Tomato yellow leaf curl virus infection of tomato does not affect the performance of the Q and ZHJ2 biotypes of the viral vector Bemisia tabaci

Abstract To better understand the etiology of begomovirus epidemics in regions under invasion we need to know how indigenous and invasive whitefly vectors respond to virus infection. We investigated both direct and indirect effects of infection with Tomato yellow leaf curl virus (TYLCV) on the performance of the invasive Q biotype and the indigenous Asian ZHJ2 biotype of whitefly Bemisia tabaci. The Q biotype performed better than the ZHJ2 biotype on either uninfected or virus‐infected tomato plants. However, virus‐infection of host plants did not, or only marginally affected, the performance of either biotype of whiteflies in terms of fecundity, longevity, survival, development and population increase. Likewise, association of the vectors with TYLCV did not affect fecundity and longevity of the Q or ZHJ2 biotypes on cotton, a non‐host of TYLCV. These results indicate that the alien Q biotype whitefly, but not the indigenous ZHJ2 biotype, is likely to become the major vector of TYLCV in the field and facilitate virus epidemics.     

Vector-virus mutualism accelerates population increase of an invasive whitefly

The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. This variation in relationships may affect the process of biological invasion and the displacement of indigenous species by invaders when the invasive and indigenous organisms occur with niche overlap but differ in the interactions. The notorious invasive B biotype of the whitefly complex Bemisia tabaci entered China in the late 1990s and is now the predominant or only biotype in many regions of the country. Tobacco curly shoot virus (TbCSV) and Tomato yellow leaf curl China virus (TYLCCNV) are two whitefly-transmitted begomoviruses that have become widespread recently in south China. We compared the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on healthy, TbCSV-infected and TYLCCNV-infected tobacco plants. Compared to its performance on healthy plants, the invasive B biotype increased its fecundity and longevity by 12 and 6 fold when feeding on TbCSV-infected plants, and by 18 and 7 fold when feeding on TYLCCNV-infected plants. Population density of the B biotype on TbCSV- and TYLCCNV-infected plants reached 2 and 13 times that on healthy plants respectively in 56 days. In contrast, the indigenous ZHJ1 performed similarly on healthy and virus-infected plants. Virus-infection status of the whiteflies per se of both biotypes showed limited effects on performance of vectors on cotton, a nonhost plant of the viruses. The indirect mutualism between the B biotype whitefly and these viruses via their host plants, and the apparent lack of such mutualism for the indigenous whitefly, may contribute to the ability of the B whitefly biotype to invade, the displacement of indigenous whiteflies, and the disease pandemics of the viruses associated with this vector.     

Different transmission efficiencies may drive displacement of tomato begomoviruses in the fields in Taiwan

A progressive displacement of Tomato leaf curl Taiwan virus (ToLCTWV) by Tomato yellow leaf curl Thailand virus (TYLCTHV) from 2005 to 2009 has been recorded in tomato fields in Taiwan. Begomoviruses are exclusively transmitted by Bemisia tabaci complex, so we hypothesised that the displacement of tomato begomoviruses in the fields may be due to the invasion of a new virus/vector and the different transmission efficiencies of the viruses by the vectors. The objective of this research was to compare the transmission efficiency of TYLCTHV and ToLCTWV by the B and Q biotypes of B. tabaci complex. When transmission efficiency, virus retention in vector, and latent period for vector transmission were compared, the B biotype transmitted TYLCTHV and ToLCTWV more efficiently than did the Q biotype, and transmitted TYLCTHV more efficiently than ToLCTWV. The B biotype retained both viruses and remained infective throughout adulthood, but the Q biotype did not keep its infectivity, although it did retain both viruses lifelong. The B biotype transmitted TYLCTHV and ToLCTWV with the shortest latent period. In summary, B. tabaci B biotype and TYLCTHV is the best alliance for disease transmission, so we conclude that this may be one of drivers responsible for the displacement of ToLCTWV by TYLCTHV in tomato fields in Taiwan.     

