Pcr-amplification of tomato yellow leaf curl virus (TYLCV) DNA from squashes of plants and whitefly vectors: Application to the study of TYLCV acquisition and transmission

DNA of tomato yellow leaf curl virus (TYLCV), a geminivirus transmitted by the whitefly Bemisia tabaci, was amplified from squashes of infected tomato plants and of viruliferous vectors using the polymerase chain reaction (PCR). Samples of infected tissues as small as 1 mm² were squashed onto a nylon membrane. A 1 × 2 mm strip containing the squash was introduced into a 25 µl PCR reaction mix. The reaction products were subjected to gel electrophoresis, blotted and hybridized with a radiolabeled virus-specific DNA probe. TYLCV DNA was amplified from squashes of leaves, roots, and stem of infected tomato and from individual viruliferous whiteflies. The same squash could be used several times to amplify different virus DNA fragments with various sets of primers. Thus plant and insect squashes can be used as templates for the amplification of geminiviral DNA with no need to prepare tissue extracts or purify nucleic acids. The squash-PCR procedure was applied to study whitefly transmission of TYLCV. Tomato plants were inoculated by placing a single viruliferous insect in the center of a young leaflet. In some plants TYLCV DNA was detected at the site of inoculation as early as 5 min after the beginning of the access feeding and in all plants after 30 min. The squash-PCR procedure also was applied to the study of TYLCV acquisition by the insect vector. TYLCV DNA was detected in the head of whiteflies as early as 5 min after the beginning of the access feeding on infected tomato plants. Viral DNA was detected in the thorax after 10 min and in the abdomen after 25 min.     

Effect of Host Plant Resistance to Tomato yellow leaf curl virus (TYLCV) on Virus Acquisition and Transmission by Its Whitefly Vector

ABSTRACT The effect that Tomato yellow leaf curl virus (TYLCV)-infected resistant tomato plants may have on virus epidemiology was studied. Four tomato genotypes that exhibit different levels of viral resistance, ranging from fully susceptible to highly resistant, served as TYLCV-infected source plants. Viral acquisition and transmission rates by white-flies following feeding on the different source plants were evaluated. TYLCV transmission rate by whiteflies that had fed on infected source plants 21 days postinoculation (DPI), shortly after the appearance of TYLCV symptoms, was negatively correlated with the level of resistance displayed by the source plant. Therefore, the higher the resistance, the lower the transmission rate. In addition, TYLCV DNA accumulation was shown to be lower in the resistant source plants compared with the susceptible plants. Whitefly survival rate, following feeding on source plants 21 DPI, was similar for all the cultivars tested. Significant differences in whitefly survival were found, however, following feeding on the infected source plants at 35 DPI; here, whitefly survival rate increased with higher levels of resistance displayed by the source plant. At 35 DPI, the susceptible plants had developed severe TYLCV disease symptoms, and transmission rates from these plants were the lowest, presumably due to the poor condition of these plants. Transmission rates from source plants displaying a medium level of resistance level were highest, with rates declining following feeding on source plants displaying higher levels of TYLCV resistance. TYLCV DNA accumulation in whiteflies following feeding on infected source plants at both 21 and 35 DPI was directly correlated with viral DNA accumulation in source plants. Results show that, in essence, the higher the resistance expressed, the less suitable the plant was as a viral source. Consequently, following acquisition from a highly resistant plant, TYLCV transmission by whiteflies will be less efficient.     

Rate of Tomato yellow leaf curl virus Translocation in the Circulative Transmission Pathway of its Vector, the Whitefly Bemisia tabaci

ABSTRACT Whiteflies (Bemisia tabaci, biotype B) were able to transmit Tomato yellow leaf curl virus (TYLCV) 8 h after they were caged with infected tomato plants. The spread of TYLCV during this latent period was followed in organs thought to be involved in the translocation of the virus in B. tabaci. After increasing acquisition access periods (AAPs) on infected tomato plants, the stylets, the head, the midgut, a hemolymph sample, and the salivary glands dissected from individual insects were subjected to polymerase chain reaction (PCR) without any treatment; the presence of TYLCV was assessed with virus-specific primers. TYLCV DNA was first detected in the head of B. tabaci after a 10-min AAP. The virus was present in the midgut after 40 min and was first detected in the hemolymph after 90 min. TYLCV was found in the salivary glands 5.5 h after it was first detected in the hemolymph. Subjecting the insect organs to immunocapture-PCR showed that the virus capsid protein was in the insect organs at the same time as the virus genome, suggesting that at least some TYLCV translocates as virions. Although females are more efficient as vectors than males, TYLCV was detected in the salivary glands of males and of females after approximately the same AAP.     

