Insect Vector Bemisia Tabaci Research Articles

Viral complexity of tomatoes yellow mosaic and leaf curl diseases in lowland and highland areas

AbstractYellow mosaic and leaf curl diseases caused by whitefly‐transmitted begomo virus genera are important problems in tomato (Solanum lycopersicon L.) production in Indonesia, particularly on Java Island. The aims of this survey are to assess the percentages of disease incidence (DI) and disease severity index (DSI), evaluate the spread and complexity of begomovirus and crinivirus infections responsible for yellow mosaic and leaf curl diseases in tomato plants, and identify the species of whitefly insect vectors and their cryptic biotypes in tomato production centers located on Java Island, Indonesia. A total of 43 locations in East, Central, and West Java were surveyed during the dry season from July 2022 to September 2022. Disease incidence and severity were determined by observing 200 samples of tomato plants from five points at each location, with 40 plants per point of land. A total of 116 whitefly samples in microtubes and 215 symptomatic leaf samples were collected. The genus begomovirus and crinivirus infecting tomato were identified by PCR and RT‐PCR using genus‐specific primers. Similarly, whitefly species and their cryptic biotypes were identified by PCR using MCoI gene‐specific primers. Results showed that DI and DSI remarkably differed between the lowlands (66%–89%) and highlands (33%–62%) in the provinces of Central Java and West Java. Furthermore, PCR analysis of 215 infected tomato showing the symptoms of yellow mosaic and curly leaf revealed that three begomoviruses, one crinivirus and their mixed combination both begomoviruses, one crinivirus has been detected in all the samples. Similarly, the whitefly insect vector Bemisia tabaci biotype Q was identified in all areas, whereas Trialeurodes vaporariorum was found only in the East Java and Java highlands, respectively.

Special issue: Relationship between insect vectors and plant pathogens

Special issue: Relationship between insect vectors and plant pathogens

Mathematical Model of Effect of Yellow Virus on Tomato Plants Through Bemisia tabaci Insects Using Verticillium lecanii Fungus

The Yellow virus is a virus that causes tomato plants to die. The insect vector Bemisia tabaci spreads this virus. The goal of this study is to identify the shape of a mathematical model of the influence of yellow virus on tomato plants via the insect Bemisia tabaci and the fungus Verticilliun lecanii, as well as to interpret the results of the mathematical model analysis. This is referred to as basic research. This study employs a descriptive method in which theories are analysed in relation to the topics to be discussed, and these theories are based on a literature review. Stability analysis is carried out using Routh-Hurwitz criteria. It indicates that the disease-free equilibrium point is asymptotically stable when Λt=μtN and the endemic equilibrium point is asymptotically stable for d1>e1, d2>e2 and a1>(a1)2+(a3)2a0)/(a3a2 ). The model simulation shows that if the efficacy of Verticillium lecanii is high, the population of infected tomato plants, as well as the population of Bemisia tabaci, will go extinct.

​RCA-based Detection of Begomoviruses in Weed Genera Associated with Legumes in Southern Karnataka

Background: Yellow mosaic disease (YMD) caused by begomoviruses transmitted through the insect vector Bemisia tabaci poses a serious threat to the production of legume crops. Methods: Season-long surveys were carried out for YMD occurrence in six different legume crops and associated natural weeds both symptomatic and asymptomatic across the districts of southern Karnataka, India. The samples were analyzed through RCA PCR using specific primer pairs. Result: Up to 94.1 per cent YMD incidence was recorded and nine weed species were commonly found associated with legume crops. The weeds viz., Ageratum conyzoides, Alternanthera sessilis, Commelina benghalensis and Euphorbia geniculata were abundantly found in the surveyed regions. The weeds were both symptomatic and asymptomatic. Rolling circle amplification coupled polymerase chain reaction method was employed to detect yellow mosaic virus in asymptomatic weeds. Phylogenetic analysis based on the sequences of PCR amplified products of weeds and symptomatic legumes revealed a close clustering of the weed samples with horsegram yellow mosaic virus, legume yellow mosaic virus and mungbean yellow mosaic virus. Overall, our data suggests the role of weed species associated with legume crops as alternative/collateral hosts of begomoviruses and their role in the epidemiology of yellow mosaic disease.

