Infection frequency of mature apple fruit with Erwinia amylovora deposited on pedicels and its survival in the fruit stored at low temperature

The infection frequency of mature apple fruit by Erwinia amylovora and the survival of E. amylovora in the fruit stored at low temperature were investigated. The fruit stems (pedicels) of 460 mature apple fruit were inoculated with 10⁵ or 10⁴ cfu of bioluminescent E. amylovora, tagged with lux genes. Nine days after inoculation, 43% and 27% of the fruit inoculated with 10⁵ and 10⁴ cfu, respectively, were infected. All infected fruit looked healthy. After 6 months of storage at 5°C, almost all of the 142 infected fruit had viable E. amylovora. Of the fruit containing E. amylovora internally, 19.5% had latent infections and the rest had blight symptoms. E. amylovora was not uniformly distributed in the fruit flesh, and internal brown lesions were observed where E. amylovora was densely distributed. These findings showed that mature apple fruit may be infected with E. amylovora, especially as latent infections, and act as a source for long-range dissemination.     

Polygalacturonase-inhibiting protein activity in cantaloupe fruit as a function of fruit maturation and tissue origin

Netted cantaloupe (Cucumis melo var. cantalupensis cv. Magnum 45) were harvested from 5 to 35 days postanthesis. The fruit of each age group were divided into exocarp, outer mesocarp, mid mesocarp, inner mesocarp, placenta, and seed. Each tissue was extracted and assayed for polygalacturonase-inhibiting protein (PGIP) activity against polygalacturonases (PGs) from three fungal pathogens of cantaloupe fruit. The PGIP activity of all tissues except placenta was high from the flower stage through the first week of fruit development but decreased markedly between 5 and 10 days postanthesis. PGIP activity against Phomopsis cucurbitae PG remained high and nearly constant in placental tissue throughout fruit development. However in this same tissue, PGIP activity against Fusarium solani PG decreased during fruit development to about 25% of its level in the 5-day-old fruit. This differential change in PGIP activity toward the two PGs suggests that different forms of the inhibitor are expressed between early and late stages of cantaloupe fruit development. The results also illustrate the importance of using multiple pathogen enzyme systems that can provide an opportunity for more accurate elucidation of mechanisms involved in the host–pathogen interaction. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. All programs and services of the US Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. The article cited was prepared by a USDA employee as part of his/her official duties. Copyright protection under US copyright law is not available for such works. Accordingly, there is no copyright to transfer. The fact that the private publication in which the article appears is itself copyrighted does not affect the material of the US Government, which can be freely reproduced by the public.     

Characterization of a new viroid strain from hops: evidence for viroid speciation by isolation in different host species

A new viroid was detected in hops cultivated in Akita Prefecture, Japan where it is prevalent in many hops fields. In a survey of hop samples collected during the 1986–2002 growing seasons, the new viroid was present in the major Japanese hop-cultivating areas as early as the 1980s. A single-stranded circular RNA of 368–372 nucleotides that assume a highly basepaired, stable, rod-like secondary structure, shares 93%–98% sequence homology with Apple fruit crinkle viroid (AFCVd) isolated from apple and 85%–87% with Australian grapevine viroid (AGVd) isolated from grapevine. Taking into account the present concept of viroid species, we conclude that the viroid is AFCVd. Circumstantial evidence suggests that AFCVd from apples and hops were endemic in Japan only where cultivation of the two host plants overlapped, thereby strongly supporting the possibility that AFCVd (or an ancestral viroid) was transmitted across the species barrier from apples to hops or hops to apples somewhere in the region. Phylogenetic analysis of AFCVd from hops, AFCVd from apples, and AGVd together with the other members of the genus Apscaviroid revealed that the Akita isolates of AFCVd from hops (AFCVd-hop) formed a cluster that is distinct from AFCVd-apple and AGVd. Accumulation of host-specific sequence variation following their isolation in different host species may be leading to the formation of two viroid species from a common ancestor.     

Influence of calcium pretreatment on pectic substance evolution in cucumber fruit (cucumis sativus) duringbotrytis cinerea infection

The role of calcium in protecting plant tissue from infection byBotrytis cinerea was studied in cucumber fruit. A self-defense reaction, consisting of an increase in cell-wall-bound Ca, occurred in the plant tissue after an injury or an infection. However, it was not sufficient to protect the tissue from the spread of the fungus, which is accompanied by pectic substance digestion. The degradation induced mainly a decrease in acid- and chelator-soluble pectin levels, and an increase in water-soluble pectin. Ca treatment of the fruit prior to infection could amplify the cell-wall-bound Ca and therefore lessen pectin digestion by fungal pectinolytic enzymes.     

