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1.
Chuan-qing Zhang Jin-wen Zhu Fang-lin Wei Shao-ying Liu Guo-nian Zhu 《Phytoparasitica》2007,35(3):300-313
Two hundred isolates ofBotrytis cinerea were collected from greenhouse vegetables between 2003 and 2006 to determine their baseline sensitivity to triadimefone,
penconazole, tebuconazole and fenhexamid. Mean values of 50% effective concentrations (EC50) of inhibiting growth were 4.853±5.102, 0.41±0.215, 0.19±0.099 and 0.36±0.891 mgl
−1, respectively (mean±SD). Individuals ofB. cinerea in the population differed by a factor (EC50 of the least sensitive isolate/EC50 of the most sensitive isolate) of 6625, 20, 603 and 1800, respectively. Naturally fenhexamid-resistant isolates were detected
with an unexpected high frequency of 10% although the pathogen population had never been exposed to this fungicide. The resistance
level (mean EC50 of resistant isolates / mean EC50 of sensitive isolates) was 19.5. These naturally resistant isolates also were resistantin vivo, and there was no significant difference in growth rate, conidial production or pathogenicity ability between naturally resistant
and wild sensitive isolates. These results indicated that there was a potential risk of practical resistance if fenhexamid
was applied alone. Negative cross-resistance was observed between fenhexamid and tebuconazole in 90% of the naturally resistant
isolates. Moreover, an obvious synergism of the antifungal activity of fenhexamid by tebuconazole was demonstrated in some
of the naturally fenhexamid-resistant isolates.
http://www.phytoparasitica.org posting May 9, 2007. 相似文献
2.
Jun Hou Ya-nan Gao Juntao Feng Zhiqing Ma Xing Zhang 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(2):261-267
The baseline sensitivity of Botrytis cinerea to propamidine and assessment of the risk of propamidine resistance in vitro are presented in this article. The baseline
sensitivities of 41 wild-type strains were distributed as a unimodal curve with EC50 values of mycelial growth ranging from 0.182 to 1.460 μg ml−1, with a mean of 0.79 ± 0.27 μg ml−1. A total of 10 resistant mutants, obtained from one parental strain, were induced by UV irradiation and selected for resistance
to propamidine with an average frequency of 1.98 × 10−9 and 0.025 respectively. These mutants were divided into three classes of resistant phenotypes with low (LR), moderate (MR)
and high (HR) levels of resistance, determined by the EC50 values of 5.0–15.0 μg ml−1, 15.1–75.0 μg ml−1 and more than 75.0 μg ml−1 respectively. Neither positive cross-resistance nor negative cross-resistance was detected between propamidine and the fungicides,
benzimidazole carbendazim, anilino-pyrimidine pyrimethanil, dicarboximide iprodione or procymidone. All 10 propamidine-resistant
mutants showed reduced mycelial growth in vitro, sporulation, spore germination and pathogenicity when compared with the parental
strain. These studies demonstrated that propamidine possesses a low risk of resistance developing. However, as B. cinerea is a high-risk pathogen, appropriate precautions against resistance development should be taken. 相似文献
3.
