Minimum Acquisition Access Period Research Articles

Host Species-Dependent Transmission of Tomato Leaf Curl New Delhi Virus-ES by Bemisia tabaci.

The tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite, single-stranded begomovirus that was first identified in India in 1995 affecting solanaceous crops. A different strain, named ToLCNDV-ES, was introduced in Spain in 2012 and causes severe symptoms in zucchini crops. Virus transmission experiments with the whitefly Bemisia tabaci, were used to compare the transmission parameters in zucchini and tomato plants. The minimum acquisition access period and inoculation access period of ToLCNDV-ES transmission was similar in zucchini and tomato. However, the transmission efficiency was significantly higher in zucchini (96%) compared to tomato (2%). The maximum retention of the virus in the vector was 16 days. B. tabaci feeding on, or recently emerged from infected zucchini plants, accumulated more virus than those from infected tomato, as determined by real-time PCR. A total of 20% of B. tabaci that were recently emerged from infected zucchini, and none from infected tomato, were able to transmit the virus to virus-free zucchini. The results may explain the different incidences of ToLCNDV-ES in zucchini and tomato crops in Spain. But they are also relevant for ToLCNDV-ES management of crops and the role of the trade and transport of infected plant material, when small-sized immature stages of B. tabaci could be a source of infection.

Transmission characteristics of allexiviruses by the eriophyid mite, Aceria tulipae (Keifer) (Acari: Eriophyidae) from naturally mixed infected garlic (Allium sativum L.)

The transmission characteristics of members of the genus Allexivirus to leek (Allium porrum L.) by its eriophyid mite vector, Aceria tulipae (Keifer), were studied. Prior to conducting transmission tests, colonies of nonviruliferous A. tulipae were established on healthy leek seedlings. A single A. tulipae transmitted the viruses with up to 50% efficiency but transmission efficiency increased when >10 mites per plant were used. Allexiviruses were acquired by A. tulipae after a minimum acquisition access period (AAP) of 30 min, whereas transmission tests suggest that a one hour inoculation access period (IAP) was needed for successful transmission. Allexiviruses were transmitted from garlic to leek plants by A. tulipae and mixed infections by more than one virus were observed. ShVX, GarV-A, -C, -D, and -B were detected in most inoculated plants, whereas other members of the genus (GarV-E, −X, and GarMbFV) were found only occasionally. None of the mites that originated from eggs deposited on infected plants transmitted allexiviruses, indicating that the viruses are not transmitted transovarially. No latent period was demonstrated. Taken together, these data suggest a semipersistent mode of transmission of Allexivirus members by A. tulipae. The output of this study will assist in the better management of the vector and the associated diseases.

Transmission and host range of Horsegram yellow mosaic virus (HgYMV) causing common bean (Phaseolus vulgaris L.) yellowing disease in Sri Lanka

The common bean (Phaseolus vulgaris L.) yellowing disease (BYD) is caused by the Horsegram yellow mosaic virus (HgYMV), which is a begomovirus transmitted by whiteflies (Bemisia tabaci Genn.). It is a serious threat to the common bean cultivation in Sri Lanka. Despite the fact that the disease has been affecting bean production for a long time, its etiology and virus vector relationships are not understood well. Therefore, the present work was carried out to identify major aspects of the etiology of the virus. Initially a survey was conducted to determine the prevalence of the virus in representative bean growing locations in Sri Lanka, followed by a host range study using 54 plant species. Characteristics of virus-vector relationships were determined by conducting a series of virus transmission tests under glass-house conditions. The survey results revealed the incidence of BYD at some time or the other in most of the sampled localities, which are scattered around all four major districts where the common bean is grown. Through the host range study, it was demonstrated that Ageratum sp., Glycine max Merrill., Macrotyloma uniflorum (Lam.) Verdc., and Phaseolus lunatus L. are susceptible to HgYMV, indicating a narrow host range. In addition to the symptomatology, the successful entry of the virus following inoculation was confirmed through PCR using degenerate primers. Relative transmission efficiency was found to be 96.7 %, which corresponds to 0.24 of the estimated probability of transmission through a single whitefly (p*). The virus could be transmitted through probing by a single viruliferous whitefly with an incidence of 36.7 % (p* = 0.37). The minimum acquisition access period and inoculation access period were 20 min in each case and the respective disease incidence values were 30.0 % (p* = 0.04) and 36.7 % (p* = 0.05). The whiteflies could retain the virus in an active state for up to 9 days.