烟粉虱及海氏桨角蚜小蜂对中国番茄黄化曲叶病毒感染烟草的嗅觉反应

双生病毒可通过调控寄主植物促进媒介昆虫烟粉虱种群增长,然而病毒侵染植物后是否通过调控植物挥发物来影响烟粉虱及其天敌的嗅觉反应还未见报道。【目的】本文旨在研究烟草植株感染中国番茄黄化曲叶病毒(Tomato yellow leaf curl China virus,TYLCCNV)后对烟粉虱Bemisia tabaci(Gennadius)及其重要寄生性天敌海氏桨角蚜小蜂Eretmocerus hayati(Zolnerowich and Rose)嗅觉反应行为的影响。【方法】利用Y形嗅觉仪方法,我们测试了烟粉虱及海氏桨角蚜小蜂对带毒植株、健康植株及烟粉虱危害植株的选择偏好性。【结果】烟粉虱及海氏桨角蚜小蜂选择携带TYLCCNV病毒的烟草显著多于健康烟草植株,但烟草被病毒与烟粉虱共同侵染时,烟粉虱对带毒烟草的选择仍显著多于无毒植株,而寄生蜂虽然仍较多选择带毒植株,但无显著差异。【结论】这些结果表明烟粉虱及海氏桨角蚜小蜂偏好选择携带TYLCCNV病毒的烟草,但这种偏好作用在烟粉虱取食共同危害时有一定程度的减弱。本研究首次报道了双生病毒侵染植物可增加烟粉虱及其天敌对植物的选择作用,并就其功能及机制进行了讨论。     

新疆地区烟粉虱生物型的区域分布及其携带的番茄黄化曲叶病毒检测

【目的】明确不同烟粉虱Bemisia tabaci (Gennadius)生物型在新疆地区的区域分布及其携带番茄黄化曲叶病毒的情况。【方法】本文利用烟粉虱mtDNA COⅠ基因片段作标记以及番茄黄化曲叶病毒(tomato yellow leaf curl virus, TYLCV)特异性引物, 鉴定新疆不同地区烟粉虱生物型, 并检测其携带TYLCV情况。【结果】石河子市、 博乐市、 岳普湖县、 泽普县、 叶城县、 莎车县、 墨玉县、 和田市与和田县烟粉虱属于B型烟粉虱, 且720 bp COⅠ基因序列一致性为100%; 阿克苏市、 哈密市、 鄯善县、 乌鲁木齐市、 克拉玛依市与伊宁市烟粉虱属于Q型烟粉虱, 720 bp COⅠ基因序列一致性为99.9%~100%; 吐鲁番市与库尔勒市兼有B型烟粉虱和Q型烟粉虱。伊宁市、 乌鲁木齐市、 鄯善县、 哈密市、 阿克苏市、 库尔勒市、 莎车县、 和田县和墨玉县的烟粉虱样本携带TYLCV, 除2011年底已经暴发危害的莎车县外, 其他区域均为番茄黄化曲叶病毒病发生的高风险区域。【结论】本研究为新疆地区烟粉虱及番茄黄化曲叶病毒病的科学防控提供依据。     

Acquisition and Transmission of two Begomoviruses by the B and a non-B Biotype of Bemisia tabaci from Zhejiang, China

Acquisition and transmission was studied of Tomato yellow leaf curl China virus (TYLCCNV) and Tobacco curly shoot virus (TbCSV) by the B and a non‐B biotype (China‐ZHJ‐1) of Bemisia tabaci from Zhejiang, China. The frequency of TYLCCNV and TbCSV detection by PCR in whitefly adults increased with increasing length of feeding on virus‐infected plants. The virus DNA was detected by PCR in 40% of the B biotype adults tested after a period of 30 min access to infected plants and in all adults after a 12‐h period of access. All ZHJ‐1 adults acquired TYLCCNV and TbCSV after a 48‐h period of access to the virus‐infected plants. Viruliferous B and ZHJ‐1 adults retained TYLCCNV DNA for their entire life when placed on healthy cotton plants. Viruliferous ZHJ‐1 adults retained TbCSV DNA for their entire life when placed on healthy cotton plants but the B biotype adults did not. Transmission of TYLCCNV was achieved with one B or ZHJ‐1 adult per plant, and the probability of transmission reached 100% when the number of adults was increased to 10 per plant. The efficiency for TYLCCNV transmission to healthy plants by adults of both B and ZHJ‐1 was much higher than that for TbCSV.     

烟粉虱携带番茄黄化曲叶病毒检测及其传入山东省的考证

【背景】番茄黄化曲叶病毒（TYLCV）是由媒介昆虫烟粉虱传播的一种双生病毒,对蔬菜及烟草等经济作物造成严重危害。前人资料表明,该病毒于2006年传人我国南方地区,2007年传人山东省,2008年后在山东各地逐渐蔓延扩散。【方法】为了考证TYLcV传人山东省的时间,本研究利用mtCOI基因对于2005和2006年7—8月份在山东省不同地区作物上共采集的15份烟粉虱样品进行了生物型鉴定,并进一步检测了烟粉虱携带TYLCV情况,同时对PCR扩增产物进行了测序分析。【结果】2005年的4份样品烟粉虱生物型均为B型,均不携带TYLCV。2006年的11份烟粉虱样品为B型与Q型混合样品,其中,2份烟粉虱样品检测到TYLCV,进一步证实该病毒为TYLCV。【结论与意义】本研究首次证实了TYLCV早在2006年就已经传入山东省。研究结果不仅对于防控该病毒具有重要指导意义,而且对于其入侵生物学研究也具有重要参考价值。     

