Plants inherently produce polyphenols (i.e., antioxidants) as a response to reduce oxidative stress caused by abusive environmental pre- and postharvest conditions. These antioxidants, as well as vitamin C, are present in considerable levels in strawberries; however, excessive oxidative stress brought on by improper postharvest handling conditions can reduce the levels of antioxidants in the fruit and shorten the shelf-life of strawberries. Nevertheless, it may be possible to utilize strawberry’s naturally occurring polyphenols to reduce postharvest stress and extend their shelf life. The polyphenolic profile has been previously investigated in several strawberry cultivars, however no studies have determined the unique polyphenolic profiles of three important Florida strawberry cultivars (‘Florida Radiance’, Sweet Sensation® ‘Florida 127’and ‘Florida Beauty’) at harvest and during cold storage. Therefore, in order to better understand the distribution of individual polyphenols within these cultivars and their impact on postharvest shelf-life, this study examined the polyphenolic profiles throughout 7 days of cold storage (1 °C) using an HPLC-DAD. The activity of phenylalanine ammonia lyase (PAL), a key enzyme in the biosynthesis of polyphenols, and polyphenol oxidase (PPO), the enzyme responsible for polyphenol degradation, were also examined during cold storage to understand their possible influences on postharvest synthesis or degradation of polyphenols. This study revealed that the polyphenolic profile of strawberry fruit was genotype dependent; however, pelargonidin 3-glucoside was consistently the anthocyanin found in higher concentrations in the fruit regardless of the cultivar. Apart from the anthocyanins, the flavonols showed the most variation among the three cultivars. PAL was slightly induced during strawberry postharvest storage suggesting that a stress response occurred during cold storage while PPO showed variable induction patterns across all three cultivars most likely due to their different polyphenol profiles. Analysis of the distribution of polyphenols in the cortex and pith of strawberries showed that polyphenols were mostly concentrated in the cortex of the fruit and that the concentration of individual polyphenol in each fruit tissue varied by cultivar. These results indicate that the oxidative stress response varies in each of the strawberry cultivars studied contributing to their unique polyphenolic profile. Results from this study can ultimately help to identify the polyphenols and enzymes related to superior postharvest quality in future studies.

Hydroponics basically is the method of growing plants using mineral nutrient solutions, in water, without soil. Vertical nutrient film technique (NFT) is one of the most used hydroponic technique that has constant flow of nutrient solution. In this study the effects of different support medium on strawberry quality and yield using vertical NFT in glass greenhouse was investigated. NFT-only system was compared to rockwool, coco fiber, perlite and expanded clay as supporting medium for strawberry production. Parameters such as weight of product, amount of product, rate of marketable product, and including physico-chemical properties such as pH, rigidity, color, dry matter amount, EC, vitamin C, sugar content, resistance to certain pathogens were observed among all supporting medium trials. NFT-only system significantly differed from other supporting medium trails by most of the parameters including fruit number per plant, average fruit weight, toughness of the fruit, vitamin C amount, sugar amount and finally soluble solid material amount in water . Revealing the effects of supporting medium on strawberry production shed light on how should NFT must be applied to fruit growing.

