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ABSTRACT: Carbendazim (MBC) was widely used to control Sclerotinia stem rot routinely during the 1980s in China, but development of
MBC resistance in the causal agent Sclerotinia sclerotiorum led to control failures of this disease. In this study it was found that the MBC resistance in S. sclerotiorum populations was widespread throughout Jiangsu Province with a resistance frequency of 29.54% in the 1786 collected isolates
during the growing seasons of 2006 to 2008. The resistance frequencies differed among sampled cities, ranging from 3.1% to
54.9%. The field MBC-resistant isolates showed comparable mycelial growth, sclerotia production and pathogenicity to the wild-type
sensitive isolates, which suggested that the field MBC-resistant isolates might have sufficient parasitic fitness to compete
with the field MBC-sensitive isolates in the field. In the in vitro sensitivity test, boscalid showed greater activity against S. sclerotiorum than dicarboximide fungicides (dimethachlon, iprodione and procymidone). The treatment 50% boscalid (WG) 125g a.i. ha−1 was comparable in efficacy to the treatment 50% iprodione (WP) 600g a.i. ha−1, and better than other treatments of 6% dimethachlon (WP) 690g a.i. ha−1 and 50% procymidone (WP) 337.5g a.i. ha−1, whereas MBC failed to control Sclerotinia stem rot (control efficacy only 16.0%). The most active agent for controlling
Sclerotinia stem rot was boscalid in our study.
Phytoparasitica 04/2012; 37(5):421-429. · 0.89 Impact Factor
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ABSTRACT: Resistance to carbendazim and other benzimidazole fungicides in Botrytis cinerea (Pers. ex Fr.) and most other fungi is usually conferred by mutation(s) in a single chromosomal beta-tubulin gene, often with several allelic mutations. In Fusarium graminearum Schwade, however, carbendazim resistance is not associated with a mutation in the corresponding beta-tubulin gene.
The beta-tubulin gene conferring carbendazim resistance in B. cinerea was cloned and connected with two homologous arms of the beta-tubulin gene of F. graminearum by using a double-joint polymerase chain reaction (PCR). This fragment was transferred into F. graminearum via homologous double crossover at the site where the beta-tubulin gene of F. graminearum is normally located (the beta-tubulin gene of F. graminearum had been deleted). The transformants were confirmed and tested for their sensitivity to carbendazim.
The beta-tubulin gene conferring carbendazim resistance in B. cinerea could not express this resistance in F. graminearum, as transformants were still very sensitive to carbendazim.
Pest Management Science 05/2010; 66(5):482-9. · 2.25 Impact Factor
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ABSTRACT: ABSTRACT Wheat head blight caused by Gibberella zeae (anamorph: Fusarium graminearum) is a threat to food safety in China because of mycotoxin contamination of the harvested grain, the frequent occurrence of the disease, and the failure of chemical control in some areas due to benzimidazole resistance in the pathogen population. The molecular resistance mechanism, however, of G. zeae to benzimidazole fungicides (especially carbendazim; active ingredient: methyl benzimidazol-2-yl carbamate [MBC]) is poorly understood. DNA sequences of a beta-tubulin gene (beta(2)tub) (GenBank access number FG06611.1) in G. zeae were analyzed. Mutations in beta(2)tub in moderately resistant strains (MBC(MR)) included TTT (Phe)-->TAT (Tyr) at codon 167 or TTC (Phe)-->TAC (Tyr) at codon 200. A highly resistant strain (MBC(HR)) had two point mutations, one at codon 73, CAG (Gln)-->CGG (Arg), and the other at codon 198, GAG (Glu)-->CTG (Leu). To confirm that mutations in the beta(2)tub confer resistance to benzimidazole fungicides, the entire beta(2)tub locus was deleted from MBC(MR) and MBC(HR) strains of G. zeae. The resulting Deltabeta(2)tub mutants from both MBC(MR) and MBC(HR) strains grew normally on MBC-free potato dextrose agar medium and were supersensitive to MBC. Complementation of the Deltabeta(2)tub mutants by transformation with a copy of the intact beta(2)tub locus from their parent strains exhibited less resistance than the original strains, and complementation of the Deltabeta(2)tub mutants by transformation with a copy of the intact beta(2)tub locus from sensitive strains restored MBC sensitivity. The results indicated that the mutations in the beta(2)tub gene conferred resistance of G. zeae to benzimidazole fungicides and this gene can be used as a genetic marker in G. zeae.
