连续施药及室内药剂驯化对番茄灰葡萄孢对咯菌腈敏感性的影响

为了解连续施药对番茄灰葡萄孢对咯菌腈敏感性的影响,在温室条件下,从灰霉病发生初期开始,按推荐剂量(有效成分67.5 g/hm2)定期向番茄苗喷施咯菌腈,通过菌丝生长速率法检测灰葡萄孢对咯菌腈的敏感性。结果表明,在番茄1个生长季节中连续施药7次后,病菌对咯菌腈仍表现敏感,其EC50值在0.004 7～0.046 2 μg/mL之间。在含咯菌腈的PDA培养基上对30个灰葡萄孢敏感菌株进行药剂驯化7代后,共产生2个抗药性突变体(Rg-12和Rdz-28),其中Rg-12对咯菌腈的EC50值是其亲本菌株g-12的46倍,Rdz-28的EC50值大于500 μg/mL,2个抗性突变体在菌丝生长速率、产孢量和产菌核能力方面均显著低于其亲本菌株。推测灰葡萄孢可能不易对咯菌腈产生抗性,咯菌腈可作为防治番茄灰霉病的理想候选药剂。     

Sensitivity of Podosphaera aphanis isolates to DMI fungicides: distribution and reduced cross‐sensitivity

BACKGROUND: Management of strawberry powdery mildew, Podopshaera aphanis (Wallr.), requires numerous fungicide treatments. Limiting epidemics is heavily dependent on sterol demethylation inhibitors (DMIs) such as myclobutanil or penconazole. Recently, a noticeable reduction in the efficacy of these triazole fungicides was reported by strawberry growers in France. The goal of this study was to investigate the state of DMI sensitivity of French P. aphanis and provide tools for improved pest management. RESULTS: Using leaf disc sporulation assays, sensitivity to myclobutanil and penconazole of 23 isolates of P. aphanis was monitored. Myclobutanil EC₅₀ ranged from less than 0.1 to 14.67 mg L^?1 and for penconazole from 0.04 to 4.2 mg L^?1. A cross‐analysis and a Venn diagram showed that there was reduced sensitivity and a positive correlation between the less sensitive myclobutanil and penconazole isolates; 73.9% of isolates were less sensitive to a DMI and 47.8% exhibited less sensitivity to both fungicides. CONCLUSION: The results show that sensitivity to myclobutanil and, to a lesser extent, penconazole has become less efficient in strawberry powdery mildew in France. Therefore, urgent action is required in order to document its appearance and optimise methods of control. Copyright © 2009 Society of Chemical Industry     

黄瓜白粉病菌对己唑醇的敏感基线及实验室抗性获得

为了评价黄瓜白粉病菌对己唑醇的抗性风险,采用子叶法测定了山东地区50个黄瓜白粉病菌菌株对己唑醇的敏感性。结果表明,各菌株敏感性存在较大差异,EC50值最低为0.0017μg/mL,最高达0.16μg/mL,平均值为0.028μg/mL,由于所有菌株均采自未使用过脱甲基抑制剂类杀菌剂的黄瓜日光温室,敏感性频率呈近似正态分布,可作为黄瓜白粉病菌对己唑醇的相对敏感基线。以野生菌株为材料,以紫外线诱导和药剂驯化相结合获得了2个黄瓜白粉病菌对己唑醇的抗性菌株,比较了抗性菌株和敏感菌株的适合度和分生孢子的竞争能力。结果表明,无药情况下2个抗性菌株与野生菌株适合度无显著差异。抗性菌株和敏感菌株分生孢子以80∶20混合培养7代后,抗性菌株的频率变化不明显;50∶50混合培养7代,中抗菌株的抗性频率明显降低,而高抗菌株的抗性频率降低不明显;20∶80混合培养7代,抗性菌株的频率变低甚至消失。     

Monitoring and characterization of Magnaporthe grisea isolates with decreased sensitivity to scytalone dehydratase inhibitors

Rice blast fungus isolates were collected in Kyushu to investigate resistance to scytalone dehydratase inhibitors of melanin biosynthesis (MBI-D). In 2001, failure of control of rice blast was reported in the Saga prefecture, where MBI-Ds have been used since 1998. At that time, the distribution of resistant isolates was mainly limited to that area. However, in 2002, resistant isolates were detected in all prefectures of Kyushu. DNA fingerprinting analysis showed that the mutation causing resistance to MBI-Ds had arisen independently in each area. These data suggest that resistant isolates may occur in any area and become dominant under continuous selection pressure for MBI-Ds. Nevertheless, resistant strains can be controlled by reductase inhibitors of melanin biosynthesis (MBI-R) or commercial rice seed disinfectants.     

2002年部分麦区小麦白粉病菌对三唑酮的抗药性监测及苯氧菌酯敏感基线的建立

 采用拌种离体叶段法测定了2002年采自北京、江苏、山东、山西、河北、新疆和四川7省市部分麦区的109个小麦白粉病菌菌株对三唑酮和苯氧菌酯的敏感性,结果表明小麦白粉病菌群体对三唑酮敏感性EC₅₀平均值是63.70 μg/mL,平均抗性水平为30.48倍,最高抗性水平达142.97倍。其中江苏、山东、四川三地的菌株抗药性水平明显高于河北、北京、山西和新疆。同时测得病菌群体对苯氧菌酯的敏感基线EC₅₀值为85.82μg/mL,且白粉病菌对甲氧基丙烯酸酯类杀菌剂苯氧菌酯和三唑类杀菌剂三唑酮之间无交互抗性。该结果可为这两类杀菌剂在生产上的合理应用和抗药性治理提供依据。     

