Microsoft word - executive summary 2000-04.doc

Project 2000-04 Biological control of Blackberry: Executive Summary Background:Blackberry interferes with silvicultural activities in New Zealand (NZ); therefore it would be of benefit to the forestryindustry if this weed could be brought under control by biological agents. The weed is also a problem in Australia, andin the late 1970s a European rust fungus (Phragmidium violaceum) was selected as the most promising biocontrol agentfor that country. In both Australia and NZ the common name ‘blackberry’ is applied to numerous species and hybrids inthe genus Rubus that differ in their susceptibility to different strains of P. violaceum. Host range studies were conductedin Europe to select the most virulent strain of P. violaceum for Australia’s worst blackberry species. Before this testingwas complete, an unknown strain (or strains) of the rust was/were illegally introduced to Australia (first detected in1984). The officially sanctioned rust strain (F15) was released in Australia in 1991 and 1992. The rust was firstrecorded on blackberry in NZ in 1990 and it was believed the illegally introduced strain/s had arrived from Australia viawind dispersal of spores across the Tasman Sea. The rust spread across NZ quickly, but disease incidence has beensporadic and uneven. It seemed that blackberry species in NZ varied in susceptibility to the rust and that susceptiblespecies were being replaced by more resistant ones. There is potential to increase the efficacy of biocontrol ofblackberry in NZ by importing further strains of the rust, either from Australia, or from Europe. However, before thiscould happen, it was important to confirm the origin and identity of the NZ strain/s.
Project aims: Collect blackberry rust from a number of sites across NZ, extract rust DNA, and send it to Australia forcomparison with the DNA of their rust strains. Project undertaken by Landcare Research (LR).
Results:Phragmidium violaceum was collected from nine Rubus species from 23 sites scattered across both islands of NZ. Theprocess to produce pure genetic lines of each rust strain proved difficult, and as a result DNA from only seven strainscould be sent to Australia to beanalysed using the ‘selectively variation that is consistent witheither multiple introductions from Australia, or diversification following establishment in NZ. The legal strain, F15, israre in Australia and was not collected in NZ.
Conclusions:1) It is highly likely that the strains of P. violaceum that occur in NZ originated from descendents of strains released 2) 2) Strain F15 and its descendents are rare in Australia and probably haven’t reached NZ yet; and3) 3) NZ could import strain F15, but the Rubus sp. it was most effective against in glasshouse tests doesn’t occur in NZ. The Australians have just (April 2004) released eight more strains of P. violaceum. To improve biocontrol ofblackberry in NZ one could: find out which Rubus sp. are susceptible to these new strains, and decide whether toseek permission to import potentially useful strains; or, wait for them to cross the Tasman on their own (the latter islikely to take ca. six years). Alternatively, the host range of strain PV23C could be tested, and if it were shown toattack more, or more important, Rubus sp. than the other NZ strains, it could be deliberately spread. As a result ofthis project, we know the likely origin and identity of the NZ strains and can make informed choices.
Acknowledgements:Shaun Pennycook (LR) collected the rust; Paula Wilkie (LR) ‘bulked up’ the rust; Duckchul Park (LR) extracted the Rust DNA; Don Gomez (CRC Australian Weed Management) performed the SAMPL analysis; Kathy Evans (WeedsCRC, now at TIAR, University of Tasmania) managed the work in Australia; and David Glenny (LR) identified theRubus sp. This research was funded by the Forest Health Research Collaborative and EBOP. The project was managed,and this summary written (in May 2004), by Jane Barton, contractor to LR.
Gomez, D.R., Evans, K.J., Harvey, P.R., Baker, J., Barton, J., Jourdan, M., Morin, L., Pennycook,S.R., Scott, E.S., 2006. Genetic diversity in the blackberry rust pathogen, Phragmidium violaceum,in Europe and Australasia as revealed by analysis of SAMPL. Mycological Research 110, 423-430.

Source: http://www.fhrc.org.nz/documents/2000-04.pdf