植原体基因组学研究进展

植原体（phytoplasma）是一类重要的植物病原细菌, 可经叶蝉、飞虱等昆虫介体传播, 感染1 000多种植物, 产生丛枝、黄化、韧皮部黑斑坏死等症状, 给农业、林业生产带来巨大的损失。本文对植原体基因组学研究的历史、现状及当前植原体效应蛋白等方面的研究进展进行了综述。     

北京地区二斑叶螨不同种群的药剂敏感性

【目的】明确北京地区作物上二斑叶螨（Tetranychus urticae Koch）不同种群对杀螨剂的敏感性水平,了解二斑叶螨对药剂敏感性与体内4种解毒酶活力的相关性。【方法】在实验室内采用改进的玻片浸渍法（slide-dip method）检测北京房山、怀柔、昌平、延庆和平谷5个地区二斑叶螨田间种群对联苯肼酯、阿维菌素、螺螨酯和哒螨灵4种杀螨剂的敏感性;采用PCR技术对单头叶螨的CYTB基因进行扩增和测序,检测二斑叶螨对联苯肼酯的抗性突变位点;并采用酶标仪微量板法,检测二斑叶螨体内与抗性相关的多功能氧化酶、乙酰胆碱酯酶、羧酸酯酶和谷胱甘肽S-转移酶的活力。【结果】5个田间种群对联苯肼酯最敏感,其LC50分别为2.4880、6.4693、6.2398、0.7882和14.7783 mg•L-1。对阿维菌素的敏感性次之,其LC50分别为22.4712、35.4431、14.5260、15.4904和14.0023 mg•L-1。对螺螨酯和哒螨灵的敏感性非常低,螺螨酯的LC50分别为49.6833、81.8826、72.9609、204.4609和1 433.5137 mg•L-1,哒螨灵的LC50分别为202.6902、806.8324、375.3518、188.3234和2 310.9040 mg•L-1。延庆地区二斑叶螨乙酰胆碱酯酶、羧酸酯酶和谷胱甘肽S-转移酶的活性显著高于其他地区,其活力分别为14.9508 U/(mg protein)、0.2271 μmol•mg-1 protein•30 min-1和58.2962 U/(mg protein)。怀柔地区多功能氧化酶的活性显著低于其他地区,其活力为1.4272 μmol•mg-1 protein•30 min-1。联苯肼酯、阿维菌素、螺螨酯和哒螨灵的敏感性水平与乙酰胆碱酯酶、羧酸酯酶、谷胱甘肽S-转移酶和多功能氧化酶的酶活力之间没有直接的线性关系;采用PCR技术对5个地区的288个二斑叶螨个体进行CYTB基因检测后,仅发现怀柔地区的一个个体CYTB基因第126位氨基酸密码子的第一位核苷酸由G突变为A导致氨基酸由G突变为S,其余地区均无突变,这与生物测定方法中各地区对联苯肼酯较敏感的结果基本一致。【结论】北京地区二斑叶螨不同种群对联苯肼酯敏感性最高,对阿维菌素的敏感性次之,对螺螨酯和哒螨灵敏感性非常低;二斑叶螨对4种杀螨剂的敏感性水平与乙酰胆碱酯酶、羧酸酯酶、谷胱甘肽S-转移酶和多功能氧化酶的酶活力之间没有直接的线性关系;通过检测到的基因突变个体,说明怀柔地区二斑叶螨种群中存在着对联苯肼酯产生高抗性风险的个体。PCR方法能够更加快速准确地检测种群抗性发展程度。基于以上结果,在农业防治二斑叶螨中应降低联苯肼酯使用频率,交替使用阿维菌素,避免使用螺螨酯,停止使用哒螨灵,以延缓和降低二斑叶螨产生抗性的风险。     