S'avaluaren 58 soques de Pseudomonas fluorescens i Pantoea agglomerans per la seva eficàcia en el biocontrol de la malaltia causada per l'oomicet Phytophthora cactorum en maduixera i pel nematode formador de gal·les Meloidogyne javanica en el portaempelt GF-677.Es desenvolupà un mètode ex vivo d'inoculació de fulla amb l'objectiu de seleccionar soques bacterianes com a agents de control biològic de P. cactorum en maduixera. Tres soques de P. fluorescens es seleccionaren com a soques eficaces en el biocontrol del patogen en fulles i en la reducció de la malaltia en plantes de maduixera. La combinació de soques semblà millorar la consistència del biocontrol en comparació amb les soques aplicades individualment.Tres soques de P. fluorescens es seleccionaren per la seva eficàcia en la reducció de la infecció de M. javanica en portaempelts GF-677. La combinació d'aquestes soques no incrementà l'eficàcia del biocontrol, però semblà reduir la seva variabilitat. / 58 Pseudomonas fluorescens and Pantoea agglomerans strains were evaluated for their biocontrol efficacy against the oomycete Phytophthora cactorum in strawberry and the root-knot nematode Meloidogyne javanica in GF-677 rootstocks.An ex vivo detached leaf inoculation method was developed to select bacterial strains as biological control agents of P. cactorum in strawberry. Three P. fluorescens strains were selected as effective in biocontrol of the pathogens on leaves and in disease reduction in strawberry plants. Combination of strains improved biocontrol consistency compared to strains applied individually. Three P. fluorescens strains were selected for their efficacy in M. javanica infection reduction in GF-677 rootstocks. Combination of these strains did not increase biocontrol efficacy, but reduced its variability.

Red mark syndrome (RMS) is a non-lethal skin condition, of unknown aetiology, affecting rainbow trout (Oncorhynchus mykiss) in the United Kingdom since 2003. It has now spread to 50% of the rainbow trout farms, resulting in great economic losses due to the downgrading of the product. There are also similar skin conditions in rainbow trout, for instance strawberry disease (SD) in the USA. As with RMS, the aetiological agent of this disease is also unknown. Several potential aetiological agents have been proposed, including a Rickettsia-like organism (RLO) in SD in the USA and Flavobacterium psychrophilum in RMS in the UK. The aim of the research presented here was to investigate the causative agent of RMS and to establish if there is a relationship between RMS and SD. An RLO was found to be associated with both RMS and SD-affected fish using immunohistochemistry (IHC) and polymerase chain reaction (PCR). The results of the IHC, together with the similarities in the pathology between the two conditions, suggest that RMS and SD are most likely the same disease (Chapter 2). In an attempt to isolate the RLO, F. psychrophilum or other suspected causative agents of RMS, several artificial bacteriological media, cell culture methods and novel techniques such as MagnaBind™ IgG beads (magnetic beads) were utilized. Although initial results appeared promising, no specific bacterial or viral agent was isolated using these methods. Transmission electron microscopy was used to analyse samples in an attempt to visualise any viruses and/or the RLO suspected of causing RMS (Chapter 3), but none were seen. Investigation into the involvement of both the RLO and F. psychrophilum in RMS using primary culture and IHC, together with the more advanced techniques of MALDI-TOF–MS and 16s rRNA gene sequencing, showed no association between F. psychrophilum and RMS. A quantitative PCR (qPCR), together with IHC, showed a positive correlation between the RLO and RMS-affected tissue, but this did not v distinguish between primary or secondary involvement of the organism. Results following analysis of samples using other assays, including ELISA and IHC, both using serum from naturally infected individuals, 16s rRNA gene PCR and bacterial isolation, were inconclusive, with methods requiring further optimisation for future use. The qPCR used in the study also needs to be fully optimised, as the results of a ring trial between three laboratories were considerably different (Chapter 4). Cohabitation challenges were conducted in the USA to investigate the involvement of the RLO in the early stages of SD. Clinical signs of SD were clearly evident in a small percentage of the cohabitated naïve fish. In most of these cases the DNA of the RLO could be detected, but again primary or secondary involvement could not be determined due to the small sample size (Chapter 5). In conclusion, the results from the analysis of samples by PCR, IHC with anti-F. psychrophilum PAbs, MALDI-TOF-MS and 16s rRNA gene sequencing indicate that F. psychrophilum is unlikely to be the causative aetiological agent of RMS. Although Koch’s postulates were not fulfilled, a strong correlation was obtained between the RLO and RMS-affected fish in the IHC, PCR and qPCR using RLO specific primers. It is unclear however, if the involvement of the RLO is as a primary or secondary pathogen. The RLO associated with RMS appears to have antigens in common with Piscirickettsia salmonis (from the results of the IHC), the causative agent of Salmon Rickettsial Syndrome, for which commercial vaccines are available, and should therefore be investigated as a form of mitigation for RMS, since the RLO has not yet been isolated and a traditional inactivated whole cell vaccine is not possible at this time. Efforts to isolate the RLO should continue and the involvement of other pathogens in RMS should be investigated further with new cutting edge techniques such as next generation sequencing or random multiplex (RT)-PCR to rule out viral involvement in the disease.

