Browsing by Author "Joyce, Daryl C."
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Item Open Access Biology and management of freesia flower specking caused by Botrytis cinerea(Cranfield University, 2003) Darras, Anastasios I.; Joyce, Daryl C.; Terry, Leon A.There is no published research regarding postharvest infection of freesia flowers by Botrytis cinerea. Although, infection problems have concerned freesia growers and wholesalers in recent years. The overall objectives of this study were firstly to evaluate the factors affecting B. cinerea postharvest disease establishment and secondly to evaluate a range of novel potential treatments to reduce postharvest freesia infection. These treatment options include plant activators such as acibenzolar-S-methyl and methyl jasmonate and biotic (Aureobasidium pullulans) and abiotic (UV-C irradiation) biological/elicitors agents. Research was undertaken in an attempt to explain the variation in B. cinerea incidence on cut freesia flowers as noted by the UK importer Zwetsloots & Sons Ltd. in 2000. Higher monthly rejections of freesia flower stems throughout 2000 due to B. cinerea infection were recorded during spring (April-May), early summer (June) and autumn (October). Comparatively higher proportions of rejected freesia stems were associated with glasshouse temperatures ranging from 13-17°C. In the presence of B. cinerea inoculum on freesia petal surface, temperature was not a limiting factor for disease establishment. Incubation of artificially inoculated freesia flowers at 12°C resulted in overall higher disease severity and lesion numbers compared to flowers incubated at 5 or 20°C. In contrast, relative humidity was the most important factor for postharvest infection by B. cinerea. Elicitor based strategies for IPM using the potent activator acibenzolar provided limited protection of freesia flowers against B. cinerea when applied postharvest. Acibenzolar significantly reduced disease severity, lesion numbers and lesion diameters compared to the untreated control when applied at 0.15 g A. 1. U1. Methyl jasmonate (MeJA) applied as gas, pulse and spray generally suppressed B. cinerea disease on cut freesia flowers. Disease severity, lesion numbers and lesion diameters of flowers gassed with 0.1 μL MeJA L"' were reduced by 56,43 and 37%, respectively compared to untreated control flowers. Gaseous MeJA treated freesia flowers at 0.1 μL L"1 increased PPO activity by 57% compared to untreated controls 24h after MeJA treatment. After 36h of incubation at 20°C, disease severity, lesion numbers and lesion diameters of gaseous MeJA treated flowers were reduced by 68,56 and 50%, respectively, compared to the untreated controls. However, PAL activity in MeJA treated freesia flowers did not decrease significantly over time compared to untreated control 12h post-inoculation and thereafter. These findings suggest that MeJA treatment might suppress the action of PAL in the phenylpropanoid pathway and consequently block SA production. UV-C irradiation might be used in an integrated postharvest disease management program for freesia flowers. UV-C irradiation after artificial inoculation resulted in markedly reduced B. cinerea disease severity scores and lesion numbers. In detail, UV-C irradiation of cut freesia flowers with 0.5,1,2.5 and 5 kJ m''` reduced disease severity by up to 44,70,74 and 59% and lesion numbers by up to 37,62,68 and 60%, respectively. UV-C irradiation at 1 kJ M-2 before artificial inoculation slightly reduced disease severity and lesion numbers possibly by inducing defence responses. However, the limited disease suppression suggested that apparently B. cinerea could overcome the UV-C induced effect. The effect of preharvest treatments on freesia crops with acibenzolar was investigated in glasshouse trials in view to suppress postharvest B. cinerea infection via SAR induction. Acibenzolar was effective in selected treatments and conditions. Disease pressure varied over the 3 years and over varieties tested. However, it was unclear whether acibenzolar induced systemic and/or local defence responses. The latter was supported by biochemical investigations in 2001 which suggested that acibenzolar did not induce PAL activity. In contrast, preharvest MeJA treatment resulted in markedly systemic protection of treated flowers compared to untreated ones. MeJA efficacy was