Use of Tomato yellow leaf curl virus (TYLCV) Rep Gene Sequences to Engineer TYLCV Resistance in Tomato

ABSTRACT Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus (family Geminiviridae), causes severe losses in tomato production in the tropics and subtropics. In order to generate engineered resistance, eight different constructs of the TYLCV replication-associated protein (Rep) and C4 gene sequences were tested in transformed tomato inbred lines. Transgenic plants were screened for resistance to TYLCV using viruliferous whiteflies. No symptoms were observed and no TYLCV genomic DNA was detected by both hybridization and polymerase chain reaction in progenies of plants transformed with three constructs. This resistance was observed in plants that contained one of the following transgenes: 2/5Rep (81 nucleotides [nt] of the intergenic region [IR] plus 426 nt of the 5' end of the TYLCV Rep gene), Delta2/5Rep (85 nt of the IR plus 595 nt of the 5' end of the TYLCV Rep gene in the antisense orientation), and RepDelta2/5Rep (81 nt of the IR, the entire Rep gene, and 41 nt 3' to the end of the Rep gene fused to Delta2/5Rep). Our study differs from other transgenic Geminivirus resistance reports involving the Rep gene in that viruliferous whiteflies were used for challenge inoculation instead of agroinoculation or biolistic inoculation, and TYLCV resistance was evaluated under field conditions.     

Co-transmission of <Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> (TYLCV)-Mld and TYLCV-IL by the whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

The ability of the whitefly Bemisia tabaci to transmit two strains of Tomato yellow leaf curl virus, the Israel and Mild strains, was studied after serial transfers of individual whiteflies that were viruliferous for both strains to tomato plants. After single whiteflies had successive acquisition feedings first on a single plant infected with one strain and then on a plant infected with the other strain, the single whiteflies later transmitted intermittently one, the other, or both strains to the test plants during serial transfers at 1-day intervals. Because both strains were found in the head, abdomen, and legs dissected from whiteflies during the retention period after the two successive acquisition feedings, both strains apparently circulate from midgut cells to salivary glands through the hemolymph.     

Epidemiology of tomato yellow leaf curl begomovirus in the Fayium area, Egypt

Tomato yellow leaf curl begomovirus (TYLCV) severely invaded tomato plantations in Egypt (Lower and Middle Egypt) in 1989. This study aimed to discover the relationship between TYLCV and other epidemic-associated factors in the Fayium area. The rate of TYLCV infection was inspected visually for three successive years (1994/1996) in the Fayium area. During the same period, whiteflies were collected for virus detection using bait-plant and DNA hybridization techniques. DAS-ELISA was used to detect mixed virus infections in tomato plants. TYLCV infection was prevalent (60–68%) and severe (2.1–3.0) in the Fayium fields. Cucumber mosaic cucumovirus (CMV) was found in some fields (5–28%) with moderate severity (1.0–20). Potato Y potyvirus (PVY) and potato leaf roll polerovirus (PLRV) were found in few fields (5–19% and 5% respectively) at very low severity. There was a negative correlation between TYLCV occurrence and distance from the source of infection, and a positive correlation (98%) between TYLCV intensity and percentage of viruliferous whiteflies in 1994 and 1995. There was no positive correlation between TYLCV and the total population of whiteflies caught during the same period. Five percent of viruliferous whiteflies, as proved by cDNA hybridization, led to 46% TYLCV infection. The same percentage of whiteflies, as shown by bioassay, led to 68% TYLCV infection. Monitoring of viruliferous whiteflies could be used for early prediction of TYLCV infection.     