Characteristics of sugarcane white leaf phytoplasma transmission by the leafhopper Matsumuratettix hiroglyphicus

AbstractThe leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is the most important vector of sugarcane white leaf (SCWL) phytoplasma that significantly affects the sugarcane crop in Asia. Here, we aimed to study the characteristics of SCWL phytoplasma transmission by M. hiroglyphicus. To this end, the stylet penetration activities performed during the acquisition access period (AAP) and inoculation access period (IAP) were investigated by the direct current electrical penetration graph technique and confirmed by quantitative polymerase chain reaction (qPCR). Additionally, the latent period (LP) of SCWL phytoplasma in the vector was determined by qPCR and localised by fluorescent in situ hybridisation. The results indicated that the acquisition of SCWL phytoplasma occurred during phloem ingestion (waveform D), whereas its inoculation was associated with salivation into the phloem sieve element (waveform C). The minimum AAP was 15 min and the minimum duration of phloem ingestion was 2.35 min. The minimum LP of SCWL phytoplasma in the vector was at least 14 days; then, SCWL phytoplasma moved to the salivary glands of the insect, enabling the transmission of the pathogen to the host plants. The minimum IAP for a successful transmission of SCWL phytoplasma to the host plants was 11–12 min, with a minimum duration of salivation into phloem of 1.35 min. The female vectors had higher SCWL phytoplasma copy numbers than the male vectors, and displayed faster AAP, IAP, and LP. Overall, our findings provide important information related to the feeding behaviour of M. hiroglyphicus and its effect on the transmission of SCWL phytoplasma.

Comparative transmission of Bhendi yellow vein mosaic virus by two cryptic species of the whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae).

The leaf sample from okra plants showing prominent yellow vein mosaic symptoms and healthy plant without any virus symptoms were collected from farmer's field. The presence of begomovirus in the infected sample was confirmed by polymerase chain reaction (PCR) and the amplicons were cloned and sequenced. The genome analysis showed that the isolate in the present study had 99% nucleotide identity with Bhendi yellow vein mosaic virus (BYVMV) revealing it as BYVMV variant. The genetic species of Bemisia tabaci collected from fields were identified as Asia-1 and MEAM-1 genetic species based on silver leaf assay, sequence characterized amplified region marker, and mtCOI gene sequence. The comparative virus-vector relationship of both genetic species of B. tabaci indicates a minimum of two and three B. tabaci in MEAM-1 and Asia-1 genetic species, respectively, per plant were required to transmit the disease. The minimum acquisition access period and inoculation access period of 15 (MEAM-1) and 20min (Asia-1) were required to transmit the YVMD; it was further confirmed by nucleic acid hybridization using coat protein gene-specific probe of BYVMV. With respect to the sex, the female B. tabaci were more efficient in transmitting the disease as compared to male ones in both the genetic species of B. tabaci. The MEAM-1 to transmit the BYVMV more efficiently than Asia-1 genetic species of B. tabaci.

Survey, symptomatology, transmission, host range and characterization of begomovirus associated with yellow mosaic disease of ridge gourd in southern India.

Ridge gourd is an important vegetable crop and is affected by several biotic and abiotic factors. Among the different biotic factors, ridge gourd yellow mosaic disease (RgYMD) is new emerging threat for the production of ridge gourd. The incidence of the RgYMD varied from 30 to 100% in southern India with highest disease incidence of 100% observed in Belagavi district of Karnataka state. The infected plants showed chlorosis, mosaic, cupping of leaves, blistering, reduction in leaf size and stunted growth. The varieties/hybrids grown in the farmer's fields were found to be susceptible to the disease. Begomovirus was detected in 61 out 64 samples collected from different areas of southern India. Further, all the samples failed to give amplification for beta and alpha satellites. The transmission studies revealed that single whitefly (Bemisia tabaci) is enough to transmit the virus, however, 100% transmission was observed with 10 whiteflies. The minimum acquisition access period and inoculation access period for transmission of virus by whitefly was 15min. Among the 56 host plants belonging to diversified families tested for host range, sponge gourd, ash gourd, bottle gourd, pumpkin, cucumber, summer squash, cluster bean, tobacco and datura were shown to be susceptible. Seventy six varieties/hybrids evaluated for identifying the resistance source for RgYMD, all were found highly susceptible. Sequence analysis of DNA-A revealed that the causal virus shared highest nucleotide sequence identity (92.3%) with Tomato leaf curl New Delhi virus (ToLCNDV) infecting sponge gourd from northern India. Sequence and phylogenetic analysis of both DNA-A and DNA-B components showed that the begomovirus associated with RgYMD is found to be strain of ToLCNDV. This is first report of ToLCNDV association with RgYMD from southern India.

