Genetic Structure of Field Populations of Begomoviruses and of Their Vector Bemisia tabaci in Pakistan

ABSTRACT The genetic structure of field populations of begomoviruses and their whitefly vector Bemisia tabaci in Pakistan was analyzed. Begomoviruses and B. tabaci populations were sampled from different crops and weeds in different locations in Punjab and Sindh provinces, in areas where cotton leaf curl disease (CLCuD) occurs or does not occur. Phylogenetic analysis based on nucleotide sequences of the intergenic region in the viral DNA-A provided evidence of two clusters of isolates: viruses isolated from species in the family Malvaceae, and viruses isolated from other dicotyledon families. Analysis of the capsid protein (CP) open reading frame grouped isolates into three geographical clusters, corresponding to isolates collected in Punjab, Sindh, or both provinces. Random amplified polymorphic DNA analyses of the B. tabaci population showed that intrapopulation diversity was high at both the local and regional scales. Sequence analysis of the mitocondrial cytochrome oxydase I (mt COI) gene showed that the B. tabaci population was structured into at least three genetic lineages corresponding to the previously described Indian, Southeast Asian, and Mediterranean-African clades. The Indian clade was present only in Punjab, the Mediterranean-African only in Sindh, and the Southeast Asian in both provinces. B. tabaci haplotypes of the Indian clade were found only in the Punjab, where CLCuD occurs. Hence, the geographical distribution of virus and vector genotypes may be correlated, because similar phylogenetic relationships were detected for the viral CP and the vector mt COI genes.     

Panel of real‐time PCRs for the multiplexed detection of two tomato‐infecting begomoviruses and their cognate whitefly vector species

A new approach for the simultaneous identification of the viruses and vectors responsible for tomato yellow leaf curl disease (TYLCD) epidemics is presented. A panel of quantitative multiplexed real‐time PCR assays was developed for the sensitive and reliable detection of Tomato yellow leaf curl virus‐Israel (TYLCV‐IL), Tomato leaf curl virus (ToLCV), Bemisia tabaci Middle East Asia Minor 1 species (MEAM1, B biotype) and B. tabaci Mediterranean species (MED, Q biotype) from either plant or whitefly samples. For quality‐assurance purposes, two internal control assays were included in the assay panel for the co‐amplification of solanaceous plant DNA or B. tabaci DNA. All assays were shown to be specific and reproducible. The multiplexed assays were able to reliably detect as few as 10 plasmid copies of TYLCV‐IL, 100 plasmid copies of ToLCV, 500 fg B. tabaci MEAM1 and 300 fg B. tabaci MED DNA. Evaluated methods for routine testing of field‐collected whiteflies are presented, including protocols for processing B. tabaci captured on yellow sticky traps and for bulking of multiple B. tabaci individuals prior to DNA extraction. This work assembles all of the essential features of a validated and quality‐assured diagnostic method for the identification and discrimination of tomato‐infecting begomovirus and B. tabaci vector species in Australia. This flexible panel of assays will facilitate improved quarantine, biosecurity and disease‐management programmes both in Australia and worldwide.     

棉花曲叶病研究进展

 棉花曲叶病(Cotton leaf curl disease,CLCuD)是棉花上的重要病害,在巴基斯坦和印度已造成严重危害。已发现7种双生病毒与亚洲和非洲发生的CLCuD相关,在田间这些双生病毒常复合侵染且病毒基因组重组现象较为普遍。CLCuD伴随不同类型的小分子DNA,其中新型卫星DNA分子——DNAβ与CLCuD致病性紧密相关,是诱导田间典型症状所必需的。重组导致CLCuD的病毒多样化,而DNAβ分子能与不同双生病毒互作,这可能是引起CLCuD流行的重要原因。本文介绍了CLCuD的分布与危害、病害病原致病因子的发现及CLCuD病害复合体各组份之间的互作、病毒及小分子DNA的变异与进化关系、病害流行及防治等方面的研究进展。     

Screening tomato genotypes for resistance and tolerance to Tomato chlorosis virus

