The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
R J Boal - One of the best experts on this subject based on the ideXlab platform.
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residual activity of fludioxonil and pyrimethanil against Penicillium expansum on apple fruit
Plant Disease, 2009Co-Authors: C. L. Xiao, R J BoalAbstract:Xiao, C. L., and Boal, R. J. 2009. Residual activity of fludioxonil and pyrimethanil against Penicillium expansum on apple fruit. Plant Dis. 93:1003-1008. Blue mold caused by Penicillium expansum is a major postharvest disease of apples (Malus × domestica). Residual activity of fludioxonil and pyrimethanil in apple fruit against P. expansum was investigated during 2005 to 2008. Fruit of the cultivar Delicious harvested from commercial orchards where fungicides were not used were either not treated or drenched with fludioxonil, pyrimethanil, or thiabendazole prior to storage and then stored in controlled atmosphere at 0°C for 5 or 7 months, after which time the fruit were removed from storage and subjected to washing and brushing, practices that are done at the time of packing. Fruit were then wounded and inoculated with conidial suspensions of P. expansum. Inoculated fruit were treated with either sterile water or fungicides. Fruit were stored at 0°C for 8 weeks and at room temperature for one additional week after cold storage. To determine distribution of fungicide residues in the fruit flesh, fruit were cut horizontally at the equator, sprayed with the conidial suspension of P. expansum, incubated at room temperature, and examined for inhibition of blue mold on the cut fruit 4 days after inoculation. Fungicide residues on/in the fruit were analyzed using a gas chromatograph. Zero to 26% blue mold incidence was observed on fludioxonil-drenched fruit that were inoculated and not treated with fungicides at packing. No decay or 32 mm inhibition zone and approximately 5 mm inhibition zone measured from the fruit peel toward the fruit core were observed on pyrimethanil-drenched and fludioxonil-drenched fruit, respectively. Washing and brushing at the time of packing 5 and 7 months after harvest did not remove or only partially removed residues of fludioxonil and pyrimethanil from apple fruit. The results suggest that residues of fludioxonil and pyrimethanil on/in apple fruit are persistent and that residual protection of apple fruit by the two fungicides can last for at least 7 months under apple-storage conditions.
C. L. Xiao - One of the best experts on this subject based on the ideXlab platform.
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use of chemosensitization to overcome fludioxonil resistance in Penicillium expansum
Letters in Applied Microbiology, 2010Co-Authors: J H Kim, Bruce C Campbell, Noreen Mahoney, Kathleen L Chan, Russell J Molyneux, C. L. XiaoAbstract:Aim: To overcome fludioxonil resistance of Penicillium expansum, a mycotoxigenic fungal pathogen causing postharvest decay in apple, by using natural phenolic chemosensitizing agents. Methods and Results: Fludioxonil-resistant mutants of P. expansum were co-treated with different oxidising and natural phenolic agents. Resistance was overcome by natural phenolic chemosensitizing agents targeting the oxidative stress–response pathway. These agents also augmented effectiveness of the fungicide, kresoxim-methyl. Results indicated that alkyl gallates target mitochondrial respiration and/or its antioxidation system. Fungal mitochondrial superoxide dismutase (Mn-SOD) plays a protective role against alkyl gallates. Conclusions: Natural chemosensitizing agents targeting the oxidative stress–response system, such as Mn-SOD, can synergize commercial fungicides. Significance and Impact of the Study: Redox-active compounds can serve as potent chemosensitizing agents to overcome resistance and lower effective dosages of fungicides. This can reduce costs with coincidental lowering of environmental and health risks.
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residual activity of fludioxonil and pyrimethanil against Penicillium expansum on apple fruit
Plant Disease, 2009Co-Authors: C. L. Xiao, R J BoalAbstract:Xiao, C. L., and Boal, R. J. 2009. Residual activity of fludioxonil and pyrimethanil against Penicillium expansum on apple fruit. Plant Dis. 93:1003-1008. Blue mold caused by Penicillium expansum is a major postharvest disease of apples (Malus × domestica). Residual activity of fludioxonil and pyrimethanil in apple fruit against P. expansum was investigated during 2005 to 2008. Fruit of the cultivar Delicious harvested from commercial orchards where fungicides were not used were either not treated or drenched with fludioxonil, pyrimethanil, or thiabendazole prior to storage and then stored in controlled atmosphere at 0°C for 5 or 7 months, after which time the fruit were removed from storage and subjected to washing and brushing, practices that are done at the time of packing. Fruit were then wounded and inoculated with conidial suspensions of P. expansum. Inoculated fruit were treated with either sterile water or fungicides. Fruit were stored at 0°C for 8 weeks and at room temperature for one additional week after cold storage. To determine distribution of fungicide residues in the fruit flesh, fruit were cut horizontally at the equator, sprayed with the conidial suspension of P. expansum, incubated at room temperature, and examined for inhibition of blue mold on the cut fruit 4 days after inoculation. Fungicide residues on/in the fruit were analyzed using a gas chromatograph. Zero to 26% blue mold incidence was observed on fludioxonil-drenched fruit that were inoculated and not treated with fungicides at packing. No decay or 32 mm inhibition zone and approximately 5 mm inhibition zone measured from the fruit peel toward the fruit core were observed on pyrimethanil-drenched and fludioxonil-drenched fruit, respectively. Washing and brushing at the time of packing 5 and 7 months after harvest did not remove or only partially removed residues of fludioxonil and pyrimethanil from apple fruit. The results suggest that residues of fludioxonil and pyrimethanil on/in apple fruit are persistent and that residual protection of apple fruit by the two fungicides can last for at least 7 months under apple-storage conditions.