Molecular identification and biological characterisation of a begomovirus associated with okra enation leaf curl disease in India

An unusual symptom was noted in okra originating from Haryana state (India) consisting of leaf curl associated with enations. These were distinct from the leaf curl and/or vein yellowing symptoms usually shown by okra. PCR-mediated amplification was used to show the presence of a begomovirus and the complete genome sequences were determined for seven isolates. The sequences showed high levels of nucleotide sequence identity (91.9–99.1 %). In comparison to begomovirus sequences available in the databases the okra sequences showed the highest levels of nucleotide sequence identity (84.5 to 87.1 %) with Mesta yellow vein mosaic virus (MeYVV) and thus were classified as belonging to a novel begomovirus species, tentatively named Okra enation leaf curl virus. In common with the majority of begomoviruses, Okra enation leaf curl virus (OELCuV) was shown to have a recombinant origin. Analysis of the transmission characteristics of a wild-type virus isolate by Bemisia tabaci showed the minimum acquisition access period to be 1 h and the minimum inoculation access period to be 30 min, with female insects transmitting with a greater efficiency than male insects. Under controlled conditions the host range of the virus was shown to be very narrow, limited to two species in the family Malvaceae, okra (Abelmoschus esculentus) and hollyhock (Althaea rosea), and seven in the family Solanaceae.

Virus–vector Relationships, Host Range, Detection and Sequence Comparison of Chilli leaf curl virus Associated with an Epidemic of Leaf Curl Disease of Chilli in Jodhpur, India

AbstractAn epidemic of chilli leaf curl disease was recorded in 2004 in Jodhpur, a major chilli‐growing area in Rajasthan, India. Several isolates were efficiently transmitted by the whitefly (Bemisia tabaci), all of which induced severe leaf curl symptoms in chilli. A single whitefly was capable of transmitting the virus, and eight or more whiteflies per plant resulted in 100% transmission. The minimum acquisition access period (AAP) and inoculation access period (IAP) were 180 and 60 min, respectively. The virus persisted in whiteflies for up to 5 days postacquisition. Of 25 species tested, the virus infected only five (Capsicum annuum, Carica papaya, Solanum lycopersicum, Nicotiana tabacum and N. benthamiana). The virus was identified as Chilli leaf curl virus (ChiLCV), which shared the closest sequence identity (96.1%) with an isolate of ChiLCV from potato in Pakistan and showed sequence diversity up to 12.3% among the ChiLCV isolates reported from India and Pakistan. A betasatellite was identified, which resembled most closely (97.3%) that of Tomato leaf curl Bangladesh betasatellite previously reported from chilli and tomato leaf curl in India. The betasatellite was very different from that reported from chilli leaf curl in Pakistan, indicating that different betasatellites are associated with chilli leaf curl in India and Pakistan. We describe here for the first time the virus–vector relationships and host range of ChiLCV.

Cytopathology, Mode of Aphid Transmission and Search for the Casual Agent of Cotton Bunchy Top Disease

AbstractThe cytopathological effects of cotton bunchy top (CBT) disease and its mode of transmission by Aphis gossypii Glover (cotton aphid), were studied. CBT infection affected the leaf epidermal layer producing a loose, ruptured and rough surface morphology with many stomata closed and misshapen. Roots of CBT‐infected plants showed reduced growth, small knots and a dark brown appearance. A single aphid per plant was capable of transmitting CBT at 5%, whereas three aphids per plant transmitted CBT to 50% of the cotton seedlings and 20 aphids per plant transmitted the disease agent to 80% of the cotton seedlings. Aphis gossypii acquired CBT after a minimum acquisition access period of 5 min and transmitted the agent after a minimum inoculation access period of 1 h. Both alate and apterous aphids and nymph instars 2, 3 and 4 of A. gossypii transmitted CBT. This preliminary data suggest that A. gossypii transmits CBT in a semi‐persistent manner. Myzus persicae Sulz (green peach aphid) was unable to transmit CBT. A comprehensive attempt to isolate the CBT agent, using a range of virological techniques including double‐stranded RNA extraction, two‐dimensional gel electrophoresis for viroid, circular DNA test, nanovirus polymerase chain reaction (PCR), luteovirus PCR and enzyme‐linked immunosorbent assay, phytoplasma test, nucleoprotein purification and electron microscopy, was unsuccessful, raising the possibility that CBT may be caused by a unique new pathogen.