Tomato chlorosis virus (ToCV) is an emerging crinivirus in Brazil that causes an economically important disease in tomato (Solanum lycopersicum) and other solanaceous species. ToCV is transmitted predominantly by the whitefly Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1, formerly biotype B), in a semipersistent manner. As all cultivated tomato varieties and hybrids are susceptible to this crinivirus, the main alternatives for the control of the disease are the use of healthy seedlings for transplanting and the chemical control of the insect vector. The objective of this work was to evaluate the responses of tomato genotypes to infection with this crinivirus and their tolerance to the disease in order to support the development of other alternatives for disease control. Resistance to infection was evaluated by ToCV inoculation with viruliferous B. tabaciMEAM1 followed by virus detection by RT‐PCR and RT‐qPCR. To measure tolerance to the disease, plant development and fruit yield of ToCV‐infected and healthy plants were compared. Among 56 genotypes, only the lineage IAC‐CN‐RT (S. lycopersicum ‘Angela Gigante’ × S. peruvianum ‘LA 444‐1’) was highly resistant to infection with ToCV. Tolerance to the disease over two trials with different genotypes showed variable results. The effect of ToCV on plant development varied from 2.9% to 71.9% reduction, while yield loss varied from 0.2% to 51.8%. The highly ToCV‐resistant lineage IAC‐CN‐RT, which is also resistant to a Spanish isolate of ToCV, might be useful for tomato breeding programmes.     

An analysis of the resistance of Gossypium arboreum to cotton leaf curl disease by grafting

Cotton leaf curl disease (CLCuD) is a serious constraint to cotton production across Pakistan and north-western India. In the Punjab province of Pakistan at this time CLCuD is associated with one virus, Cotton leaf curl Burewala virus (CLCuBuV), and its associated betasatellite, Cotton leaf curl Multan betasatellite (CLCuMuB). Although some resistance to the virus complex causing CLCuD has been identified in Gossypium hirsutum, this has in the past proven not to be durable. At this time no commercial lines with strong resistance (immunity) to CLCuD are available. Although the cotton fibre produced by Gossypium arboreum is not of the quality required by processors, the species has a number of desirable characters, including resistance to a number of abiotic and biotic stresses, including CLCuD. For this reason there have been efforts to introgress CLCuD-resistance from G. arboreum into G. hirsutum. However, the nature of the resistance of G. arboreum to the viruses causing CLCuD remains unknown. An initial analysis of the resistance was herein conducted by graft inoculation. Graft inoculation of G. arboreum genotype Ravi with scions from severely infected G. hirsutum genotype CIM 496 plants showed that G. arboreum is able to support virus/betasatellite replication and long-distance spread. However, following grafting, only a small number of leaves developing at the time of grafting became mildly symptomatic and symptomatic tissue contained low amounts of virus/satellite DNA, as detected by Southern blot hybridisation; significantly less than the levels seen in G. hirsutum. The symptoms did not spread to the young upper leaves of graft inoculated plants, which contained DNA levels that could only be detected by polymerase chain reaction (PCR) or PCR following an initial amplification by rolling circle amplification–indicating very low DNA levels. The results showed that the resistance of G. arboreum to the virus complex causing CLCuD likely does not involve a mechanism that interferes with delivery of virus by the insect vector. Rather the resistance appears to be due to poor virus replication and possibly interference in short distance (cell-to-cell) spread.     

First record of the Q Biotype of the sweetpotato whitefly, Bemisia tabaci, intercepted in the UK

For the UK, Bemisia tabaci poses a threat primarily to protected vegetable crops due to the transmission of several plant-pathogenic viruses. There are at least 24 different biotypes of B. tabaci that cannot be differentiated through morphological traits. The B (Middle East-Asia Minor 1 species) and Q (Mediterranean species) biotypes are widely considered to be the most important and, as such, the ability to rapidly and precisely biotype B. tabaci interceptions is vital when developing effective control strategies. Intercepted adult/pupal B. tabaci received from the UK Plant Health and Seeds Inspectorate (PHSI) during 2002–2003 (n?=?60) and 2010–2011 (n?=?42) were both biotyped and tested for the presence of Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) using a real-time PCR assay based on TaqMan? chemistry. The positive results indicated that during 2002–2003 the Q biotype comprised 68.3?% of the interceptions whilst in 2010–2011 it comprised 66.7?% of the B. tabaci samples intercepted. Only three of the B biotypes collected during 2002–2003 were positive for TYLCSV, two originating from Israel and the other of unknown origin. The implications in regards to pest management of the insect are discussed.     