Analysis of Colletotrichum musae populations from Brazil reveals the presence of isolates with high competitive ability and reduced sensitivity to postharvest fungicides

In this study, the sensitivity of 218 isolates of Colletotrichum musae to imazalil and thiabendazole was evaluated, as well the fitness and competitive ability of less sensitive isolates. There was a positive correlation between the sensitivity to the two fungicides, but the isolates were more sensitive to imazalil. The estimated effective concentration of the fungicide able to inhibit mycelial growth by 50% (EC₅₀) was used to select four isolates with the lowest and the highest values for both fungicides, which were considered as sensitive (S) and less sensitive (LS), respectively. The level of sensitivity was maintained after 10 successive transfers on fungicide-free medium. Both fungicides were effective in controlling the disease caused by S isolates of C. musae in detached banana fruit when recommended doses were used. However, only imazalil was able to control the disease caused by LS isolates. For both fungicides, analysis of fitness-related variables (mycelial growth, sporulation, germination, and virulence) showed no difference between the groups of S and LS isolates, but a large variation was observed within the group. The LS isolates to thiabendazole that showed a mutation (F200Y) in the β-tubulin gene did not have fitness penalties. Our results allow a better understanding of the sensitivity and fitness of isolates of C. musae from Brazil, and demonstrate the importance of periodic monitoring to determine the frequency of LS isolates in populations, aiming at more effective management of anthracnose in banana orchards in Brazil.     

Increased activity and reduced sensitivity of acetylcholinesterase associated with malathion resistance in a field population of the oriental migratory locust, Locusta migratoria manilensis (Meyen)

The susceptibility to malathion, and the activity and sensitivity of acetylcholinesterase (AChE, EC 1.1.1.7) were compared between two populations of the oriental migratory locust, Locusta migratoria manilensis (Meyen) collected from Wudi County of Shandong Province in East China and Huangliu County of Hainan Province in South China. Huangliu population showed 8.5-fold resistance to malathion compared with Wudi population. AChE from Huangliu population showed 4.8-fold higher activity than that from Wudi population toward the model substrate acetylthiocholine (ATC). Kinetic studies indicated that AChE from Huangliu population had 2.6-fold lower affinity, but 5.0-fold higher catalytic activity toward ATC than AChE from Wudi population. Significantly increased activity of AChE in Huangliu population was also confirmed by non-denaturing polyacrylamide gel electrophoresis. Inhibition kinetics revealed that AChE from Huangliu population was 9.8-, 2.4-, 8.0- and 7.7-fold less sensitive to inhibition by paraoxon, malaoxon, chlopyrifos oxon, demeton-S-methyl, respectively, than that from Wudi population. Our studies revealed that a mild resistance to malathion in Huangliu population was associated with reduced sensitivity and increased catalytic activity of AChE. Our results suggest that alterations of AChE may play an important role conferring or contribute to malathion resistance in Huangliu population of the locust.     

梨黑斑病菌抗药性检测及其对啶酰菌胺的敏感性基线

黑斑病是梨的主要病害之一,近年来不少地区反映多菌灵等传统常用杀菌剂对其防治效果已出现下降。作者从浙江、江苏和安徽3省分离了252株梨黑斑病菌Alternaria kikuchiana,采用菌丝生长速率法检测了其抗药性发生情况。结果发现:所检测的黑斑病菌群体(n=252)对苯并咪唑类杀菌剂多菌灵的抗性频率为57.1%,且全部为高水平抗性(HR);对二甲酰亚胺类杀菌剂异菌脲的抗性频率为46.8%,全部为低水平抗性(LR);对甾醇脱甲基抑制剂类杀菌剂苯醚甲环唑的抗性为低水平(LR)及中等水平(MR),抗性频率均为28.6%;表明梨黑斑病菌对常用杀菌剂已产生较为严重的抗性。供试252株梨黑斑病菌对琥珀酸脱氢酶抑制剂啶酰菌胺的EC50值分布在0.12~3.85μg/m L之间,平均EC50值为(1.21±0.12)μg/m L,且其分布呈近似正态的单峰曲线。研究表明,啶酰菌胺可作为潜在的梨黑斑病防治替代药剂,其平均EC50值(1.21±0.12)μg/m L可作为梨黑斑病菌对啶酰菌胺的敏感性基线。     

小麦白粉病菌对喹氧灵和苯菌酮的敏感基线及药剂的生物活性

采用离体叶段法,分别测定了从河北、河南、湖北、陕西和四川5省分离的53个小麦白粉病菌单孢菌株对苯菌酮和喹氧灵的敏感性,并分析了白粉病菌对三唑酮和苯菌酮以及喹氧灵之间的 交互抗性。结果表明:小麦白粉病菌群体对苯菌酮和喹氧灵的平均EC50值分别为(0.001 9±0.000 6) 和(0.013 1±0.002 0) mg/L,苯菌酮比喹氧灵具有更高的抑菌活性;小麦白粉病菌对三唑酮和苯菌酮与喹氧灵之间均不存在交互抗性(R2值分别为0.102 6和0.491 9);室内盆栽试验结果显示:接种前1 d和接种后1d施药,苯菌酮和喹氧灵对小麦白粉病的保护与治疗作用防效分别为92.21%、84.25%和82.43%、70.25%,表明这2种药剂不仅具有优异的保护作用,同时还具有较好的治疗作用。