| Benzimidazole fungicides, as a group of systemic fungicides with broad sprectrum of fungicidal activity, were widely used to control diseases caused by plant pathogenic fungi. The benzimidazoles envoid the harmless in the enviroment with protective fungicides, and reduce the requirment of application technique and time, further increase the control effect.Because benzimidazoles are characterized by high specificy, single action position, and high application frequency, many plant pathogenic fungi occurred resistance to these fungicides after 2-3 years' application. Benzimidazole fungicides bind to β -tubulin, inhibiting microtubulin function or disassembling microtubulin, further prevent cell's mitosis of fungi for growth. Mutations of pathogen's β-tubulin gene make three-dimensional configuration of P -tubulin protein change and lose affinity with fungicides, leading to resistance to carbendazim.Many benzimidazole-resistant mutations in a variety of fungi have been mapped to the structural P -tubulin gene and the mutant genes were cloned and sequenced. Although single base-pair point mutations leading to the substitution of the amino acid by another occurred at least 10 different sites within the P -tubulin gene, these mutations are confined to amino acid codons 198 and 200 in resistant field strains of plant pathogens. Except for the pathogen Gibberella pulicaris causing potato dry rot, in recent years resistance to benzimidazoles in fungal pathogens has been attributed to single amino acid changes in the P -tubulin subunit. The majority of these changes in field benzimidazoles-resistant isolates were located in amino acids 198 or/and 200.Wheat head blight(caused by Fusarium graminearuni), Rape sclerotiniose (caused by Sclerotinia sclerotiorum), Tomato Grey(caused by Botrytis cinerea) and Pepper anthracnose(caused by Colletotrichum gloeosporiodies) are important crop and invegetable diseases in China. These diseases have been controlled by benzimidazole fungicides or its mixture with other fungicides with different mechnisms for 30 years.Carbendazim-resistant B. cinerea, F. graminearum and S.sclerotiorum isolates were detected out in the field populations in 1987,1992 and 1996, respectively.Sensitivity of the four plant pathogenic fungi to carbendazim(MBC) and diethofencarb(NPC) was tested with mycelial growth test. The result showed EC50 of carbendazim-sensitive isolates(MBCs) from F.graminearum was less than 1μg/mL. EC50 of field and induced carbendazim-resistant isolates(MBCR) was about 10μg/mL. There didn't exist negative cross-resistance between carbendazim and diethofencarb in F. graminearum .223 S.sclerotiorum isolates were isolated from Tongzhou of Jiangsu Province in 2002. Two phenotypes were identified when these isolates were tested for sensitivity to carbendazim and diethofencarb. 143 of these isolates showed phenotype of carbendazim-sensitivity and diethofencarb-high-resistance (MBCsNPCHR and other 80 isolates showed carbendazim-high-resistance and diethofencarb-sensitivity (MBCHRNPCS). The MBCHRNPCS isolates were not sensitive to temperature Variation between 7℃ and 28℃. 14 isolates of Botrytis cinerea were isolated from Jiangyin of Jiangsu Province in 2002. Two phenotypes were identified when the isolates were tested for sensitivity to carbendazim and diethofencarb. 2 of the isolates showed phenotype of MBCSNPCHRand other 12 isolates showed MBCHRNPCS. 17 C.gloeosporiodies isolates were isolated from Yancheng of Jiangsu Province in 2001. Three phenotypes were identified when tested for sensitivity to carbendazim anddiethofencarb. One of these isolates showed MBC NPC , another showed carbendazim-low-resistance and diethofencarb-resistance (MBCLRNPCR) and other 80 isolates showed MBCSNPCHR.In this study, the whole β-tubulin genes were amplified from F.graminearum, S.sclerotiorum and B.cinerea using three pairs of chemic primers synthesized to conserved sequences of the P -tubulin gene derived from related fungi. Partical sequence of P -tubulin gene from C. gloeosporiod...
|
PDF Full Text Request