Rita M. De Miccolis Angelini Wassim Habib Caterina Rotolo Stefania Pollastro Francesco Faretra 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(2):185-199
Resistance to the fungicide boscalid in laboratory mutants of Botryotinia fuckeliana (Botrytis cinerea) was investigated. The baseline sensitivity to boscalid was evaluated in terms of colony growth (EC50 = 0.3–3 μg ml−1; MIC = 10–30 μg ml−1) and conidial germination (EC50 = 0.03–0.1 μg ml−1; MIC = 1–3 μg ml−1) tests. Mutants were selected in vitro from wild-type strains of the fungus on a fungicide-amended medium containing acetate as a carbon source. Mutants showed
two different levels of resistance to boscalid, distinguishable through the conidial germination tests: low (EC50 ∼ 0.3 μg ml−1, ranging from 0.03 to 1 μg ml−1; MIC > 100 μg ml−1) and high (EC50 > 100 μg ml−1) resistance. Analysis of meiotic progeny from crosses between resistant mutants and sensitive reference strains showed that
resistant phenotypes were due to mutations in single major gene(s) inherited in a Mendelian fashion, and linked with both
the Daf1 and Mbc1 genes, responsible for resistance to dicarboximide and benzimidazole fungicides, respectively. Gene sequence analysis of
the four sub-units of the boscalid-target protein, the succinate dehydrogenase enzyme, revealed that single or double point
mutations in the highly conserved regions of the iron-sulphur protein (Ip) gene were associated with resistance. Mutations
resulted in proline to leucine or phenylalanine replacements at position 225 (P225L or P225F) in high resistant mutants, and
in a histidine to tyrosine replacement at position 272 (H272Y) in low resistant mutants. Sequences of the flavoprotein and
the two transmembrane sub-units of succinate dehydrogenase were never affected. 相似文献
4.
Wilmer Pérez Johanna Lara Gregory A. Forbes 《European journal of plant pathology / European Foundation for Plant Pathology》2009,125(1):87-95
Fifty-eight isolates of Phytophthora infestans were evaluated in vitro and on detached leaves of potato for their sensitivities to metalaxyl-M and cymoxanil. The isolates belonged to the clonal
lineage, EC-1, which is dominant on potato in Peru and Ecuador. All isolates were collected in Huánuco, Peru, an area of year-round
potato production, where the potential for development of fungicide resistance is high. All isolates were resistant to metalaxyl-M,
with in vitro EC50 values ranging from 468.30—813.57 mg l−1. In contrast, we found no evidence for resistance to cymoxanil for which in vitro EC50 values ranged from 0.03—1.11 mg l−1. Resistance to each fungicide was also evaluated for five isolates in a detached leaf assay in which the fungicide was sprayed
on the leaf surface prior to inoculation. With metalaxyl-M, the range of EC50 values was 158.85—828.29 mg l−1, similar to that for the in vitro assay. For cymoxanil, EC50 values ranged from 1.41 to 2.31 mg l−1, which was higher than in the in vitro assay but still two orders of magnitude lower than the concentration applied by farmers in the field. 相似文献
5.
T. Miedaner C. Bolduan A. E. Melchinger 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(1):113-123
Fusarium graminearum and F. verticillioides are among the most important pathogens causing ear rot of maize in Central Europe. Our objectives were to (1) compare eight
isolates of each species on two susceptible inbred lines for their variation in ear rot rating and mycotoxin production across
3 years, and (2) analyse two susceptible and three resistant inbred lines for potential isolate x line interactions across
2 years by silk-channel inoculation. Ear rot rating, zearalenone (ZEA) and deoxynivalenol (DON) concentrations were evaluated
for all F. graminearum isolates. In addition, nivalenol (NIV) concentrations were analysed for two NIV producers. Fumonisin (FUM) concentrations
were measured for all F. verticillioides isolates. Mean ear rot severity was highest for DON producers of F. graminearum (62.9% of the ear covered by mycelium), followed by NIV producers of the same species (24.2%) and lowest for F. verticillioides isolates (9.8%). For the latter species, ear rot severities differed highly among years (2006: 24%, 2007: 3%, 2008: 7%). Mycotoxin concentrations among isolates showed
a broad range (DON: 100–284 mg kg−1, NIV: 15–38 mg kg−1, ZEA: 1.1–49.5 mg kg−1, FUM: 14.5–57.5 mg kg−1). Genotypic variances were significant for isolates and inbred lines in all traits and for both species. Isolate x line interactions
were significant only for ear rot rating (P < 0.01) and DON concentration (P < 0.05) of the F. graminearum isolates, but no rank reversals occurred. Most isolates were capable of differentiating the susceptible from the resistant
lines for ear rot severity. For resistance screening, a sufficiently aggressive isolate should be used to warrant maximal
differentiation among inbred lines. With respect to F. verticillioides infections, high FUM concentrations were found in grains from ears with minimal disease symptoms. 相似文献
6.