共存阳离子（Ca、Zn、K）对土壤镉有效性的影响

采用盆栽与吸附试验,研究了镉污染赤红壤上,施用相同摩尔浓度的钙、钾与锌对小油菜生物量、镉吸收量及土壤镉吸附的影响。结果表明,低和高镉污染赤红壤上,施用锌明显增加小油菜地上部生物量,较对照分别增产21.1%和7.82%。不同阳离子（钠、钙、钾和锌离子）共存改变土壤吸附镉能力的程度不同,与钠体系相比,钙、钾和锌体系中土壤镉吸附量分别降低65.6%、72.0%和96.9%,共存离子降低土壤镉吸附量的次序为锌离子〉钾离子和钙离子,锌离子的影响最为明显。高镉污染赤红壤上,钙和钾使小油菜吸镉量分别增加5.5%和14.4%,低于低镉污染赤红壤上钙和钾使小油菜吸镉的增加量（分别为16.6%和19.6%）;锌明显降低小油菜吸镉量,高和低镉污染赤红壤上,较对照分别减少45.8%和35.0%。3种阳离子与镉共存时,对土壤镉生物有效性的影响差异取决于竞争吸附与竞争吸收的大小,其机制有待进一步探讨。     

Interactions of arbuscular-mycorrhizal fungi and Bacillus strains and their effects on plant growth,microbial rhizosphere activity (thymidine and leucine incorporation) and fungal biomass (ergosterol and chitin)

The effects of two Bacillus strains (Bacillus pumillus and B. licheniformis) on Medicago sativa plants were determined in single or dual inoculation with three arbuscular-mycorrhizal (AM) fungi and compared to P-fertilization. Shoot and root plant biomass, values of thymidine and leucine incorporation as well as ergosterol and chitin in rhizosphere soil were evaluated to estimate metabolic activity and fungal biomass, respectively, according to inoculation treatments. For most of the plant parameters determined, the effectiveness of AM fungal species was influenced by the bacterial strain associated. Dual inoculation of Bacillus spp. and AM fungi did not always significantly increase shoot biomass compared to single AM-colonized plants. The most efficient treatment in terms of dry matter production was the dual Glomus deserticola plus B. pumillus inoculation, which produced similar shoot biomass and longer roots than P-fertilization and a 715% (shoot) and 190% (root length) increase over uninoculated control. The mycorrhizas were more important for N use-efficiency than for P use-efficiency, which suggests a direct mycorrhizal effect on N nutrition not mediated by P uptake. Both chemical and biological treatments affected thymidine and leucine incorporation in the rhizosphere soil differently. Thymidine was greater in inoculated than in control rhizospheres and B. licheniformis was more effective than B. pumillus in increasing thymidine. Non-inoculated rhizospheres showed the lowest thymidine and leucine values, which shows that indigenous rhizosphere bacteria increased with introduced inocula. The highest thymidine and leucine values found in P-fertilized soils indicate that AM plants are better adapted to compete with saprophytic soil bacteria for nutrients than P-amended plants. Chitin was only increased by coinoculation of B. licheniformis and G. intraradices. B. pumillus increased ergosterol (indicative of active saprophyte fungal populations) in the rhizosphere of AM plants and particularly when colonized by G. mosseae. The different AM fungi have different effects on bacterial and/or fungal saprophytic populations and for each AM fungus, this effect was specifically stimulated or reduced by the same bacterium. This is an indication of ecological compatibilities between microorganisms. Particular Glomus–bacterium interactions (in terms of effect on plant growth responses or rhizosphere population) do not seem to be related to the percentage of AM colonization. The effect on plant growth and stimulation of rhizosphere populations, as a consequence of selected microbial groups, may be decisive for the plant establishment under limiting soil conditions.     

