several Gram-positive and Gram-negative bacteria. Antifungal activity against phytopathogenic fungi was also observed. Antibacterial activity production started at early exponential growth phase, and maximum activity was reached at the stationary phase. This antibacterial activity was neither affected by proteases, lipase, and organic solvents, nor by surfactants. It was stable over a wide pH range and still active after autoclaving at 121 °C during 20 min. Thin layer chromatography followed by bioautography assay allowed the detection of four active spots with R
f values of 0.30, 0.47, 0.70, and 0.82. The single spot with R
f 0.30 showed antifungal activity, whereas the spots with R
f values of 0.47, 0.70, and 0.82 exhibited antibacterial activity.
Possible reasons for, and prevention of, postharvest floral organ fall in Geraldton waxflower (Chamelaucium unciizatum Schauer) were studied. An 11-kg compression load, equivalent to the lidding of a carton, caused flower fall amounting to 1% of the fresh mass of 420-g bunches. Fungal development also resulted in flower abscission. Healthy flowers produced little ethylene (e.g. 0.05 ¦L/kg.h), while infected flowers produced much more (e.g. 7.71 ¦L/kg.h) and were shed. Treatment with fungicide (iprodione + mancozeb) and antiethylene compounds [e.g. silver thiosulfate (STS) pulse, Purafil sorbant] reduced flowerfall in packaged flowers. Cut sprigs which suffered severe water deficit also shed flowers. In cv. Elegance, drying to -3.61 MPa elevated ethylene production (e.g. 1.35 ¦L/kg . h). Flowerfall induced by water deficit could be reduced by pretreatment with a STS pulse (0.5 mmol Ag+/L for 15-22 h at 0¦C or 4 mmol Ag+/L for 20-30 min at about 20¦C). Pretreatment with a naphthaleneacetic acid dip (50 mg/L for 1 min at room temperature) shortened the vase life of Elegance.
A simple bioautographic agar overlay assay using Candida albicans as the indicator organism for the detection and activity-guided fractionation of antifungal compounds by thin layer chromatography has been developed. Inhibition of fungal growth was assessed by the detection of dehydrogenase activity with thiazolyl blue (methylthiazolyltetrazolium chloride; MTT). A series of clinically used antimycotic agents were tested in order to determine the sensitivity of the assay. The compatibility of the agar overlay technique with chemically modified silica gel (Diol and RP-18) plates and with various organic solvents was evaluated. The methodology is also applicable to the search for antibacterial compounds, as shown with Bacillus subtilis as a test organism.
Pyrimethanil (Scala) is a fungicide that might be used for control of Botrytis cinerea infecting Geraldton waxflower. New treatments are sought to reduce the risk of developing strains of B. cinerea that are resistant to fungicides commonly used against it, such as benomyl (Benlate) or iprodione (Rovral). Scala was applied to waxflower as a postharvest dip at 1.5 or 2 mL product/L. Disease severity on and flower and leaf drop from waxflower bunches pre-inoculated with B. cinerea were significantly (P = 0.05) reduced by treatment with Scala. Further, flower and foliage vase lives were significantly (P = 0.05) longer as a result of postharvest treatment with Scala as compared with water-treated (control) stems. Similar degrees of disease control where achieved with either Scala or Rovral. The results demonstrate that Scala has real potential as an alternative fungicide for control of B. cinerea on waxflower.
Geraldton waxflower (Chamelaucium uncinatum Schauer) is Australia's most economically important cut-flower export. Its small, attractive flowers make it particularly suitable as a filler in floral arrangements. However, postharvest bud and flower abscission is a major problem during transport, handling and marketing. Abscission may be caused by wound-induced endogenous ethylene production brought about by flower tissue infection with fungal pathogens such as Botrytis cinerea. Botany and postharvest characteristics are discussed in relation to flower abscission and how resultant postharvest losses may be minimised.