Khalid A. Hussein Mohamed A. A. Abdel-Rahman Ahmed Y. Abdel-Mallek Saad S. El-Maraghy Jin Ho Joo 《Phytoparasitica》2012,40(2):117-126
The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have
recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between
the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 × 106 conidia ml−1, 5.86 × 105 conidia ml−1, and 4.8 × 106 conidia ml−1, respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark
and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC50 values were 1.43 × 103, 1.04 × 105 and 5.06 × 104 for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis
program as 0.738 ± 0.008, 0.635 ± 0.007 and 1.120 ± 0.024, respectively. 相似文献
7.
The baseline sensitivity ofFusarium graminearum Schwade [teleomorph =Gibberella zeae (Schweinitz) Petch] to the fungicide JS399-19 (development code no.) [2-cyano-3-amino-3-phenylacrylic acetate] and the assessment
of risk to JS399-19 resistancein vitro are presented. The mean EC50 values for JS399-19 inhibiting mycelial growth of three populations of wild-typeF. graminearum isolates were 0.102±0.048, 0.113±0.035 and 0.110±0.036 μg ml−1, respectively. Through UV irradiation and selection for resistance to the fungicide, we obtained a total of 76 resistant
mutants derived from five wild-type isolates ofF. graminearum with an average frequency of 1.71 × 10−7% and 3.5%, respectively. These mutants could be divided into three categories of resistant phenotypes with low (LR), moderate
(MR) and high (HR) level of resistance, determined by the EC50 values of 1.5–15.0 μg ml−1, 15.1–75.0 μg ml−1 and more than 75.0 μg ml−1, respectively. There was no positive cross-resistance between JS399-19 and fungicides belonging to other chemical classes,
such as benzimidazoles, ergosterol biosynthesis inhibitors and strobilurins, suggesting that JS399-19 presumably has a new
biochemical mode of action. Although the resistant mutants appeared to have comparable pathogenicity to their wild-type parental
isolates, they showed decreased mycelial growth on potato-sucrose-agar plates and decreased sporulation capacity in mung bean
broth. Nevertheless, most of the resistant mutants possessed fitness levels comparable to their parents and had MR or HR levels
of resistance. As these studies yielded a high frequency of laboratory resistance inF. graminearum, appropriate precautions against resistance development in natural populations should be taken into account.
http://www.phytoparasitica.org posting August 7, 2008. 相似文献
8.
Christiane von der Ohe Victoria Gauthier Lily Tamburic-Ilincic Anita Brule-Babel W. G. Dilantha Fernando Randy Clear Todd J. Ward Thomas Miedaner 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(3):407-417
Twenty four isolates of Fusarium graminearum, half of which were 3-acetyldeoxynivalenol (3-ADON) and half 15-acetyldeoxynivalenol (15-ADON) chemotypes, were tested for
their ability to produce deoxynivalenol and to cause Fusarium head blight (FHB) in spring wheat cultivars. The objectives
of this study were to determine (1) whether 3-ADON isolates differ in aggressiveness, as measured by the FHB index, and DON
production from 15-ADON isolates under field conditions, and (2) whether the performance of resistant host cultivars was stable
across isolates. Field tests of all isolates were conducted with three replicates at each of two locations in Canada and Germany
in 2008 with three host genotypes differing in FHB resistance level. The resistant host genotype showed resistance regardless
of the chemotype or location. The differences between mean FHB indices of 3-ADON and 15-ADON isolates were not significant
for any wheat genotype. In contrast, average DON production by the 3-ADON isolates (10.44 mg kg−1) was significantly (P < 0.05) higher than for the 15-ADON isolates (6.95 mg kg−1) at three of the four locations where moderately resistant lines were tested, and at both locations where susceptible lines
were evaluated. These results indicate that 3-ADON isolates could pose a greater risk to food safety. However, as the mean
aggressiveness and DON production of 3-ADON and 15-ADON chemotypes was similar on highly resistant lines, breeding and use
of highly resistant lines is still the most effective measure of reducing the risks associated with DON in wheat. 相似文献
9.