精甲霜灵与百菌清在黄瓜和土壤中的残留降解规律研究

[目的]研究精甲霜灵与百菌清在黄瓜和土壤中的残留状况与残留降解规律,评价精甲霜灵与百菌清在黄瓜上使用的安全性,建立同时测定黄瓜和土壤中精甲霜灵与百菌清残留量的液相色谱分析方法。[方法]黄瓜和土壤中的精甲霜灵与百菌清采用乙腈溶液振荡提取,使用酸性氧化铝固相萃取小柱净化,液相色谱带二极管阵列检测器（DAD）测定,外标法定量;田间试验按照NY/T 788-2004《农药残留试验准则》进行。[结果]在添加量为0.02～2.00 mg/kg时,精甲霜灵在黄瓜和土壤中的添加平均回收率为84.7%～101.0%,变异系数为2.72%～6.46%;当添加量为0.01～1.00 mg/kg时,百菌清在黄瓜和土壤中的添加平均回收率为76.9%～95.8%,变异系数为3.36%～4.90%。精甲霜灵的最小检出量为5×10-10 g,百菌清为2×10-10 g;精甲霜灵的最低检出质量分数为0.02 mg/kg,百菌清为0.01 mg/kg。精甲霜灵和百菌清在黄瓜和土壤中的残留消解动态符合方程Ct=Coe-kt;精甲霜灵在黄瓜中的半衰期为2.8～3.2 d,在土壤中的半衰期为7.8～9.8 d;百菌清在黄瓜中的半衰期为1.3～2.1 d,在土壤中的半衰期为3.7～4.0 d。在黄瓜上施用精甲霜灵.百菌清440 g/L悬浮剂,施药剂量为推荐用量990 g a.i/hm2和推荐用量的1.5倍1 485 g a.i./hm2,施药3～4次,末次施药1 d后黄瓜中的精甲霜灵残留量低于联合国食品法典委员会（CAC）规定的最大残留限量值（MRL）0.5 mg/kg,百菌清残留量低于CAC规定的MRL值5.0mg/kg。[结论]精甲霜灵.百菌清440 g/L悬浮剂按推荐剂量施用,1 d后收获的黄瓜食用安全。     

香蕉弯孢霉叶斑病菌生物学特性及对杀菌剂敏感性研究

香蕉弯孢霉叶斑病菌［Curvularia lunata (Wakker) Boed］适合生长的培养基有PSA、PDA和OMA;菌落生长、产孢和孢子萌发最适宜的温度为25～30 ℃,pH要求不严格为5～9;在碳源和氮源中,蔗糖、葡萄糖、尿素、磷酸氢二氨和硝酸钠有利于病菌生长和产孢;分生孢子萌发对湿度有严格的要求,RH≥80%以上分生孢子萌发,随湿度增加萌发率增高;光照对菌丝体无显著影响,光暗交替有利于孢子的形成; 孢子致死温度为55 ℃(10 min)。药物敏感性测定结果表明,6%戊唑醇微乳剂、25%丙环唑乳油、25%咪鲜胺水乳剂、25%戊唑醇乳油和25%苯醚甲环唑乳油对香蕉弯孢霉叶斑病菌菌丝生长均有较好的抑制效果,其中25%咪鲜胺水乳剂和25%苯醚甲环唑乳油的抑菌效果最好。     

A newly devised electric field screen for avoidance and capture of cigarette beetles and vinegar flies

A bifunctional electric field screen was proposed to physically exclude insect pests from warehouses. The screen consists of insulated iron wires (ICW) arranged in parallel and two earthed conductor nets placed on both sides of the ICW. A negative charge (0.1-8.0 kV) was applied to the insulated wires with a voltage generator to polarize an insulator sleeve used to cover the wire, negatively on the outer surface and positively on the inner conductor wire surface of the sleeve. The negative surface charge of the ICW caused an electrostatic induction in the earthed nets and an opposite charge on the net surfaces facing the ICW. An electric field formed in a space between the ICW and the earthed net, and the field strength increased in direct proportion to increasing voltages applied to the ICW. Adults of the test insects (cigarette beetle (Lasioderma serricorne) and vinegar fly (Drosophila melanogaster)) reaching the outer surface of the earthed net were deterred from entering the inside of the charged screen, whereas all insects immediately passed through the screen when the ICW was not charged. This avoidance was directly proportional to the increase in the voltage. In addition, the capability of the screen to capture insects that enter inside the screen was proven by introducing insects into the space between the ICW and the earthed net. Strong capture was observed when the ICW was negatively charged with more than 4.1 kV, under which conditions a short-term electric current (peaking at 0.3-0.6 μA, for 3 min) occurred transiently. This electric current was due to the release of electricity from the insects, giving a net overall positive charge to the insects, which therefore were attracted more strongly to the negatively charged ICW. A test using an attractant-set chamber showed that the insects were completely prevented from passing through the charged screen, in contrast to a rapid transfer of all insects when the screen was not charged. Thus, the present results show that the described screen is a promising physical tool for controlling insect pests in warehouses.     