辽宁省冬季温室内越冬粉虱伪蛹的种类鉴定及烟粉虱体内番茄黄化曲叶病毒的检测

为了揭示辽宁省冬季温室内越冬粉虱伪蛹的种类及烟粉虱Bemisia tabaci （Gennadius）携带番茄黄化曲叶病毒（tomato yellow leaf curl virus, TYLCV）情况, 于2012年1月份在辽宁省不同县市区的温室作物上采集了17份粉虱伪蛹样品（每样品含30头粉虱伪蛹） , 镜检鉴别粉虱种类并利用mtCOI基因对烟粉虱生物型进行了鉴定; 检测了烟粉虱携带TYLCV情况并对其PCR扩增产物进行了测序分析。结 果表明： 辽宁省冬季温室内存在越冬温室白粉虱Trialeurodes vaporariorum （Westwood）与烟粉虱。17份粉虱样品中, 11份样品为烟 粉虱样品, 6份样品为温室白粉虱和烟粉虱混合样品。混合样品中, 温室白粉虱仅在锦州凌海（LH）样品中占优势。17份烟粉虱样品（包 括混合样品）中, 仅有4份样品为B型与Q型混合样品, 其他13份样品烟粉虱生物型均为Q型。17份烟粉虱样品中有3份Q型烟粉虱样品检测 到TYLCV, 系统树分析进一步证实该病毒是TYLCV。调查结果为辽宁省粉虱与TYLCV的早期测报和防控提供了科学依据。     

烟粉虱传播双生病毒研究进展

综述了烟粉虱Bemisia tabaci对双生病毒的获取、传播及存留等方面的特性。烟粉虱最短的获毒和接种时间为15～30 min;双生病毒在烟粉虱体内可存留1至数周,有的终身存在。烟粉虱对双生病毒的传毒效率除了随其获毒及传毒时间的延长、传毒烟粉虱个体数量的增加以及病毒体浓度的增加而提高外,还与烟粉虱的龄期及性别有关。双生病毒除了在植物与粉虱之间直接传播外,还可通过烟粉虱交配及经卵携带的途径在烟粉虱个体和代别间进行传播。寄主植物、双生病毒的一些特殊蛋白以及烟粉虱内共生菌产生的GroEL蛋白,都可影响烟粉虱携带的双生病毒种类及传毒的可能性。双生病毒可对烟粉虱的发育、存活和生殖产生不利或有利的影响。雌成虫携带番茄黄化曲叶病毒（tomato yellow leaf curl virus, TYLCV）后,存活力和生殖力均下降; 而携带番茄斑驳病毒（tomato mottle virus, ToMoV）后,生殖力提高。此外,植物感染双生病毒后,其对烟粉虱的适合性可能提高。     

Induced systemic resistance to tomato leaf curl virus and increased yield in tomato by plant growth promoting rhizobacteria under field conditions

The talc-based formulation of two Pseudomonas fluorescens strains (Pf1 and VPT10) and its mixture (with and without chitin) were tested against tomato leaf curl virus in tomato under greenhouse and field conditions. The mean percentage of tomato leaf curl virus infected plants were significantly lower (25%) with less symptom severity and delayed symptom expression up to nine additional days in Pseudomonas with chitin (VPT10 + chitin) treated tomato plants compared to non-bacterised control plants upon challenge inoculation with tomato leaf curl virus. Tomato leaf curl virus was partially purified and antiserum was developed. Using the antiserum the tomato leaf curl virus was detected in symptomatic leaves and in whitefly vector through direct antigen coating enzyme linked immunosorbent assay which revealed the low virus titre in Pseudomonas treated plants (VPT10 + chitin) and insect vector compared to untreated tomato plants. The results indicate the potentiality of plant growth promoting rhizobacteria strains and talc-powder formulations in the effective management of this tomato leaf curl virus in tomato under field conditions.     

