Yellow Leaf Curl China Virus Research Articles

An invasive whitefly feeding on a virus-infected plant increased its egg production and realized fecundity.

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

Low frequency of horizontal and vertical transmission of two begomoviruses through whiteflies exhibits little relevance to the vector infectivity

Transmissions of plant viruses between individuals of their vector insects through mating are rare events. Recently, three begomoviruses were found to be transmitted between males and females of the whitefly Bemisia tabaci through mating, and two viruses were shown to be transmitted transovarially to progeny. However, results between reports were not consistent. Here we examined the horizontal and vertical transmission of Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl China virus (TYLCCNV) by the B and Q biotypes of B. tabaci, using virus isolates and whitefly colonies established recently in China. Both TYLCV DNA and TYLCCNV DNA were shown to be transmitted horizontally and vertically by each of the two biotypes of the whitefly, but frequency of transmission was usually low. In transovarial transmission, virus DNA was detected in eggs and nymphs but not in the adults of the first generation progeny, except in the combination of TYLCV and Q biotype whitefly where 2–3% of the offspring adults contained the virus DNA. We also showed that the first generation adults, which developed from eggs of viruliferous whiteflies, were not infective to plants. These results demonstrated that for the viruses and whiteflies tested here low frequency of horizontal and vertical transmission can be expected but these two modes of transmission are unlikely to have much epidemiological relevance in the field.

Viral infection of tobacco plants improves performance of Bemisia tabaci but more so for an invasive than for an indigenous biotype of the whitefly

The ecological effects of plant-virus-vector interactions on invasion of alien plant viral vectors have been rarely investigated. We examined the transmission of Tomato yellow leaf curl China virus (TYLCCNV) by the invasive Q biotype and the indigenous ZHJ2 biotype of the whitefly Bemisia tabaci, a plant viral vector, as well as the influence of TYLCCNV-infection of plants on the performance of the two whitefly biotypes. Both whitefly biotypes were able to acquire viruses from infected plants and retained them in their bodies, but were unable to transmit them to either tobacco or tomato plants. However, when the Q biotype fed on tobacco plants infected with TYLCCNV, its fecundity and longevity were increased by 7- and 1-fold, respectively, compared to those of the Q biotype fed on uninfected tobacco plants. When the ZHJ2 biotype fed on virus-infected plants, its fecundity and longevity were increased by only 2- and 0.5-fold, respectively. These data show that the Q biotype acquired higher beneficial effects from TYLCCNV-infection of tobacco plants than the ZHJ2 biotype. Thus, the Q biotype whitefly may have advantages in its invasion and displacement of the indigenous ZHJ2 biotype.

Differential indirect effects of two plant viruses on an invasive and an indigenous whitefly vector: implications for competitive displacement

AbstractThe role of vector–begomovirus–plant interactions in the widespread invasion by some members of the whitefly species complex Bemisia tabaci is poorly understood. The invasive B biotype of B. tabaci entered China in the late 1990s and had become the predominant or only biotype of the whitefly in many regions of the country by 2005–2006. Meanwhile epidemics of begomoviruses have been observed in many crops including tomato for which Tomato yellow leaf curl China virus (TYLCCNV) and Tomato yellow leaf curl virus (TYLCV) have been identified as two major disease‐causing agents. Here, we conducted laboratory experiments to compare the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on uninfected, TYLCCNV‐infected and TYLCV‐infected plants of tomato cv. Hezuo903, a cultivar that has been widely cultivated in many regions of China. The infection of tomato plants by either of the viruses had no or only marginal effects on the development, survival and fecundity of the B biotype. In contrast, survival and fecundity of the ZHJ1 biotype were significantly reduced on virus‐infected plants compared to those on uninfected plants. Populations of the B biotype on uninfected and TYLCCNV‐infected plants increased at similar rates, whereas population increase of the ZHJ1 biotype on TYLCCNV‐infected plants was affected adversely. These asymmetric responses to virus infection of tomato plants between the B and ZHJ1 biotypes are likely to offer advantages to the B biotype in its invasion and displacement of the indigenous biotype.

