The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Aliki K. Tzima - One of the best experts on this subject based on the ideXlab platform.
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A non-Mendelian inheritance of Resistance to strobilurin fungicides in Ustilago maydis†
Pest Management Science, 2002Co-Authors: Basil N. Ziogas, Anastasios N. Markoglou, Aliki K. TzimaAbstract:Mutants of Ustilago maydis (DC) Corda with high Resistance to azoxystrobin (RF 164 to 4714, based on EC 50 values), an inhibitor of mitochondrial electron transport at the cytochrome bc 1 complex, were isolated in a mutation frequency of 2.3 x 10 7 after nitrosoguanidine mutagenesis and selection on media containing 1 μgml -1 azoxystrobin in addition to 0.5 mM salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strains by azoxystrobin (1.5 μg ml -1 ) in addition to SHAM (1 mM), but not in the mutant isolates. Genetic analysis with nine such mutant isolates resulted in progeny phenotypes which did not follow Mendelian segregation, but satisfied the criteria of non-Mendelian (cytoplasmic) heredity. In crosses between three mutant isolates with the compatible wild-type strains, the sensitivity was inherited by progeny maternally from the wild-type parent strain (criterion of uniparental inheritance). In crosses between wild-type strains and remaining mutant isolates, a continuous distribution of sensitivity in the progeny was found (criterion of vegetative segregation). The third criterion of cytoplasmic Resistance (criterion of intracellular selection) was fulfilled by experiments on the stability of Resistance phenotypes. With two exceptions, a Reduction of Resistance was observed in the mutant strains when they were grown on inhibitor-free medium. Recovery of the high Resistance level was observed after they were returned to the selection medium. Cross-Resistance studies with other fungicides, which also inhibit electron transport through complex III of respiratory chain, showed that mutations for Resistance to azoxystrobin were also responsible for reduced sensitivity to kresoxim-methyl (RF 18 to 1199) and to antimycin-A (RF 20 to 305), which act at the Q o and Q i sites of the cytochrome bc 1 complex, respectively. Studies of the fitness of azoxystrobin-resistant isolates showed that these mutations appeared to be pleiotropic, having significant adverse effects on growth in liquid culture and pathogenicity on young corn plants.
Basil N. Ziogas - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Laboratory Mutants of Botrytis cinerea Resistant to QoI Fungicides
European Journal of Plant Pathology, 2006Co-Authors: Anastasios N. Markoglou, Anastasios A Malandrakis, Andreas G Vitoratos, Basil N. ZiogasAbstract:Mutants of Botrytis cinerea with moderate and high Resistance to pyraclostrobin, a Qo inhibitor of mitochondrial electron transport at the cytochrome bc _1 complex, were isolated at a high mutation frequency, after nitrosoguanidine mutagenesis and selection on medium containing pyraclostrobin and salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strain by pyraclostrobin and SHAM, but not in the mutant isolates. Cross-Resistance studies with other Qo and Qi inhibitors (QoIs and QiIs) of cytochrome bc _1 complex of mitochondrial respiration showed that the mutation(s) for Resistance to pyraclostrobin also reduced the sensitivity of mutant strains to other QoIs as azoxystrobin, fluoxastrobin, trifloxystrobin and picoxystrobin, but not to famoxadone and to the QiIs cyazofamid and antimycin-A. An increased sensitivity of pyraclostrobin-resistant strains to the carboxamide boscalid, an inhibitor of complex II, and to the anilinopyrimidine cyprodinil, a methionine biosynthesis inhibitor, was observed. Moreover, no effect of pyraclostrobin Resistance mutation(s) on fungitoxicity of the hydroxyanilide fenhexamid, the phenylpyrrole fludioxonil, the benzimidazole benomyl, and to the phenylpyridinamine fluazinam, which affect other cellular pathways, was observed. Study of fitness parameters in the wild-type and pyraclostrobin-resistant mutants of B. cinerea showed that most mutants had a significant Reduction in the sporulation, conidial germination and sclerotia production. Experiments on the stability of the pyraclostrobin-resistant phenotype showed a Reduction of Resistance, mainly in moderate resistant strains, when the mutants were grown on inhibitor-free medium. However, a rapid recovery of the Resistance level was observed after the mutants were returned to a selective medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain, by applications of a mixed conidial population, showed that, in vitro , all mutants were less competitive than the wild-type strain. However, the competitive ability of high resistant mutants was higher than the moderate ones. Pathogenicity tests on cucumber seedlings showed that all mutant strains tested exhibited an infection ability similar with the wild-type parent strain. Preventive applications of the commercial product of F-500 25EC (pyraclostrobin) were effective against lesion development on cotyledons by the wild-type, but ineffective, even at high concentrations, against disease caused by the pyraclostrobin-resistant isolates. Boscalid (F-510 50WG) was found equally effective against the disease caused by the wild-type or pyraclostrobin-resistant mutants. This is the first report indicating the appearance of B. cinerea strains resistant to QoI fungicides by the biochemical mechanism of site modification and the risk for field Resistance.
