Dicofol resistance in Tetranychus cinnabarinus: resistance and stability of resistance in populations from Antalya, Turkey

Resistance against dicofol was investigated in the carmine spider mite, Tetranychus cinnabarinus. Higher resistance levels were detected by leaf residual bioassays than by topical bioassays, both done using a Potter spray tower, in almost all populations of T cinnabarinus examined from Antalya, Turkey. For instance, the resistance level at LC₉₅ was 17.5‐fold in topical bioassays but 58.9‐fold in leaf residual bioassays for the population collected from greenhouses in the Topçular district. There were differences of resistance levels at LC₉₅, ranging between 2.6‐ and 23.9‐fold using topical bioassays and between 5.0‐ and 58.9‐fold in residual bioassays, in populations collected from greenhouses from various districts. Populations from cotton showed lower resistance levels against dicofol than populations from greenhouses. Resistance to dicofol at LC₅₀ as indicated by topical and residual bioassays increased 19.7‐ and 100.7‐fold, respectively, in a colony from the laboratory strain of T cinnabarinus selected with dicofol alone for 16 cycles. However, the dicofol resistance at LC₅₀ increased 19.4‐ and 52.0‐fold in another colony selected in rotation with dicofol and tetradifon for six and eight cycles, respectively. The changes in resistance to dicofol 5 months after the selection ceased were as follows: in the colony selected for dicofol alone, using topical and residual bioassays, the resistance levels at LC₅₀ decreased to 11.7‐ and 99.1‐fold, respectively, and in the colony selected in rotation with dicofol and tetradifon to 10.8‐ and 15.8‐fold, respectively. © 2001 Society of Chemical Industry     

Cytochrome P-based resistance mechanism and pyrethroid resistance in the field Anopheles albimanus resistance management trial

The relative rates of cytochrome P⁴⁵⁰ selection in southern Mexican Anopheles albimanus populations were investigated during a 3 years indoor residual house spraying intervention with a pyrethroid (PYR) or DDT, a mosaic of organophosphate (OP)-PYR, and the annual rotation of OP-PYR-carbamate (CARB). This insecticide resistance mechanism, initially evenly spread in the mosquito population, correlated with PYR resistance during the second treated year, when cytochrome P⁴⁵⁰ contents increased in most villages of the PYR, rotation and mosaic schemes. However, by the third year, mean cytochrome P⁴⁵⁰ contents declined to susceptible levels in mosquitoes of the rotation and one mosaic group but not in the PYR-treated villages. In DDT-treated villages, a continuous decrement of cytochrome P⁴⁵⁰ levels occurred since the first treatment year, and susceptible levels were observed at the end of the intervention. Most correlations of cytochrome P⁴⁵⁰ levels and PYR resistance were lost during the third year, indicating that another mechanism evolved in resistant mosquito populations.     

METI-acaricide resistance in Tetranychus urticae does not confer resistance to the naphthoquinones

The naphthoquinones and the METI group of compounds act on sites associated with mitochondrial respiration, but METI-resistant strains of two-spotted spider mite from Japan and the UK exhibited no cross-resistance to the naphthoquinones. The potential for developing commercial naphthoquinones therefore remains high.     

反枝苋对咪唑乙烟酸抗性水平及分子机制

为初步明确大豆田反枝苋对咪唑乙烟酸的抗药性水平,并从分子角度对抗药性机制进行解释,以我国四川成都和黑龙江嫩江采集的反枝苋种子为材料,通过琼脂法检测了反枝苋对咪唑乙烟酸的抗药性水平,并分别对R(嫩江抗性种群)和S(成都敏感种群)的乙酰乳酸合成酶(ALS)部分序列进行扩增和测序。皿内生测结果表明,成都种群的GI50为11.20,嫩江种群的GI50为52.26,其抗药性指数RI为4.67。分子检测结果表明,与S种群相比,R种群反枝苋ALS位于高度保守区Domain B编码574位氨基酸的基因发生突变,TGG突变为TTG,导致色氨酸被亮氨酸取代。ALS保守区域氨基酸的替换可能是嫩江反枝苋种群对咪唑乙烟酸产生抗性的重要原因之一。     

