Project title
Spread of grapevine leafroll-associated virus 3 (GLRaV-3) by scale insects

Project leader
Krüger, K

Institution
University of Pretoria

Team members
Mawela, K V
Saccaggi, D

Project description
A transmission protocol - assay, which is required as support technology for the development of virus-resistant grapevines has been developed based on the transmission characteristics of Planococcus ficus. The transmission experiments have demonstrated that an acquisition access period (AAP) of 24 hours is sufficient for P. ficus to acquire the virus, and not more than 24 hours as stated in the literature. The experiments have further shown that an inoculation access period (IAP) of 24 hours or less is enough for the vector to inoculate healthy grapevine plants. Experiments on the persistence of the virus in P. ficus indicate that the virus persists for at least 24 hours in the vector when feeding on healthy grapevine plants.

The present study is the first to develop a method to detect GLRaV in individual mealybugs, including first-instar nymphs. This result is of great importance as it is now possible directly to determine the percentage of mealybugs or the percentage of different developmental stages in a population that carry the virus.

Trials are under way to determine alternative vectors, their transmission biology and life cycle in controlled laboratory experiments. A survey to determine alternative host plants of vectors is ongoing.

The project has been expanded to examine the movement of mealybugs in the field to determine their role in the secondary spread of the disease. In addition, the transmission efficiency of GLRaV-3 in the presence and absence of GVA (grapevine virus A) will be evaluated.

Presentation(s)
1. Kruger, K. 2003. Transmission of grapevine leafroll-associated virus 3 (GLRaV-3) by Planococcus ficus (Hemiptera: Pseudococcidae). 14th Entomological Congress of the Entomological Society of Southern Africa, 6-9 July. Pretoria, South Africa.
2. Saccaggi, D L, Kruger, K, Pietersen, G and MacDonald, C. 2006. A PCR-based method for identification of three mealybug species (Hemiptera: Pseudococcidae). 15th Congress of the Entomological Society of South Africa. July. Grahamstown, South Africa.
3. Mawela, K V, Douglas, N, van der Merwe, J and Kruger, K. 2006. Temperature-dependent development of the longtailed mealybug Pseudococcus longispinus Targioni-Tozzetti (Hemiptera: Pseudococcidae) on grapevine. 15th Congress of the Entomological Society of South Africa. July. Grahamstown, South Africa.
4. Douglas, N and Kruger, K. 2006. Persistence of grapevine leafroll-associated virus 3 (GLRaV-3) in Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae). 15th Congress of the Entomological Society of South Africa. July. Grahamstown, South Africa.
5. Saccaggi, D L, Kruger, K and Pietersen, G. 2006. Rapid identification of three mealybug species by multiplex PCR. 15th Meeting of the International Council for the Study of Virus and Virus-like Diseases of the Grapevine (ICVG). April. Stellenbosch, South Africa.
6. Kruger, K, Douglas, N and Sacaggi. 2006. Grapevine leafroll-associated virus 3 - vector interactions: transmission by the mealybugs Planococcus ficus and pseudococcus longispinus (Hemiptera: Pseudococcidae). 15th Meeting of the International Council for the Study of Virus and Virus-like Diseases of the Grapevine (ICVG). April. Stellenbosch, South Africa.
7. Douglas, N and Kruger, K. 2006. Grapevine leafroll-associated virus 3 transmission efficiency of Planococcus ficus and Pseudococcus longispinus (Hemiptera: Pseudoccidae). 15th Meeting of the International Council for the Study of Virus and Virus-like Diseases of the Grapevine (ICVG). April. Stellenbosch, South Africa.
8. Douglas, N, Malherbe, G P and Kruger, K. 2008. Grapevine leafroll-associated virus 3 (GLRaV-3) extraction from grapevines and mealybugs (Hemiptera: Pseudococcidae) for quantitative real-time PCR. XXIIIrd International Congress of Entomology. July. Durban, South Africa.
9. Ferreira, M, Pietersen, G, Barros, E and Kruger, K. 2008. Determining dispersal patterns of Planococcus ficus (Hemiptera: Pseudococcidae) among South African vineyards using RAPD markers. XXIIIrd International Congress of Entomology. July. Durban, South Africa.

Douglas, N, Krüger, K. 2008. Transmission efficiency of grapevine leafroll-associated virus 3 (GLRaV-3) by the mealybugs (Planococcus ficus and Pseudococcus longispinus) European Journal of Plant Pathology. Mnth Oct v. 122 n. 2 p. 207-212

Article

Saccaggi, D L, Krüger, K, Pietersen, G. 2008. A multiplex PCR assay for the simultaneous identification of three mealybug species (Hemiptera: Pseudococcidae) Bulletin of Entomological Research. Mnth Feb v. 98 n. 1 p. 27-33

Walton, V M, Kruger, K, Saccaggi, D L, Millar, I M. 2009. A survey of scale insects (Sternorryncha: Coccoidea) occurring on table grapes in South Africa. Journal of Insect Science. v. 9 n. 47

Article (web)

Saccaggi, D. 2006. Development of molecular techniques to identify mealybugs (Hemiptera: Pseudococcidae) of importance on grapevines in South Africa. (M.Sc.)

Thesis

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