油菜菌核病菌对多菌灵和乙霉威的抗药性机理

生物测定结果表明,油菜菌核病菌田间菌株对多菌灵(MBC)敏感性表型呈多样性,即存在MBCS、MBCLRLR、MBCHRHR和MBCVHR表型.而对乙霉威(DIE)则只检测到DIES和DIEHR表型.MBCS、MBCLR和MBCHR菌株中除JD2-3菌株为DIES外,其余菌株均为DIEHR,MBCVHR菌株对DIE表现为DIES.MBC和DIE之间存在典型的负相关交互抗性.序列分析结果表明,表型为MBCVHRDIES菌株的β-微管蛋白基因,第198位氨基酸由Glu(GAG)突变为Ala(GCG);表型为MBCHRDIEHR菌株的β-微管蛋白基因的突变位点在第200位,由Phe(TTC)突变为Tyr(TAC);而表型为MBCSDIES和MBCLRDIEHR的菌株在所扩增的β-微管蛋白基因片段中未发生突变.初步表明,β-微管蛋白基因198和200位氨基酸的突变是引起油菜菌核病菌对多菌灵抗药性呈多样性的分子机理.     

陕西省小麦赤霉病菌对多菌灵敏感性研究

 The mycelium growth rate method was used to test the sensitivity to carbendazim (MBC) at distinctive concentrations in 136 isolates of Fusarium graminearum from 19 counties of 6 districts in Shaanxi Province in 2008. The distinctive MBC concentration was 4 mg / L for testing of resistance and sensitivity. The results showed that average 50% effective concentration (EC50 ) of 136 tested sensitive isolates were (0. 908 6 ± 0. 062 3) mg / L. All the isolates were sensitive to MBC. The fungicide of MBC could be continually applied wheat production in Shaanxi.     

抗戊唑醇苹果轮纹病菌的紫外诱导及其生物学特性

在含戊唑醇的马铃薯葡萄糖琼脂(PDA)培养基上,通过紫外线诱导获得了9株对戊唑醇具有不同抗性水平的苹果轮纹病菌 Botryosphaeria berengriana f.sp. piricola 抗药性突变体,其抗性指数在11.00~67.88之间。将该抗药性突变体继代培养9代后,大多数突变体的抗性指数逐渐下降,但其中有2 株抗药性突变体(UV-TS1-f和UV-TS1-10)仍保持较高的抗性水平;抗药性突变体的致病力与敏感菌株相比未发生明显变化;与敏感菌株一样,抗药性突变体适宜生长的温度也为25~28 ℃,pH值为7~8;在含不同碳、氮源的培养基中,抗药性突变体的菌丝生长与菌丝干重与敏感菌株相比差异明显。研究表明,苹果轮纹病菌在药剂选择压下易形成抗戊唑醇群体,具有中等或高抗药性风险。     

番茄叶霉病菌对多菌灵抗药性的诱导及抗性菌株特性研究

采用紫外线诱导及药剂驯化两种方法对番茄叶霉病菌的目标菌株进行多菌灵抗性诱导,分别经7、9代诱导后获得抗性突变体。突变体菌株的EC₅₀均大于500μg／mL,达高抗水平。突变体菌株与自然抗性菌株无药继代培养10代后,抗性程度没有明显变化。与亲本菌株比较,突变体菌株菌落生长速率、产孢量及产毒量有所下降。室内交互抗性测定表明:多菌灵与苯菌灵、菌核净及克霉灵之间具有正交互抗性,与瑞毒霉、扑海因及速克灵无交互抗性。乙霉威对多菌灵的高抗菌株表现负交互抗性或无交互抗性,但对敏感菌株不表现负交互抗性。     

Characterization and fitness of carbendazim-resistant strains of Fusarium graminearum (wheat scab)

BACKGROUND: Carbendazim (MBC) has failed to control wheat scab, caused by Fusarium graminearum Schwabe, on the eastern coast of China in recent years after about 30 years of application. RESULTS: MBC resistance was found to be common in pathogen populations on the eastern coast and along areas of the Yangtze River. EC(50) and minimum inhibitive concentration (MIC) values of MBC inhibiting mycelium growth of wild-type isolates were less than 0.9 and 1.4 microg mL(-1) respectively, while EC(50) values of resistant collections averaged 7.02 +/- 11.86 microg mL(-1). The slope of the MBC dosage-response curve (DRC) for resistant isolates of F. graminearum was flat: 1 < b < 2.8 for resistant isolates and 3.5 < b < 11 for sensitive isolates). Both field resistant and sensitive MBC strains shared similar temperature sensitivity, fitness and virulence on ears. Field resistant strains and UV-induced mutants showed positive cross-resistance to other benzimidazole derivatives and were mainly at intermediate MBC resistance level. Highly resistant field MBC strains rarely appeared, but only some of the highly resistant MBC UV mutants were insensitive to N-phenylaminecarbamates. No mutation in beta-tubulin was found in F. graminearum, in contrast to mutation in this tubulin which has led to MBC resistance in other plant pathogens. CONCLUSION: MBC(R) isolates have high fitness and competition in field, conferred by a novel molecular mechanism.     