Biochemistry of insecticide resistance

After briefly summarizing various resistance mechanisms and their effects on certain types of insecticides, attention is focused on gaps in the understanding of resistance. Most resistance mechanisms consist either of a change in sensitivity of the site of action or an increased capacity for detoxication. In both cases such changes could theoretically be due to quantitative changes of an enzyme (more sites of action or more detoxication enzyme) or to qualitative changes (less-sensitive site of action or more efficient detoxication enzyme). Examples have now been found for each of these possible causes of resistance to insecticides, except for an increased amount of sites of action. Whereas examples of the latter mechanism are known for cell lines resistant to anti-cancer chemicals, so far they have not been found in resistance to insecticides. The impact of the different mechanisms on development and stability of resistance is discussed.     

Insect resistance to insecticides

The past 40 years have seen insect resistance to insecticides develop from a scientific curiosity to an immense practical problem that threatens man's ability to control not only the insect pests of agriculture but also the insect vectors that transmit major human and animal diseases. The spread of genes for cross and multiple resistance among insect pests has rendered most of our present insecticides obsolescent and very few novel insecticides are under development as substitutes. The most feasible strategy to maintain adequate control of insect pests is integrated pest management or I P M, in which insecticide management is a useful component. However, much of our present planning for the future of insect control is carried out in ignorance of past failures. We must learn from the past if we are to retain the use of chemical insecticides as a viable component of IPM.     

小麦高代系的抗旱性状筛选与抗旱性评价

于2020—2021年度和2021—2022年度两个生长季,在杨凌抗旱棚（DS）、杨凌农作一站（YAS）和乾县试验站（QX）3个环境下分别测定了43份和20份小麦高代系的8个农艺性状及8个产量性状,通过计算抗旱指数评价各性状对小麦抗旱指标的贡献率,同时利用隶属函数法、聚类分析等方法进行综合分析,筛选抗旱性强的小麦高代系。结果表明,在干旱胁迫环境（DS）下,小麦的农艺性状和产量性状均受到不同程度的抑制。基于各性状对小麦抗旱指数的贡献度,筛选出生物量、产量、小穗数和千粒重等作为评价小麦抗旱性的重要指标。通过抗旱性综合评价值D和聚类分析将供试小麦品种（系）分为高抗旱、抗旱、中等抗旱、干旱敏感和干旱高敏感5个等级,两年度鉴定出21-1、21-34、21-39、21-18、21-2和22-17共6份高抗旱小麦品系。     

棉叶螨的抗药性现状与治理策略

棉叶螨也称为棉红蜘蛛,属蛛形纲叶螨科,其种类繁多,分布范围广,世代周期短,是为害棉花的一类重要害螨。目前,用于防治棉叶螨的化学药剂主要是神经毒剂及呼吸抑制剂2大类,且棉叶螨对多数药剂产生了不同程度的抗性,以二斑叶螨Tetranychus urticae为首的植食性害螨已成为世界上抗药性最严重的节肢动物之一。美国路易斯安那州棉田二斑叶螨种群对阿维菌素产生了1 415倍抗性,而国内棉花上棉叶螨主要对有机磷类药剂产生了较强抗性,最高为467倍。棉叶螨产生抗药性的机制主要涉及靶标突变及解毒代谢增强,其中靶标突变主要涉及乙酰胆碱酯酶、电压门控钠离子通道和谷氨酸门控氯离子通道等;细胞色素P450单加氧酶、羧酸酯酶和谷胱甘肽S-转移酶等一种或多种解毒酶共同参与害螨对化学药剂的解毒代谢。该文主要从棉叶螨的种类及分布、用于防治棉叶螨的化学药剂、棉叶螨的抗药性现状、抗药性机制解析和抗药性治理策略5个方面进行阐述,提出因地制宜的抗药性治理策略,旨在为棉叶螨的田间防治提供指导。     