dependent on variety and on postharvest incubation temperatures. Disease severity, lesion numbers and lesion diameters on MeJA treated freesia var. `Dukaat' flowers incubated at 20°C were reduced by 56,61, and 49% compared to controls, respectively. Also, disease severity, lesion numbers and lesion diameters on MeJA treated `Cote d'Azur' flowers incubated at 20°C were reduced by 36,26, and 49% compared to controls, respectively.Item Open Access Discrimination of Allium headspace volatiles affected by variations in genotype growing environment and storage using an electronic noses(2003) Abbey, Lord; Joyce, Daryl C.; Terry, Leon A.Alliums are valued mainly for their unique organosulphur-derived flavours and aromas. Traditional sensory and analytical determinations of Allium quality are constrained by high cost, technical difficulties and, time and human limitations. This thesis investigates the potential for use of relatively novel electronic nose (E-nose) technology for Allium discrimination. Chapters 3, 4 (Sections 4.1 to 4.3), 5 (Sections 5.1 and 5.2) and Appendices II and III inclusive have been published or submitted for publication. Consequently, Chapters in this thesis are presented in the form of papers. The E-nose AromaScan LabStation A32/8S (Osmetech Pic., UK) consists of 32 conducting polymer miniature sensors. Adsorbed odour molecules alter the electric conduction mechanism of the sensor polymer. The response is measured as proportional (%) change in sensor resistance ratio (%dR/R). The E-nose discriminated Allium types (Chapter 3), varieties of spring onion grown with or without sulphur addition and a single variety of spring onion grown under different levels of sulphur, nitrogen, water-deficit stress and soil type (Chapter 4). Bulb onion affected by nitrogen, sulphur and soil type and diced onion sealed in polyethylene bags stored at 4°C for 9 days were also discriminated by the E-nose (Chapter 5). A descriptive model for the direction of E-nose sensor polymer response to Allium headspace volatiles affected by genotypic differences and edaphic variables was outlined in Section 6.2. Principal Component Analyses (PCA) of E-nose data sets output accounted for >75% to nearly 100% of variations in the Alliums. The variations in Allium genotype differentially affected the E-nose sensor conductivity following headspace volatiles interaction with sensor polymer element. Classification of data sets output showed greater (Mahalanobis distance statistic, D² >3.0) sensitivity of spring onion cvs Guardsman and Fragrance to S fertilisation while the headspace volatiles characteristics of cvs Winter Over and Paris Silverskin were not significantly (D²<3.0) altered by S. The headspace volatiles of onion bulb cv. Sprinters also responded to S fertilisation (D²>3.0) and thus, increased %dR/R. Overall, N-fertilised onion cv. Sprinters reduced E-nose sensor conductivity leading to an increase in %dR/R. Increases in water-deficit stress i.e. > -0. 80 MPa soil water potential, SWP generally reduced separation between E-nose data set clusters for clay versus sandy loam soils from D² = 43.2 for -0.01 MPa SWP to D² = 6.2 for -1.19 MPa. Headspace volatiles of onions grown in the glasshouse clay increased %dR/R compared to reduced %dR/R values for both glasshouse and field sandy loam soils. The E-nose detected gradual changes in headspace volatiles of diced onion wrapped in polyethylene bags stored at 4°C for 9 days. The changes in headspace volatiles reduced %dR/R values while data set cluster separations with reference to day 0 for each sampling time increased from D² = 3.6, 5.8 and 7.0 on days 3, 6 and 9, respectively. The results suggested that Allium quality can be assessed with ease along production, postharvest and marketing chains compared to traditional destructive methods. Linear correlations for E-nose data sets versus Allium pungency determinants (pyruvic acid and lachrymatory potency), total soluble solids and dry-matter were poor. The thesis discusses the commercial significance of the result and its implication for the development of E-nose sensor tailored for Alliums. This would promote application and use of E-nose technology in the Allium industry, germplasm evaluation, and discrimination of agronomic variables and possibly, monitoring spoilage pathogens during storage. The effects of nitrogen, sulphur, water-deficit