First report of Melon yellow spot virus infecting balsam pear (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.) in Japan

A new disease causing necrotic spots and yellowing on leaves of balsam pear (Momordica charantia) was found in Kochi Prefecture, Japan. In this study, we identified the causal pathogen as Melon yellow spot virus (MYSV) based on morphology of virus particles, serology, and the nucleotide sequence of the nucleocapsid protein gene. This is the first report of natural infection of balsam pear by MYSV. We propose the name spotted wilt for this new disease of balsam pear.     

Aloe ring spot,a new disease of aloe caused by <Emphasis Type="Italic">Haematonectria haematococca</Emphasis> (Berk. &; Broome) Samuels &; Nirenberg (anamorph: <Emphasis Type="Italic">Fusarium</Emphasis> sp.)

A ring spot disease of Aloe vera was found on leaves of potted seedlings of Aloe vera in Hachijojima and Chichijima Islands, Tokyo. From tissue of ring spot lesions, a fungus producing Fusarium-type conidia was consistently isolated. After 1 month, reddish perithecia of nectriaceous fungus had formed on the colonies of this isolate on PDA. These nectriaceous and Fusarium fungi were identified as Haematonectria haematococca and Fusarium sp., respectively. From a single ascospore isolation, the former was confirmed to be the teleomorph of the Fusarium sp. Typical ring spot lesions were reproduced by artificial inoculations using single ascospore and single conidium isolates. Inoculations of five species of genus Aloe revealed that they were highly susceptible except for A. arborescens. This is the first report of a disease on Aloe caused by H. haematococca (anamorph: Fusarium sp.) in Japan, and it was named aloe ring spot.     

光周期和温度对苹果蠹蛾滞育诱导的影响

为探讨光周期和温度对苹果蠹蛾Cydia pomonella滞育诱导的影响,通过人工诱导的方法对其滞育的光周期、温度诱导条件及滞育的敏感光照虫期进行了研究。结果表明:20℃时,光照时间短于12 h,苹果蠹蛾的滞育率可达到100%;25℃时,光周期为L 8∶D 16时滞育率最高,为98.3%;30℃时,光照时间少于10 h,苹果蠹蛾的滞育率可达85%以上。在20、25和30℃条件下,幼虫滞育的临界日长分别为14.21、13.68和13.73 h。苹果蠹蛾对光照反应有2个最敏感时期,即幼虫初孵化阶段和预蛹期阶段,卵期对光照反应不敏感。表明苹果蠹蛾是一种典型的短日照滞育型种类,光周期、温度及其交互作用均对其滞育诱导具有重要影响,其中光周期占主导作用,温度随着光周期起作用,低温对滞育诱导有很好的促进作用。     

甜菜夜蛾中肠碱性磷酸酶alp2基因的克隆、表达及功能分析

为探究甜菜夜蛾Spodoptera exigua中肠碱性磷酸酶(alkaline phosphatase protein 2,ALP2)是否为Cry1Ac杀虫蛋白的受体,采用同源克隆和RACE技术克隆了编码alp2基因的完整c DNA序列,利用荧光定量PCR比较了甜菜夜蛾幼虫中肠不同龄期ALP2表达量的差异,利用Ligand blot方法检测了中肠ALP2与Cry1Ac杀虫蛋白的结合。结果表明,alp2基因序列全长1 629 bp(Gen Bank序列号为KP420013),编码542个氨基酸,预测在氨基酸序列N端包含1个由21个氨基酸组成的信号肽,在C端存在1个GPI修饰的锚定位点,且在整个氨基酸序列中存在多个糖基化修饰位点。在整个甜菜夜蛾幼虫期均有ALP2表达,但不同龄期的表达量差异显著,1龄幼虫期表达量最低,4龄幼虫期最高。Ligand blot方法检测结果表明原核表达的ALP2片段与活化的Cry1Ac杀虫蛋白可以结合。研究表明,甜菜夜蛾中肠的ALP2可能是Cry1Ac的受体之一。     

黄翅绢丝野螟气味受体基因GcaeOR10的鉴定及组织表达分析

为明确黄翅绢丝野螟Glyphodes caesalis气味受体基因GcaeOR10(GenBank登录号MW701397)的生物信息学特征及组织表达谱,使用生物信息学软件对其进行序列分析,并通过实时荧光定量PCR(real-time fluorescence quantitative PCR,qPCR)技术检测其在黄翅绢丝野螟成虫不同组织中的表达量。结果显示,黄翅绢丝野螟GcaeOR10基因开放阅读框（open reading frame,ORF）全长为1 200 bp,编码399个氨基酸残基,预测其编码的蛋白质分子量为45.67 kD,等电点为8.65,无信号肽,具有昆虫气味受体家族7个跨膜蛋白（7 transmembrane proteins,7tm-6）超家族的保守结构域,存在26个潜在的磷酸化位点,含有7个跨膜结构域,且N端位于细胞膜内,C端位于细胞膜外。黄翅绢丝野螟GcaeOR10与桑螟Glyphodes pyloalis的GpylOR17亲缘关系最近,其次与松蛀螟Conogethes pinicolalis的CpinOR39、CpinOR36和桃蛀螟Conogethes p...     