Phytopathology 12/2009; 99(12):1403-11. · 2.80 Impact Factor
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ABSTRACT: ABSTRACT Monoconidial isolates of 33 carbendazim-sensitive isolates and 31 carbendazim-resistant isolates of Fusarium graminearum were selected from three regions of China for vegetative compatibility group (VCG) analysis. A total of 213 and 224 nit mutants were recovered from the 33 sensitive and the 31 resistant isolates, respectively. Of all the nit mutants, the frequency of the different phenotypes was 44.6, 46.5, 5.7, and 3.2% for nit1, nit3, nitM, and nitA, respectively. VCG analysis identified 30 different VCGs among the 33 sensitive- and the 31 carbendazim-resistant isolates, with VCG diversity 0.91 and 0.97, respectively. Both, a carbendazim-sensitive and a -resistant isolate from the same field belonged to the same VCG. In all then, a total of 59 VCGs were identified among the 64 isolates with an overall VCG diversity 0.92. Direct hyphal fusion was observed in six pairs of vegetatively compatible complements, which is evidence of heterokaryon formation. It was hypothesized that carbendazim resistance could not be transferred by hyphal fusion or there is a small chance to be transferred between two compatible isolates. Three stable sexual recombinants of F. graminearum were randomly chosen from each of the three genetic crosses to study their biological properties. There were no significant differences in mycelial linear growth and pathogenicity between recombinants and their parents, but they differ in sporulation ability and capacity to produce perithecia. We concluded that sexual recombination presumably played a role in the development of carbendazim resistance under field conditions.
Phytopathology 01/2008; 97(12):1584-9. · 2.80 Impact Factor
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ABSTRACT: The full-length nucleotide sequence of alpha-tubulin gene from each of 6 Fusarium graminearum strains from China which had different carbendazim (MBC) sensitivity phenotypes were separated using PCR with 4 primer sets designed in accordance with nucleotide sequence of the gene from the reference isolate, NRRL 31084 (PH-1). The DNA sequence comparison showed that there was no difference in the nucleotide sequence of alpha-tubulin gene amongst 3 sensitive and 3 resistant strains from China. This result demonstrates that there is no relationship between MBC-resistance and alpha-tubulin gene. The full-length of the gene spans 1718 bp, including 6 introns, encoding 449 amino acids. With 99% homology, there is 5 nucleotide differences in alpha-tubulin gene between PH-1 isolate and the 6 strains from China. The homology of the deduced amino acid sequence of the gene is 99.78% between the 6 strains and PH-1 isolate, and 37%-86% between the 6 strains and other 6 species of fungi.
ACTA MICROBIOLOGICA SINICA 05/2005; 45(2):288-91.