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Effect of Phenylpyrrole-Resistance Mutations on Ecological Fitness of Botrytis cinerea and their Genetical Basis in Ustilago maydis
European Journal of Plant Pathology, 2005Co-Authors: Basil N. Ziogas, Anastasios N. Markoglou, Vaso SpyropoulouAbstract:Mutants of Botrytis cinerea and Ustilago maydis highly resistant to fludioxonil were isolated at a high frequency, after nitrosoguanidine or UV mutagenesis, respectively, and selection on media containing fludioxonil. Tests on the response of mutant strains to high osmotic pressure resulted in the identification of two fludioxonil-resistant phenotypes (FLD_osm/s and FLD_osm/r), regarding the sensitivity to high osmolarity. Approximately 95% of fludioxonil-resistant mutants were found to be more sensitive to high osmotic pressure than the wild-type parent strains. Genetic analysis of phenylpyrrole-Resistance in the phytopathogenic basidiomycete U. maydis , showed that fludioxonil-Resistance was coded by three unlinked chromosomal loci ( U/fld -1, U/fld -2 and U/fld -3), from which only the U/fld -1 mutation coded an osmotic sensitivity similar to that of the wild-types. Cross-Resistance studies with fungicides from other chemical groups showed that the mutations for Resistance to phenylpyrroles affect the sensitivity of mutant strains to the aromatic hydrocarbon and dicarboximide fungicides, but not to the benzimidazoles, anilinopyrimidines, phenylpyridinamines, hydroxyanilides or the sterol biosynthesis inhibiting fungicides. A study of fitness parameters in the wild-type and fludioxonil-resistant mutants of B. cinerea , showed that all osmotic sensitive (B/FLD_osm/s) isolates had significant Reductions in the characteristics determining saprophytic fitness such as mycelial growth, sporulation, conidial germination and sclerotial production. Contrary to that, with the exception of mycelial growth, the fitness parameters were unaffected or only slightly affected in most of the osmotic resistant (B/FLD_osm/r) isolates. Tests on cucumber seedlings showed that the osmotic-sensitive strains were significantly less pathogenic compared with the wild-type and B/FLD_osm/r strains of B. cinerea . Preventative applications of the commercial products Saphire 50 WP (fludioxonil) and Rovral 50 WP (iprodione) were effective against lesion development on cotyledons by the wild-type and the mutant strains of B. cinerea that were resistant to the anilinopyrimidine cyprodinil (B/CPL-27) and to the hydroxyanilide fenhexamid (B/FNH-21), but ineffective, even at high concentrations, against disease caused by the fludioxonil-resistant isolates (B/FLD) and a mutant strain resistant to the dicarboximide iprodione (B/IPR-1). Experiments on the stability of the fludioxonil-resistant phenotype showed a Reduction of Resistance, mainly in osmotic-sensitive isolates, when the mutants were grown on inhibitor-free medium. A rapid recovery of the high Resistance was observed after mutants were returned to the selection medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain of B. cinerea , by applications of a mixed conidial population, showed that, in vitro , all mutants were less competitive than the wild-type strain. However, the competitive ability of osmotic-resistant mutants was higher than the osmotic-sensitive ones. Furthermore, competition tests, in planta , showed a significant Reduction of the frequency of both phenylpyrrole-resistant phenotypes, with a respective increase in the population of the wild-type strain of the pathogen.