Molecular characterization and pathogenicity of tomato yellow leaf curl virus in China

Several tomato production regions in China were surveyed for tomato yellow leaf curl disease (TYLCD), and 31 tomato leaf samples showing TYLCD-like symptoms were collected. The partial or full-length genomes of these isolates were sequenced and tomato yellow leaf curl virus (TYLCV) was detected in Shanghai, Zhejiang, Jiangsu Shandong and Hebei provinces of China. The TYLCV isolates found in China share high sequence identity ([98%) and have more than 97% sequence identity with TYLCVIL[ IL:Reo] (X15656). Phylogenetic relationship analysis reveals that although with little genetic variability, they can form two groups and all the TYLCV isolates in China belong to the group I. An infectious clone of TYLCV-[CN:SH2] (AM282874) was constructed and agro-inoculated into Nicotiana benthamiana, N. tabacum Samsun, N. glutinosa, Solanum lycopersicum, Petunia hybrida, Cucumis sativus, Gossypium hirsutum, S. melongena, and Capsicum annuum. TYLCV-[CN:SH2] can induce severe leaf curling and stunting symptoms in these plants except C. sativus, G. hirsutum, S. melongena and C. annuum.We verified that TYLCV can trans-replicate tomato yellow leaf curl China virus DNA-b in N. benthamiana and S. lycopersicum and induced more severe symptoms with distortion and yellow vein.

Genetic Determinants of Symptoms on Viral DNA Satellites

Begomovirus-DNA-beta disease complexes induce different symptom phenotypes in their hosts. To investigate the genetic determinants of the phenotypic differences, Nicotiana spp. and tomato plants were inoculated with infectious clones of Tobacco curly shoot virus (TbCSV)/TbCSV DNA-beta (TbCSB) and Tomato yellow leaf curl China virus (TYLCCNV)/TYLCCNV DNA-beta (TYLCCNB) pseudorecombinants and showed that TYLCCNB induced characteristic vein-thickening and enation symptoms, while TbCSB only slightly exacerbated the leaf-curling symptoms, regardless of the helper virus being used. The roles of DNA-beta-encoded betaC1 and a 430-nucleotide fragment containing the A-rich region and the putative betaC1 promoter region of the betaC1 gene (referred to as AP) in symptom development were further investigated by constructing hybrid satellites in which the betaC1 coding region or AP was exchanged between the two satellite molecules. A TYLCCNB hybrid with TbCSB betaC1 lost the ability to elicit the vein-thickening and enation phenotypes. TbCSB hybrids containing the TYLCCNB betaC1 or AP fragment failed to induce the characteristic vein thickening and enations. A TYLCCNB hybrid having the TbCSB AP fragment produced the enations, but the number of enations was less and their sizes were reduced. Differently from the phloem-specific pattern of the TYLCCNB promoter, a full-length fragment upstream of the TbCSB betaC1 gene confers a constitutive beta-glucuronidase expression pattern in transgenic tobacco plants. The above results indicate that the DNA-beta-encoded betaC1 protein is the symptom determinant, but the promoter of the betaC1 gene has influence on symptom production.

Trans-Replication of, and Competition Between, DNA β Satellites in Plants Inoculated with Tomato yellow leaf curl China virus and Tobacco curly shoot virus