Microsatellites reveal widespread predominance of an invasive over an indigenous <Emphasis Type="Italic">Bemisia tabaci</Emphasis> in Venezuela

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an important pest due to its capacity for producing strong infestations and transmitting plant viruses. The New World putative species of B. tabaci complex (NW) is the indigenous whitefly of the Americas, but only the invasive Middle East-Asia Minor 1 putative species of B. tabaci complex (MEAM1), commonly referred to as the “B biotype” was identified in a limited scope sampling in Venezuela. Similarly to MEAM1 invasions elsewhere, in this South American country there has been an increase in the geographic range and abundance of B. tabaci, and in the number of viruses that it transmits since the late 1980s. We estimated the diversity of B. tabaci to elucidate their role in the epidemiology of geminiviruses in Venezuela. Thirteen microsatellite loci were screened in samples collected from 19 localities in ten major agricultural states. A Bayesian clustering method (Structure) grouped the samples into two genetic groups. Control samples from whiteflies NW and MEAM1 and partial sequencing of the mitochondrial cytochrome oxidase I gene showed that our samples of B. tabaci populations from Venezuela fall within NW and MEAM1 groups. In this survey, MEAM1 was predominant over NW whitefly in a proportion of 35:1. No evidence was observed for gene flow between indigenous and invader whitefly. Altogether, our results stress the urgency for controlling the proliferation of the invasive whitefly.     

Loop-mediated isothermal amplification for rapid identification of biotypes B and Q of the globally invasive pest Bemisia tabaci, and studying population dynamics

BACKGROUND: Bemisia tabaci, the sweetpotato whitefly, is a globally invasive pest that causes serious agricultural damage by transmitting plant viruses. This pest forms a cryptic species complex that displays morphologically indistinguishable biotypes. Among them, the B and Q biotypes are the most important pests worldwide. Because they have different levels of insecticide resistance, these biotypes must be identified in order to achieve proper pest control. Therefore, a convenient, rapid and specific detection method for identifying the two biotypes is necessary. RESULTS: Loop‐mediated isothermal amplification (LAMP) was employed for rapid identification of B. tabaci B and Q biotypes. By combining a quick DNA extraction method, identification of the two biotypes was achieved within 1 h of detection time. The LAMP assay was applied to study the dynamics of B. tabaci biotypes both in the field and in greenhouses. It was found that, while temperature may be important for population dynamics of the whitefly in the field, population dynamics in greenhouse conditions may be influenced by the types of insecticide. CONCLUSION: The newly designed LAMP assay is a simple, rapid and accurate method for identifying the B and Q biotypes. It can be conducted by non‐specialists and can contribute to pest management. Copyright © 2012 Society of Chemical Industry     

Biotype and insecticide resistance status of the whitefly Bemisia tabaci from China

BACKGROUND: Resistance to numerous insecticide classes in Bemisia tabaci Gennadius has impaired field control efficacy in south‐eastern China. The biotype and resistance status of B. tabaci collected from these areas was investigated. RESULTS: Two different biotypes of B. tabaci (B‐biotype and Q‐biotype) were detected in south‐eastern China, and the samples collected from geographical regions showed a prevalence of the Q‐biotype and the coexistence of B‐ and Q‐biotypes in some regions. Moderate to high levels of resistance to two neonicotinoids were established in both biotypes (28–1900‐fold to imidacloprid, 29–1200‐fold to thiamethoxam). Medium to high levels of resistance to alpha‐cypermethrin (22–610‐fold) were also detected in both biotypes. Four out of 12 populations had low to medium levels of resistance to fipronil (10–25‐fold). Four out of 12 populations showed low levels of resistance to spinosad (5.7–6.4‐fold). All populations tested were susceptible to abamectin. CONCLUSION: The Q‐biotype B. tabaci is supplanting the B‐biotype which used to be ubiquitous in China. Field populations of both B‐ and Q‐biotypes of B. tabaci have developed high levels of resistance to imidacloprid and thiamethoxam. Abamectin is the most effective insecticide against adult B. tabaci from all populations. Copyright © 2010 Society of Chemical Industry     

Detection of Bemisia tabaci Mediterranean cryptic species on soybean in São Paulo and Paraná States (Brazil) and interaction of cowpea mild mottle virus with whiteflies