Rachid Lahlali Sébastien Massart Deborah De Clercq M. Najib Serrhini Piet Creemers M. Haïssam Jijakli 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(1):37-45
The yeast Pichia anomala strain K was selected in Belgium from the apple surface for its antagonistic activity against post-harvest diseases of apples.
The efficacy of this strain against P. expansum was evaluated in the laboratory in three scenarios designed to mimic practical conditions, with different periods of incubation
between biological treatment, wounding of fruit surface, and pathogen inoculation. Higher protection levels and higher final
yeast densities were obtained when the applied initial concentration was 1 × 108 cfu ml−1 than when it was only 1 × 105 cfu ml−1. The protection level correlated positively with the yeast density determined in wounds and was influenced by apple surface
wetness. In orchard trials spanning two successive years, biological treatment against P. expansum, based on a powder of P. anomala strain K (1 × 107 cfu ml−1), β-1,3-glucans (YGT 2 g l−1), and CaCl2.2H20 (20 g l−1), was applied to apples pre- or post-harvest under practical conditions and its effect compared with standard chemical treatments.
The first year, the highest reduction (95.2%) against blue decay was obtained by means of four successive fungicide treatments
and the next-highest level (87.6%) with pre-harvest high-volume spraying of the three-component mixture 12 days before harvest.
The second year, the best results were obtained with post-harvest Sumico (carbendazim 25% and diethofencarb 25%) treatment
and post-harvest biological treatment, both by dipping the apples, 88.3 and 56.3% respectively. A density threshold of 1 × 104 cfu cm−2 of strain K on the apple surface seemed to be required just after harvest for high protective activity, whatever the method
and time of application. In the case of pre-harvest biological treatments, variations in meteorological conditions between
the 2 years may have considerably affected strain K population density and its efficacies. 相似文献
10.
Alba Valéria da Silva Pereira Ricardo Brainer Martins Sami Jorge Michereff Marcelo Bezerra da Silva Marcos Paz Saraiva Camara 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(4):489-498
Stem rot caused by Lasiodiplodia theobromae is an important postharvest disease of papaya in Brazil, responsible for reducing the quality and quantity of fruits. Fungicide
use is one of the main disease management measures. However, there are no estimates available of pathogen sensitivity to commonly
employed fungicides. Therefore, the EC50 from 120 isolates of L. theobromae from northeastern Brazil, representative of six populations of the pathogen, was estimated in vitro for fungicides of the
methyl benzimidazole carbamates—MBC (benomyl and thiabendazole) and demethylation-inhibiting—DMI (imazalil, prochloraz, tebuconazole)
groups. Mycelial growth on fungicide-free media and virulence on papaya fruits of the MBC-sensitive and non-sensitive isolates
were compared. For MBCs, 8.4% of isolates were non-sensitive to fungicides. For the remaining 91.6%, the mean EC50 ranged from 0.002 to 0.13 μg ml−1 and 0.36 to 1.27 μg ml−1 for benomyl and thiabendazole, respectively. For DMIs, the mean EC50 range for imazalil was 0.001 to 2.27 μg ml−1, 0.04 to 1.75 μg ml−1 for prochloraz, and 0.14 to 4.05 μg ml−1 for tebuconazole. The EC50 values of non-sensitive isolates were significantly (P≤0.05) higher those for the sensitive isolates for each of the DMI fungicides. Differences (P≤0.05) were found in the levels of sensitivity to DMI fungicides among the isolate populations associated with orchards. The
populations from two orchards were less sensitive to DMIs. No solid evidence was found for fitness costs relating to MBC non-sensitive
isolates because mycelial growth in fungicide-free media and virulence on papaya fruits were similar to those of sensitive
isolates. 相似文献
11.