Tomato yellow leaf curl China virus (TYLCCNV) Y10 isolate (Y10) and Tobacco curly shoot virus (TbCSV) Y35 isolate (Y35), both obtained from Yunnan Province, were each found to be associated with a distinct species of satellite DNA (DNA beta). Here, we demonstrate that both Y10 DNA beta (Y10beta) and Y35 DNA beta (Y35beta) were stably trans-replicated by the noncognate Begomovirus, although the noncognate DNA beta accumulated in plants at a lower level than did the cognate DNA beta. In Nicotiana benthamiana and N. glutinosa plants agroinoculated with Y10+Y10beta+Y35beta or with Y35+Y35beta+Y10beta, all components accumulated in the early stages of infection but, at later stages, the noncognate DNA beta decreased in relative concentration and was undetectable at 80 to 120 days after inoculation. The helper viruses and cognate DNA beta species persisted at higher levels throughout the experiments. When the initiation codon of the betaC1 gene of the cognate DNA beta was mutated, the dominance of the cognate over the noncognate DNA beta in mixed infections was unimpaired. These results imply that the cognate DNA beta competes with the noncognate DNA beta and that the ability for selective maintenance of DNA beta is not controlled by the betaC1 protein.

Efficient virus‐induced gene silencing in plants using a modified geminivirus DNA1 component

Virus-induced gene silencing (VIGS) is currently recognized as a powerful reverse genetics tool for application in functional genomics. DNA1, a satellite-like and single-stranded DNA molecule associated with begomoviruses (Family Geminiviridae), has been shown to replicate autonomously but requires the helper virus for its dissemination. We developed a VIGS vector based on the DNA1 component of tobacco curly shoot virus (TbCSV), a monopartite begomovirus, by inserting a multiple cloning site between the replication-associated protein open reading frame and the A-rich region for subsequent insertion of DNA fragments of genes targeted for silencing. When a host gene (sulphur, Su) or transgene (green fluorescent protein, GFP) was inserted into the modified DNA1 vector and co-agroinoculated with TbCSV, efficient silencing of the cognate gene was observed in Nicotiana benthamiana plants. More interestingly, we demonstrated that this modified DNA1 could effectively suppress GFP in transgenic N. benthamiana or endogenous Su in tobacco plants when co-agroinoculated with tomato yellow leaf curl China virus (TYLCCNV), another monopartite begomovirus that does not induce any viral symptoms. A gene-silencing system in Nicotiana spp., Solanum lycopersicum and Petunia hybrida plants was then established using TYLCCNV and the modified DNA1 vector. The system can be used to silence genes involved in meristem and flower development. The modified DNA1 vector was used to silence the AtTOM homologous genes (NbTOM1 and NbTOM3) in N. benthamiana. Silencing of NbTOM1 or NbTOM3 can reduce tobamovirus multiplication to a lower level, and silencing of both genes simultaneously can completely inhibit tobamovirus multiplication. Previous studies have reported that DNA1 is associated with both monopartite and bipartite begomoviruses, as well as curtoviruses. This vector system can therefore be applied for the study, analysis and discovery of gene function in a variety of important crop plants.

βC1, the pathogenicity factor of TYLCCNV, interacts with AS1 to alter leaf development and suppress selective jasmonic acid responses

Viruses induce pathogenic symptoms on plants but the molecular basis is poorly understood. Here, we show that transgenic Arabidopsis expressing the pathogenesis protein betaC1 of Tomato yellow leaf curl China virus (TYLCCNV), a geminivirus, can phenocopy to a large extent disease symptoms of virus-infected tobacco plants in having upward curled leaves, radialized leaves with outgrowth tissues from abaxial surfaces, and sterile flowers. These morphological changes are paralleled by a reduction in miR165/166 levels and an increase in PHB and PHV transcript levels. Two factors, ASYMMETRIC LEAVES 1 (AS1) and ASYMMETRIC LEAVES 2 (AS2), are known to regulate leaf development as AS1/AS2 complex. Strikingly, betaC1 plants phenocopy plants overexpressing AS2 at the morphological and molecular level and betaC1 is able to partially complement as2 mutation. betaC1 binds directly to AS1, elicits morphological and gene expression changes dependent on AS1 but not AS2, and attenuates expression of selective jasmonic acid (JA)-responsive gene. Our results show that betaC1 forms a complex with AS1 to execute its pathogenic functions and to suppress a subset of JA responses.