The virus-vector relationship of the tomato leafcurl virus (TLCV) and its vector,Bemisia tabaci gennadius (Hemiptera: aleyrodidae)

Basic studies carried out in India showed that the incubation period of TLCV in plants varied from 8 days in August to 90 days in winter. The acquisition threshold for the whitefly,Bemisia tabaci Gen., was 31 min; it resulted in 3% transmission. An acquisition access of 24 h for a female whitefly on a TLCV source resulted in 30% transmission. A minimum feeding period of 32 min was required by a viruliferous whitefly to cause infection on tomato test plants; this gave 4% transmission. With inoculation access of 24 h on tomato test plants, the transmission rose to 24%. Starving the vector for 1 h pre-acquisition or 1 h pre-inoculation resulted in higher levels of transmission of TLCV: 36 and 40%, respectively, compared with 20% for non-starved whiteflies. Extending the fasting period beyond 1 h resulted in a reduced transmission level. The whiteflies could acquire the virus from the cotyledonary leaves of an infected tomato plant, with a resultant 28% transmission; but infection did not occur when the whiteflies had an inoculation access to such leaves. Higher transmission rates were obtained when the younger leaves on tomato plants were used for acquisition and inoculation. Transmission was 8 and 38% when five whiteflies per plant were allowed 24 h of acquisition access to 11- and 2-month-old virus sources, respectively. After an acquisition access of 24 h to a TLCV source, male and female whiteflies retained their infectivity for 5 and 53 days, respectively. Nymphs can acquire and transmit the virus. When ten whiteflies of each sex were given 24 h of acquisition and of inoculation access, the subsequent transmission rate of males and females was 56 and 86%, respectively. This virus is not transovarially transmitted. Whitefly colonies raised on brinjal were more efficient (70 and 84% transmission in two experiments) than those raised on chilli, cotton, cowpea, tobacco or tomato.     

Capsicum Species: Symptomless Hosts and Reservoirs of Tomato yellow leaf curl virus

ABSTRACT Five Capsicum species were tested for susceptibility to Tomato yellow leaf curl virus (TYLCV) and the mild strain of TYLCV (TYLCV-Mld). TYLCV was able to infect 30 of 55 genotypes of C. annuum, one of six genotypes of C. chinense, one of two genotypes of C. baccatum, and the only genotype of C. frutescens tested but was unable to infect the one genotype of C. pubescens tested. This is the first evidence for the susceptibility of C. baccatum, C. chinense, and C. frutescens to TYLCV. Unlike TYLCV isolates, TYLCV-Mld was unable to infect C. chinense. No host differences were observed between the Israeli and Florida isolates of TYLCV. None of the Capsicum species showed symptoms after infection with TYLCV or TYLCV-Mld. TYLCV was detected in fruits of C. annuum, but whiteflies were unable to transmit virus from fruits to plants. White-flies were able to transmit both TYLCV and TYLCV-Mld from infected pepper plants to tomato plants. Pepper plants in research plots were found infected with TYLCV at rates as much as 100%. These data demonstrate the ability of some genotypes of pepper to serve as reservoirs for the acquisition and transmission of TYLCV and TYLCV-Mld.     

Pymetrozine interferes with transmission of<Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> by the whitefly<Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Pymetrozine, a novel compound belonging to the class pyridine-azomethines, is a feeding inhibitor labeled for use against plant pests in the order Hemiptera. Pymetrozine was evaluated for its ability to interfere with whitefly transmission of the begomovirusTomato yellow leaf curl virus (TYLCV). Pymetrozine was applied as Fulfill ^TM 50 WG at two rates (0.291 and 0.582 g formulationl ⁻¹) to tomato seedlings with four to six true leaves. Viruliferous whiteflies (three to five per plant) were added 1, 4, 7 and 11 d after a single application of pymetrozine, and transmission rates were determined 4 wk after the addition of whiteflies. Pymetrozine provided protection against transmission of TYLCV by viruliferous whiteflies for up to 1 wk after a single apliation. No phytotoxicity was observed on tomato transplants. These results indicate that pymetrozine could be an effective tool for tomato transplant producers to protect susceptible transplants from infection by begomoviruses, such as TYLCV. Pymetrozine might also work well as part of an integrated approach to begomovirus management in greenhouse tomato fruit production. http://www.phytoparasitica.org positing Oct. 20, 2003.     