During 2009–2010, a total of 323 isolates of Xanthomonas oryzae pv. oryzae were obtained from rice with symptoms of bacterial leaf blight (BLB) in four provinces (Zhejiang, Jiangsu, Anhui and Hubei) in China. These isolates were tested for baseline sensitivity to zinc thiazole, a novel bactericide with strong antibacterial activity against Xanthomonas. The sampled pathogenic population had similar sensitivity to zinc thiazole (0·1–16·8 mg L?1) in all four regions and over the whole two‐year study period. The baseline sensitivity was distributed as a unimodal curve with a mean EC50 value of 6·79 ± 1·61 mg L?1. The risk of mutation to resistance of zinc thiazole in X. oryzae pv. oryzae was further evaluated in vitro and in vivo. Twelve zinc thiazole‐resistant mutants were obtained through ultraviolet (UV) irradiation, culturing on zinc thiazole‐amended nutrient agar (NA) plates, and culturing on zinc thiazole‐treated rice plants. These zinc thiazole‐resistant mutants had resistance factors (RF = EC50 value of a mutant / EC50 value of the wildtype parent of this mutant) of 12·4 to 186·1 with a mean RF value of 44·1. Mutants obtained via UV irradiation, culturing on NA plates and culturing on rice plants had mean RF values of 51·8, 24·5 and 14·4, respectively. All mutants showed decreases in resistance to zinc thiazole after 20 successive transfers on bactericide‐free media or 10 successive inoculation–reisolations on bactericide‐free rice plants. No significant difference was found in bacterial growth and sensitivity to bismerthiazol between zinc thiazole‐resistant mutants and their parents. However, a significant decrease was observed in the pathogenicity of zinc thiazole‐resistant mutants compared with their parents, especially for mutants obtained via UV irradiation. 相似文献
12.
Giulia Alberoni Davide Cavallini Marina Collina Agostino Brunelli 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(4):453-457
Up to 2005 the sensitivity of Stemphylium vesicarium (Wallr.) Simm., the causal agent of pear brown spot, to the strobilurin fungicides kresoxim-methyl, trifloxystrobin and pyraclostrobin
was still comparable with baseline values associated with good efficacy in the field. During 2006, the first resistant isolates
were detected in two commercial pear orchards in the Emilia-Romagna region (Italy), one of which was affected by considerable
control failure linked to strobilurin treatments as demonstrated in a field trial. In vitro sensitivity tests with 0.5 mg l−1 of kresoxim-methyl, trifloxystrobin and pyraclostrobin showed that in the population collected in the orchard with control
failure the conidial germination was greater than 90% compared to an untreated control both in 2006 and in 2007, i.e. 1 year
after the suspension of strobilurin applications. In the other orchard, where only a few symptomatic fruits were found and
the strobilurins were still in use, the conidial germination was lower, about 50% in 2006 and 25% in 2007. The molecular analysis
of mitochondrial cytochrome b gene of some monospore isolates with different levels of sensitivity confirmed the presence
of the mutation causing G143A substitution in all the resistant isolates. In conclusion, both in vitro tests and molecular
analysis confirmed the first occurrence of Stemphylium vesicarium resistance to all strobilurin fungicides tested. 相似文献
13.