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A non-Mendelian inheritance of Resistance to strobilurin fungicides in Ustilago maydis†
Pest Management Science, 2002Co-Authors: Basil N. Ziogas, Anastasios N. Markoglou, Aliki K. TzimaAbstract:Mutants of Ustilago maydis (DC) Corda with high Resistance to azoxystrobin (RF 164 to 4714, based on EC 50 values), an inhibitor of mitochondrial electron transport at the cytochrome bc 1 complex, were isolated in a mutation frequency of 2.3 x 10 7 after nitrosoguanidine mutagenesis and selection on media containing 1 μgml -1 azoxystrobin in addition to 0.5 mM salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strains by azoxystrobin (1.5 μg ml -1 ) in addition to SHAM (1 mM), but not in the mutant isolates. Genetic analysis with nine such mutant isolates resulted in progeny phenotypes which did not follow Mendelian segregation, but satisfied the criteria of non-Mendelian (cytoplasmic) heredity. In crosses between three mutant isolates with the compatible wild-type strains, the sensitivity was inherited by progeny maternally from the wild-type parent strain (criterion of uniparental inheritance). In crosses between wild-type strains and remaining mutant isolates, a continuous distribution of sensitivity in the progeny was found (criterion of vegetative segregation). The third criterion of cytoplasmic Resistance (criterion of intracellular selection) was fulfilled by experiments on the stability of Resistance phenotypes. With two exceptions, a Reduction of Resistance was observed in the mutant strains when they were grown on inhibitor-free medium. Recovery of the high Resistance level was observed after they were returned to the selection medium. Cross-Resistance studies with other fungicides, which also inhibit electron transport through complex III of respiratory chain, showed that mutations for Resistance to azoxystrobin were also responsible for reduced sensitivity to kresoxim-methyl (RF 18 to 1199) and to antimycin-A (RF 20 to 305), which act at the Q o and Q i sites of the cytochrome bc 1 complex, respectively. Studies of the fitness of azoxystrobin-resistant isolates showed that these mutations appeared to be pleiotropic, having significant adverse effects on growth in liquid culture and pathogenicity on young corn plants.
Hua-xin Peng - One of the best experts on this subject based on the ideXlab platform.
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Magnetocaloric effect in bamboo-grained Ni-Mn-Ga microwires over a wide working temperature interval
Materials & Design, 2020Co-Authors: Mingfang Qian, Jianfei Sun, Xinjiang Zhang, Ruliang Zhang, Peter George Martin, L. Geng, Thomas Bligh Scott, Hua-xin PengAbstract:Abstract Bamboo-grained Ni-Mn-Ga microwire is promising for achieving considerable magnetic-field-induced strain due to less neighboring grain constraints to the twin boundary motion. Such Reduction of Resistance to interface motion also favors the Reduction of hysteresis in magnetic refrigeration. Here, bamboo-grained Ni-Mn-Ga microwires were successfully synthesized by a melt-extraction technique and subsequent high temperature heat treatment at 1323 K for 3 h under Argon atmosphere. Corresponding microstructure, martensite transformation (MT) behaviors and magnetocaloric properties were investigated. The high specific surface area of the microwires favored the element evaporation at high temperature, leading to a heterogeneous composition state, which is responsible for the MT temperature (range) change and the multi-variants state in the bamboo-grained microwires. Nearly no magnetic hysteresis loss was obtained. The increased compositional variation led to the partial overlap of the MT and the magnetic transition, resulting in the improvement of the working temperature interval ~71 K and net refrigeration capacity ~255 J/kg under μ0H = 5 T, which is heretofore the largest value reported in Ni-Mn-based Heusler alloys. When utilized as refrigerant in a cooling device, such small-sized microwires can increase the contacting area between the material and the heat-transfer agent, which helps the heat exchange and thus improve the refrigeration efficiency.