Estudo da interação de um begomovírus isolado de tomateiro com a mosca branca

No estudo da interação de um begomovírus isolado de tomateiro (Lycopersicon esculentum) em Anápolis-GO, denominado GO-ANPL (taxonomicamente relacionado ao Tomato rugose mosaic virus, ToRMV) com o vetor Bemisia tabaci biótipo B, determinaram-se o período de acesso de aquisição do vírus (PAA), o período de acesso de inoculação (PAI), o período de latência (PL), a sua retenção e transmissão à progênie. Nos experimentos empregaram-se plantas de tomateiro 'Santa Clara' e cinco insetos por planta. Constatou-se um PAA mínimo de 15 min com o qual 6% dos tomateiros foram infetados. Este percentual aumentou para 65% quando o PAA foi estendido para 24 h. O PAI mínimo foi de 30 min registrando-se 18% de infecção, o qual foi elevado para 67% com 24 h de PAI. Observou-se o término do PL 16 h após o vetor adquirir o vírus. Na detecção do GO-ANPL no vetor via PCR, testes com mais de 2.500 espécimens constataram o vírus em ninfas desenvolvidas em tomateiro infetado, em adultos com diferentes PAAs, mas não em ovos de fêmeas avirulíferas ovipositados em planta infetada. Observou-se a passagem transestadial em 100% dos adultos testados que transmitiram o vírus em 33% dos casos. Evidenciou-se a transmissão à progênie pela detecção do vírus em ovos, ninfas e adultos provenientes de fêmeas virulíferas, contudo, a transmissão do vírus pelos adultos não foi observada. Os resultados obtidos indicam que a interação vírus-vetor é estabelecida desde a fase inicial do desenvolvimento do inseto e podem ser considerados relevantes para os estudos epidemiológicos dos begomovírus associados ao biótipo B de B. tabaci no país.

Transmission of Pigeon pea sterility mosaic virus by the Eriophyid Mite, Aceria cajani (Acari: Arthropoda).

The transmission characteristics of Pigeon pea sterility mosaic virus (PPSMV) to pigeon pea (Cajanus cajan) by its eriophyid mite vector, Aceria cajani, were studied. Nonviruliferous A. cajani colonies were established on detached healthy leaflets of a PPSMV-immune pigeon pea cultivar floating on water. The transmission efficiency of single A. cajani was up to 53% but was 100% when >5 mites per plant were used. A. cajani acquired PPSMV after a minimum acquisition access period (AAP) of 15 min and inoculated virus after a minimum inoculation access period (IAP) of 90 min. No latent period was observed. Starvation of A. cajani prior to, or following, PPSMV acquisition reduced the minimum AAP and IAP periods to 10 min and 60 min, respectively, and mites retained virus for up to 13 h. None of the mites that developed from eggs taken from PPSMV-infected leaves transmitted the virus, indicating that it is not transmitted transovarially. Taken together, these data suggest a semipersistent mode of transmission of PPSMV by A. cajani.

Biology of the Transmission of Peach Mosaic Virus by Eriophyes insidiosus (Acari: Eriophyidae).

Experiments were undertaken to elucidate the characteristics of the transmission of peach mosaic virus (PMV) by Eriophyes insidiosus. Transmission efficiency by single E. insidiosus was as high as 17%. The minimum inoculation access period was between 3 and 6 h. E. insidiosus acquired the virus after a minimum acquisition access period of 3 days. No latent period was demonstrated. While most plant viruses which are transmitted by eriophyid mites are transmitted in a persistent mode, our data are more consistent with a semipersistent model.