Keshav Birla Viviana Rivera-Varas Gary A. Secor Mohamed F. R. Khan Melvin D. Bolton 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(3):475-488
Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most important foliar disease of sugar beet worldwide. Control strategies for CLS rely heavily on quinone outside inhibitor (QOI) fungicides. Despite the dependence on QOIs for disease control for more than a decade, a comprehensive survey of QOI sensitivity has not occurred in the sugar beet growing regions of France or Italy. In 2010, we collected 866 C. beticola isolates from sugar beet growing regions in France and Italy and assessed their sensitivity to the QOI fungicide pyraclostrobin using a spore germination assay. In total, 213 isolates were identified with EC50 values greater than 1.0???g?ml?1 to pyraclostrobin, all of which originated from Italy. To gain an understanding of the molecular basis of QOI resistance, we cloned the full-length coding region of Cbcytb, which encodes the mitochondrial QOI-target enzyme cytochrome b in C. beticola. Cbcytb is a 1,162-bp intron-free gene with obvious homology to other fungal cytb genes. Sequence analysis of Cbcytb was carried out in 32 QOI-sensitive (<0.080???g?ml?1) and 27 QOI-resistant (>1.0???g?ml?1) isolates. All tested QOI-resistant isolates harboured a point mutation in Cbcytb at nucleotide position 428 that conferred an exchange from glycine to alanine at amino acid position 143 (G143A). A PCR assay developed to discriminate QOI-sensitive and QOI-resistant isolates based on the G143A mutation could detect and differentiate isolates down to approximately 25?pg of template DNA. Microsatellite analyses suggested that QOI resistance emerged independently in multiple genotypic backgrounds at multiple locations. Our results indicate that QOI resistance has developed in some C. beticola populations in Italy and monitoring the G143A mutation is essential for fungicide resistance management in this pathosystem. 相似文献
14.
Occurrence and molecular characterization of azoxystrobin resistance in cucumber downy mildew in Shandong province of China 总被引:1,自引:0,他引:1
Cucumber downy mildew caused byPseudoperonospora cubensis (Berk. and Curt.) Rostov. limits crop production in Shandong Province of China. Since management of downy mildew is strongly
dependent on fungicides, a rational design of control programs requires a good understanding of the fungicide resistance phenomenon
in field populations of the pathogen. A total of 106 and 97 isolates ofP. cubensis were obtained in 2006 and 2007, respectively. The EC50 values for the growth of all the 106 isolates collected in 2006 were 0.0063–0.0688μg ml−1 (average: 0.0196±0.0048μg ml−1) azoxystrobin and these were therefore considered sensitive isolates. However, 57 field isolates ofP. cubensis of the 97 collected in 2007 with EC50 values that ranged from 0.609 to >51.2μg ml−1 were considered resistant to azoxystrobin. Fragments of the fungicide-targeted mitochondrial cytochromeb gene from total pathogen DNA were amplified using polymerase chain reaction and their sequences analyzed to elucidate the
molecular mechanism of resistance. A single point mutation (GGT to GCT) in the cytochromeb gene, resulting in substitution of glycine by alanine at position 143, was found in the three selected azoxystrobin-resistant
isolates of downy mildew. This substitution in cytochromeb exhibited different resistance levels, with the resistance factor from 21.15 to greater than 2618.9. In addition, the different
resistance levels seemed to appear within 1 year (between 2006 and 2007). Therefore, growers of Shandong Province in China
now are faced with a challenge in managing the azoxystrobin resistance in cucumber downy mildew.
http://www.phytoparasitica.org posting March 10, 2008. 相似文献
15.
Avia E. Rubin Ayelet-Chen Werdiger Mathias Blum Ulrich Gisi Helge Sierotzki Dietrich Hermann Yigal Cohen 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(2):339-351
Wild type (WT) field isolates of Bremia lactucae failed to germinate in vitro or infect lettuce leaves in the presence of CAA (carboxylic acid amide) fungicides. Minimal
inhibitory concentrations (MIC) for mandipropamid, dimethomorph, benthiavalicarb and iprovalicarb were 0.005, 0.5, 0.5 and
5 μg ml−1, respectively. Mutagenesis experiments showed that spores exposed to EMS (ethyl methane sulphonate) or UV irradiation (254 nm)
could infect lettuce leaves in the presence of up to 100 μg ml−1 CAA. The proportion of infected leaves relative to the number of spores inoculated (infection frequency) was inversely related
to the concentration of CAA used, ranging between 0 and 160 per 1 × 106 spores. Resistant mutants (RM) lost their resistance within 1–14 reproduction cycles on CAA-treated plants. Crosses were
made between RMxWT isolates and RMxRM isolates with an attempt to obtain stable homozygous resistant off-springs. Such crosses
yielded few resistant but unstable progeny isolates. Mutagenic treatments given to hybrid isolates also failed to produce
stable resistance. Previous gene sequencing data showed that stable resistance to CAAs is based on a single SNP in the cellulose synthase 3 (CesA3) gene of Plasmopara viticola. Therefore, we sequenced a 582 bp DNA fragment of Ces3A of WT, RM and hybrid isolates of B.lactucae. No mutation in this gene fragment was found. We conclude that mutagenic agents like EMS or UV may induce resistance to CAA
in Bremia lactucae but this resistance is not stable and not linked to mutations in CesA3 gene. 相似文献
16.
