Comparative toxicity of two ecdysteroid agonists,RH-2485 and RH-5992, on susceptible and pyrethroid-resistant strains of the Egyptian cotton leafworm,Spodoptera littoralis

The comparative toxicity of two non-steroidal ecdysteroid agonists, RH-2485 and RH-5992 (tebufenozide), on development stages, fecundity and egg viability of a susceptible laboratory strain and a pyrethroid-resistant field strain ofSpodoptera littoralis (Boisduval) was evaluated. Taking the LC₅₀s as the criterion, RH-2485 was 3–7-fold more potent than RH-5992 against the susceptible and 7–14-fold more against the field strain. The LC₅₀ of RH-2485 in the 1st and 6th instars of the susceptible strain was 0.32 and 0.57 mg a.i./l, respectively. The field strain showed a mild cross-resistance of about threefold to both compounds in 1st instars and to a lesser extent in 6th instars. A considerable increase in fecundity (~3-fold) and no effect on egg viability was observed when 6th instars were fed on cotton leaves treated with 0.25 mg a.i./l RH-2485 (~LC₄₀). Our results indicate that both compounds are potentially potent insecticides for controllingS. littoralis larvae, being 10-60-fold more potent than a previous ecdysteroid agonist, RH-5849.     

小菜蛾对阿维菌素B1抗药性选育及交互抗性

用阿维菌素B1（abamectin)对小菜蛾敏感种群在室内进行抗性品系选育。经过25代连续汰选，获得抗性种群Laba-R，与选育前比较，抗性提高100倍，La-ba-R种群在不接触任何药剂条件下饲养20代，抗性逐渐下降，很难恢复到选育前的敏感状态。抗性汰选前后分别测定10种药剂的剂量-死亡率毒力回归线，发现Laba-R抗性种群对乙酰甲胺磷、锐劲特、灭多威、敌敌畏不存在交互抗性；对溴氰菊酯、氯氰菊酯、杀虫双、巴丹和Bt的第三性略有下降，但无明显交互抗性。活性增效剂试验表明，增效醚（PBO）和磷酸三苯酯（TPP）对阿维菌素B1均有明显的增效作用，其中PBO的增效活性尤为显著，它能使对阿维菌素B1产生100多倍抗药性的小菜蛾完全恢复其敏感性，说明多功能氧化酶解毒代谢增强可能是小菜蛾对阿维菌素B1产生抗性的主导因素之一。     

A single polymerase chain reaction-based assay for simultaneous detection of two mutations conferring resistance to tubulin-binding herbicides in Setaria viridis

A simple method based upon polymerase chain reaction (PCR) was developed to detect mutant alleles of the gene encoding α2-tubulin, which confers recessive resistance to tubulin-binding herbicides in Setaria viridis. Multiplex, bidirectional allele-specific PCR (Mbi-PASA) was shown to specifically and reliably detect the presence of all sensitive (Leu₁₃₆, Thr₂₃₉) and resistant (Phe₁₃₆, Ile₂₃₉) α2-tubulin alleles in a single reaction. Double-blind analysis of 2000 S. viridis seedlings using seed bioassay and Mbi-PASA confirmed that the presence of two mutant α2-tubulin alleles in a seedling was always associated with cross-resistance to dinitroaniline and benzoic acid herbicides, sensitivity to a benzamide herbicide, and hypersensitivity to carbamate herbicides. No other resistance mechanism was detected in the S. viridis populations screened. Successful Mbi-PASA genotyping was achieved with fresh and dried plant fragments from the field. Compared with bioassays, Mbi-PASA is faster and more robust, removing the need for live plant material. It is the only way of detecting recessive resistance before resistant plants occur in a field. Mbi-PASA can be performed with basic molecular biology laboratory equipment, and is suitable for high-throughput genotyping adaptation. It is the tool of choice for resistance diagnosis in such cases where only a few recessive, target-derived, genes control resistance to herbicides.     