Use of the modified viral satellite DNA vector to silence mineral nutrition-related genes in plants: silencing of the tomato ferric chelate reductase gene, FRO1, as an example

Virus-induced gene silencing (VIGS) is potentially an attractive reverse-genetics tool for studies of plant gene function, but whether it is effective in silencing mineral nutritional-related genes in roots has not been demonstrated. Here we report on an efficient VIGS system that functions in tomato roots using a modified viral satellite DNA (DNAmbeta) associated with Tomato yellow leaf curl China virus (TYLCCNV). A cDNA fragment of the ferric chelate reductase gene (FROl) from tomato was inserted into the DNAmbeta vector. Tomato roots agro-inoculated with DNAmbeta carrying both a fragment of FRO1 and TYLCCNV used as a helper virus exhibited a significant reduction at the FRO1 mRNA level. As a consequence, ferric chelate reductase activity, as determined by visualization of the pink FeBPDS3 complex was significantly decreased. Our results clearly demonstrated that VIGS system can be employed to investigate gene function associated with plant nutrient uptake in roots.

Pathogenicity of a naturally occurring recombinant DNA satellite associated with tomato yellow leaf curl China virus

Recombinant DNA beta molecules (RecDNA-Abeta) comprising parts of DNA A and DNA beta associated with tomato yellow leaf curl China virus (TYLCCNV) have been identified in naturally infected tobacco plants. Several examples of the recombinant DNA have been cloned and characterized by sequence analysis. All are approximately half the size of TYLCCNV genomic DNA, and all contain the betaC1 gene and the A-rich region from TYLCCNV DNA beta as well as intergenic region sequences and the 5' terminus of the AC1 gene from TYLCCNV DNA A. RecDNA-Abeta was detected by PCR in five of 25 TYLCCNV isolates. Co-inoculation of TYLCCNV DNA A and RecDNA-Abeta induced symptoms indistinguishable from those induced by TYLCCNV DNA A and DNA beta in Nicotiana benthamiana, Nicotiana glutinosa, Solanum lycopersicum and Petunia hybrida plants, and Southern blot hybridization results showed that RecDNA-Abeta could replicate stably in N. benthamiana plants.

First Report of Ageratum yellow vein virus Causing Tobacco Leaf Curl Disease in Fujian Province, China.