Karin Thygesen Lise Nistrup Jørgensen Kim Skov Jensen Lisa Munk 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(4):435-447
Field experiments, involving various fungicide strategies with pyraclostrobin and/or epoxiconazole were carried out in 2004
and 2005, with the overall purpose of monitoring the evolution of fungicide sensitivity in Mycosphaerella graminicola on different isolates per leaf, leaf levels at different points of time, and points in the field. Sensitivity was assessed
on single isolates by means of epoxiconazole EC50-values, and monitoring of the G143A-mutation, which confers strobilurin resistance. In both years, fungicide application
strategies did not cause any significant shifts in epoxiconazole sensitivity of the population median or variance over time
compared to the starting population. In 2004, the end-population median was the same for all sprayed strategies, although
compared to untreated median sensitivities were higher. In 2005, epoxiconazole sensitivity levels were similar on individual
flag leaves and different points in the field. Measured on all isolates the EC50-values ranged from 0.007–1.15 mg l−1. In 2004, due to the high initial level of pyraclostrobin resistance, stabilisation of pyraclostrobin resistance was observed
following the various combination treatments. No correlation between epoxiconazole sensitivities and pyraclostrobin resistance
were observed. High input strategies using a mixture of epoxiconazole and pyraclostrobin resulted in the best control and
yield response. A subpopulation of the isolates from 2004 was also screened for sensitivity towards five different triazoles
of which tebuconazole proved to be least sensitive, and this could further be split into two subpopulations. 相似文献
17.
Susceptibility of eggs of Tribolium confusum du Val. (Coleoptera: Tenebrionidae), Ephestia kuehniella (Zell.) (Lepidoptera: Phycitidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) to vapors of essential oil from garlic (Allium sativum L.), birch (Betula lenta L.), cinnamon (Cinnamonum zeylanicum (Blume)) and aniseed (Pimpinella anisum L.) was studied. Preliminary bioassay tests indicated that vapors of the essential oils had a significant effect on the eggs
of tested insect species when exposed to a concentration of 20 μl l
−1 air for 24 h. Generally, garlic and birch essential oils were more toxic to the eggs of tested insect species than cinnamon
and aniseed essential oils (except for eggs of T. confusum). There was also a significant difference between susceptibility of eggs of T. confusum, E. kuehniella and P. interpunctella to tested essential oils. Toxicity data indicated that eggs of T. confusum were more susceptible to tested essential oils, with LC90 values ranging from 3.11 to 33.49 μl l
−1 air, than those of E. kuehniella and P. interpunctella; eggs of P. interpunctella were the most tolerant to the essential oils, with LC90 values ranging from 22.02 to 72.42 μl l
−1 air. Concentration × time (Ct) products of 0.29, 0.22, 0.13 and 1.37 mg h l
−1 for garlic, birch, cinnamon and aniseed essential oil, respectively, were required to obtain 90% kill of T. confusum eggs. Although cinnamon essential oil had a much closer Ct product value to methyl bromide, garlic and birch essential oils
were found to be the most promising ones since they had also high fumigant toxicity on eggs of both E. kuehniella and P. interpunctella. 相似文献
18.
Kishor Bhandari Pankaj Sood Pawan K. Mehta Amit Choudhary Chandra S. Prabhakar 《Phytoparasitica》2009,37(4):317-322
A granulosis virus strain infecting Pieris brassicae (PbGV) was isolated from the dry temperate region of northwestern Himalayas as a potential microbial agent for its management.