This study investigated treatment of mango (Mangifera indica L.) fruit with 2 host defence-promoting compounds for suppression of anthracnose disease (Colletotrichum gloeosporioides). Cultivar ‘Kensington Pride’ fruit were treated at concentrations of up to 1000 mg/L with either potassium phosphonate or salicylic acid. Applications were by various combinations of pre- and postharvest dips and vacuum infiltration. Postharvest treatments at up to 2000 mg/L salicylic acid were evaluated in a second fruiting season. Fruit were either uninoculated or inoculated with the fungal pathogen. Colour, firmness and disease-severity were assessed during shelf life at 23°C. There were no significant (P>0.05) effects of potassium phosphonate or salicylic acid on anthracnose disease severity in the first season. Moreover, phosphonate or salicylic acid treatment did not significantly affect fruit colour or firmness changes. There were significant (P<0.05) reductions in anthracnose severity in the second season, especially at the highest concentration of 2000 mg/L salicylic acid. Mango fruit skin colour and firmness changes were also slowed down significantly (P<0.05). These effects of salicylic acid were attributed to inhibition of mango fruit skin ripening (senescence).
Variation in leaf essential oils and morphometric characters among 38 locations of Chamelaucium uncinatum were used to describe infraspecific diversity and geographic patterns of variation. Four chemical types were designated: citronellal, α-pinene or limonene dominant, or one in which all three monoterpenes were co-dominant. The citronellal and limonene types were geographically restricted but the α-pinene and co-dominant types were widespread. The citronellal type also demonstrated higher diversity (by Shannon–Weiner index) in the oil profile than the other types. Biochemical differentiation was not strongly paralleled by morphological differences between chemotypes; only the citronellal-type differed morphologically from the other three types with respect to floral bud and leaf characters. Based on biochemical and morphological differences, and geographic localization, it was concluded that the citronellal type may represent a recently evolved ecotype of C. uncinatum.
A rapid assay to determine antifungal activity in plant extracts and essential oils is described. Wells in microtiter plates were loaded with Botrytis cinerea spores and plant extracts or essential oils. Subsequent changes in optical density following spore germination in the wells was measured after 24 h using an automatic microtiter plate reader driven by a software program developed for this purpose. Extracts from 345 plants and 49 essential oils were evaluated for their antifungal activity against B. cinerea. Among 345 plant extracts analyzed, 13 showed high levels of antifungal activity, with species of Allium and Capsicum predominating. Among the 49 essential oils tested, palmarosa (Cymbopogon martini), red thyme (Thymus zygis), cinnamon leaf (Cinnamomum zeylanicum), and clove buds (Eugenia caryophyllata) demonstrated the most antifungal activity against B. cinerea. The most frequently occurring constituents in essential oils showing high antifungal activity were: D-limonene, cineole; beta-myrcene; alpha-pinene, beta-pinene; and camphor.
Sugar and protein levels and rates of respiration and ethylene production were measured for Geraldton waxflower (Chamelaucium uncinatum) flowers in order to characterise flower development and senescence in this cut flower crop. Ten sequential stages of floral development were identified. Sugar levels increased during bud development, the highest concentrations (c. 130 mg sucrose equivalents/g dry weight (DW) being measured during the nectiferous stages of flower opening. There was little variation in either soluble or insoluble protein levels during flower development, levels averaging around 19 and 25 mg bovine serum albumin (BSA) equivalents/g DW, respectively. In flowers cut and maintained individually, sugar and protein levels decreased rapidly after harvest, suggesting their use as respiratory substrates. Sprig senescence was characterised by loss in fresh weight and decreasing water use. In flowers taken from sprigs in vases, sugar and protein levels increased slightly (Day 4) before decreasing with senescence (Day 8). Flowers on sprigs appeared to deteriorate at c. 8 days after harvest, in concert with the decreasing sugar and protein levels. Respiration rates were initially high (1432 ml/kg per h) for the flowers from harvested sprigs, and declined during vase life. Ethylene production also decreased during vase life from an initial level of 1.32 μJ/kg per h. The absence of respiratory and ethylene production peaks indicates that Geraldton waxflower flowers are non‐climacteric in nature.