辽宁省稻瘟病菌对稻瘟灵的抗性监测及其对稻瘟病的田间防治效果

为明确辽宁省水稻稻瘟病菌Magnaporthe oryzae对稻瘟灵的抗性水平及变化动态，本研究于2017—2019年自辽宁省6个市的6个稻区采集并分离获得187株稻瘟病菌，利用菌丝生长速率法测定这187株稻瘟病菌菌株对稻瘟灵的敏感性及抗性，并采用茎叶喷雾法测定稻瘟灵对水稻稻瘟病的田间防治效果以及该药剂与其它药剂的交互抗性。结果表明：供试187株稻瘟病菌菌株对稻瘟灵的EC₅₀范围为0.94~34.96 μg/mL，左侧正态分布峰内EC₅₀平均值为5.05 μg/mL，稻瘟病菌对稻瘟灵的敏感性分布频率不符合正态分布，表明菌群中已经出现对稻瘟灵敏感性下降的亚群体。187株稻瘟病菌菌株对稻瘟灵的平均抗性倍数为3.70，抗性菌株出现频率为55.61%，平均抗性指数为0.40，抗性水平呈逐年增加趋势。2017—2019年稻瘟灵对水稻叶瘟病的防治效果分别为82.97%、78.86%和81.36%，对水稻穗颈瘟的防治效果分别为79.81%、77.68%和80.20%，说明在现有防控手段下未产生高水平抗性群体。稻瘟灵与肟菌酯、戊唑醇之间无交互抗性。与不同药剂轮换使用的前提下，稻瘟灵仍可作为主要药剂防治稻瘟病。     

抗多菌灵的芒果炭疽病菌的杀菌剂筛选及其交互抗性测定

为筛选抗多菌灵的芒果炭疽病菌的杀菌剂,采用生长速率法测定23种杀菌剂对8株抗、感多菌灵的芒果炭疽病菌(Colletotrichum gtoeosporioides Penz.)的室内毒力.通过EC50值、EC90值及杀菌剂间的交互抗性测定等综合分析表明:对芒果炭疽病菌毒力最强的杀菌剂是咪鲜胺,其平均EC50值和EC90值分别为0.04、0.21μg/mL;苯醚甲环唑、丙环唑、吡唑醚菌酯、氟硅唑、氟硅唑·恶唑菌酮、戊唑醇、腈菌唑和多抗霉素对芒果炭疽病菌的毒力也较强,与多菌灵不存在交互抗性,这9种杀菌剂均可作为防治芒果炭疽病的首选杀菌剂.另外,三唑酮、异菌脲、三环唑和代森锰锌也有较好的抑菌效果,可用于芒果炭疽病的防治.通过交互抗性分析,在苯并咪唑类杀菌剂之间,苯并眯唑类杀菌剂与烯唑醇,嘧菌酯、醚菌酯与腈菌唑·醚菌酯,嘧菌酯、醚菌酯与三唑酮,苯醚甲环唑与氟硅唑·恶唑菌酮之间存在交互抗性;而百菌清与嘧菌酯、醚菌酯和腈菌唑·醚菌酯,恶霉灵与嘧菌酯、醚菌酯、腈菌唑·醚菌酯和三唑酮之间存在负交互抗性.     

Spatial and temporal impact of fungicide spray strategies on fungicide sensitivity of <Emphasis Type="Italic">Mycosphaerella graminicola</Emphasis> in winter wheat