Transmission characteristics of Spiroplasma citri and its effect on leafhopper vectors from the Circulifer tenellus complex

Summary.Several leafhopper variants of the Circulifer tenellus complex were collected in “citrus stubborn” affected areas in Israel. Two of these variants transmitted the Spiroplasma citri to Matthiola incana after being injected with the disease agent. The variant from Atriplex halimus was designated Circulifer tenellus‐A (CTA) and the variant from Portulaca oleracea was designated Circulifer tenellus‐? (CTP). Transmission characteristics were determined for both leafhoppers. A high rate of transmission (43.3%) was obtained by single CTA leafhoppers that were injected with the Amiad S. citri isolate from the Upper Galilee, compared with 7% transmission obtained with the CTP leafhoppers. The Gilgal S. citri isolate from the Jordan Valley, was not transmitted by either. Injection was more effective than acquisition access feeding to render the leafhopper infective for both CTA and CTP. The minimum acquisition access period needed for the CTA variant to transmit the Amiad isolate was 1 h. Longer AAPs did not necessarily result in a higher rate of transmission. The minimum incubation period was 6 days and the maximum was 32 days. The LP50 calculated from the logarithmic curve y = 45.74Ln(x)–53.68 was 9.64 days. The minimum inoculation access period (IAP) was lh. The same transmission parameters for the CTP variant could not be determined, as no transmission was obtained even when groups of five‐six insects were placed on a single plant.

Virus‐vector relationships of chickpea chlorotic dwarf geminivirus and the leafhopper Orosius orientalis (Hemiptera: Cicadellidae)

SummaryChickpea chlorotic dwarf geminivirus (CCDV) is one of the viruses associated with chickpea stunt disease. It is transmitted by the leafhopper Orosius orientalis. The minimum acquisition access period (AAPmin) and inoculation access period (IAPmin) were found to be less than 2 min, while the minimum latency period (LPmin) was less than 2 h. The median AAP, IAP and LP were 8.0 h, 2.3 h and 27.7 h, respectively. No difference in transmission rates (proportion of leafhoppers able to transmit) was observed between male and female leafhop‐pers. In serial transmission experiments, transmission was shown to be persistent, and after a 2‐day AAP about 80% of the leafhoppers transmitted the virus for most of their life. The virus could be detected in individual leafhoppers by DAS‐ELISA. It did not multiply in the leafhopper, but, instead, decreased in concentration during leafhopper feeding on a non‐host of the virus.

Relations of rice tungro bacilliform and rice tungro spherical viruses with their vector Nephotettix virescens.

Rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV) were isolated from rice plant infected with a Philippines isolate of tungro. RTBV was transmitted alone or together with RTSV by the leafhopper Nephotettix virescens from rice plants infected with both RTBV and RTSV, but not from plants with RTBV alone, while RTSV was transmitted alone. RTBV transmission by the leafhopper also occurred when the leafhoppers were previously fed on RTSV diseased plants. The minimum acquisition access period of RTSV and hypothetical “helper factor” for RTBV transmission by the leafhopper was 10min, and RTBV was acquired in a 30min access. The “helper factor” was retained for 7 days by the leafhopper, whereas RTSV was retained for 2 days. The “helper factor” was not retained in the leafhopper after the moulting.

Vector relationships and other characteristics of barley yellow striate mosaic virus (BYSMV)

SUMMARYBarley yellow striate mosaic virus (BYSMV) was inoculated by its planthopper vector Laodelphax striatellus (Homoptera, Delphacidae) to 44 species of Gramineae, 26 of which in eight tribes were infected. The virus was not transmitted through wheat seed nor did it infect five dicotyledonous hosts of other rhabdoviruses. The most susceptible species were in the tribes Festuceae and Hordeae. Barley, Bromus spp., oats, Phalaris canariensis, Setaria italica, Sorghum spp., and sweet corn cv. Golden were diagnostic hosts. Electron microscopy of crude sap was also a sensitive diagnostic method. Properties of BYSMV were determined by injecting L. striatellus with crude sap from infected barley. Sap was infectious after 10 min at 50–55 °C but not after 10 min at 60 °C, when diluted with buffer to 10‐‐2 but not to 10‐‐3, when stored for 2 but not 4 days at 5 °C or when kept for 1 but not 2 days at 22 °C.The planthopper Javesella pellucida was an experimental vector of BYSMV but the virus was not transmitted by the leafhoppers Macrosteles sexnotatus or Psammotettix striatus (Homoptera, Cicadellidae). The latent period of BYSMV in L. striatellus was most commonly 15 or 16 days (minimum, 9 days; maximum, 29 days). The minimum acquisition access period for transmission was between 1 h and 5 h, and the minimum inoculation feeding time was 15 min. After 24 h and 8 day acquisition feeds, 30.4% and 42.8% respectively of L. striatellus transmitted BYSMV. When transferred daily, infective hoppers transmitted virus intermittently. The maximum retention of infectivity by L. striatellus was 36 days.Two of five infective females transmitted BYSMV transovarially. Larvae became infective in the second wk after hatching and transmitted for up to 3 wk.