The essential oils from two clonal types of Thymus vulgaris (Laval-1 and Laval-2) were characterized and tested for antifungal activity. Contents were high in p-cymene, linalool, terpinen-4-ol and thymol which constituted 53.5% and 66.2% of Laval-1 and Laval-2 essential oils respectively. The essential oil volatiles from two clonal types exhibited antifungal activity against Botrytis cinerea and Rhizopus stolonifer, two common storage pathogens of strawberries (Fragaria ananassa). The inhibition of B. cinerea and R. stolonifer ranged from 26.5 to 63.5% and 5.5 to 50.5% respectively by oil from Laval-1, when exposed to concentrations of 50 to 200 ppm, while values of 36.9 to 90.5% and 11.5 to 65.8% were observed from oil from Laval-2. The decay of strawberry fruits caused by B. cinerea and R. stolonifer was controlled up to 73.6 and 73.0% respectively by volatiles from maximin concentration of Laval-1, and up to 75.8 and 74.8% from Laval-2. No visual phytotoxic symptoms were noticed for the observed period. Essential oil from Laval-2 exhibited higher antifungal activity which was related to its relatively higher content of antimicrobial compounds.
The composition of the essential oils of different genotypes of Chamelaucium uncinatum has been examined. The major compounds were identified as α-pinene, citronellal, limonene, linalool and α-terpinyl acetate. Three chemotypes of C. uncinatum were identified based on the relative proportions of α-pinene, citronellal and limonene present. Oils with α-pinene as the principal constituent were the most common.
The essential oils of species of the genus Lophostemon have been examined. The oils, which were obtained in 0.03–0.5% yields, were similar in that the principal components were α-pinene, aromadendrene, allo-aromadendrene, globulol and spathulenol. Copyright © 2000 John Wiley & Sons, Ltd.
Immunology and Cell Biology focuses on the general functioning of the immune system in its broadest sense, with a particular emphasis on its cell biology. Areas that are covered include but are not limited to: Cellular immunology, Innate and adaptive immunity, Immune responses to pathogens,Tumour immunology,Immunopathology, Immunotherapy, Immunogenetics, Immunological studies in humans and model organisms (including mouse, rat, Drosophila etc)
Grey mould caused by Botrytis cinerea is the most important post-harvest disease affecting strawberry fruit. This disease is normally controlled by application of fungicides. Increasing public concern over the use of conventional pesticides prompted an investigation as to whether induced systemic acquired resistance (SAR) might be used to help suppress B cinerea on strawberry fruit. Acibenzolar (S-methyl benzo[1,2,3]thiadiazole-7-carbothioate) is a chemical activator of SAR. When applied to strawberry plants at 0.25–2.0 mg AI ml −1, acibenzolar delayed by about 2 days the development of grey mould disease on harvested strawberry fruit held at 5 °C. This delay was equivalent to a 15–20% increase in storage life of the fruit. This preliminary finding suggests that acibenzolar, or perhaps other chemical plant activators, could prove valuable in the commercial management of grey mould on strawberry fruit.© 2000 Society of Chemical Industry
Botrytis cinerea was isolated from Geraldton waxflower (Chamelaucium uncinatum) flowers collected in Queensland and Western Australia. Isolates were shown to be pathogenic on the two flower selections
used, ‘Herb Morrow’ and ‘Alba’. Separation of the flower from the pedicel occurred for single cut flowers inoculated with
the fungus. This observation supports the hypothesis that infection commonly contributes to premature flower drop in cut,
packaged Geraldton waxflower.