stress and soil type and their interactions have given new insight into agronomic inputs on growth and microbial load (Chapters 4.3, 5.1 and Appendix III).Item Open Access Effects of 1-MCP on storage of "Queen cox" and "Bramley" apple fruit(2007) Dauny, Paul Trevor; Warner, P.; Joyce, Daryl C.Better maintenance of firmness and suppression of ethylene production in 'Queen Cox' and 'Bramley' apple [Ma/us sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit was achieved by prestorage applications of 1-MCP. 1-MCP concentration, exposure time and exposure temperature ranges of 0.1 to 10.0 µl r1 1-MCP, 6 to 48 h and O to 20°C, respectively, were effective on fruit subsequently stored for 2 ('Cox') and 3 ('Bramley') months in air at 3 to 4°C. However, 1-MCP had little effect on either firmness or ethylene production after 4 ('Cox') or 6 ('Bramley') months storage. Nonetheless, 1-MCP treated 'Bramley' fruit had reduced rot and superficial scald incidence compared with untreated control fruit. 1-MCP application was most effective when applied within 24 h of harvest · compared to 14 d later. Earlier-harvested 'Cox' and 'Bramley' apple fruit showed better response to 1-MCP-treatment than those harvested towards the end of the picking season. 1-MCP-treatment was shown to improve apple storage alone and in combination with controlled atmosphere (CA) storage. Furthermore, 1-MCPtreatment maintained fruit quality during shelf-life better than CA storage alone. Chlorophyll fluorescence was not demonstrated to be an effective method to determine 'Cox' and 'Bramley' apple fruit quality. There was no recorded correlation between the concentration of five antifungal compounds and 1-MCP-treatment after inoculation with Penicillium expansum or Botrytis cinerea. 1-MCP treatment for apple storage was developed for AgroFresh Inc., the holder of the 1-MCP patent. Part of this research was used for the UK efficacy trials for registration of 1-MCP as an apple storage treatment. On the 18th July 2002 the US Environmental Protection Agency (EPA) granted approval for 1-MCP to be applied to food crops. Approval was granted in the UK in time for the 2003 apple harvest, and for 2004 across Europe.Item Open Access Natural disease resistance in strawberry fruit and Geraldton waxflower flowers(2002) Terry, Leon Alexander; Joyce, Daryl C.Antifungal activity against Botrytis cinerea and Cladosporium cladosporioides declined with increasing fruit maturity as shown by thin layer chromatography (TLC) bioassay. Preformed antifungal activity was also demonstrated in flower tissue. Decline in fruit antifungal compounds was correlated with a decline in natural disease resistance (NDR) against B. cinerea. Crude extracts of green stage I fruit contained at least two previously unreported preformed antifungal compounds (Rf = 0.44 and 0.37) that were not present in white and red stage fruit. These compounds were confirmed by TLC reagent sprays not to be phenolics or alkaloids. Positive reactions to Ehrlich’s reagent suggested that Rf = 0.37 was a teipene. The majority of 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 showed that all fruit stages showed antifungal activity at the origin (Rf = 0.00). The approximate area of fungal inhibition at origin in green stage 1 fruit extracts was 90 and 70% greater than in white and red stages. TLC reagent sprays confirmed that antifungal compounds at origin contain phenolics. This is consistent with previously reported phenolic compounds in strawberry fruit that are inhibitory to B. cinerea. An investigation into the potential of enhancing NDR using different chemical (acibenzolar), biological (Aureobasidium pullulons) and physical (UV-C) elicitors was conducted with a view to developing an integrated pest management (EPM) strategy. The most promising results were achieved with pre-harvest treatments of the chemical plant activator acibenzolar. Seven glasshouse trials were conducted over a three year period. Preharvest application of acibenzolar (0.25 - 2.0 mg AI ml'1) were effective in suppressing grey mould on strawberry fruit harvested from winter grown plants. Conversely, acibenzolar was ineffective at suppressing grey mould on fruit harvested from summer grown plants. However, where acibenzolar was effective, disease development was delayed by as much as 2 days. This delay was equivalent to a 15-20% increase in