Tomato yellow leaf curl virus in the Dominican Republic: Characterization of an Infectious Clone, Virus Monitoring in Whiteflies, and Identification of Reservoir Hosts

ABSTRACT Epidemics of tomato yellow leaf curl disease (TYLCD) in the Dominican Republic in the early to mid-1990s resulted in catastrophic losses to processing tomato production. As part of an integrated management approach to TYLCD, the complete nucleotide sequence of a full-length infectious clone of an isolate of Tomato yellow leaf curl virus (TYLCV) from the Dominican Republic (TYLCV-[DO]) was determined. The TYLCV-[DO] genome was nearly identical in sequence (>97%) and genome organization to TYLCV isolates from Israel and Cuba. This established that TYLCV-[DO] is a bonafide TYLCV isolate (rather than a recombinant virus, such as isolates from Israel [Mild], Portugal, Japan, and Iran), and provided further evidence for the introduction of the virus from the eastern Mediterranean. A reduction in the incidence of TYLCV in the northern and southern processing tomato production areas of the Dominican Republic has been associated with the implementation of a mandatory 3-month whitefly host-free period (including tomato, common bean, cucurbits, eggplant, and pepper). Monitoring TYLCV levels in whiteflies, by polymerase chain reaction with TYLCV-specific primers, established that the incidence of TYLCV decreased markedly during the host-free period, and then gradually increased during the tomato-growing season. In contrast, TYLCV persisted in whiteflies and tomato plants in an area in which the host-free period was not implemented. Surveys for TYLCV reservoir hosts, conducted to identify where TYLCV persists during the host-free period, revealed symptomless infections in a number of weed species. The implications of these findings for TYLCV management in the Dominican Republic are discussed.     

Comparative spatial dispersal ofTomato yellow leaf curl virus vectored by B and Q biotypes ofBemisia tabaci in Tomato glasshouses

The spatial dispersal patterns ofTomato yellow leaf curl virus (TYLCV) disease vectored by the B and Q biotypes of the whiteflyBemisia tabaci in tomato glasshouses were compared. Tomato plants were arranged in glasshouses and TYLCV-infected plants were placed in the center of each plot. Adult whiteflies of each biotype were released onto TYLCV-infected plants and the insects were then freely dispersed in the glasshouses under high or moderate temperature conditions. The abundance and spatial distribution of dispersed whiteflies did not differ between the B and Q biotypes in tomato glasshouses. The disease incidence and dispersion of TYLCV as a result of short-distance movement of the whiteflies were also similar between the two biotypes, although on several investigation dates there was a tendency for the disease incidence caused by the B biotype to be slightly greater than that caused by the Q biotype. These results demonstrated that the aspects of spatial spread of TYLCV vectored by the B and Q biotypes ofB. tabaci in tomato glasshouses are similar. http://www.phytoparasitica.org posting Dec. 11, 2007.     

番茄黄化曲叶病毒与番茄褪绿病毒复合侵染对番茄黄化曲叶病毒传播的影响

番茄黄化曲叶病毒(tomato yellow leaf curl virus, TYLCV)是一种由烟粉虱传播的单链环状DNA病毒, 在田间可与多种病毒发生复合侵染, 如番茄褪绿病毒(tomato chlorosis virus, ToCV)等?本文对比了TYLCV单独侵染和TYLCV与ToCV复合侵染对烟粉虱获取和传播TYLCV的影响?结果表明, 与取食TYLCV单独侵染的番茄相比, 取食复合侵染番茄的烟粉虱对TYLCV的传毒率显著提高, 且番茄植株和烟粉虱体内TYLCV的病毒积累量也显著提高?试验结果说明复合侵染会提高烟粉虱的传毒率, 促进TYLCV的发生与流行?     

Identification of whitefly transmitted tomato yellow leaf curl geminivirus from Iran and a survey of its distribution with molecular probes

A virus causing a disease of tomato, prevalent in the southern provinces of Iran, with symptoms of leaf-curling, stunting, reduction of leaf size, leaf corrugation, shortening of internodes and severe reduction in fruit yield, was shown to be transmissible to healthy tomato plants by grafting and by whiteflies ( Bemisia tabaci ), but not by sap inoculation. Geminivirus DNA was detected in extracts of diseased tomato plants by dot-blot hybridization assays using as probes full-length cloned DNA of Australian, Italian (Sardinian) or Jordanian strains of tomato yellow leaf curl virus (TYLCV). Geminivirus coat protein was detected in whitefly inoculated plants by dot immunobinding assay using polyclonal antibody raised against Jordanian TYLCV. A limited survey using the dot-blot hybridization assay for virus detection indicated the presence of the virus in tomato-growing provinces of southern but not northern Iran. Whitefly transmission experiments to tomato under controlled greenhouse conditions showed that some isolates of TYLCV-like geminiviruses from different parts of Iran differ in symptomatology.     