Since the detection of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) species in Brazil in the early 1990s, this whitefly has been the predominant species and the main viral vector in the country. In this work, whiteflies were collected from commercial soybean fields near and far from greenhouses where Mediterranean (MED) species had previously been detected infesting vegetable crops. Results indicated that MEAM1 was the predominant whitefly species in soybean in most sampling sites, while MED was found colonizing soybean plants in open field conditions alone and/or with MEAM1 in several places. Among the tested insects, MED species was mostly detected harbouring the facultative endosymbiont Hamiltonella. We also detected cowpea mild mottle virus (CPMMV) infecting soybean plants. Transmission assays demonstrated that MED species was more efficient transmitting CPMMV from beans to beans and from soybean to soybean plants than MEAM1, while MEAM1 was more efficient in transmitting the virus from soybean to bean than MED. Performance assays indicated that adult emergence of both species on CPMMV-infected soybean plants was higher when compared with the emergence on healthy plants. Moreover, nonviruliferous MED and MEAM1 adults preferred to settle more often on healthy plants, while viruliferous adults settled more often on CPMMV-infected soybean plants. As MED has already been found in soybean open fields in São Paulo and Paraná States, Brazil, and it is a good vector of CPMMV, we anticipate problems related to whitefly management and to increase in the incidence of the virus in soybean.     

中国部分农区作物上本地烟粉虱隐种的鉴定

烟粉虱Bemisia tabaci是一个至少包括36个不同隐种的物种复合体,为明确中国本地烟粉虱隐种的分布,采用线粒体COI基因(mt COI)分子标记法对2011—2012年在中国27个省(市)61个烟粉虱种群中获得的45个非B/Q隐种烟粉虱个体进行了隐种鉴定和分析,并利用邻接法基于mt COI序列构建了本地烟粉虱隐种的系统发育树。结果显示:45个非B/Q隐种烟粉虱对应的45条线粒体COI序列中共有10个单倍型,所有单倍型分别属于烟粉虱Asia II 2、Asia II 6、Asia II 7、Asia I与China1隐种,均为我国本地隐种。其中,在安徽省发现烟粉虱Asia II 2和China1隐种,在福建省发现Asia II 6和China1隐种,在海南省发现Asia II和Asia I隐种,在广东省发现Asia II 7隐种,在江西省发现China1隐种。表明中国部分农区作物上仍然存在少量的本地烟粉虱。     

传播木尔坦棉花曲叶病毒的烟粉虱隐种鉴定

为明确广东地区传播木尔坦棉花曲叶病毒(Cotton leaf curl Multan virus,CLCu Mu V)的烟粉虱隐种,采用分子鉴定、烟粉虱传毒试验与分子检测的方法,对传播CLCu Mu V的烟粉虱隐种进行了鉴定。结果表明:在广东棉花、红麻和黄秋葵曲叶病发生的田间,2014年采集的30头烟粉虱mt COI与Asia II 7隐种序列同源性为98.3%~99.6%,2015年采集的10头烟粉虱中,8头烟粉虱mt COI与MEAM1隐种序列同源性为99.2%~99.5%,2头烟粉虱mt COI与Asia II 7隐种序列同源性为99.8%~99.9%,说明烟粉虱种群包括入侵隐种MEAM1和土著隐种Asia II 7。在利用烟粉虱人工传毒试验中,MEAM1、Asia II 7和Asia II 1这3个隐种均可在棉花曲叶病株上饲毒获得CLCu Mu V及β卫星分子;除MEAM1隐种外,Asia II 7、Asia II 1隐种可传播CLCu Mu V,侵染红麻及黄秋葵植株引起曲叶病,前者传毒效率分别为50%和100%;而后者为33%和100%。以上3个烟粉虱隐种传毒接种棉花未见成功。     

Analysis of Iris yellow spot virus replication in vector and non‐vector thrips species

Iris yellow spot virus (IYSV, genus Tospovirus) is a viral disease of bulb and seed onion crops and is transmitted by Thrips tabaci. Foliage damage of up to 75% has been reported in Kenya and Uganda. In this study, the rate of IYSV replication in the larva, pupa and adult stages of T. tabaci and other non‐vector thrips species and colour forms such as Frankliniella occidentalis, F. schultzei (dark) and F. schultzei (pale) was evaluated by monitoring relative levels of nucleocapsid (N) and non‐structural (NSs) proteins using N‐ and NSs‐specific antibodies. The effect of IYSV replication on mortality of thrips was also determined. N protein levels increased in all three stages of IYSV‐fed T. tabaci, indicating replication of IYSV. In IYSV‐fed non‐vector thrips, the increase of N protein levels in the larval stage was lower than IYSV‐fed T. tabaci but higher than their healthy counterparts. The N protein levels did not increase at pupal and adult stages. NSs protein was not detected in first instar of either vector or non‐vector thrips species. After a 4 h post‐acquisition period, a significant increase in NSs proteins was only observed in IYSV‐fed T. tabaci, clearly differentiating vectors and non‐vectors of IYSV. IYSV replication did not influence the survival of the vector thrips species, T. tabaci populations or the non‐vector thrips species. This study indicates the effectiveness of monitoring non‐structural proteins such as NSs, compared to nucleocapsid proteins, for differentiating vectors and non‐vectors of IYSV.     