Rolf D. Schmid - One of the best experts on this subject based on the ideXlab platform.
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Purification and properties of a lipase from Penicillium expansum
Biochimica et biophysica acta, 1993Co-Authors: W. Stöcklein, Helena Sztajer, Ulrich Menge, Rolf D. SchmidAbstract:Penicillium expansum DSM 1994 produces a new, inducible extracellular lipase when grown in medium containing 0.1% olive oil. Maximum activity was obtained after 4 days of incubation at 20°C. The enzyme was purified 219-fold by cross-flow filtration, ammonium sulfate precipitation and hydrophobic interaction chromatography to a final specific activity of 558 U/mg. The molecular weight of the homogeneous lipase was (25 kDa) determined by gel filtration and SDS-PAGE, however, it forms active dimers and higher aggregates as observed after native PAGE. The enzyme was identified as a glycoprotein with a pI of 5.5. The N-terminal sequence shows a homology to sequences of other lipase just behind their consensus sequence. Enzyme stability was enhanced by the addition of Tween 20 and Lubrol PX. The enzyme showed a maximum activity at pH 9 at 45°C and was stable at a broad pH range of 6–10. Lipase of P. expansum showed a preference for triacylglycerols, but no positional specificity.
Rosa Oria - One of the best experts on this subject based on the ideXlab platform.
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In vitro antifungal activity of several antimicrobial compounds against Penicillium expansum.
Journal of food protection, 2002Co-Authors: María E. Venturini, Domingo Blanco, Rosa OriaAbstract:Fungicides used in the prevention and control of mold rots in stored apples are subjected to legal, social, and biological limitations. The aim of this study was to find an alternative to postharvest fungicides currently used in the prevention and control of blue mold rot caused by Penicillium expansum in apples. For this purpose, the antimicrobial activity and MIC of several substances against P. expansum were evaluated in vitro using different end point methods: agar diffusion assay, volatility method, and agar dilution and broth dilution MIC assays. Most of the substances tested are common food ingredients and have a recognized antimicrobial activity. Essential oils, such as thymol, eugenol, citral and cineole, vanillin, sodium hypochlorite, acetic acid, potassium sorbate, and hydrogen peroxide, were the substances evaluated. Thymol and citral were the essential oil components that showed the greatest inhibitory effects. The effectiveness of 5 and 10% hydrogen peroxide in growth inhibition of P. expansum in the agar diffusion assay was total, and its MIC as determined by the agar and broth dilution assays was less than 0.025%. These results indicate that the application of small quantities of hydrogen peroxide to the apple skin might be an alternative to fungicides in the elimination of P. expansum. Le but de cette etude est de definir une alternative aux fongicides utilises couramment apres la recolte dans la prevention et le controle de la pourriture causee par Penicillium expansum dans les pommes. Pour cela, l'activite antimicrobienne et la concentration minimum d'inhibition (MIC) de substances comme des huiles essentielles, la vaniline, l'hypochlorite de sodium, l'acide acetique, le sorbate de potassium et le peroxyde d'hydrogene, contre P. expansum sont evaluees in vitro.
R.l. Evans - One of the best experts on this subject based on the ideXlab platform.
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Effect of osmotic stress on the respiratory activity of Penicillium expansum
Microbiological Research, 1998Co-Authors: M.a. Hefnawy, R.l. EvansAbstract:Penicillium expansum is able to tolerate sugar concentration in the medium up to 80% (w/v). Respirometric studies with mitochondrial fractions and whole cells revealed the presence of more actively functioning respiratory system in presence of 50% and 80% sucrose in the growth medium. Levels of respiratory enzymes such as succinate dehydrogenase, NADH dehydrogenase, cytochrome oxidase, NADH oxidase and succinoxidase were higher in the cells grown in presence of 50% and 80% sucrose. Electron microscopic observations of P. expansum grown in presence of 50% and 80% sucrose revealed a larger size of mitochondria than in the control cells. The mean mitochondrial diameter at 50% and 80% sucrose was approximately 1.6 and 2.4 fold respectively bigger than in the control cells grown at 3% sucrose.