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ABSTRACT: Dimethomorph is a fungicide with high activity against Peronosporomycetes plant pathogens. The present study showed that dimethomorph is effective on controlling the oomycete fungal pathogen Pseudoperonospora cubensis causing downy mildew on cucumber. The fungicide did not affect zoospores discharge from sporangia of P. cubensis, but it strongly inhibited mycelial growth and sporangial production in vitro and increased lysis of zoospores. Dose of 2 mg L−1 of dimethomorph was sufficient to inhibit mycelial growth and sporangial production of P. cubensis on leaf disks, 5 mg L−1 was enough to lyse zoospores of P. cubensis, and 25 mg L−1 was required to inhibit sporangial production on detached leaves. In whole plant tests, dimethomorph exhibited strong protective and curative activity. Dimethomorph when applied at a dose of 300 mg L−1 for 1, 3, 5, 7 days before inoculation exhibited 100% efficacy on disease control. On the other hand, efficacies of 67.1 and 31.5% were obtained when the same dose of dimethomorph was applied for 1 and 3 days after inoculation, respectively. So dimethomorph had persistence effect on leaves for 7 days at least and exhibited strong protective and curative activity. Bioassay analyses showed that dimethomorph could be translocated in the xylem system, redistributed in the leaf, and penetrated from the upper surface to the lower surface of the leaf but could not be translocated in phloem system or transferred from the roots to leaves of cucumber plants in sufficient amounts for disease control. The biocharacteristics of dimethomorph make it well suitable for integration of a control programme against downy mildew disease on cucumber and as a component to delay other peronosporomycetes fungicide-resistance development.
Agricultural Sciences in China.
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ABSTRACT: The study was conducted to make clear the activity of azoxystrobin to 4 plant pathogens and the synergistic effects of salicylhydroxamic acid (SHAM), which acted on the alternative oxidase. It was also conducted to be aware of the mechanism of azoxystrobin in inhibition on mycelial respiration and the influence of SHAM. The activity test of azoxystrobin and SHAM was carried out with a mycelial linear growth test and spore germination test. Other related biological properties were also observed. Inhibition of azoxystrobin and SHAM on 4 pathogens was determined by using SP-II oxygraph system. Azoxystrobin inhibited mycelial growth in Colletotrichum capsici, Botrytis cinerea, Rhizoctonia solani, and Magnaporthe grisea, respectively; it also inhibited conidia germination, and conidia production in C. capsici, B. cinerea M. grisea, and sclerotia formation in R. solani. Moreover, it created stayed pigment biosynthesis in C. capsici and M. grisea somehow. Salicylhydroxamic acid enhanced inhibition by azoxystrobin. An oxygen consuming test of the mycelia showed that azoxystrobin inhibited all the 4 fungi's respiration in the early stages. With the concentration rising up, the effectiveness increased. However, as time went on, the respiration of the mycelia treated with fungicides recovered and SHAM could not inhibit the oxygen consuming. This reaction between the mycelia and the fungicides appeared not to initiate alternative respiration but rather the other mechanism created a lack of efficacy.
Agricultural Sciences in China 8(7):835-842. · 0.45 Impact Factor
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ABSTRACT: The impact of four modern fungicides JS399-19 (2-cyano-3-amino-3-phenylancryic acetate) (novel fungicide), azoxystrobin (a strobilurin), tebuconazole (a triazole) and carbendazim (a benzimidazole), applied as foliar spray at the recommended field rate, on the physiology and biochemistry of the senescence process and grain yield was studied in winter wheat (Triticum aestivum L. cv. ‘Nannong No. 9918’) under natural environmental conditions. Fungicide treatments to wheat plants at growth stage [ZGS] 57 (3/4 of head emerged) significantly increased the chlorophyll (CHL) and soluble protein (SP) content and decreased the malondialdehyde (MDA) content and electrolyte leakage. Additionally, activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in flag leaves of the fungicide-treated plants were also higher than that in untreated plants. These coincided with elevated levels of H2O2 and reduced level of in the fungicide-treated plants. The results suggested that the fungicide-induced delay of senescence was due to an enhanced antioxidant enzyme activity protecting the plants from harmful active oxygen species (AOS). Because all fungicides can induce the delay of wheat senescence, fungicide-treated wheat shown higher grain yield than untreated wheat. Of all tested fungicides, JS399-19, azoxystrobin and tebuconazole showed similar effects on delaying senescence of wheat and enhancing the grain yield of wheat, but JS399-19 was more efficient in general.
Pesticide Biochemistry and Physiology.