两种蚜小蜂对烟粉虱MED隐种的田间笼罩控效评价

为明确烟粉虱Bemisia tabaci MED隐种优势寄生蜂海氏桨角蚜小蜂Eretmocerus hayati ZolnerowichRose与浅黄恩蚜小蜂Encarsia sophia GiraultDodd对其控制效果的影响,在棉田尼龙纱网笼罩中释放烟粉虱之后,再分别单独释放海氏桨角蚜小蜂、浅黄恩蚜小蜂以及二者以不同比例组合(1∶1、1∶3、3∶1)释放,定期调查统计2种蚜小蜂对烟粉虱的寄生量和烟粉虱的种群动态。结果表明,相对于不放蜂对照,自首次放蜂后40 d开始,所有放蜂处理均能显著降低烟粉虱若虫种群密度,每100 cm~2叶片上均少于1.00头,但各处理间的烟粉虱种群密度无显著差异;海氏桨角蚜小蜂和浅黄恩蚜小蜂以3∶1比例组合释放的处理中对烟粉虱的寄生量最高,每100 cm~2棉花叶片上能达到4.25头。表明在棉田中对烟粉虱进行生物防治时,以初级寄生蜂海氏桨角蚜小蜂与复寄生蜂浅黄恩蚜小蜂为3∶1的比例释放,可以到达较好的控制效果。     

High-throughput allelic discrimination of B and Q biotypes of the whitefly, Bemisia tabaci, using TaqMan allele-selective PCR

BACKGROUND: B and Q biotypes of the whitefly, Bemisia tabaci (Gennadius), are generally regarded as the most significant given their global distribution and strong resistance to insecticides. Since these biotypes can coexist and differ markedly in their insecticide resistance profiles, a rapid but reliable means of discriminating between them would be a valuable complement to resistance monitoring and management programmes. Recently, PCR‐based methods have been developed to determine the biotype status of B. tabaci populations. However, these require post‐amplification procedures, which increase time and labour. RESULTS: The authors have developed an allelic discrimination real‐time PCR assay using fluorescent dye‐labelled probes to distinguish the B and Q biotypes. The assay targets a single nucleotide polymorphism (SNP) in the mitochondrial cytochrome oxidase I (mtCOI) gene. To evaluate the assay, DNA was extracted from individual whiteflies of six known biotype strains, and all scored correctly as either a B or Q biotype. As further validation, 72 individuals from field samples collected in different parts of the world were also tested by the assay. No failed reactions were observed, with all 72 samples scoring clearly as either the B or Q biotype. CONCLUSION: The development of this rapid and high‐throughput assay has important potential for routine monitoring of B and Q biotypes on ornamental plants and for the screening of B. tabaci populations in countries where these biotypes are not yet established. Copyright © 2007 Society of Chemical Industry     

The transmission of geminiviruses by Bemisia tabaci

The cosmopolitan whitefly species, Bemisia tabaci (Gennadius) and Trialeurodes taporariorum (Westwood) have always been regarded as pests to a large range of worldwide crops. Both species are capable of transmitting plant viruses, with T. vaporariorum being the vector of only a few ‘clostero’-like viruses and B. tabaci the vector of viruses in several groups. The largest group of viruses transmitted by B. tabaci are the geminiviruses and B. tabaci is known to transmit around 60 members. Until recently, B. tabaci had been associated with only a limited range of host plants within any one region, although its total potential host range was large. Virus transmission was confined within the plant host range of each regional population of B. tabaci. The emergence of the polyphagous ‘B’ biotype of B. tabaci with its increased host range of more than 600 plant species, has resulted in geminiviruses infecting previously unaffected crops. As the ‘B’ biotype spreads further into Europe, European field and glasshouse crops have been shown to be susceptible to whitefly-transmitted viruses already endemic to other parts of the world. More than 20 colonies of B. tabaci, including both ‘B’ and non-‘B’ biotypes from disparate global locations have been compared for their ability to transmit more than 20 geminiviruses. All but two highly host-specific colonies were capable of transmitting most geminiviruses tested. However, some viruses were transmitted more efficiently than others. The virus coat protein or capsid is essential for vector recognition and transmission. By comparing transmissible viruses at the molecular level to viruses that are no longer whitefly-transmissible, the active epitope on the virus coat protein could be identified for designing future virus control strategies.     