A leaf curling disease was observed on 7% of tobacco plants during December 2005 in research plots in the Cangshan District of Fuzhou, Fujian, China. Tobacco plants were infested with Bemisia tabaci, suggesting begomovirus etiology. To identify possible begomoviruses, total DNA was extracted from four symptomatic leaf samples (F1, F2, F3, and F4). The degenerate primers PA and PB were used to amplify part of the intergenic region and AV2 gene of DNA-A-like molecules (3). A 500-bp DNA fragment was amplified by PCR from all four samples. The PCR products were cloned and sequenced (GenBank Accession Nos. EF531601-EF531603 and EF527823). Alignment of the 500-bp sequences for the four isolates indicated that they shared 98.5 to 99.6% nt identity, suggesting that the plants were all infected by the same virus. Overlapping primers TV-Full-F (5'-GGATCCTCTTTTGAACGAGTTTCC-3') and TV-Full-R (5'-GGATCCCACATGTTTAAAATAATAC-3') were then designed to amplify the full-length DNA-A from sample F2. The sequence was 2,754 nucleotides long (GenBank Accession No. EF527823). A comparison with other begomoviruses indicated the F2 DNA-A had the highest nucleotide sequence identity (95.7%) with Ageratum yellow vein virus (AYVV; GenBank Accession No. X74516) from Singapore. To further test whether DNAβ was associated with the four viral isolates, a universal DNAβ primer pair (beta 01 and beta 02) was used (4). An amplicon of approximately 1.3 kb was obtained from all samples. The DNAβ molecule from F2 was then cloned and sequenced. F2 DNAβ was 1,345 nucleotides long (GenBank Accession No. EF527824), sharing the highest nucleotide sequence identity with the DNAβ of Tomato leaf curl virus (97.2%) from Taiwan (GenBank Accession No. AJ542495) and AYVV (88.8%) from Singapore (GenBank Accession No. AJ252072). The disease agent was transmitted to Nicotiana tabacum, N. glutinosa, Ageratum conyzoides, Oxalis corymbosa, and Phyllanthus urinaria plants by whiteflies (B. tabaci) when field infected virus isolate F2 was used as inoculum. In N. tabacum and N. glutinosa plants, yellow vein symptoms were initially observed in young leaves. However, these symptoms disappeared later during infection and vein swelling and downward leaf curling symptoms in N. tabacum and vein swelling and upward leaf curling in N. glutinosa were observed. In A. conyzoides, O. corymbosa, and P. urinaria plants, typical yellow vein symptoms were observed. The presence of the virus and DNAβ in symptomatic plants was verified by PCR with primer pairs TV-Full-F/TV-Full-R and beta 01/beta 02, respectively. The above sequence and whitefly transmission results confirmed that the tobacco samples were infected by AYVV. In China, Tobacco leaf curl Yunnan virus, Tobacco curly shoot virus, and Tomato yellow leaf curl China virus were reported to be associated with tobacco leaf curl disease (1,3). To our knowledge, this is the first report of AYVV infecting tobacco in China. A. conyzoides is a widely distributed weed in south China and AYVV was reported in A. conyzoides in Hainan Island, China (2). Therefore, this virus may pose a serious threat to tobacco production in south China.

Efficiency for Gene Silencing Induction in Nicotiana Species by a Viral Satellite DNA Vector

Abstract Virus‐induced gene silencing (VIGS) is a useful technique for rapid plant gene function analysis. We recently reported a new VIGS vector modified from Tomato yellow leaf curl China virus (TYLCCNV) DNAβ (DNAmβ). In this study we compared in detail DNAmβ‐induced gene silencing in four Nicotiana species including N. benthamiana, N. glutinosa, N. tabacum and N. paniculata. We found that DNAmβ‐induced gene silencing in the four species was distinct in developing dynamics, tissue specificity, efficiency, and constancy in the plant life span. It was most efficient in N. benthamiana, where development of VIGS was most rapid, without tissue specificity and nearly 100% efficient. DNAmβ‐induced gene silencing in N. glutinosa was also efficient despite being slightly less than in N. benthamiana. It initially occurred in veins, later was scattered to mesophyll, finally led to complete silencing in whole leaves. In both species, VIGS constantly expressed until the plants died. However, DNAmβ‐mediated VIGS in the other two Nicotiana species, N. tabacum and N. paniculata, was significantly less efficient. It was strictly limited within the veins of the silenced leaves, and constantly occurred only over 3–4 weeks. The upper leaves that emerged later stopped showing the silencing phenotype. DNAmβ‐induced gene silencing in N. benthamiana and N. glutinosa was not significantly influenced by the growth stage when the plants were agro‐inoculated, and was not sensitive to high growth temperature up to 32 °C. Our results indicate that this system has great potential as a versatile VIGS system for routine functional analysis of genes in some Nicotiana species.