The effect of different botanicals (having insecticidal action against P. brassicae) on the bioefficacy of PbGV was evaluated under laboratory conditions using leaf disc bioassays on cabbage for improving
the insecticidal performance of the PbGV. The synergistic action of different botanical extracts was evident in terms of reduction
in LC50 values against different botanical extracts. Among different extracts, petroleum-ether extract of neem seed kernel (NSK)
when combined with PbGV resulted in maximum reduction of LC50 value (4.39 × 102 occlusion bodies [OBs] ml−1) followed by methanolic extract (7.38 × 102 OBs ml−1) and aqueous extract (9.36 × 103 OBs ml−1) as compared with PbGV alone (1.85 × 104 OBs ml−1) for 2nd instar larvae of the test insect. These trends were found analogous in cases of 3rd and 4th instars of P. brassicae with different solvent extracts of NSK. The other botanicals evaluated, viz., Eupatorium and Artemesia, also resulted in reduction of LC50 values for 2nd, 3rd and 4th instars as compared with PbGV alone when different extracts were combined with virus for bioassays.
The studies suggest that the PbGV in combination with botanical pesticides could be more useful as a bio-pesticide against
cabbage butterfly (P. brassicae) in IPM programs. 相似文献
19.
Single-lesion isolates ofCercospora beticola (n=150) were collected in 1998 from sugar beet fields in the area of Serres, N. Greece. In this area, sterol demethylation-inhibiting
(DMI) fungicides have been used for almost 20 years to control sugar beet leaf spot. The sensitivity of these isolates to
the DMI fungicides flutriafol and difenoconazole (EC50 values) was determined on the basis of inhibition of mycelial growth at several fungicide concentrations. The relative growth
(RG) of isolates was correlated at all tested concentrations with the respective EC50 values, indicating that RG provides a reliable estimate for the sensitivity of the isolates. The highest correlation coefficients
were obtained for concentrations of 1 μg ml−1 flutriafol and of 0.05 μg ml−1 difenoconazole, respectively. Consequently, they are proposed for monitoring of DMI sensitivity inC. beticola populations, as single discriminatory concentrations in a simplified test method. Based on the RG values at the discriminatory
concentration of 1 μg ml−1 flutriafol,C. beticola isolates were classified as either resistant or sensitive. The efficacy of flutriafol, applied at the commercially recommended
dose, in controlling Cercospora leaf spot was examined in field experiments conducted during 1999 and 2000. Disease incidence
in plots artificially inoculated with resistant isolates and treated with flutriafol was significantly higher than in similar
plots inoculated with sensitive strains. These results suggest that poor disease control after application of flutriafol may
be based on the presence of resistant strains within the pathogen population in northern Greece. This emphasizes the risk
of the development of practical resistance if there is increased frequency of such strains within the population.
http://www.phytoparasitica.org posting July 13, 2003. 相似文献
20.
The apple rust mite Aculus schlechtendali (Nal.) (Acari: Eriophyidae), is a main pest in apple-growing areas in Ankara, Turkey, and chemical control applications have
some limitations. Entomopathogenic fungi have a potential for biological control of mites. In this study, an entomopathogenic
fungus, Paecilomyces lilacinus (Thom) Samson (Deuteromycota: Hyphomycetes), was first isolated from the mite cadavers on Japanese crab apple leaves and
pathogenicity of the fungus was observed in different inoculum densities and relative humidities. The pathogen caused up to
98.22% mortality of the mite population. The effects of some fungicides on the entomopathogenic fungus were determined in
in vitro studies. Carbendazim, penconazole and tebuconazole were the most effective fungicides on mycelial growth of P. lilacinus, with EC50 values under 3 μg ml−1. In spore germination tests, captan, mancozeb, propineb were the most effective fungicides, followed by tebuconazole, penconazole,
nuarimol and chlorothalonil. Sulphur could not inhibit the conidia germination totally at 5,000 μg ml−1. Copper oxychloride and fosetyl-al prevented conidia formation at concentrations above 1,000 μg ml−1. 相似文献