Cold hardiness and resistance in winter are key factors determining the geographical distribution of plants. In addition, these factors have a huge impact on harvest of cultural plants. Strawberries, which are among the most important berry plants in the world and in Lithuania, are vulnerable to cold because of unstable snow cover, which is more and more often occurring during variable wintering conditions. Insufficient resistance of strawberries in winter, absence of clear criteria, which enable to select the most resistant varieties during a shorter time than the few year period, impedes the development and introduction of new, adaptive, fertile, and of high-quality berries strawberry cultivars. The mechanisms of cold hardiness were intensively investigated using model plants. However, there is a lack of knowledge about the genetic regulation mechanisms of winterhardiness of cultural plants. For the selection of resistant to cold plants, the knowledge about plants cold acclimation and factors determining cold resistance and controlling genes is necessary. Investigating the plants under controlled conditions in vitro, it is possible to investigate the influence of individual factors on acclimation and cold hardiness by disassociating from the influence of many different factors, which is unavoidable under natural conditions. The cold acclimation and cold hardiness of strawberries are important not only for breeding. Preservation of plant genetic resources for future... [to full text] / Atsparumas šalčiui ir ištvermingumas žiemą – pagrindiniai veiksniai, lemiantys augalų geografinį pasiskirstymą. Be to, šie veiksniai turi didžiulę įtaką kultūrinių augalų derlingumui. Braškės, kurios yra tarp svarbiausių uoginių augalų pasaulyje ir Lietuvoje, stipriai pašąla esant nepastoviai sniego dangai, vis dažniau pasitaikančiomis permainingomis žiemojimo sąlygomis. Nepakankamas braškių ištvermingumas žiemą, aiškių kriterijų, kurie leistų per trumpesnį nei kelių metų laikotarpį atrinkti ištvermingas veisles nebuvimas, apsunkina naujų, adaptyvių, derlingų, kokybiškomis uogomis, braškių veislių sukūrimą ir introdukciją. Atsparumo šalčiui mechanizmai intensyviai tirti naudojant modelinius augalus, tačiau žinių apie žiemojančių kultūrinių augalų, kurių įvairovė labai didelė, ištvermingumo žiemą mechanizmus ir jo genetinį reguliavimą labai trūksta. Atsparių šalčiui augalų atrankai vykdyti reikalingos žinios apie augalų užsigrūdinimą, apie atsparumą šalčiui lemiančius veiksnius ir juos kontroliuojančius genus. Tiriant augalus kontroliuojamomis sąlygomis in vitro, galima ištirti atskirų veiksnių įtaką užsigrūdinimui ir atsparumui šalčiui, atsiribojant nuo, neišvengiamo natūraliomis sąlygomis, daugelio įvairių veiksnių poveikio. Braškių užsigrūdinimas ir atsparumas šalčiui svarbūs ne vien tik atrankai. Genetinių išteklių išsaugojimas ateities kartoms - svarbus šiuolaikinės biologijos uždavinys. Didelių kolekcijų išsaugojimą palengvina ir sąnaudas sumažina, augalų laikymas... [toliau žr. visą tekstą]

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Pervaporation is a selective membrane technique in which a liquid feed mixture is separated by means of partial vaporization through a non-porous perm-selective membrane. This method can be used for the recovery of heat sensitive aroma compounds to avoid them from thermal damage in beverage industries. The main objective of this study was to determine the effects of feed temperature (30, 40, 50&deg / C), composition (different model solutions, strawberry essence), concentration (50, 100, 150 ppm) and permeate pressure (4, 8 mbar) on the recovery of aroma compounds of strawberry by pervaporation in terms of mass flux and selectivity. In addition, it was aimed to optimize the extraction conditions (extraction time, temperature, agitation speed, strawberry matrix) of Solid-phase microextraction (SPME), which is used for the analysis of strawberry aroma compounds. Optimum results for SPME were obtained at 40&deg / C, 700 rpm for 30 min and no matrix effect was observed. Pervaporation experiments were performed using a hydrophobic membrane, PERVAP 1070 (PDMS). As the feed temperature increased, the mass flux and selectivity increased and the total mass flux followed an Arrhenius type relation. Decreasing downstream pressure increased both total flux and selectivity, while increase in feed concentration led to higher organic fluxes but lower selectivities. In general, PERVAP 1070 showed a higher selectivity towards Methyl butyrate (MTB) than Ethyl butyrate (ETB) and MTB flux was affected negatively by the presence of ETB in the feed solution. Pervaporation experiments were also performed with a strawberry essence and strawberry model solution. The selectivities of MTB and ETB were negatively affected by the presence of other aroma compounds.