Transmission of the Pepino mosaic virus by whitefly

Two experiments were conducted to investigate the transmission of the Pepino mosaic virus (PepMV) by the greenhouse whitefly (Trialeurodes vaporariorum) from tomato to tomato. In the 1:1 system (in which a single virus-contaminated plant was placed next to a healthy plant in a cage containing 469 whiteflies on average) the virus was transmitted to three out of 10 plants. In the 1:4 system (in which a virus-contaminated plant was surrounded by four healthy plants in a cage with 601 whiteflies on average) the virus was transmitted to five out of 32 plants. In order to investigate the mechanism involved in the transmission, the insect bodies were washed to determine the external presence of viral particles. The results showed that the number of PepMV particles carried on whitefly bodies was low, with an average occurrence of 1.33 on the 55 whiteflies tested after the insects were in contact with infected plants for 5 days. This low occurrence was confirmed by observation under microscope, which showed an absence of PepMV-contaminated tomato sap on the insect bodies, suggesting that PepMV transmission by whiteflies could occur when they feed on the plant.     

基于Real-time PCR监测番茄黄化曲叶病毒在番茄植株中的动态变化

 本研究根据番茄黄化曲叶病毒(Tomato yellow leaf curl virus, TYLCV)分离物-SH2基因组序列,设计了一对引物,以番茄25S rRNA基因为内参,建立了番茄黄化曲叶病毒SYBR GreenⅠ实时荧光定量PCR检测方法。该方法可检测到浓度为4.64×10^-7 ng/μL的植物DNA中含有TYLCV,其灵敏度是常规PCR的1 000倍。利用该方法,研究了温室条件下以侵染性克隆接种TYLCV后的番茄植株中病毒DNA含量的变化情况。根、茎、叶中病毒DNA定量检测结果表明,TYLCV在3种植物器官中都呈现一个上升、稳定和下降的变化规律;病毒DNA在植株根部最早累积,累积的速度较慢,在叶部和茎部累积较快;叶部和茎部接种18 d后病毒DNA含量达到稳定期;在不同的器官中,病毒的含量不同,在茎部的含量最高,接种33 d后茎部病毒DNA的含量约为根部的100倍。本研究通过对TYLCV含量的动态监测,明确了病毒DNA在番茄植株中的累积和变化规律,为研究TYLCV侵染机制、病毒与寄主互作及病害防治提供了理论依据。     

Current situation of Tomato yellow leaf curl virus in Portugal

The name Tomato yellow leaf curl virus (TYLCV) has been applied to a group of virus species of the genus Begomovirus in the family Geminiviridae that cause a similar tomato disease worldwide. In 1995, TYLCV was first reported in Algarve (southern Portugal) as responsible for an epidemic outbreak of a severe tomato disease. Molecular data have shown that this Portuguese TYLCV isolate was distinct from those previously reported in Europe, as it belonged to the TYLCV-Israel species ¹ . Since then, TYLCV epidemics have occurred annually, being a limiting factor mainly for autumn/winter glasshouse tomato crops. In 1998, TYLCV was also found associated with the emergence of a novel disease of Phaseolus vulgaris in Algarve. The affected bean plants were severely stunted and gave no marketable yield. However, the disease occurs only sporadically, even in conditions of high TYLCV infection pressure. Recently, Tomato chlorosis virus (ToCV), a whitefly-transmitted bipartite closterovirus (genus Crinivirus , family Closteroviridae ), was found associated with an unusual tomato yellow leaf syndrome, in single or mixed infection with TYLCV. The impact of this new pathosystem on tomato production has yet to be determined. Surveys are in progress in mixed cropping systems infested with whiteflies. So far, TYLCV and ToCV diseases are limited to the Algarve region.     