​RCA-based Detection of Begomoviruses in Weed Genera Associated with Legumes in Southern Karnataka

Background: Yellow mosaic disease (YMD) caused by begomoviruses transmitted through the insect vector Bemisia tabaci poses a serious threat to the production of legume crops. Methods: Season-long surveys were carried out for YMD occurrence in six different legume crops and associated natural weeds both symptomatic and asymptomatic across the districts of southern Karnataka, India. The samples were analyzed through RCA PCR using specific primer pairs. Result: Up to 94.1 per cent YMD incidence was recorded and nine weed species were commonly found associated with legume crops. The weeds viz., Ageratum conyzoides, Alternanthera sessilis, Commelina benghalensis and Euphorbia geniculata were abundantly found in the surveyed regions. The weeds were both symptomatic and asymptomatic. Rolling circle amplification coupled polymerase chain reaction method was employed to detect yellow mosaic virus in asymptomatic weeds. Phylogenetic analysis based on the sequences of PCR amplified products of weeds and symptomatic legumes revealed a close clustering of the weed samples with horsegram yellow mosaic virus, legume yellow mosaic virus and mungbean yellow mosaic virus. Overall, our data suggests the role of weed species associated with legume crops as alternative/collateral hosts of begomoviruses and their role in the epidemiology of yellow mosaic disease.

Molecular Characterization of a Novel Begomovirus Infecting Malva (Gaya guerkeana K. Schum.)

The genus Begomovirus (family Geminirvidae) comprises circular single-stranded DNA viruses that infect both cultivated and non-cultivated hosts, being transmitted by the insect vector Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). This study aimed to conduct the molecular characterization of a novel begomovirus infecting the non-cultivated plant Gaya guerkeana K. Schum. (Malvaceae). A leaf sample of G. guerkeana was collected in the State of Pernambuco, Brazil, in 2010. Viral genomic components were amplified via RCA, cloned, and commercially sequenced. The full-length DNA-A sequence was used for phylogenetic analysis and pairwise comparisons with other previously reported begomoviruses. The begomovirus DNA-A from G. guerkeana was most closely related to the Sida mottle Alagoas virus (SiMoAV, JX871386), having 84.8% nucleotide identity. Using the ≥ 91% identity criteria for DNA-A established by the Geminivirus Study Group of the International Committee on Taxonomy of Viruses, this isolate was considered a putative new begomovirus species, and the name Gaya yellow mosaic virus (GaYMV) is suggested. The GaYMV isolate grouped with SiMoAV and other begomoviruses infecting Sida spp. from the State of Alagoas, Brazil. This is the first report of a begomovirus infecting G. guerkeana, indicating that this non-cultivated plant can act as a reservoir/source of begomoviruses.

Molecular variation of tomato yellow leaf curl virus in the insect vector Bemisia tabaci

Insect vectors play significant roles in geminivirus spread and evolution in nature. To date little is known about the population dynamics of begomoviruses in their insect vector Bemisia tabaci. In this study we analyzed the genetic variation of tomato yellow leaf curl virus (TYLCV) in its host plant, Solanum lycopersicum, in its transmission vector B. tabaci raised on TYLCV-infected S. lycopersicum plants, and in B. tabaci after being transferred from S. lycopersicum to Gossypium hirsutum. We found that the levels of variability of TYLCV remained stable in S. lycopersicum plants, but increased significantly in both invasive and indigenous species of B. tabaci. We also presented evidence that the elevated mutation frequencies in TYLCV populations from vector whiteflies were caused mainly by mutations that occurred at several distinct sites within the TYLCV genome. Simultaneous introduction of mutations in the hot spots did not affect the ability of TYLCV to be transmitted by B. tabaci, but reduced its pathogenicity in both S. lycopersicum and Nicotiana benthamiana. Our findings provide new information on population variability of TYLCV in its insect vector, extending the knowledge of the influence of insect vector on plant virus population dynamics.

Tomato yellow leaf curl virus: No evidence for replication in the insect vector Bemisia tabaci.

Begomovirus ssDNA plant virus (family Geminiviridae) replication within the Bemisia tabaci vector is controversial. Transovarial transmission, alteration to whitefly biology, or detection of viral transcripts in the vector are proposed as indirect evidence of replication of tomato yellow leaf curl virus (TYLCV). Recently, contrasting direct evidence has been reported regarding the capacity of TYLCV to replicate within individuals of B. tabaci based on quantitave PCR approaches. Time-course experiments to quantify complementary and virion sense viral nucleic acid accumulation within B. tabaci using a recently implemented two step qPCR procedure revealed that viral DNA quantities did not increase for time points up to 96 hours after acquisition of the virus. Our findings do not support a recent report claiming TYLCV replication in individuals of B. tabaci.