Efficacy and mode of action were investigated fox Aureobasidium pullulans, a potential biocontrol agent for grey mould on strawberry fruit. Wound inoculation of detached green strawberry cv. Elsanta
fruit with Aureobasidium pullulans prevented grey mould rot on fruit inoculated 2 days later with Botrytis cinerea. Treatment of white, pink and red-ripe fruit did not, however, control grey mould. Treatment of wound sites on green fruit
with both live and heat-killed A. pullulans cells reduced B. cinerea infection compared to controls. Dip-inoculation of unwounded green strawberry fruit with A pullulans when still attached to the plant delayed the development of grey mould after harvest at the fully ripe stage. The (i) efficacy
of A. pullulans on green but not on ripening fruit, (ii) partial inhibitory effect of both live and heat-killed A. pullulans cells and (iii) absence of evidence for antibiotic production from in vitro competition tests suggest that control of grey mould on green fruit is at least partly due to a mechanism other than antagonism
and / or competition. Bioassays showed that skin tissue from green fruit treated with A. pullulans had greater antifungal activity than control tissue. Thus, enhanced natural disease resistance in green strawberry fruit
contributed to grey mould rot suppression by A. pullulans.
Additional keywords
Botrytis cinerea
–postharvest
Six isolates of Altemaria alternata were tested and shown to be pathogenic on detached flowers of Geraldton waxflower cv. Alba. The fungus caused petal blight
and abscission ofthe pedicel from inoculated flowers. This finding strengthens the hypothesis that fungal infection of Geraldton
waxflower flowers commonly leads to premature flower drop. Furthermore, it shows that, in addition to Bohytis cinerea, which has been shown previously to cause flower abscission, A. alternata can also cause flower abscission.
An antifungal agent consisting of a mixture of 5-(12-cis-heptadecenyl)- and 5-pentadecyl-resorcinol was isolated from the peel of unripe mango (Mangifera indica L.) fruits, and its relation to the latency of Alternaria alternata investigated. The ED50 of the compound for inhibition of germ-tube growth of germinated conidia of A. alternata was 120 μg ml−1. The concentration of the 5-substituted resorcinols in peels of unripe fruits was about 200 μg g−1 fresh weight and it decreased during ripening to about 100 μg g−1 fresh weight. This decrease was accompanied by development of previously latent A. alternata infections. Treatments of mango fruits with ethylene reduced the latency period and reduced the concentrations of the antifungal compound. Storage of fruits at hypobaric pressures (20kPa) maintained latency and delayed the reduction of the antifungal resorcinols. The concentrations of the 5-substituted resorcinols decreased differentially during ripening of two mango cultivars which also differed in the rates of the development of A. alternata symptoms. In a resistant mango cv., Kitt, the concentrations in the peel did not decrease to a non-fungitoxic concentration when the flesh had ripened. The results support the hypothesis that the mixture of the 5-substituted resorcinols are involved in the latency of A. alternata infections in unripe mango fruits.
(+)-Aromadendrene ( 1 ) is a sesquiterpene present in the distillation tail of the oil of Eucalyptus globulus . This distillation tail is commercially available in large quantities at low price and is an interesting starting material for the synthesis of other chiral products. A fair amount of research has already been carried out on aromadendrene (Chapter 1). This research was mainly focussed on transformation and isomerization of the double bond, opening of the cyclopropane ring, oxidations of derivatives of aromadendrene, and rearrangement of the aromadendrene skeleton. In this thesis, the possibilities to use aromadendrene for other synthetic strategies were explored and the first interest was the development of an economically feasible route toward the fragrance compound 167 (Chapter 2). Ledene epoxide ( 154 ), easily available from aromadendrene, was selected as the starting material for this route, and rearrangements of this b -epoxide were investigated. The formation of products with the cubebane ( 159 ) and cadinane skeleton ( 160 ) indicates that bridgehead carbocations are the prefered intermediates in these rearrangements. From these experiments it was concluded that the synthetic route toward 167 as published by Gijsen is the most efficient route known so far. Scheme 1 Synthesis of guaiane-type compounds by opening the cyclopropane ring in aromadendrene