George G Kennedy - One of the best experts on this subject based on the ideXlab platform.
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Interaction of fertilizer regime with host-plant Resistance in tomato
Entomologia Experimentalis et Applicata, 1991Co-Authors: James D. Barbour, Robert R. Farrar, George G KennedyAbstract:The effect of fertilizer regime on trichome- and lamellar-based Resistance in the wild tomato species, Lycopersicon hirsutum f. glabratum C.H. Mull accession PI 134417, to three insect pests of tomato, the tobacco hornworm, Manduca sexta (L.), the colorado potato beetle, Leptinotarsa decemlineata (Say), and the tomato fruitworm, Heliocoverpa zea (Boddie), was examined. Increasing the rate at which NPK fertilizer was applied, from 1.8 to 19.6 g/plant/week, reduced the trichome-based Resistance of PI 134417 to M. sexta and L. decemlineata by lowering both the density of type VI ( sensu Luckwill, 1943) glandular trichomes and the amount of 2-tridecanone contained in the tips of these trichomes. 2-Tridecanone is a toxic methyl-ketone responsible for glandular trichome-mediated Resistance in PI 134417 to M. sexta and L. decemlineata . A similar increase in the application rate of NPK fertilizer reduced the lamellarbased Resistance of PI 134417 to L. decemlineata and H. zea . The meachanisms for this Reduction of Resistance are unknown, but may be related to improved nutritional quality of hosts at higher fertilizer regimes.
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Interaction of fertilizer regime with host‐plant Resistance in tomato
Entomologia Experimentalis Et Applicata, 1991Co-Authors: James D. Barbour, Robert R. Farrar, George G KennedyAbstract:The effect of fertilizer regime on trichome- and lamellar-based Resistance in the wild tomato species, Lycopersicon hirsutum f. glabratum C. H. Mull accession PI 134417, to three insect pests of tomato, the tobacco hornworm, Manduca sexta (L.), the Colorado potato beetle, Leptinotarsa decemlineata (Say), and the tomato fruitworm, Heliocoverpa zea (Boddie), was examined. Increasing the rate at which NPK fertilizer was applied, from 1.8 to 19.6 g/plant/week, reduced the trichome-based Resistance of PI 134417 to M. sexta and L. decemlineata by lowering both the density of type VI (sensu Luckwill, 1943) glandular trichomes and the amount of 2-tridecanone contained in the tips of these trichomes. 2-Tridecanone is a toxic methyl-ketone responsible for glandular trichome-mediated Resistance in PI 134417 to M. sexta and L. decemlineata. A similar increase in the application rate of NPK fertilizer reduced the lamellar-based Resistance of PI 134417 to L. decemlineata and H. zea. The meachanisms for this Reduction of Resistance are unknown, but may be related to improved nutritional quality of hosts at higher fertilizer regimes.