New invasion of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Mediterranean species in Brazil associated to ornamental plants

In Brazil, the first major invasion event of Bemisia tabaci was that of Middle East–Asia Minor 1 (MEAM1) species, formerly termed as B biotype, which commenced in the 1990s mainly by ornamental plants in São Paulo State. More than two decades after this invasion, the presence of the Mediterranean (MED) species of B. tabaci, formerly Q biotype, was reported in Rio Grande do Sul, the southernmost State of Brazil, and now in São Paulo and Paraná States, in southeastern Brazil. Specimens of whiteflies collected from commercial begonia, hydrangea, petunia and poinsettia greenhouses in São Paulo, and also from begonias and poinsettias collected in flower shops in Paraná, were all identified as belonging to MED species. Furthermore, the secondary endosymbionts Arsenophonus, Hamiltonella and Rickettsia of MED from São Paulo and Paraná were detected by PCR and their presence confirmed by sequencing and FISH analysis, and those results differed from MED detected in Rio Grande do Sul that harbored only Hamiltonella and Cardinium. Our results suggest a new MED invasion into Brazil and is associated with ornamental plants. The two MED populations are genetically different and suggest that they are separate invasions.     

Control of three major bollworm pests of cotton in Pakistan by a single application of their combined sex pheromones

Abstract

In the Punjab province of Pakistan, cotton is subject to attack by three major bollworm pests: Pectinophora gossypiella, Earias vittella and £ insulana. Because of the difficulty of controlling these pests once their larvae have penetrated the bolls, early season control is essential. A non‐toxic method is desirable if beneficial insects are not to be destroyed. Tests with a Mitsubishi ‘twist‐tie’ pheromone formulation containing the major components of Pectinophora and the two Earias spp. achieved almost complete trap suppression of all three species for up to eight weeks duration following a single application at the pin‐square stage. Visual observations confirmed a complete lack of moth activity indicating that control by mating disruption was attainable.     

Evaluation of Datura stramonium and Nicandra physaloides as reservoirs of tomato severe rugose virus and whiteflies

Tomato severe rugose virus (ToSRV) is the most important begomovirus transmitted and spread by the whitefly Bemisia tabaci in tomato crops in Brazil. Cultural practices are being adopted, along with insecticides, for controlling this virus. However, little is known about the importance of weeds in the pathosystem, which can contribute to the failure of these practices. This work aimed to evaluate the role of Datura stramonium and Nicandra physaloides as alternative hosts of ToSRV and verify the viral influence on the biological performance of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species. N. physaloides was a better alternative host for ToSRV when combined with MEAM1 whiteflies, while D. stramonium was mostly a good host for whitefly reproduction. Viral infection improved MEAM1 performance on both host plants but affected MED performance negatively. These data suggest that both weeds can be of some importance for the pathosystem, and their control should be included in management programmes.     

L-阿拉伯糖对B型和Q型烟粉虱毒性及取食行为的影响

为明确L-阿拉伯糖对B型和Q型烟粉虱毒性及其取食行为的影响,调查了饲喂含有L-阿拉伯糖人工饲料后烟粉虱的死亡率,利用刺吸电位技术(EPG)记录其取食行为,并观察了饲喂后其在人工饲料膜上的刺孔数量及直径。结果表明,B型和Q型烟粉虱的校正死亡率均随L-阿拉伯糖浓度及饲喂时间的增加而升高;在3种浓度下,B型烟粉虱校正死亡率均显著高于Q型烟粉虱;在5%、10%浓度下,Q型烟粉虱校正死亡率分别在第5天和第3天达100%,B型烟粉虱分别在第3天和第2天达到100%;5%L-阿拉伯糖对B型烟粉虱取食行为影响比Q型大;在5%浓度下,B型和Q型烟粉虱在膜上的刺孔数量总体少于对照组。研究表明,L-阿拉伯糖对烟粉虱具有杀虫活性,且对B型和Q型烟粉虱的毒性效果不同。