Tomato Yellow Leaf Curl Virus: A Serious Threat to Tomato Plants World Wide

Tomato (Solanum lycopersicum) is one of the widely grown crops worldwide. It is consumed in various forms and has excellent nutritional values. Presently, this crop is facing a serious threat to its yield and survival because of Geminivirus infection. One of the Geminivirus species hampering tomato productions world-wide is Tomato yellow leaf curl virus (TYLCV). Tomato yellow leaf curl disease is one of the most destructive plant diseases destroying the tomato crops globally. It has spread to many countries worldwide including Southern, Central and Northern parts of America, Southern Asia, Africa and Mediterranean basin. TYLCV genome consists of a circular single stranded DNA of 2.7 kb in size and occasionally contains beta satellite of 1.3 kb. TYLCV genome encodes six open reading frames, of which two are in the viral orientation and four are in the complementary orientation. TYLCV is transmitted by the insect vector Bemisia tabaci, commonly known as the silverleaf white fly. This review provides an overview of Geminiviruses with special emphasis on TYLCV, virus vector relationship between TYLCV and white fly, different strains of TYLCV, its genome organization and replication, present status of its spread in different parts of the world and strategies employed for controlling it. The knowledge about the recent progress in the study of TYLCV would help develop novel strategies for its control in agriculture.

Rapid accumulation and low degradation: key parameters of Tomato yellow leaf curl virus persistence in its insect vector Bemisia tabaci.

Of worldwide economic importance, Tomato yellow leaf curl virus (TYLCV, Begomovirus) is responsible for one of the most devastating plant diseases in warm and temperate regions. The DNA begomoviruses (Geminiviridae) are transmitted by the whitefly species complex Bemisia tabaci. Although geminiviruses have long been described as circulative non-propagative viruses, observations such as long persistence of TYLCV in B. tabaci raised the question of their possible replication in the vector. We monitored two major TYLCV strains, Mild (Mld) and Israel (IL), in the invasive B. tabaci Middle East-Asia Minor 1 cryptic species, during and after the viral acquisition, within two timeframes (0–144 hours or 0–20 days). TYLCV DNA was quantified using real-time PCR, and the complementary DNA strand of TYLCV involved in viral replication was specifically quantified using anchored real-time PCR. The DNA of both TYLCV strains accumulated exponentially during acquisition but remained stable after viral acquisition had stopped. Neither replication nor vertical transmission were observed. In conclusion, our quantification of the viral loads and complementary strands of both Mld and IL strains of TYLCV in B. tabaci point to an efficient accumulation and preservation mechanism, rather than to a dynamic equilibrium between replication and degradation.

Seed transmission of Sweet potato leaf curl virus in sweet potato (Ipomoea batatas)

Sweet potato leaf curl virus (SPLCV) infects sweet potato and is a member of the family Geminiviridae (genus Begomovirus). SPLCV transmission occurs from plant to plant mostly via vegetative propagation as well as by the insect vector Bemisia tabaci. When sweet potato seeds were planted and cultivated in a whitefly‐free greenhouse, some sweet potato plants started to show SPLCV‐specific symptoms. SPLCV was detected by PCR from all leaves and floral tissues that showed leaf curl disease symptoms. More than 70% of the seeds harvested from SPLCV‐infected sweet potato plants tested positive for SPLCV. SPLCV was also identified from dissected endosperm and embryos. The transmission level of SPLCV from seeds to seedlings was up to 15%. Southern blot hybridization showed SPLCV‐specific single‐ and double‐stranded DNAs in seedlings germinated from SPLCV‐infected seeds. Taken altogether, the results show that SPLCV in plants of the tested sweet potato cultivars can be transmitted via seeds and SPLCV DNA can replicate in developing seedlings. This is the first seed transmission report of SPLCV in sweet potato plants and also, to the authors' knowledge, the first report of seed transmission for any geminivirus.

Ageratum yellow vein virus isolated from tomato plants with leaf curl on Ishigaki Island, Okinawa, Japan

In 2005, severe leaf curling and yellowing were observed on tomato plants on Ishigaki Island. Because the symptoms were consistent with infection by a begomovirus, we used a polymerase chain reaction (PCR) with specific primers for begomovirus DNA-A and DNA satellite component (DNA-β) and detected products of the expected sizes from symptomatic tomato plant samples. DNA sequence analyses of the PCR products revealed that the symptomatic tomato plants were associated with Ageratum yellow vein virus (AYVV) infection. We confirmed AYVV transmission from the naturally infected weed host, Ageratum conyzoides, to healthy tomato plants by the insect vector Bemisia tabaci B biotype. This report is the first of AYVV occurrence in Japan.