Mealybug Transmission of Grapevine Leafroll Viruses: An Analysis of Virus–Vector Specificity

Department of Entomology, National Taiwan University, Taipei 106, Taiwan.
Phytopathology (Impact Factor: 3.12). 08/2010; 100(8):830-4. DOI: 10.1094/PHYTO-100-8-0830
Source: PubMed


To understand ecological factors mediating the spread of insect-borne plant pathogens, vector species for these pathogens need to be identified. Grapevine leafroll disease is caused by a complex of phylogenetically related closteroviruses, some of which are transmitted by insect vectors; however, the specificities of these complex virus-vector interactions are poorly understood thus far. Through biological assays and phylogenetic analyses, we studied the role of vector-pathogen specificity in the transmission of several grapevine leafroll-associated viruses (GLRaVs) by their mealybug vectors. Using plants with multiple virus infections, several virus species were screened for vector transmission by the mealybug species Planococcus ficus and Pseudococcus longispinus. We report that two GLRaVs (-4 and -9), for which no vector transmission evidence was available, are mealybug-borne. The analyses performed indicated no evidence of mealybug-GLRaV specificity; for example, different vector species transmitted GLRaV-3 and one vector species, Planococcus ficus, transmitted five GLRaVs. Based on available data, there is no compelling evidence of vector-virus specificity in the mealybug transmission of GLRaVs. However, more studies aimed at increasing the number of mealybug species tested as vectors of different GLRaVs are necessary. This is especially important given the increasing importance of grapevine leafroll disease spread by mealybugs in vineyards worldwide.

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    • "P. maritimus overwinters as first-instar nymphs or eggs on canes and trunks and emerges around bud swell to feed and develop to adulthood and their offspring hatch in mid-summer (Grimes and Cone 1985, Geiger and Daane 2001). Although all life stages are capable of transmitting GLRaVs, the first-instar " crawlers " are considered the most efficient vectors because of their high relative mobility compared with older stages, which are typically sessile upon reaching adulthood (Mahfoudhi et al. 2009, Tsai et al. 2010, Daane et al. 2012). There are two generations of P. maritimus in most regions, therefore two periods of high crawler activity which are the times of greatest concern for virus management (Daane et al. 2012). "
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    ABSTRACT: Vineyards were surveyed for grapevine leafroll-associated viruses and their insect vectors in New York State's Finger Lakes region in 2006-2008. Grape mealybug, Pseudococcus maritimus (Erhorn) (Hemiptera: Pseudococcidae), European Fruit Lecanium, Parthenolecanium corni (Bouche), and Cottony Maple Scale, Pulvinaria acericola (Walsh and Riley) (Hemiptera: Coccidae) were identified as vector species in this region. An increase in the incidence of Grapevine leafroll-associated virus 1 (GLRaV-1) and GLRaV-3 was observed in 8 of the 20 vineyards surveyed, which implies transmission by these insect vectors. Two of the vineyards for which a temporal increase in disease incidence was documented were then used to evaluate the efficacy of foliar applications of horticultural oil and two classes of insecticides for control of P. maritimus and for slowing virus spread over 2 years of vine protection. Delayed dormant applications of horticultural oil contributed to control of early season crawlers; however, this was not the case for control of summer populations. Applications of acetamiprid and spirotetramat achieved control in summer populations; however, spirotetramat outperformed acetamiprid in percent reduction of treated compared with control vines and in a side-by-side trial. Vines treated with spirotetramat had a lower percentage of new vines testing positive for GLRaV-1 than control vines after 2 years, while no other spray program altered the increase in incidence of GLRaV-1 or -3. © The Author 2015. Published by Oxford University Press on behalf of the Entomological Society of America.
    Full-text · Article · Jul 2015 · Journal of Insect Science
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    • "Grapevine leafroll-associated virus-3 (GLRaV-3), in the family Closteroviridae, genus Ampelovirus, is only known to affect Vitis spp. (grapevines), and is transmitted by several species of mealybugs and soft scale insects (Hemiptera, Pseudococcidae, and Coccidae, respectively; Tsai et al. 2010, Klaassen et al. 2011, Le Maguet et al. 2012, Almeida et al. 2013, Maree et al. 2013). It is transmitted by mealybugs in a semipersistent manner or can be transmitted via grafting, but cannot be transmitted by leaf-rub inoculations. "
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    ABSTRACT: Coinfections are common, leading to pathogen interactions during transmission and establishment in a host. However, few studies have tested the relative strengths of pathogen interactions in vectors and hosts that determine the outcome of infection. We tested interactions between two genetically distinct variants of the mealybug-transmitted Grapevine leafroll-associated virus 3. The transmission efficiency of each variant in single variant inoculations by two vector species was determined. The effects of vector species, a coinfected source, and simultaneous inoculation from multiple hosts to one host on variant establishment were examined. Within-vector interactions could have a role in transmission from hosts containing mixed infections, but not when vectors were moved from separate singly infected source plants to a single recipient plant. The invasive Planococcus ficus (Signoret) was a more efficient vector than Pseudococcus viburni (Signoret). Transmission efficiency of the two variants did not differ in single variant inoculations. Overall infections were the same whether from singly or coinfected source plants. In mixed inoculations, establishment of one variant was reduced. Mixed inoculations from two singly infected source plants resulted in fewer mixed infections than expected by chance. Therefore, the observed outcome was determined subsequent to host inoculation rather than in the vector. The outcome may be due to resource competition between pathogens. Alternatively apparent competition may be responsible; the pathogens’ differential ability to overcome host defenses and colonize the host may determine the final outcome of new infections. Detailed knowledge of interactions between pathogens during transmission and establishment could improve understanding and management of disease spread.
    Full-text · Article · Jun 2015 · Journal of Economic Entomology
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    • "1 ; Tsai , Rowhani , Golino , Daane , & Almeida , 2010 ) . Trans - mission seems to occur in a semi - persistent manner and instar nymphs are more efficient vectors of GLRaV - 3 than adult mealybugs ( Tsai et al . , 2008 ) . Nevertheless , there is no indication of virus - vector specificity in the transmission process ( Le Maguet et al . , 2012 ; Tsai et al . , 2010 ) . So far , no vector has been identified for GLRaV - 7 and GLRaV - 4 strain Car and none is suspected for GLRaV - 2 ."
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    ABSTRACT: Grapevine is a high value vegetatively propagated fruit crop that suffers from numerous viruses, including some that seriously affect the profitability of vineyards. Nowadays, 64 viruses belonging to different genera and families have been reported in grapevines and new virus species will likely be described in the future. Three viral diseases namely leafroll, rugose wood, and infectious degeneration are of major economic importance worldwide. The viruses associated with these diseases are transmitted by mealybugs, scale and soft scale insects, or dagger nematodes. Here, we review control measures of the major grapevine viral diseases. More specifically, emphasis is laid on (i) approaches for the production of clean stocks and propagative material through effective sanitation, robust diagnosis, as well as local and regional certification efforts, (ii) the management of vectors of viruses using cultural, biological, and chemical methods, and (iii) the production of resistant grapevines mainly through the application of genetic engineering. The benefits and limitations of the different control measures are discussed with regard to accomplishments and future research directions. © 2015 Elsevier Inc. All rights reserved.
    Full-text · Article · Jan 2015 · Advances in Virus Research
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