Field experiments, involving various fungicide strategies with pyraclostrobin and/or epoxiconazole were carried out in 2004 and 2005, with the overall purpose of monitoring the evolution of fungicide sensitivity in Mycosphaerella graminicola on different isolates per leaf, leaf levels at different points of time, and points in the field. Sensitivity was assessed on single isolates by means of epoxiconazole EC₅₀-values, and monitoring of the G143A-mutation, which confers strobilurin resistance. In both years, fungicide application strategies did not cause any significant shifts in epoxiconazole sensitivity of the population median or variance over time compared to the starting population. In 2004, the end-population median was the same for all sprayed strategies, although compared to untreated median sensitivities were higher. In 2005, epoxiconazole sensitivity levels were similar on individual flag leaves and different points in the field. Measured on all isolates the EC₅₀-values ranged from 0.007–1.15 mg l⁻¹. In 2004, due to the high initial level of pyraclostrobin resistance, stabilisation of pyraclostrobin resistance was observed following the various combination treatments. No correlation between epoxiconazole sensitivities and pyraclostrobin resistance were observed. High input strategies using a mixture of epoxiconazole and pyraclostrobin resulted in the best control and yield response. A subpopulation of the isolates from 2004 was also screened for sensitivity towards five different triazoles of which tebuconazole proved to be least sensitive, and this could further be split into two subpopulations.     

Cry1Ac抗性亚洲玉米螟对四种Bt蛋白的交互抗性

种Bt蛋白Cry1Ac、Cry1Ab、Cry1Ah和Cry1Ie对敏感品系ACB-BtS和抗性品系ACB-AcR的毒力,结果显示,ACB-AcR对Cry1Ah的相对抗性倍数达14.9倍,有显著的交互抗性;对Cry1Ab的相对抗性倍数为4.3倍,交互抗性水平较低;对Cry1Ie的相对抗性倍数为0.9,即无交互抗性.4种蛋白对抗、感品系的EC50表明,ACB-AcR品系对Cry1Ac蛋白产生了显著的抗性,相对抗性达到32.6倍,对Cry1Ah和Cry1Ab有低水平的交互抗性,而对Cry1Ie没有交互抗性.     

福建省番茄灰霉病菌对氟啶胺敏感基线建立及与不同杀菌剂的交互抗性

为明确中国福建省番茄灰霉病菌对氟啶胺的敏感性及其与不同杀菌剂的交互抗性,采用菌丝生长速率法测定了106株采自福建省主要番茄产区的番茄灰霉病菌对氟啶胺的敏感性。结果表明,氟啶胺对福建省番茄灰霉病菌菌丝生长的EC50值在0.0037～0.0452 μg/mL之间,平均值为（0.0221 ±0.0098）μg/mL,其敏感性频率分布呈连续单峰曲线,符合正态分布,因此可将该EC50平均值（0.0221±0.0098）μg/mL作为福建省番茄灰霉病菌对氟啶胺的敏感基线,用于其田间抗药性监测。从106株菌株中选择15株对氟啶胺敏感性不同的菌株,测定了其对嘧霉胺、异菌脲、腐霉利和啶氧菌酯的敏感性。结果表明,供试5种杀菌剂对15株番茄灰霉病菌菌丝生长的平均抑制活性依次为氟啶胺 >异菌脲 >腐霉利 >啶氧菌酯 >嘧霉胺,氟啶胺与异菌脲、腐霉利、啶氧菌酯和嘧霉胺之间均不存在交互抗性。     

灰飞虱对毒死蜱的抗性风险评估、抗性遗传及交互抗性

采用群体筛选法对2001年采自云南楚雄对毒死蜱敏感的灰飞虱(SS)进行连续筛选,筛选13代后,获得抗性为107.86倍的抗性(RR)品系.估计其抗性现实遗传力为0.33,在室内同等选择条件下,致死率为50%～90%时,抗性上升10.00倍需4～9代.利用RR品系与敏感品系SS进行遗传杂交分析灰飞虱对毒死蜱的抗性遗传规律,结果表明正、反交后代对毒死蜱的抗性分别为12.96倍和12.78倍,显性度D值分别为0.095和0.089,说明灰飞虱对毒死蜱的抗性为常染色体遗传,主效基因为不完全显性.通过分析杂交F1代和敏感品系SS回交后代对毒死蜱的LD-P线,表明灰飞虱对毒死蜱的抗性为单基因性状.交互抗性谱测定结果表明,RR品系对有机磷杀虫剂敌敌畏有5.82倍的交互抗性,对烟碱类噻虫嗪、苯基吡唑类氟虫腈和大环内酯类阿维菌素没有交互抗性.