Activity of carbendazim,dimethachlon, iprodione,procymidone and boscalid against Sclerotinia stem rot in Jiangsu Province of China

Carbendazim (MBC) was widely used to control Sclerotinia stem rot routinely during the 1980s in China, but development of MBC resistance in the causal agent Sclerotinia sclerotiorum led to control failures of this disease. In this study it was found that the MBC resistance in S. sclerotiorum populations was widespread throughout Jiangsu Province with a resistance frequency of 29.54% in the 1786 collected isolates during the growing seasons of 2006 to 2008. The resistance frequencies differed among sampled cities, ranging from 3.1% to 54.9%. The field MBC-resistant isolates showed comparable mycelial growth, sclerotia production and pathogenicity to the wild-type sensitive isolates, which suggested that the field MBC-resistant isolates might have sufficient parasitic fitness to compete with the field MBC-sensitive isolates in the field. In the in vitro sensitivity test, boscalid showed greater activity against S. sclerotiorum than dicarboximide fungicides (dimethachlon, iprodione and procymidone). The treatment 50% boscalid (WG) 125 g a.i. ha⁻¹ was comparable in efficacy to the treatment 50% iprodione (WP) 600 g a.i. ha⁻¹, and better than other treatments of 6% dimethachlon (WP) 690 g a.i. ha⁻¹ and 50% procymidone (WP) 337.5 g a.i. ha⁻¹, whereas MBC failed to control Sclerotinia stem rot (control efficacy only 16.0%). The most active agent for controlling Sclerotinia stem rot was boscalid in our study.     

海南芒果可可球二孢的致病力及其对多菌灵抗性

从海南5个芒果主产区采集分离芒果蒂腐病菌可可球二孢菌株,采用室内人工接种的方法对110个可可球二孢菌株进行致病力测定,采用区分剂量法和菌丝生长速率法测定其中106个菌株对多菌灵的抗性。结果表明:芒果蒂腐病自然发病率29.37%;人工接种的发病率100.00%,110株可可球二孢菌株中强致病力、中等致病力及弱致病力菌株分别占64.55%、25.45%和10.00%;在106株可可球二孢菌株中,抗性菌株发生频率为52.83%,其中高抗菌株可在含100 mg/L多菌灵培养基上生长,发生频率为45.28%,中抗菌株在含100 mg/L多菌灵培养基上不能正常生长,抗性频率为7.55%;没有发现低抗菌株。多菌灵对可可球二孢田间分离菌株EC_(50)的频率分布为不连续分布,研究结果表明海南地区危害芒果的可可球二孢对多菌灵抗性非常严重。     

Characterization of carbendazim sensitivity and trichothecene chemotypes of Fusarium graminearum in Jiangsu Province of China

Fusarium head blight, one of the most damaging plant diseases in Jiangsu province of China, is a leading cause of economic loss and toxin accumulation in the crop, including nivalenol, deoxynivalenol and its acetylated derivatives. Disease control by carbendazim (MBC) has been applicated for many years, and the resistance frequency increased steadily. Furthermore, resistance may trigger toxin growth. Here, a total of 7261 isolates were collected throughout Jiangsu province from 2010 to 2012 to determine their sensitivity to MBC and trichothecene chemotypes. We studied the relevance between trichothecene chemotype and MBC-sensitivity, and found that the MBC-sensitive isolates occupied more NIV chemotype proportion up to date; 15-AcDON chemotype only existed in MBC-sensitive isolates; and most MBC-resistant isolates secreted 3-AcDON in chemotype. Besides, trichothecene production analyses indicated that MBC resistance increased 3-AcDON yield and percentage, especially site-directed mutants at codon 167 in the β2-tubulin gene.     

Carbendazim resistance in the eyespot pathogen Pseudocercosporella herpotrichoides

Mycelial isolates (115) of Pseudocercosporella herpotrichoides were obtained from five field sites in England. Carbendazim-resistant isolates were detected by their mycelial growth on agar containing 1 μg/ml carbendazim. Resistant isolates were found at two of the five sites examined and one of these had never been treated with benzimidazole fungicides. Amongst the carbendazim- resistant isolates there was a predominance of isolates with pale mycelium, an irregular colony margin and a relatively slow growth rate; however, this association was not absolute. Large differences in the effects of carbendazim on mycelial growth of sensitive and resistant isolates were demonstrated; growth of sensitive isolates was completely inhibited at 0.5 μg /ml carbendazim whilst five of the six resistant isolates examined grew on agar containing 1000 μg/ml fungicide. The carbendazim-resistant isolates were cross-resistant to benomyl, thiophanate-methyl and to a Icsser degree thiabendazole, but not to prochloraz. Conidia of carbendazim-resistant isolates were as resistant. Carbendazim-resistant isolates were just as pathogenic to wheat as sensitive isolates. The implications of these results and other reports of benzimidazole resistance in P. herpotrichoides are discussed in relation to disease control.     

Differential efficacy of three commonly used pyrethroids against laboratory and field‐collected larvae and adults of Helicoverpa zea (Lepidoptera: Noctuidae) and significance for pyrethroid resistance management

BACKGROUND: Helicoverpa zea (Boddie) pyrethroid resistance monitoring programs typically utilize cypermethrin in the adult vial test. Here we investigated if differences in insect growth stage and pyrethroid structure affect resistance ratios and discuss implications for pyrethroid resistance management. RESULTS: Vial bioassays with cypermethrin, esfenvalerate and bifenthrin were conducted on H. zea third instars and male moths from a susceptible laboratory colony and the F1 generation of a pyrethroid‐resistant field population. In the susceptible population, both growth stages were most sensitive to bifenthrin and adults were more sensitive to esfenvalerate than cypermethrin. LC₅₀ resistance ratios for the larvae and adults of the resistant population were approximately two times higher for bifenthrin than cypermethrin or esfenvalerate. CONCLUSION: For the resistant population, vial assays using either growth stage gave similar resistance ratios for each of the three pyrethroids, respectively, proving the adult vial test accurately reflects larval resistance. However, as resistance ratios varied considerably depending on the pyrethroid used, resistance ratio values obtained with one pyrethroid may not be predictive of resistance ratios for other pyrethroids. Our results suggest that carefully chosen pyrethroid structures diagnostic for specific mechanisms of resistance could improve regional monitoring programs. Copyright © 2009 Society of Chemical Industry