Knowledge of disease epidemiology and the impact of plant nutrient status on development of disease is fundamental in establishing effective management strategies for crop pathogens such as Podosphaera aphanis Br. (Braun et al., 2002), the causal agent of powdery mildew on strawberries. The following study investigated the conditions conducive for powdery mildew in strawberry crops in South Australia, the effect of foliar concentration of potassium and calcium on yield and pathogen development on the strawberry cultivars Aromas (resistant to powdery mildew) and Selva (susceptible), the potential for use of foliar-applied potassium silicate to control disease and identification of genes differentially expressed during disease. Meteorological conditions associated with establishment of powdery mildew were observed over three consecutive seasons in commercial strawberry crops grown in Woodside, South Australia. Conducive conditions appear to be >28 oC, <55 % relative humidity (RH) with no rain during the day (for conidiation), followed by a night with >10 oC, >90 % RH and no rain (for germination). Colony development was then promoted by days of >15 oC and <70 % RH, with nights of >8 oC, >80 % RH and less than 2 mm rain in every 24 hour period. These are consistent with epidemiological studies of this pathogen (Peries, 1962a; Jhooty and McKeen, 1964; Mukerji, 1968; Perera and Wheeler, 1975; Byrne et al, 2000; Miller et al, 2003; Blanco et al, 2004; Davik and Honne, 2005; Amsalem et al, 2006). This knowledge may facilitate prediction of times considered high risk for establishment of powdery mildew in strawberry crops. Subsequently, this may allow optimisation of fungicide application and improved management of this disease and reduced yield loss and management expenses. P. aphanis developed at an increased rate on leaves of Selva with low calcium content compared with development on normally fertilised leaves. Increased numbers of conidia germinated successfully on leaves of Aromas with low calcium content compared with development on normally fertilised Aromas leaves, however, the germinated conidia still failed to develop into sporulating colonies. Potassium nutrition had no obvious effect on P. aphanis development. Foliar concentration found to be adequate for growth of cultivars, Selva and Aromas were 6.0 mg/g and 4.5 mg/g Calcium, dry weight and 11.0 mg/g and 12.5 mg/g potassium, dry weight (respectively). Potassium silicate, buffered to pH 7.0 and applied as a foliar fertiliser, reduced the severity of powdery mildew below the economic threshold, though not below the disease severity on plants treated with the fungicide, Systhane® (Bayer CropScience). As potassium silicate can be produced organically this compound may provide a useful management tool for both organic and conventional strawberry growers. Although the cultivar Aromas was not immune to disease under conducive conditions and high inoculum load in the field, inoculation of healthy Aromas plants with P. aphanis in the laboratory failed to produce disease. Conidia were seldom found attached to the leaf surface of healthy Aromas leaves. Germination and subsequent colony development were also not observed in inoculated samples. This suggests there is some mechanism of Aromas that inhibits development of this fungus. Preliminary investigation of differential expression in Aromas inoculated with P. aphanis, identified sequences with homology to a putative antimicrobial protein and photosynthesis-related genes. The results of these studies should enable growers to increase both crop yields and control of powdery mildew, one of the major economic diseases in South Australia. The epidemiological knowledge attained will be valuable, and may provide the basis for future forecast modelling for P. aphanis in strawberry crops in South Australia. Recommendations for calcium and potassium leaf content will allow growers to monitor their fertiliser regime for increased yield of these cultivars. Aromas was identified as a powdery mildew resistant cultivar potentially suitable for production in South Australia, and the genes associated with this resistance response may be used in studies of Fragaria species and breeding for powdery mildew resistant cultivars. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297684 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Knowledge of disease epidemiology and the impact of plant nutrient status on development of disease is fundamental in establishing effective management strategies for crop pathogens such as Podosphaera aphanis Br. (Braun et al., 2002), the causal agent of powdery mildew on strawberries. The following study investigated the conditions conducive for powdery mildew in strawberry crops in South Australia, the effect of foliar concentration of potassium and calcium on yield and pathogen development on the strawberry cultivars Aromas (resistant to powdery mildew) and Selva (susceptible), the potential for use of foliar-applied potassium silicate to control disease and identification of genes differentially expressed during disease. Meteorological conditions associated with establishment of powdery mildew were observed over three consecutive seasons in commercial strawberry crops grown in Woodside, South Australia. Conducive conditions appear to be >28 oC, <55 % relative humidity (RH) with no rain during the day (for conidiation), followed by a night with >10 oC, >90 % RH and no rain (for germination). Colony development was then promoted by days of >15 oC and <70 % RH, with nights of >8 oC, >80 % RH and less than 2 mm rain in every 24 hour period. These are consistent with epidemiological studies of this pathogen (Peries, 1962a; Jhooty and McKeen, 1964; Mukerji, 1968; Perera and Wheeler, 1975; Byrne et al, 2000; Miller et al, 2003; Blanco et al, 2004; Davik and Honne, 2005; Amsalem et al, 2006). This knowledge may facilitate prediction of times considered high risk for establishment of powdery mildew in strawberry crops. Subsequently, this may allow optimisation of fungicide application and improved management of this disease and reduced yield loss and management expenses. P. aphanis developed at an increased rate on leaves of Selva with low calcium content compared with development on normally fertilised leaves. Increased numbers of conidia germinated successfully on leaves of Aromas with low calcium content compared with development on normally fertilised Aromas leaves, however, the germinated conidia still failed to develop into sporulating colonies. Potassium nutrition had no obvious effect on P. aphanis development. Foliar concentration found to be adequate for growth of cultivars, Selva and Aromas were 6.0 mg/g and 4.5 mg/g Calcium, dry weight and 11.0 mg/g and 12.5 mg/g potassium, dry weight (respectively). Potassium silicate, buffered to pH 7.0 and applied as a foliar fertiliser, reduced the severity of powdery mildew below the economic threshold, though not below the disease severity on plants treated with the fungicide, Systhane® (Bayer CropScience). As potassium silicate can be produced organically this compound may provide a useful management tool for both organic and conventional strawberry growers. Although the cultivar Aromas was not immune to disease under conducive conditions and high inoculum load in the field, inoculation of healthy Aromas plants with P. aphanis in the laboratory failed to produce disease. Conidia were seldom found attached to the leaf surface of healthy Aromas leaves. Germination and subsequent colony development were also not observed in inoculated samples. This suggests there is some mechanism of Aromas that inhibits development of this fungus. Preliminary investigation of differential expression in Aromas inoculated with P. aphanis, identified sequences with homology to a putative antimicrobial protein and photosynthesis-related genes. The results of these studies should enable growers to increase both crop yields and control of powdery mildew, one of the major economic diseases in South Australia. The epidemiological knowledge attained will be valuable, and may provide the basis for future forecast modelling for P. aphanis in strawberry crops in South Australia. Recommendations for calcium and potassium leaf content will allow growers to monitor their fertiliser regime for increased yield of these cultivars. Aromas was identified as a powdery mildew resistant cultivar potentially suitable for production in South Australia, and the genes associated with this resistance response may be used in studies of Fragaria species and breeding for powdery mildew resistant cultivars. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297684 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Knowledge of disease epidemiology and the impact of plant nutrient status on development of disease is fundamental in establishing effective management strategies for crop pathogens such as Podosphaera aphanis Br. (Braun et al., 2002), the causal agent of powdery mildew on strawberries. The following study investigated the conditions conducive for powdery mildew in strawberry crops in South Australia, the effect of foliar concentration of potassium and calcium on yield and pathogen development on the strawberry cultivars Aromas (resistant to powdery mildew) and Selva (susceptible), the potential for use of foliar-applied potassium silicate to control disease and identification of genes differentially expressed during disease. Meteorological conditions associated with establishment of powdery mildew were observed over three consecutive seasons in commercial strawberry crops grown in Woodside, South Australia. Conducive conditions appear to be >28 oC, <55 % relative humidity (RH) with no rain during the day (for conidiation), followed by a night with >10 oC, >90 % RH and no rain (for germination). Colony development was then promoted by days of >15 oC and <70 % RH, with nights of >8 oC, >80 % RH and less than 2 mm rain in every 24 hour period. These are consistent with epidemiological studies of this pathogen (Peries, 1962a; Jhooty and McKeen, 1964; Mukerji, 1968; Perera and Wheeler, 1975; Byrne et al, 2000; Miller et al, 2003; Blanco et al, 2004; Davik and Honne, 2005; Amsalem et al, 2006). This knowledge may facilitate prediction of times considered high risk for establishment of powdery mildew in strawberry crops. Subsequently, this may allow optimisation of fungicide application and improved management of this disease and reduced yield loss and management expenses. P. aphanis developed at an increased rate on leaves of Selva with low calcium content compared with development on normally fertilised leaves. Increased numbers of conidia germinated successfully on leaves of Aromas with low calcium content compared with development on normally fertilised Aromas leaves, however, the germinated conidia still failed to develop into sporulating colonies. Potassium nutrition had no obvious effect on P. aphanis development. Foliar concentration found to be adequate for growth of cultivars, Selva and Aromas were 6.0 mg/g and 4.5 mg/g Calcium, dry weight and 11.0 mg/g and 12.5 mg/g potassium, dry weight (respectively). Potassium silicate, buffered to pH 7.0 and applied as a foliar fertiliser, reduced the severity of powdery mildew below the economic threshold, though not below the disease severity on plants treated with the fungicide, Systhane® (Bayer CropScience). As potassium silicate can be produced organically this compound may provide a useful management tool for both organic and conventional strawberry growers. Although the cultivar Aromas was not immune to disease under conducive conditions and high inoculum load in the field, inoculation of healthy Aromas plants with P. aphanis in the laboratory failed to produce disease. Conidia were seldom found attached to the leaf surface of healthy Aromas leaves. Germination and subsequent colony development were also not observed in inoculated samples. This suggests there is some mechanism of Aromas that inhibits development of this fungus. Preliminary investigation of differential expression in Aromas inoculated with P. aphanis, identified sequences with homology to a putative antimicrobial protein and photosynthesis-related genes. The results of these studies should enable growers to increase both crop yields and control of powdery mildew, one of the major economic diseases in South Australia. The epidemiological knowledge attained will be valuable, and may provide the basis for future forecast modelling for P. aphanis in strawberry crops in South Australia. Recommendations for calcium and potassium leaf content will allow growers to monitor their fertiliser regime for increased yield of these cultivars. Aromas was identified as a powdery mildew resistant cultivar potentially suitable for production in South Australia, and the genes associated with this resistance response may be used in studies of Fragaria species and breeding for powdery mildew resistant cultivars. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297684 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007