Resistance to the thrips vectors of tomato spotted wilt virus (TSWV) in potato
Westmore GC1, Allen GR1, Davies NW2, Wilson CR1
1 Tasmanian Institute of Agricultural Research, University of Tasmania, Private Bag 98, Hobart, Tasmania 7001, Australia.
2 Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania 7001, Australia.
Correspondence: Calum.Wilson@dpiw.tas.gov.au
In potato, infections with Tomato spotted wilt tospovirus (TSWV) are sporadic, but losses are considerable (Wilson 2001). Potato cropping regions of south-eastern Australia are particularly prone to TSWV epidemics (Wilson CR. 2001. Plant Pathology 50: 402 每 410). Typically TSWV infections in potato are clustered along crop borders, with no aggregation within the crop and infections are associated with summer thrips flights. This suggests a major role of external virus inoculum, and limited internal secondary spread of infection. However, in some varieties, TSWV spread from infected potato has been noted. Whilst four of the known TSWV thrips vector species are found in Australia (Mound LA. 1996. Acta Horticulturae 431: 298 每 309), only two (Thrips tabaci and Frankliniella schultzei) are associated with potato in Southern Australia, and in Tasmania only T. tabaci (Wilson 2001). There are no current effective methods available for controlling TSWV in potato. Host resistance provides a promising long-term strategy for TSWV management (Cho JJ et al. 1989. Plant Disease 73: 375每83). Most breeding programs focus on virus resistance (eg. Black LL et al. 1991. Plant Disease 75: 863), however resistance to the vector can provide valuable disease control (Jones AT. 1987. Annuals of Applied Biology 111: 745每772). Differences in the perception and performance of T. tabaci on potatoes has been previously described (Jericho C. 2005. Epidemiology and the development of risk assessment models for the management of tomato spotted wilt virus (TSWV) in potatoes. PhD Thesis, University of Tasmania). Field performance of some potato varieties highly susceptible to TSWV infection when mechanically challenged, has seen few plants succumb to infection within field trials. Other field trials have shown differences in number of onion thrips and feeding damage across potato cultivars, suggesting resistance to the thrips vector was most likely. Resistance may be in the form of attraction/deterrence and/or resistance to thrips reproduction. A range of plant characteristics are known to alter thrips landing, feeding and reproductive behaviour (eg. Brodbeck BV et al. 2001. Entomologia Experimentalis et Applicata 99: 165每72; Koschier EH et al. 2002. In: Marullo R, Mound L, Editors. Thrips and tospoviruses. Proceedings of -the seventh International Symposium on Thysanoptera, 185每187). Subtle volatile chemical differences in potato cultivars have been identified, particularly in the level of monoterpenes and sesquiterpenes. Paired colour preference trials have shown onion thrips differentiate between subtle colour differences, which may extend to potato cultivars ranging from light- to dark-green foliage, and light-green to dark-purple stems. Virus transmission trials have shown varying levels of vector competence in onion thrips populations sourced from different locations and from different hosts. Our efforts are now focused on a broad approach investigating colour preference, chemical deterrence, and factors underpinning vector competence.