Begomoviruses Associated with Leaf Curl Disease of Tomato in Java,Indonesia*

We report that several begomoviruses are associated with tomato leaf curl disease in Java, Indonesia. Tomato plants with leaf curl symptoms were collected from Bandung (west Java), Purwokerto (central Java), Magelang (central Java) and Malang (east Java) of Indonesia, the major tomato‐growing areas of the country. Viruses were detected using the polymerase chain reaction (PCR), with universal primers for the genus Begomovirus. PCR‐amplified fragments were cloned and sequenced. Based on sequence comparisons and phylogenetic analyses, the viruses were divided into three groups. With respect to amino acid (aa) identities of the N‐terminal halves of the coat proteins compared in this study, group I was most closely related to Ageratum yellow vein virus (AYVV) (97%), Ageratum yellow vein China virus‐[Hn2] (AYVCNV‐[Hn2]) (96%) and Ageratum yellow vein virus‐[Taiwan] (AYVV‐[Tai]) (95%), and ageratum‐infecting begomovirus from Java (99%). Group II had high sequence identity with a tentative species of tomato leaf curl Java virus (ToLCJAV) (96% aa) for the CP. Group III was most closely related to a proposed species of Pepper yellow leaf curl Indonesia virus (PepYLCIDV) (90% aa identity) by its partial CP sequence.     

Performance on different host plants of an alien and an indigenous Bemisia tabaci from China

The capacity of the Middle East‐Asia Minor 1 putative species of the whitefly Bemisia tabaci (Gennadius) species complex, commonly referred to as the ‘B biotype’, to invade has often been linked to its presumed wider host range than the indigenous competitors. To determine whether this alien putative species and the indigenous Asia II 1 whitefly putative species, commonly referred to as the ‘ZHJ2 biotype’, differ in their ability to use different host plants, we compared their development, survival and reproduction on eight crop species/cultivars that are commonly cultivated in Zhejiang, China. Of the eight host plants tested, B performed substantially better than ZHJ2 on squash, tomato and tobacco, B and ZHJ2 preformed equally well on cotton and sweet potato, while ZHJ2 performed better than B on kidney bean and pepper. These results indicate that while B generally has a wider host range than many indigenous B. tabaci, an indigenous B. tabaci can perform as well as or better on some host plants. These results combined with the cropping patterns in Zhejiang suggested that the differential capacity to use various host plants between whitefly species is important in mediating the process of invasion by an alien whitefly species.     

Comparison of performance on different host plants between the B biotype and a non-B biotype of Bemisia tabaci from Zhejiang, China

The capacity of the B biotype of the whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), to invade has often been linked to its presumably wider host range than the non‐B indigenous biotypes. However, there are few experimental studies of the relative performance of the B biotype and non‐B biotypes on different host‐plant species. Here, we compared the performance of the B biotype and an indigenous non‐B biotype (China‐ZHJ‐1) of B. tabaci from Zhejiang, China on five commonly cultivated host plants, each from a different family: cotton, tobacco, cabbage, squash, and kidney bean. We also examined the effect of rearing host plants on the performance of the B biotype. Overall, the performance of the B biotype on the five species of plants was much better than that of the indigenous non‐B population. On tobacco, cabbage, and kidney bean, no individuals of ZHJ‐1 completed development to adulthood, whereas the B biotype developed successfully from egg to adult on all three plants. On squash, the B biotype survived better, developed to adulthood earlier and had a higher fecundity than ZHJ‐1. The two biotypes performed more equally on cotton, but even on this plant the B biotype female adults lived nearly twice as long as that of ZHJ‐1 and may have realized a higher life‐time fecundity. The B biotype also showed a substantial capacity to acclimatize to alternative host plants for improved survival and reproduction, on both highly suitable and marginally suitable host plants. We conclude that the host range of the B biotype of B. tabaci may be much wider than those of some indigenous biotypes, and this advantage of the B biotype over the non‐B biotypes may assist in its invasion and displacement of some indigenous biotypes in the field.     

An Invasive Whitefly Feeding on a Virus-Infected Plant Increased Its Egg Production and Realized Fecundity

Background

Plant-pathogenic begomoviruses have a complex association with their insect vectors. The interactions of begomoviruses and reproduction of their vectors are poorly understood. Bemisia tabaci is known to transmit many begomoviruses, and the spread of B. tabaci, especially the B and Q ‘biotypes’, has been accompanied by the epidemics of begomoviruses. One of these identified disease-causing agents was Tomato yellow leaf curl China virus (TYLCCNV).

Methodology/Principal Findings

In this study, we compared the egg production and realized fecundity of two ‘biotypes’ or putative species of the whitefly B. tabaci, including the alien invasive B and the indigenous ZHJ1 from Zhejiang, China, feeding on either healthy or TYLCCNV-infected tobacco plants. The ovary of the whitefly was composed of 12–22 telotrophic ovarioles. According to the morphology of the oocytes and level of yolk content, oocytes in ovarioles were divided into four developmental phases (I-IV). Significantly higher proportion of immature oocytes (phase II, III) and mature oocytes (phase IV) was observed in ovary of females that fed on TYLCCNV-infected tobacco compared to that on healthy plants. Moreover, there was significant increase of eggs laid of B whitefly that fed on TYLCCNV-infected tobacco plants during the early developmental stages. In contrast, the proportion of oocytes of different developmental phases and eggs laid had no significant differences between ZHJ1 whiteflies feeding on TYLCCNV-infected and non-infected host plants.