虱螨脲亚致死浓度对小菜蛾保护酶系和解毒酶系活力的影响

为阐明虱螨脲对小菜蛾亚致死效应的生化机制,采用室内生物测定法测定了LC_(10)和LC_(25)亚致死浓度处理小菜蛾3龄幼虫1、6、12、24、48和72 h后其体内保护酶系和解毒酶系的活力变化。结果表明:虱螨脲LC_(10)处理对小菜蛾幼虫体内超氧化物歧化酶(SOD)活力表现为早期诱导、后期抑制的作用,而对过氧化物酶(POD)则表现为先抑制后诱导的作用,对过氧化氢酶(CAT)仅在72h时具有诱导作用;LC_(25)处理对SOD表现为诱导-抑制-诱导-抑制的作用,对POD具有抑制作用,而对CAT具有诱导作用。经虱螨脲亚致死浓度处理后,小菜蛾幼虫体内酯酶和多功能氧化酶活力被明显抑制,且基本表现为浓度越高抑制作用越强;而谷胱甘肽S-转移酶(GST)活力仅在处理后1 h被诱导,之后被显著抑制。表明虱螨脲进入小菜蛾幼虫体内后,初期可诱导SOD、CAT和GST活力升高,以适应外界毒害的影响;但随着时间的延长,3种解毒酶活力被抑制,使其难以代谢,从而增强了对小菜蛾的毒性。     

A juvenile hormone analog, pyriproxifen, affects some biochemical components in the hemolymph and fat bodies of Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Endocrine system has a critical role during the developmental stages of insects by synthesis of several regulatory hormones. One of these hormones is juvenile hormone that several insecticides have been driven based on its biochemical structure e.g. pyriproxifen. Due to various disadvantages of fenitrothione spraying, this study was carried out finding the possible usage of pyriproxifen to control the destructive population of Eurygaster integriceps. After bioassay treatments to acquire the appropriate concentrations, the treatment repeated to find possible changes in the biochemical compounds of hemolymph and reserved macromolecules in fat bodies. Results showed significant discrepancies in amount of biochemical components of the hemolymph and the reserved macromolecules in E. integriceps after pyriproxifen treatment. In hemolymph, activity level of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase as enzymatic components and uric acid as non-enzymatic one increased but acid phosphatase, lactate dehydrogenase, protein, trehalose and lipid showed adverse results. In fat bodies, the amount of all measured reserves including glycogen, lipid and protein decreased and showed significant differences. These kinds of changes have been supported by several studies due to using insecticides. These negative effects on overall physiology of the Sunn pest by depleting the essential compounds cause sensitivity to fungal infections and several shortages for normal development and reproduction of insect. Also, the adaptability of pyriproxifen to increase the effect of entomopathogenic fungus, Beauveria bassiana, should be considered to initiate a new pest management program to decrease the production loss made by E. integriceps in wheat fields.     

新疆外来入侵害虫欧洲甘蓝粉虱主要生物学特性分析

为明确近年来入侵我国蔬菜和园艺作物的新害虫——欧洲甘蓝粉虱Aleyrodes proletella的主要生物学特性,于2017—2018年在新疆维吾尔自治区(简称新疆)乌鲁木齐市通过田间定点调查、随机调查以及室内饲养观察,对其年生活史、越冬虫态及越冬场所等进行了研究。结果显示,在室内不同温度条件下饲养,欧洲甘蓝粉虱各龄期的发育历期存在显著差异,在15、20、25、30℃下,卵至羽化阶段的发育历期分别为56.12、25.63、22.00、20.95 d。欧洲甘蓝粉虱在新疆1年发生6～7代,其中第7代的伪蛹少数能羽化为成虫后越冬,其余各虫态入冬后就停止发育,且不能越冬。欧洲甘蓝粉虱于新疆在夏季完成1代需要20～25 d,从第2代开始在田间出现世代重叠;该虫以雌性成虫在甘蓝Brassica oleracea、青菜B. chinensis var. chinensis、大蒜芥Sisymbrium loeselii、晚期油麦菜(莴苣栽培变种)Lactuca sativa var. longifolia、晚期野莴苣L. serriola、苦苣菜Sonchus oleraceus、肥皂草Saponaria officinaiis和蜀葵Althaea rosea等耐寒植物叶背越冬。表明欧洲甘蓝粉虱在乌鲁木齐市显示出极强的适生性,而且其发生世代较国内外已报道的有所增加。     