shelf-life. If systemic acquired resistance and/or other inducible mechanisms are to be implemented as part of an IPM strategy for controlling B. cinerea more research is required on how environment and management factors affect the efficacy of elicitors such as acibenzolar. Geraldton waxflower is the most economically important native Australian cut flower export. Infection of Geraldton waxflower by B. cinerea can lead to unacceptable levels of flower abscission after harvest. Thus, an investigation was conducted into the nature and identities of constitutive antifungal compounds in imported Geraldton waxflower flower and leaf tissues. Antifungal activity against B. cinerea and C. cladosporioides was observed in both Geraldton waxflower leaf and flower tissue. Leaf tissue contained considerably less antifungal activity than flower tissue. Some antifungal compounds were common to the three different waxflower cultivars studied. Through TLC reagent sprays and NMR GC-MS spectra, these antifungal compounds were identified as the sesquiterpenes, globulol and grandinol. There were also at least two unidentified phenolics. Notwithstanding similarities in antifungal profiles, it was also evident from TLC bioassays that significant variations exist between different waxflower cultivars. Further work is required to fully characterise the preformed antifungals compounds found in strawberry and Gerladton waxflower tissues and to elucidate pathways involved in their biosynthesis. In addition, work is also required to look at the full spectrum of antifungal activity of these antifungal compounds. Such information will allow precise definition of the roles that these compounds may play in suppression of in strawberry and waxflower NDR against B. cinerea. In turn, this knowledge should enable the introduction of improved and/or novel IPM strategies that enhance levels of these compounds.Item Open Access Postharvest quality of conventionally and organically grown banana fruit(Cranfield University, 2001-09) Caussiol, Laure; Joyce, Daryl C.Quality is increasingly important for retailers, who tend to look for more definitive assessment criteria. Taste has become a major issue over past years for consumers, who are seeking higher quality produce. For banana fruit, at least one major retailer is asking TSS measurement in addition to the usual assessment based on skin colour. At the same time organic produce sales are increasingly important for ripeners and retailers to consumers. This study investigated variability in banana pulp with regard to sampling position from proximal, middle and distal portions. Also two different devices, the traditional pocket refractometer and the digital refractometer were evaluated. TSS was measured on juice obtained directly from the pulp, as practised by one supermarket representative, versus the more conventional method of homogenizing pulp samples in distilled water. Finally, a comparison of postharvest qualities of conventionally and organically grown banana fruit from nearby plantations in the Dominican Republic was made. This comparison involved several harvest times over the seasonal period from February to June 2001. Green mature Cavendish bananas var. Grand Nain were imported from the Dominican Republic by SH Pratt’s & Co. (Luton, UK). Both the conventionally and the organically grown bananas from the same area were held at about 15 degrees C during shipping and handling. The fruit were then ripened in a postharvest laboratory in the UK with a shot of 100 muL/L ethylene applied for 48 hours at 20 ±1 degree C. They were then assessed over 12 days of shelf life at this same temperature and at 60 ±10 % relative humidity. Fruit weight (g), colour (L* and H degrees), acidity (ml of 0.1 N NaOH), firmness (N) and TSS (%Brix) were assessed every second day during shelf life. In addition, starch breakdown was visualised by dipping slices of banana in iodine solution. Sensory analysis on the ripened fruit was also made with 30 panellists for four out of six of the harvest times.Item Open Access Preformed antifungal compounds in strawberry fruit and flower tissues(Elsevier Science B.V., Amsterdam., 2004-02-01T00:00:00Z) Terry, Leon A.; Joyce, Daryl C.; Adikaram, Nimal K. B.; Khambay, Bhupinder P. S.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-fold 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. cinere