The Study On Resistance Of Cladosporium Fulvum To Azoxystrobin

The baseline-sensitivity of Cladosporium fulvum to azoxystrobin was established,the present resistance situation of C.fulvum in different areas to Azoxystrobin was studied,and the resistant risk of C.fulvum to azoxystrobin was also assessed in laboratory.Resistance mechanism of C.fulvum to azoxystrobin was studied preliminarily.The results are shown as follows.1.The baseline-sensitivity of Cladosporium fulvum to azoxystrobin was established.The sensitivity to azoxystrobin of 27 wild isolates of C.fulvum collected from Baoding of Hebei, Hangzhou of Zhejiang,Meishan of Sichuan and Nanjing of Jiangsu,was determined by conidial germination test.The EC₅₀values rang from 0.02840μg/mL to 1.610μg/mL,and the average was (0.5443±0.3485)μg/mL,which showed a single-peak distribution.No resistant subpopulation appeared among these isolates,so this baseline-sensitivity was suitable for the field resistance monitoring.2.106 isolates of C.fulvum were obtained in 2006 and 2007 from Hebei,Zhejiang,Jiangsu, Shandong and Sichuan provinces.Sensitivity of these isolates to azoxystrobin was determined by conidial germination test.These 106 isolates were classified into five kinds of isolates:sensitive, low-level resistant,moderate-level resistant,high-level resistant and very-high-level resistant,accounted for 55.66%,16.04%,11.32%,9.43%,7.55%respectively.There are 59 isolates obtained from Dingzhou of Hebei province,where the strobilurin fungicides were applied frequently.Resistant isolates accounted for 66.1%among these isolates.The results showed that resistance to azoxystrobin in C. fulvum occurred in certain degree in the monitered area.The data of resistance monitoring of C.fulvum to azoxystrobin indicated that the resistance of C.fulvum to azoxystrobin increase as the application times of strobilurin fungicides increased.3.Azoxystrobin-resistant mutants were obtained from wild-type parental isolates through ultraviolet-induction or azoxystrobin-taming of C.fulvum.In vitro,the colony growth rate,quantity of conidial reduction,percentage of conidial germination and pathogenicity of some azoxystrobin -resistant mutants were similar to their parental isolate and the resistance of some mutants was stable.Data also showed that no positively-correlated cross resistance existed between azoxystrobin andchlorothalonil,mancozeb,iprodione,thiophanate-methyl,carbendazim,difenoconazole. enestroburin or kresoxim-methyl.The results of field resistance detection and lab resistance risk assessment indicated that resistance risk of C.fulvum to azoxystrobin could be relatively high.4.The data of the activity of Phenylalanine Ammonia-Lyase of the mutants and parental isolates showed that the resistance of C.fulvum to azoxystrobin may be related to the The activity of PAL.