番茄叶霉病菌对嘧菌酯的抗性检测及抗性风险评估

利用孢子萌发法测定了从河北、浙江、江苏、山东、四川等省田间采集的97个番茄叶霉病菌菌株对嘧菌酯的敏感性。结果表明,田间番茄叶霉病菌已对嘧菌酯产生不同程度的抗药性。97个菌株可分为敏感菌株(EC50值50值5.4~54 μg/mL),中抗菌株(EC50值54~270 μg/mL)、高抗菌株(EC50值270~1 350 μg/mL)、特高抗菌株(EC50值>1 350 μg/mL) 5种类型,分别占55.67%、14.43%、11.34%、10.31%和8.25%。其中从未用过甲氧基丙烯酸酯类杀菌剂的27个菌株的EC50平均值为(0.544±0.349) μg/mL,可作为敏感基残;高抗和特高抗菌株集中在常施用甲氧基丙烯酸酯类杀菌剂的河北定州。通过紫外线诱导和药剂驯化的方法获得了番茄叶霉病菌5个抗嘧菌酯突变体,其抗药性不稳定,在不含药PDA平板上继代培养后抗药性水平下降,甚至恢复至敏感状态;除突变体cf 21M1的产孢量高于其亲本外,抗药性突变体的菌落生长速率、产孢量、孢子萌发率均显著低于其亲本菌株,所有抗嘧菌酯突变体及其亲本菌株接种于番茄离体叶片后,突变体病情指数与亲本菌株之间没有显著差异。嘧菌酯与多菌灵、苯醚甲环唑之间不存在交互抗药性。田间抗药性检测及室内抗药性风险评估结果表明,番茄叶霉病菌对嘧菌酯具有较高的抗药性风险。

Resistance Detection and Assessment of Resistance Risk ofCladosporium fulvum to Azoxystrobin

Sensitivity of 97 isolates of Cladosporium fulvum collected from the tomato fields of Hebei,Zhejiang,Jiangsu,Shandong and Sichuan provinces to azoxystrobin was tested by spore germination. The results showed that resistance to azoxystrobin in C.fulvum had occurred at different levels in collected areas.All the 97 isolates were classified into sensitive,lowly resistant,mediately resistant,highly resistant and very highly resistant isolates,accounted for 55.67%,14.43%,11.34%,10.31% and 8.25%,respectively.Among 97 isolates,their mean of the EC50 values for 27 isolates where the strobilurins have never been used was (0.544±0.349) μg/mL ,and the highly resistant and very highly resistant isolates were collected from Ding zhou,Hebei province where the strobilurin fungicides were applied frequently.Five mutants resistant to azoxystrobin were obtained from wild-type parent isolates through ultraviolet-induction or azoxystrobin-taming of C.fulvum.The resistance to azoxystrobin of the five mutants was unstable,the resistance level declined as the 5 mutants were subcultured on PDA plates in absence of fungicide,some resistant mutants even became as sensitive as their parental isolates.Comparing with their parent isolate ,the colony growth rate,quantity of conidial reduction and percentage of conidial germination of the resistance mutants were all decreased significantly,except that of the mutant of cf 21M1 .There was no significant difference between the disease index on the detached tomato leaves inoculated with the 3 mutants and that on the detached leaves inoculated with their parent isolates.No positively-correlated cross resistance existed between azoxystrobin and difenoconazole,carbendazim.The results of field resistance detection and lab resistance risk assessment indicated that resistance risk of C.fulvum to azoxystrobin could be relatively high.