Anastasios N. Markoglou - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Laboratory Mutants of Botrytis cinerea Resistant to QoI Fungicides
European Journal of Plant Pathology, 2006Co-Authors: Anastasios N. Markoglou, Anastasios A Malandrakis, Andreas G Vitoratos, Basil N. ZiogasAbstract:Mutants of Botrytis cinerea with moderate and high Resistance to pyraclostrobin, a Qo inhibitor of mitochondrial electron transport at the cytochrome bc _1 complex, were isolated at a high mutation frequency, after nitrosoguanidine mutagenesis and selection on medium containing pyraclostrobin and salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strain by pyraclostrobin and SHAM, but not in the mutant isolates. Cross-Resistance studies with other Qo and Qi inhibitors (QoIs and QiIs) of cytochrome bc _1 complex of mitochondrial respiration showed that the mutation(s) for Resistance to pyraclostrobin also reduced the sensitivity of mutant strains to other QoIs as azoxystrobin, fluoxastrobin, trifloxystrobin and picoxystrobin, but not to famoxadone and to the QiIs cyazofamid and antimycin-A. An increased sensitivity of pyraclostrobin-resistant strains to the carboxamide boscalid, an inhibitor of complex II, and to the anilinopyrimidine cyprodinil, a methionine biosynthesis inhibitor, was observed. Moreover, no effect of pyraclostrobin Resistance mutation(s) on fungitoxicity of the hydroxyanilide fenhexamid, the phenylpyrrole fludioxonil, the benzimidazole benomyl, and to the phenylpyridinamine fluazinam, which affect other cellular pathways, was observed. Study of fitness parameters in the wild-type and pyraclostrobin-resistant mutants of B. cinerea showed that most mutants had a significant Reduction in the sporulation, conidial germination and sclerotia production. Experiments on the stability of the pyraclostrobin-resistant phenotype showed a Reduction of Resistance, mainly in moderate resistant strains, when the mutants were grown on inhibitor-free medium. However, a rapid recovery of the Resistance level was observed after the mutants were returned to a selective medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain, by applications of a mixed conidial population, showed that, in vitro , all mutants were less competitive than the wild-type strain. However, the competitive ability of high resistant mutants was higher than the moderate ones. Pathogenicity tests on cucumber seedlings showed that all mutant strains tested exhibited an infection ability similar with the wild-type parent strain. Preventive applications of the commercial product of F-500 25EC (pyraclostrobin) were effective against lesion development on cotyledons by the wild-type, but ineffective, even at high concentrations, against disease caused by the pyraclostrobin-resistant isolates. Boscalid (F-510 50WG) was found equally effective against the disease caused by the wild-type or pyraclostrobin-resistant mutants. This is the first report indicating the appearance of B. cinerea strains resistant to QoI fungicides by the biochemical mechanism of site modification and the risk for field Resistance.
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Effect of Phenylpyrrole-Resistance Mutations on Ecological Fitness of Botrytis cinerea and their Genetical Basis in Ustilago maydis
European Journal of Plant Pathology, 2005Co-Authors: Basil N. Ziogas, Anastasios N. Markoglou, Vaso SpyropoulouAbstract:Mutants of Botrytis cinerea and Ustilago maydis highly resistant to fludioxonil were isolated at a high frequency, after nitrosoguanidine or UV mutagenesis, respectively, and selection on media containing fludioxonil. Tests on the response of mutant strains to high osmotic pressure resulted in the identification of two fludioxonil-resistant phenotypes (FLD_osm/s and FLD_osm/r), regarding the sensitivity to high osmolarity. Approximately 95% of fludioxonil-resistant mutants were found to be more sensitive to high osmotic pressure than the wild-type parent strains. Genetic analysis of phenylpyrrole-Resistance in the phytopathogenic basidiomycete U. maydis , showed that fludioxonil-Resistance was coded by three unlinked chromosomal loci ( U/fld -1, U/fld -2 and U/fld -3), from which only the U/fld -1 mutation coded an osmotic sensitivity similar to that of the wild-types. Cross-Resistance studies with fungicides from other chemical groups showed that the mutations for Resistance to phenylpyrroles affect the sensitivity of mutant strains to the aromatic hydrocarbon and