has proven to be difficult. In Chapter 3 it was shown that the conversion of isoledene ( 107 ), a double bond isomer of aromadendrene, to compounds with the guaiane skeleton can be performed in a fairly easy way. The synthesis of the blue colorant guaiazulene ( 35 ) in 22% isolated yield over two steps from isoledene is an improvement of the existing methods for the dehydrogenation with sulfur of aromadendrane or guaiane type sesquiterpenes. Figure 1 A number of guaianes, for example the cyclic ethers 198 and 200 , were synthesized from isoledene epoxide ( 193 ). Isoledene epoxide can be converted by (Lewis) acid to a stabilized cyclopropylcarbinyl cation, which undergoes opening of the cyclopropane ring to a guaiane skeleton. When no water is present during the reaction, ether 198 is obtained and the presence of water leads to formation of ether 200 . Several functionalized derivatives of 198 have been prepared. These compounds were tested for their use as fragrances, but unfortunately they were not suitable as such. Scheme 2 A relatively new method for crop protection is the use of pheromone traps for monitoring or mass trapping of insects. By using these pheromone traps, the amount of insecticides often can be reduced considerably, which is more environmentally friendly and more selective. In Chapter 4 a method is described for the conversion of aromadendrene to methyl-branched linear pheromones. These pheromones ( R )-224 , ( S )-298 , and meso -306 were all synthesized from the common linear intermediate 290 . One of the key steps in the synthesis of 290 is the Baeyer-Villiger reaction of bromide 284 , and opening of the lactone ring in a one-pot reaction to give the hydroxy ester 286 . Via a Grob fragmentation using NaOEt in the presence of NaBH 4 and catalytic hydrogenation, 286 was then converted to compound 290 . In Chapter 5 investigations towards the synthesis of dimethyl-branched linear pheromones have been described. It was shown that it is possible to convert aromadendrene to the dimethyl-branched linear intermediate 308 , following a route similar to the one described in Chapter 4. Scheme 3
A new bioassay has been developed combining the simplicity of direct bioautography with the improved chromatographic resolution of 2D-TLC. Mixtures of structurally diverse antifungal agents were tested to establish the validity and utility of this method in the discovery of new natural products with activity against agriculturally important fungal pathogens.
Aromadendrene as a chiral starting material in the synthesis of flavours fragrances and crop protecting agents. http://www.ftns.wau.nl/oc/research/ synthetic_organic_chem/Aromadendrene/aromadendrene
- Y Lamers
- H Wijnberg
- De
- A Groot
Analysis of phenolic plant metabolism A new 2D-TLC bioautography method for the discovery of novel antifungal agents to control plant pathogens
- Waterman Pg
- Mole
- L A Oxford
- Terry
Waterman PG, Mole S (1994) 'Analysis of phenolic plant metabolism.' p. 146 (Blackwell Scientific Publications: Oxford) L. A. Terry et al. http://www.publish.csiro.au/journals/app Wedge DE, Nagle DG (2000) A new 2D-TLC bioautography method for the discovery of novel antifungal agents to control plant pathogens. Journal of Natural Products 63, 1050–1054.
Prospects for exploitation of natural disease resistance in harvested horticultural crops
- Joyce Dc Johnson
- Gi
Joyce DC, Johnson GI (1999) Prospects for exploitation of natural disease resistance in harvested horticultural crops. Postharvest News and Information 10, 45N-48N.
Strategies for control of Botrytis cinerea on Geraldton waxflower flowers The University of Queensland A review of the flower characteristics of Geraldton waxflower and factors affecting their abscission from harvested stems
- Beasley
- Dr
Beasley DR (2001) 'Strategies for control of Botrytis cinerea on Geraldton waxflower flowers'. PhD Thesis, The University of Queensland. Beasley DR, Joyce DC (2002) A review of the flower characteristics of Geraldton waxflower and factors affecting their abscission from harvested stems. Australian Journal of Experimental Agriculture 42, 519–525.
The antifungal ethyl acetate fraction was partitioned three times with hexane and ethanol (80% v/v) and evaporated to dryness. 1-D TLC C. cladosporioides bioassays were run for hexane and ethanol fractions
- D Tlc
D TLC bioassays were performed on each extract. The antifungal ethyl acetate fraction was partitioned three times with hexane and ethanol (80% v/v) and evaporated to dryness. 1-D TLC C. cladosporioides bioassays were run for hexane and ethanol fractions (5 PL;
Fungicides fight flower drop
- Dc Joyce
- Ah Wearing