内蒙古亚洲小车蝗种群遗传多样性和遗传分化的ISSR分析

亚洲小车蝗Oedaleus asiaticus Bei-Bienko是我国北方草原和农牧交错区的主要害虫。为评价内蒙古地区亚洲小车蝗种群的遗传多样性和遗传分化,应用ISSR标记方法对内蒙古15个亚洲小车蝗种群遗传多样性及遗传分化进行了分析。结果表明,7条引物扩增出85条ISSR条带,均为多态性条带。多态性比例（P）、Nei''s遗传多样性指数（H）和香农多样性指数（I）分别为82.59%、0.2319和0.3421,表明亚洲小车蝗种群具有较高的遗传多样性。基因流（Nm）和基因分化系数（Gst）分别为1.2298和0.3352,表明亚洲小车蝗不同地理种群具有明显的遗传分化。遗传距离与地理距离呈极显著正相关关系。表明地理距离和地形差异可能是形成亚洲小车蝗种群遗传分化的主要原因。     

茶翅蝽非典型气味受体基因的克隆及其生物信息学特征和组织特异性表达分析

为明确茶翅蝽Halyomorpha halys的非典型气味受体（odorant receptor co-receptor,Orco）基因的生物信息学特征和组织特异性表达谱,采用Trizol法提取茶翅蝽成虫触角的总RNA,利用RTPCR技术克隆其Orco基因,使用生物信息学软件对茶翅蝽Orco蛋白进行跨膜区域预测、结构分析和系统发育分析,并采用实时荧光定量PCR技术测定Orco的组织表达谱。结果表明,克隆获得茶翅蝽Orco基因并命名为Hhal Orco,该基因的开放阅读框全长1 428 bp,编码475个氨基酸。Hhal Orco蛋白的二级结构中,α螺旋占34.11%,无规则卷曲占36.84%,延伸链占29.05%;其分子质量为53.49 kD,等电点为6.16,无信号肽,是非分泌蛋白;有7个跨膜区,是疏水性蛋白,疏水性系数的平均值为0.297;预测的Hhal Orco蛋白为对称亚基构成的同源四聚体。系统进化分析发现,Hhal Orco与同为半翅目的荔蝽Tessaratoma papillosa亲缘关系最近。qPCR检测结果显示,Hhal Orco基因主要在雌雄成虫的触角中表达,在成虫的头、胸、腹、足中仅有微量表达。     

我国东北地区亚洲玉米螟种群发生动态与寄主植物来源

为明确我国东北地区亚洲玉米螟Ostrinia furnacalis(Guenée)不同世代的种群动态及寄主植物来源,利用性诱捕器监测了其不同世代的种群动态,并以雄蛾翅的稳定性同位素δ13C为标记鉴定其寄主植物的光合作用类型。结果表明,亚洲玉米螟成虫越冬代始见期在5月底,第1代终见期在9月中旬。公主岭、齐齐哈尔、沈阳等地越冬代和第1代亚洲玉米螟幼虫主要以C4植物为寄主,以C4植物为寄主的种群占所有种群的比例分别为72.19%~97.71%和95.18%~100%;2014年公主岭、齐齐哈尔、沈阳等地之间越冬代和第1代亚洲玉米螟幼虫以C3植物为寄主的种群比例无显著差异,2013年公主岭和2014年沈阳的越冬代和第1代幼虫期之间以C3植物为寄主的种群比例差异显著。研究表明,东北地区以C3植物为寄主的亚洲玉米螟种群较少。     

Flufenoxuron, an acylurea insect growth regulator, alters development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) by modulating levels of chitin, soluble protein content, and HSP70 and p34 in the larval tissues

The effect of sublethal concentrations, 0.00141% (LC₂₀), 0.00251% (LC₃₀), and 0.0036% (LC₄₀) of a dispersible formulation of an acylurea insect growth regulator, flufenoxuron (Cascade) on certain biochemical parameters in the larvae of Tribolium castaneum was investigated. When neonates were fed on diet treated with sublethal concentrations for 24 h, it was observed that at all concentrations tested, there was a significant reduction in chitin content on the 15th day of development. Total soluble protein content at LC₂₀ and LC₃₀ decreased with increasing age of the larvae. At LC₂₀ and LC₄₀ concentrations there was a progressive increase in the protein: chitin ratio as a function of increase in age of the larvae. SDS-PAGE analysis of the larval tissue extracts indicated gross quantitative changes in some of the protein bands (MW 50-97 kDa). Western blot analysis revealed significant increase in the level of HSP70 in the extracts of larvae fed on LC₃₀ treated diet, on the 7th and 10th day of development in the decreasing order. Conversely, a significant decrease in the hyper-phosphorylated form of p34^cdc2 kinase due to flufenoxuron treatment indicating modulation of cell cycle regulation was observed. Thus, sublethal concentrations of flufenoxuron alter expression of developmentally regulated proteins, HSP70 and p34^cdc2 and chitin formation in a stage-specific manner thereby resulting developmental abnormalities in T. castaneum.