Ceratocystis platani is killing plane trees in Istanbul (Turkey)

Ceratocystis platani was detected at several locations in the European side of Istanbul, causing severe dieback and mortality, mainly on Platanus × acerifolia imported from Italy approximately 160 years ago, but also on Platanus orientalis. In the work reported here, the causal agent of the dieback and mortality was identified based on morphological characteristics in culture and internal transcribed spacer (ITS) sequencing, confirming the presence of C. platani in Turkey. All analysed C. platani isolates from Istanbul shared the same ITS sequence with European C. platani strains available in the NCBI, but differed from other species previously ascribed to the Ceratocystis fimbriata species complex. Pathogenicity of C. platani was proven by inoculation onto 25‐cm‐long and 4–9 mm diam. P. orientalis twigs and the causal agent reisolated from symptomatic tissues. In a survey of 976 Platanus in streets and parks of Istanbul, 26.5% of trees showed symptoms of C. platani infections, whilst 5.6% were dead. The proportion of symptomatic trees was higher where management interventions, such as topping or pruning and felling infected trees had been carried out.     

Genetic diversity of the myrtle rust pathogen (Austropuccinia psidii) in the Americas and Hawaii: Global implications for invasive threat assessments

Since the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in Brazil on guava (Psidium guajava) in 1884, it has been found infecting diverse myrtaceous species. Because A. psidii has recently spread rapidly worldwide with an extensive host range, genetic and genotypic diversities were evaluated within and among A. psidii populations in its putative native range and other areas of myrtle rust emergence in the Americas and Hawaii. Microsatellite markers revealed several unique multilocus genotypes (MLGs), which grouped isolates into nine distinct genetic clusters [C1–C9 comprising C1: from diverse hosts from Costa Rica, Jamaica, Mexico, Puerto Rico, and USA‐Hawaii, and USA‐California; C2: from eucalypts (Eucalyptus spp.) in Brazil/Uruguay and rose apple (Syzygium jambos) in Brazil; C3: from eucalypts in Brazil; C4: from diverse hosts in USA‐Florida; C5: from Java plum (Syzygium cumini) in Brazil; C6: from guava and Brazilian guava (Psidium guineense) in Brazil; C7: from pitanga (Eugenia uniflora) in Brazil; C8: from allspice (Pimenta dioica) in Jamaica and sweet flower (Myrrhinium atropurpureum) in Uruguay; C9: from jabuticaba (Myrciaria cauliflora) in Brazil]. The C1 cluster, which included a single MLG infecting diverse host in many geographic regions, and the closely related C4 cluster are considered as a “Pandemic biotype,” associated with myrtle rust emergence in Central America, the Caribbean, USA‐Florida, USA‐Hawaii, Australia, China‐Hainan, New Caledonia, Indonesia and Colombia. Based on 19 bioclimatic variables and documented occurrences of A. psidii contrasted with reduced sets of specific genetic clusters (subnetworks, considered as biotypes), maximum entropy bioclimatic modelling was used to predict geographic locations with suitable climate for A. psidii which are at risk from invasion. The genetic diversity of A. psidii throughout the Americas and Hawaii demonstrates the importance of recognizing biotypes when assessing the invasive threats posed by A. psidii around the globe.     

当前中国木薯种植业所面临的主要植保问题及其对策

木薯是中国热区重要的经济作物之一,相关产业在当地占有重要地位。近年来,重要病虫草害在中国木薯种植区频繁发生,已经成为相关产业发展的限制性因素之一。本文介绍了当前中国木薯种植中的病虫草害为害现状并提出了相应的对策。