辣椒炭疽病菌Colletotrichum gloeosporioides对啶氧菌酯的敏感基线及抗性突变体生物学性状

Baseline sensitivity of Colletotrichum gloeosporioides to picoxystrobin and biological characteristics of resistant mutants

为评估辣椒炭疽病菌Colletotrichum gloeosporioides对啶氧菌酯的抗性风险,建立了辣椒炭疽病菌对啶氧菌酯的敏感基线,室内筛选获得了辣椒炭疽病菌抗啶氧菌酯突变体,并对突变体生物学性状进行了研究。在山西省3个未使用过啶氧菌酯及QoI类药剂的地区采集并分离到45株辣椒炭疽病菌。采用菌丝生长速率法测定其对啶氧菌酯的敏感性,结果显示,EC_(50)值介于1.404~16.650μg/mL,平均EC_(50)值为(6.783±3.499)μg/mL。啶氧菌酯与水杨肟酸(SHAM)共同处理时(SHAM的处理浓度为100μg/mL),EC_(50+S)为0.022~0.275μg/mL,平均(0.109±0.058)μg/mL,EC_(50+S)呈连续性单峰曲线,且敏感性频率分布呈近似正态分布,EC_(50+S)平均值可作为辣椒炭疽病菌对啶氧菌酯的敏感基线。且水杨羟肟酸旁路氧化贡献值F(F=EC_(50)/EC_(50+S))最低为6.039,最高为301.441,平均78.026。室内诱导获得8株抗性突变体,其中低抗突变体6株,中抗突变体2株。中抗突变体无性繁殖10代,其抗性可稳定遗传。突变体产孢量和菌丝生长速率与敏感菌株相比均无显著差异,但无药条件下,突变体致病力较敏感菌株有所降低。抗感菌株均以淀粉作为碳源、硝酸钾作为氮源时利用率最高;最适pH均为5和6;菌丝的最适生长温度均为25℃。表明辣椒炭疽病菌抗啶氧菌酯突变体具有较高的适合度,对啶氧菌酯具有较高抗性风险,这一研究结论为指导生产用药,延缓抗药性发展提供理论依据。

To evaluate the resistance risk of Colletotrichum gloeosporioides to picoxystrobin,the baseline sensitivity of C.gloeosporioides to this fungicide was established,and the biological characteristics of the picoxystrobin-resistant mutants obtained in the laboratory were studied.Forty-five C.gloeosporioides isolates were collected from three areas of Jinzhong,Shanxi Province,where picoxystrobin and the other fungicides with the same mode of action had not been used before.The sensitivities of 45 C.gloeosporioides to picoxystrobin were determined by growth rate method.The results showed that the EC_(50) values ranged from1.404μg/mL to 16.650μg/mL,with a mean of(6.783±3.499)μg/mL.The EC_(50+S) values of 45 C.gloeosporioides to picoxystrobin combined with100μg/mL salicylic acid oxime(SHAM)ranged from0.022μg/mL to 0.275μg/mL,with a mean of(0.109±0.058)μg/mL.The frequency of EC_(50+S) values was distributed as a unimodal curve,and the frequency of sensitivity was in approximately normal distribution,and the mean EC_(50+S) values could be used as the relative baseline sensitivity of C.gloeosporioides to picoxystrobin.The compensation efficiency value in the bypass oxidation way showed thatthe lowest value was 6.039,and the highest was 301.441,with a mean value of 78.026.Eight picoxystrobin-resistant mutants were obtained,of which6 were low resistance and 2 medium resistance to picoxystrobin.The resistance of moderately resistant mutants was stable after 10 generations of asexual cultivation.The mycelium growth rates,spore germination rates of mutants were similar with those of sensitive isolates,but the pathogenicity of the mutants was lower than that of the sensitive ones in absence of fungicides.The best carbon source of both sensitive and resistant isolates was starch and best nitrogen source was potassium nitrate;the optimum pH values were 5 and 6 and the optimum temperature was 25℃ for the mycelial growth of both sensitive and resistant isolates.The results showed that the C.gloeosporioides resistant mutants were in high fitness and in high risk of resistance to picoxystrobin.The conclusion provides the theoretical basis for guiding fungicide use and the strategic buildup of delaying resistance development.