葡萄白粉病抗性鉴定方法优化及品种抗性评价

本研究通过对叶盘保湿方法的改进, 不同菌源接种后发病严重度的分析, 抗?感病对照品种的确定, 建立了一种更为便捷?可靠?稳定的葡萄白粉病室内抗性鉴定方法:取葡萄藤自上而下第2~4片幼嫩叶片, 打取直径15 mm的叶盘置于1.5%水琼脂平板进行保湿, 采集田间菌源直接制备孢子浓度为2×105个/mL的孢子悬浮液接种, 选定抗?感病葡萄品种做对照, 14 d即可完成抗性鉴定?采用此方法对11个葡萄品种(品系)进行了葡萄白粉病抗性评价, 结果表明:供试的11个品种(品系)对葡萄白粉病的抗性存在明显差异, 其中高感品种为‘巨峰’‘夏黑’和‘阳光玫瑰’等, 感病品种为‘玫瑰香’和‘马瑟兰’, 抗病品种为‘瑞都科美’和‘无核翠宝’, 高抗品种为‘北冰红’?试验结果为葡萄抗病品种的选育及利用提供了方法和基础参考数据?     

The effective dominance of resistance genes in relation to the evolution of resistance

Field selection for a rare insecticide resistance (R) gene can be substantially delayed if R is rendered effectively recessive [if all or most heterozygotes ( R + ) are killed by the field dosages] and if a representative sample (+ +, R +, RR) of the population is permitted to escape exposure. The relationship between heterozygote mortality and escape in influencing selection rates has been considered at various frequencies of R. The cases when mating precedes selection, and when selection precedes mating, have been calculated using computer simulations. It is concluded that when R genes are rare it is advantageous (a) to apply the highest possible doses of insecticide in such a form that all exposed insects pick up an amount sufficient to kill all or most heterozygotes, (b) to apply the insecticide to adults after they have mated, rather than to younger adults or to larvae, and (c) to ensure that the proportion of insects given the opportunity to escape contact is as high as practical considerations allow. Once resistance is obvious (when samples are brought into the laboratory for tests), the R gene frequency will have risen to a level which makes the suggested strategy no longer valuable. Alternative strategies are briefly discussed.     

Induced resistance for plant disease control: maximizing the efficacy of resistance elicitors

ABSTRACT Plants can be induced to develop enhanced resistance to pathogen infection by treatment with a variety of abiotic and biotic inducers. Biotic inducers include infection by necrotizing pathogens and plant-growth-promoting rhizobacteria, and treatment with nonpathogens or cell wall fragments. Abiotic inducers include chemicals which act at various points in the signaling pathways involved in disease resistance, as well as water stress, heat shock, and pH stress. Resistance induced by these agents (resistance elicitors) is broad spectrum and long lasting, but rarely provides complete control of infection, with many resistance elicitors providing between 20 and 85% disease control. There also are many reports of resistance elicitors providing no significant disease control. In the field, expression of induced resistance is likely to be influenced by the environment, genotype, and crop nutrition. Unfortunately, little information is available on the influence of these factors on expression of induced resistance. In order to maximize the efficacy of resistance elicitors, a greater understanding of these interactions is required. It also will be important to determine how induced resistance can best fit into disease control strategies because they are not, and should not be, deployed simply as "safe fungicides". This, in turn, will require information on the interaction of resistance elicitors with crop management practices such as appropriate-dose fungicide use.     

Breeding for resistance: breeding for resistance to Plum pox virus in Italy

Plum pox virus (PPV) resistance in apricot and peach in Italy has been researched in several Italian institutions, including the Institutes for Fruit Tree Culture and Plant Pathology in Rome, which are assessing resistance, and the Universities of Bari, Bologna and Milan, examining breeding techniques, both by cross-breeding and genetic transformation approaches. A reliable protocol for resistance assessment has been set up, in which biological indexing, ELISA and PCR techniques are used. No source of resistance has yet been found in peach. Hybridization with Prunus davidiana could be investigated given the promising results obtained within the INRA programme in France. Almost 6000 apricot seedlings from controlled crosses between resistant parents have been investigated in search of possible molecular markers, but no positive results have been obtained so far, probably due the fact that resistance to both D and M strains is sought. The transformation of cultivars has proven difficult in apricot where the regeneration step is particularly critical, while in peach a reliable regeneration protocol still remains to be set up.     