dicarboximide fungicides, but not to the benzimidazoles, anilinopyrimidines, phenylpyridinamines, hydroxyanilides or the sterol biosynthesis inhibiting fungicides. A study of fitness parameters in the wild-type and fludioxonil-resistant mutants of B. cinerea , showed that all osmotic sensitive (B/FLD_osm/s) isolates had significant Reductions in the characteristics determining saprophytic fitness such as mycelial growth, sporulation, conidial germination and sclerotial production. Contrary to that, with the exception of mycelial growth, the fitness parameters were unaffected or only slightly affected in most of the osmotic resistant (B/FLD_osm/r) isolates. Tests on cucumber seedlings showed that the osmotic-sensitive strains were significantly less pathogenic compared with the wild-type and B/FLD_osm/r strains of B. cinerea . Preventative applications of the commercial products Saphire 50 WP (fludioxonil) and Rovral 50 WP (iprodione) were effective against lesion development on cotyledons by the wild-type and the mutant strains of B. cinerea that were resistant to the anilinopyrimidine cyprodinil (B/CPL-27) and to the hydroxyanilide fenhexamid (B/FNH-21), but ineffective, even at high concentrations, against disease caused by the fludioxonil-resistant isolates (B/FLD) and a mutant strain resistant to the dicarboximide iprodione (B/IPR-1). Experiments on the stability of the fludioxonil-resistant phenotype showed a Reduction of Resistance, mainly in osmotic-sensitive isolates, when the mutants were grown on inhibitor-free medium. A rapid recovery of the high Resistance was observed after mutants were returned to the selection medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain of B. cinerea , by applications of a mixed conidial population, showed that, in vitro , all mutants were less competitive than the wild-type strain. However, the competitive ability of osmotic-resistant mutants was higher than the osmotic-sensitive ones. Furthermore, competition tests, in planta , showed a significant Reduction of the frequency of both phenylpyrrole-resistant phenotypes, with a respective increase in the population of the wild-type strain of the pathogen.
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A non-Mendelian inheritance of Resistance to strobilurin fungicides in Ustilago maydis†
Pest Management Science, 2002Co-Authors: Basil N. Ziogas, Anastasios N. Markoglou, Aliki K. TzimaAbstract:Mutants of Ustilago maydis (DC) Corda with high Resistance to azoxystrobin (RF 164 to 4714, based on EC 50 values), an inhibitor of mitochondrial electron transport at the cytochrome bc 1 complex, were isolated in a mutation frequency of 2.3 x 10 7 after nitrosoguanidine mutagenesis and selection on media containing 1 μgml -1 azoxystrobin in addition to 0.5 mM salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strains by azoxystrobin (1.5 μg ml -1 ) in addition to SHAM (1 mM), but not in the mutant isolates. Genetic analysis with nine such mutant isolates resulted in progeny phenotypes which did not follow Mendelian segregation, but satisfied the criteria of non-Mendelian (cytoplasmic) heredity. In crosses between three mutant isolates with the compatible wild-type strains, the sensitivity was inherited by progeny maternally from the wild-type parent strain (criterion of uniparental inheritance). In crosses between wild-type strains and remaining mutant isolates, a continuous distribution of sensitivity in the progeny was found (criterion of vegetative segregation). The third criterion of cytoplasmic Resistance (criterion of intracellular selection) was fulfilled by experiments on the stability of Resistance phenotypes. With two exceptions, a Reduction of Resistance was observed in the mutant strains when they were grown on inhibitor-free medium. Recovery of the high Resistance level was observed after they were returned to the selection medium. Cross-Resistance studies with other fungicides, which also inhibit electron transport through complex III of respiratory chain, showed that mutations for Resistance to azoxystrobin were also responsible for reduced sensitivity to kresoxim-methyl (RF 18 to 1199) and to antimycin-A (RF 20 to 305), which act at the Q o and Q i sites of the cytochrome bc 1 complex, respectively. Studies of the fitness of azoxystrobin-resistant isolates showed that these mutations appeared to be pleiotropic, having significant adverse effects on growth in liquid culture and pathogenicity on young corn plants.