侵染甜椒的番茄黄化曲叶病毒的分子鉴定和全序列分析

<正>番茄黄化曲叶病毒(Tomato yellow leaf curl virus,TYLCV)在世界范围内可危害多种作物,造成植株矮化、叶片皱缩变形、局部黄化等症状。该病毒自1964年首次报道以来已蔓延至世界多地。在我国2006年上海首次报道该病毒[1],随后江苏、山东、安徽、北京、河北、天津等地相继报道,危害严重。TYLCV为双生病毒科(Geminiviridae)菜豆金色花叶病毒属(Begomovirus)成员,基因组为单组     

Tomato Breeding Lines Resistant and Tolerant to Tomato Yellow Leaf Curl Virus Issued from Lycopersicon hirsutum

ABSTRACT Two tomato yellow leaf curl virus (TYLCV)-resistant plants from accessions LA1777 and LA386 of the wild tomato species Lycopersicon hirsutum have been crossed. The resulting resistant F1 plants were crossed with the domesticated tomato L. esculentum, and a series of selfing was performed. At each generation, individuals were selected for resistance (no symptoms and undetectable viral DNA) and tolerance (no symptoms but with detectable viral DNA) following controlled massive and repeated inoculations with viruliferous whiteflies. A stable BC1F4 line (denominated 902) that does not segregate for resistance was obtained. This line does not support virus accumulation, even upon extensive whitefly-mediated inoculation of young seedlings, and does not need protection with nets or insecticides. Another stable BC1F4 line (denominated 908) was tolerant to the virus. Both lines have good horticultural characteristics and bear 80- to 120-g red fruits. Analysis of segregation of susceptibility, tolerance, and resistance during the BC1F1 to BC1F4 crosses indicated that tolerance is controlled by a dominant major gene and resistance by two to three additive recessive genes. The resistant and tolerant lines do not need to be protected by insecticides or nets.     

Relationships of the Sardinian isolate of tomato yellow leaf curl geminivirus with its whitefly vectorBemisia tabaci Gen

Relationships of an Italian isolate of tomato yellow leaf curl geminivirus from Sardinia (TYLCV-S) with its whitefly vectorBemisia tabaci were studied by means of experimental transmissions from tomato to tomato plants. TYLCV-S was confirmed to be transmitted in a persistent, circulative manner. The minimum latent period in the vector was between 17 and 20 h from the beginning of the acquisition access period (AAP). The maximum retention of infectivity was 8 days from the end of the AAP. Both acquisition and inoculation feeding times influenced the detected proportion of infective insects, with patterns well described by an exponential model. Acquisition was more efficient than inoculation. Males were significantly less efficient vectors than females. Nymphs were as efficient as adults in acquiring the virus. The length of AAP influenced both the retention of infectivity, and the pattern of transmission in serial transfer transmission tests with individual females. No significant difference in transmission efficiency was detected between two colonies ofB. tabaci, one inducing typical silverleaf symptoms on squash, the other inducing only mild symptoms with more than 50 whiteflies per plant. The phenomenon of periodic acquisition was not unequivocally proved for TYLCV-S.Research supported by the National Research Council of Italy, Special Project RAISA, Sub-project N. 2. Paper N. 1961.Supported by a grant from the Istituto Agronomico Mediterraneo, Valenzano (Bari), Italy.     

媒介虫口密度、植株苗龄及温度对B型烟粉虱传播台湾番茄曲叶病毒的影响

台湾番茄曲叶病毒(Tomato leafcurl Taiwan virus,ToLCTWV)近年来在我国部分番茄种植区流行成灾,对番茄生产造成了严重损失。作者研究了B型烟粉虱对ToLCTWV的获取、保持,并测定了虫口密度、温度及植株苗龄对其传播该病毒的影响。结果表明,B型烟粉虱在感染ToLCTWV的番茄植株上取食0.5h即可在3.3%个体内检测到ToLCTWV DNA,取食48h后,带毒率达100%;ToLCTWV DNA可在B型烟粉虱体内终生存留。B型烟粉虱是ToLCTWV的高效媒介,每株1头带毒烟粉虱取食48h,植株发病率达50%～60%;每株5头取食,发病率达到或接近100%。介体虫口密度及植株苗龄是决定苗期发病程度的重要因子,虫口密度增加,病情指数上升;苗龄增大,病情指数下降。温度对发病率有显著影响,但对病情指数影响不显著。此外,温度与苗龄的互作、虫口密度与苗龄的互作以及三因子之间的互作都对病情指数有显著影响。这些结果提示,培育无病壮苗是防治台湾番茄曲叶病毒病的关键。