昆虫对Bt杀虫蛋白的抗性机制及治理策略

转Bt基因抗虫作物在害虫综合防治中发挥重要作用，是新一代植物保护产品，其抗虫性能和经济效益已得到普遍肯定。然而由于转基因抗虫植物在整个生育阶段高水平的表达Bt杀虫蛋白，有可能会导致害虫对Bt杀虫蛋白产生抗性，抗性的产生将严重影响Bt植物的应用。田间已经发现小菜蛾Plutella xylostella（Linnaeus）对Bt杀虫剂产生了抗性，实验室人工汰选条件下已经有多种害虫对Bt杀虫蛋白产生了抗性，并对抗性产生的机制进行了研究，目前主要认为害虫产生抗性与杀虫蛋白与中肠细胞上受体蛋白结合能力的改变以及Bt杀虫蛋白在中肠的水解作用的变化有关，但抗性产生的机制还与其它因素有关，估计是多方面因素造成的，因此，抗性机制的产生还不十分清楚。目前已经制订了“高剂量＋庇护所”和多基因策略等一系列有效抗性治理策略，这些策略还需要在深入研究并阐明抗性机制的基础上，进一步完善，以实现Bt抗虫植物在害虫防治中的可持续利用。     

Systemic acquired resistance delays race shifts to major resistance genes in bell pepper

ABSTRACT The lack of durability of host plant disease resistance is a major problem in disease control. Genotype-specific resistance that involves major resistance (R) genes is especially prone to failure. The compatible (i.e., disease) host-pathogen interaction with systemic acquired resistance (SAR) has been studied extensively, but the incompatible (i.e., resistant) interaction less so. Using the pepper-bacterial spot (causal agent, Xanthomonas axonopodis pv. vesicatoria) pathosystem, we examined the effect of SAR in reducing the occurrence of race-change mutants that defeat R genes in laboratory, greenhouse, and field experiments. Pepper plants carrying one or more R genes were sprayed with the plant defense activator acibenzolar-S-methyl (ASM) and challenged with incompatible strains of the pathogen. In the greenhouse, disease lesions first were observed 3 weeks after inoculation. ASM-treated plants carrying a major R gene had significantly fewer lesions caused by both the incompatible (i.e., hypersensitive) and compatible (i.e., disease) responses than occurred on nonsprayed plants. Bacteria isolated from the disease lesions were confirmed to be race-change mutants. In field experiments, there was a delay in the detection of race-change mutants and a reduction in disease severity. Decreased disease severity was associated with a reduction in the number of race-change mutants and the suppression of disease caused by the race-change mutants. This suggests a possible mechanism related to a decrease in the pathogen population size, which subsequently reduces the number of race-change mutants for the selection pressure of R genes. Thus, inducers of SAR are potentially useful for increasing the durability of genotype-specific resistance conferred by major R genes.     

Field resistance against potato virus Y infection using natural and genetically engineered resistance genes

Commercial tobacco cultivars BB16 (burley) and PBD6 (dark air cured) were transformed with the coat protein gene of lettuce mosaic potyvirus (LMV). Transgenic BB16 plants showed resistance to potato virus Y (PVY) infection, against the necrotic strain PVY-N Versailles, as well as the resistance breaking necrotic strain PVY-N 107. Transgenic PBD6, which carries the recessive va gene conferring resistance to PVY, was also protected against PVY-N 107. In the progenies of most BB16 and PBD6 transformants, 45% to 100% of the inoculated plants were immune to PVY infection. The rest of the plants were tolerant, with atypical attenuated non necrotic symptoms and reduced virus accumulation. No recovery was observed in the tolerant plants, which stably expressed detectable level of LMV coat protein. This suggested a protein-mediated mechanism of heterologous protection.     

桔全爪螨对甲氰菊酯的抗性选育及交互抗性的研究

采集桔全爪螨敏感种群 ,在室内用甲氰菊酯处理 ,以选育其抗药性。结果显示 :选育至 12代 ,抗性达 17 11倍 ,且发展速度越来越快。交互抗性测定结果显示 ,甲氰菊酯抗性品系对功夫和哒螨灵有非常明显的交互抗性 ,对卡死克有非常明显的负交互抗性现象。