Tomato leaf curl Guangxi virus is a distinct monopartite begomovirus species

Three begomovirus isolates were obtained from tomato plants showing leaf curl symptoms in Guangxi province of China. Typical begomovirus DNA components representing the three isolates (GX-1, GX-2 and GX-3) were cloned and their full-length sequences were determined to be 2752 nucleotides. Nucleotide identities among the three viral sequences were 98.9–99.7%, but all shared <86.7% nucleotide sequence identity with other reported begomoviruses. The sequence data indicated that GX-1, GX-2 and GX-3 are isolates of a distinct begomovirus species for which the name Tomato leaf curl Guangxi virus (ToLCGXV) is proposed. Further analysis indicated that ToLCGXV probably originated through recombination among viruses related to Ageratum yellow vein virus, Tomato leaf curl China virus and Euphorbia leaf curl virus. PCR and Southern blot analyses demonstrated that isolates GX-1 and GX-2 were associated with DNAβ components, but not isolate GX-3. Sequence comparisons revealed that GX-1 and GX-2 DNAβ components shared the highest sequence identity (86.2%) with that of Tomato yellow leaf curl China virus (TYLCCNV). An infectious construct of ToLCGXV isolate GX-1 (ToLCGXV-GX) was produced and determined to be highly infectious in Nicotiana benthamiana, N. glutinosa, tobacco cvs. Samsun and Xanthi, tomato and Petunia hybrida plants inducing leaf curl and stunting symptoms. Co-inoculation of tomato plants with ToLCGXV-GX and TYLCCNV DNAβ resulted in disease symptoms similar to that caused by ToLCGXV-GX alone or that observed in infected field tomato plants.

Genetic Structure and Population Variability of Tomato Yellow Leaf Curl China Virus

Geminiviruses have circular single-stranded DNA genomes and are important pathogens in tropical and subtropical regions, but their population diversity and variability are poorly understood. Here, we have investigated variations accumulating in Tomato yellow leaf curl China virus (TYLCCNV), a geminivirus in the genus Begomovirus of the family Geminiviridae. The population variation was analyzed in a naturally infected tomato (Solanum lycopersicom) plant and in Nicotiana benthamiana and tomato plants experimentally infected with a swarm of TYLCCNV DNA clones to provide an identical sequence for initiation of infection. Our results demonstrate that the population of TYLCCNV in a naturally infected tomato plant was genetically heterogeneous and that rapid mutation occurred in the populations amplified from N. benthamiana and tomato plants that had been infected with cloned DNA. This feature of the population of TYLCCNV in these plants consisted of the consensus sequence and a pool of mutants that are not identical but are closely related to the consensus sequence, and it coincides with the quasispecies concept described for many RNA viruses. The mutation frequency was circa 10(-4) in N. benthamiana and tomato at 60 days postinoculation, a value comparable to that reported for plant RNA viruses. The quasispecies-like nature of the TYLCCNV populations suggested that TYLCCNV is capable of rapid evolution and adaptation in response to changing agricultural practices.

First report of Tomato yellow leaf curl China virus infecting kidney bean in China

First report of <i>Tomato yellow leaf curl China virus</i> infecting kidney bean in China

Efficient gene silencing induction in tomato by a viral satellite DNA vector

Virus-induced gene silencing (VIGS) in tomato ( Lycopersicon esculentum Mill.) is currently routinely analysed using Tobacco rattle virus (TRV)-based vector. We recently reported a new vector system modified from DNAβ (DNAmβ) of Tomato yellow leaf curl China virus (TYLCCNV) for VIGS analysis in Solanaceous species including tomato. Here, we describe DNAmβ-induced gene silencing in tomato. We found that DNAmβ-induced gene silencing was initiated from vascular tissues, and later scattered to other tissues. Once initiated in seedlings, the silencing phenotype lasted for the entire life span of the plants, was expressed in a variety of tissues and organs including leaf, shoot, stem, flower and fruit, and could be achieved at any growth stage. It was insensitive to temperature as high as 32 °C and no symptoms were observed in silenced plants. The DNAmβ vector worked efficiently in at least seven tomato cultivars, indicating that this system has great potential as a versatile VIGS system for routine functional analysis of genes in tomato.

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.

First report ofTomato yellow leaf curl China viruswith DNA β infectingDatura stramoniumin China

Tomato yellow leaf curl China virus, associated with a satellite DNA β, has been detected in Datura stramonium (jimsonweed) with leaf curl disease for the first time in China.

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

AbstractAcquisition 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.