Conclusions/Significance

The invasive B whitefly benefits from feeding on a begomovirus-infected plant through increased egg production and realized fecundity.     

Tomato yellow leaf curl virus and Tomato leaf curl Taiwan virus Invade South-east Coast of China

An epidemic outbreak of severe yellow leaf curl disease was reported in field grown tomato within Zhejiang Province of China in the autumn–winter cropping season of 2006. A molecular diagnostic survey was carried out based on comparisons of partial and complete viral DNA sequences. Comparison of partial DNA‐A sequences amplified with degenerate primers specific for begomoviruses confirmed the presence of two types of begomoviruses. The complete DNA sequences of five isolates, corresponding to the two types, were determined. Sequence comparisons and phylogenetic analysis revealed that they correspond to two previously identified begomoviruses, Tomato yellow leaf curl virus and Tomato leaf curl Taiwan virus. The satellite DNAβ molecule was not detected in these samples by either PCR or Southern blot hybridization analysis. There has been no previous report of geminivirus disease incidence in Zhejiang Province, indicating that the introduction of these two tomato infecting geminiviruses into the agro‐ecological zone of South‐eastern China is a fairly recent event. The implications for disease control are discussed.     

Chinese tomato yellow leaf curl virus--a new species of geminivirus

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A rapid detection of tomato yellow leaf curl virus using recombinase polymerase amplification-lateral flow dipstick assay

Tomato yellow leaf curl disease which is caused by Tomato yellow leaf curl virus (TYLCV) is economically important and a widely spread tomato disease in China. Rapid and accurate detection methods are important in the control TYLCV. Here, a rapid method was developed to identify TYLCV on the basis of recombinase polymerase amplification (RPA) that can be visualized in 5 min using lateral flow dipsticks. The sensitivity and the specificity of this method were evaluated. This method can detect 0·5 pg DNA after 30 min at 37°C without any expensive instrumentation. In addition, it showed higher sensitivity than a PCR method when purified DNA was used. Moreover, the TYLCV was specifically detected, whereas other viruses infecting tomato produced negative results. The crude tomato extracts used in this assay has potential application in minimally equipped plant clinic laboratories. This method will facilitate the early and rapid detection of TYLCV for the timely application of control measures.     

Incidences and progression of tomato chlorosis virus disease and tomato yellow leaf curl virus disease in tomato under different greenhouse covers in southeast Spain

Epidemics of whitefly‐transmitted Tomato chlorosis virus, Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus have been present in the south east of Spain since the 1990s. A survey was performed in 40 greenhouses and nethouses during 2003 to establish the relationship between the disease incidence and the quality of greenhouse or nethouse coverings, providing a physical protection of crops against whiteflies. For tomato chlorosis virus disease (ToCD), the incidence correlated with the type of greenhouse cover and was most reduced under higher quality covers. Control of tomato yellow leaf curl disease (TYLCD) was achieved only for crops grown in the highest quality greenhouses. TYLCD incidence in tolerant tomatoes remained below 100% within the 5 months of sampling, despite the disease progress rate at the initial stage of the cultivation being higher than that of ToCD, which did reach 100% incidence in many greenhouses. Linear regression analysis showed that the development of ToCD and TYLCD in most of the greenhouses was best described by the monomolecular model and the Gompertz model, respectively. Tomato infectious chlorosis virus was not detected in parallel surveys carried out during this study, although it has been described previously in the area studied.     

Engineering resistance against tomato yellow leaf curl virus (TYLCV) using antisense RNA

One of the most severe diseases of cultivated tomato worldwide is caused by tomato yellow leaf curl virus (TYLCV), a geminivirus transmitted by the whitefly Bemisia tabaci. Here we describe the application of antisense RNAs to interfere with the disease caused by TYLCV. The target of the antisense RNA is the rare messenger RNA of the Rep protein, encoded by the C1 gene. Transgenic Nicotiana benthamiana plants expressing C1 antisense RNA were obtained and shown to resist infection by TYLCV. Some of the resistant lines are symptomless, and the replication of challenge TYLCV almost completely suppressed. The transgenes mediating resistance were shown to be effective through at least two generations of progeny.