Enhancing Noogoora Burr biocontrol in northern Australia

Citation

Land & Water Australia. 2008. Enhancing Noogoora Burr biocontrol in northern Australia. [Online] (Updated April 28th, 2009)
Available at: http://lwa.gov.au/node/2573 [Accessed Tuesday 26th of April 2011 04:09:26 AM ].

Summary

This project investigated ways to improve the biollgical control of the highly invasive weed Noogoora Burr (Xanthium occidentale). The project was designed to assemble the necessary information to support an application to release additional strains of the Noogoora Burr rust fungus to enhance the impact of biological control in northern Australia. The introduction of additional exotic rust strains better adapted to tropical conditions is being investigated as a means of controlling Noogoora Burr in tropical areas.

Aims

The project objectives were:

collect, characterise and test host-specificity of exotic strains of Puccinia xanthii that are better adapted to the tropical climate, and
gather baseline data of Noogoora burr populations in northern Australia.

Outcomes

Following field surveys carried out in tropical America, rust-infected material from 12 sites in Dominican Republic and Mexico was imported into the containment facility. No infection of Australian Noogoora burr accessions was obtained with the imported rust material. In contrast, plants inoculated with two Australian rust strains developed severe symptoms; confirming that experimental conditions were suitable for infection. As a result, it was not possible to establish cultures of exotic strains and perform host-specificity tests.

Microscopic examination of leaves inoculated with exotic rust-infected material revealed typical plant resistance responses. Xanthium specimens collected in Dominican Republic and Mexico were found to be morphologically and genetically different to Australian Noogoora burr accessions and other Xanthium spp. These genetic differences may explain why no infection occurred on Australian Noogoora burr inoculated with rust-infected material from tropical America.

A diagnostic microsatellite marker to differentiate between exotic and Australian rust strains was successfully developed to provide a tool for monitoring strain establishment after release. Baseline data on Noogoora burr populations and prevalence of biocontrol agents were collected at sites on three river systems in the Northern Territory and northern Western Australia. This data will be essential to assess the impact of additional strains of P. xanthii, should any be released in the future in Australia.

Background

Noogoora burr (Xanthium occidentale; ranked 28th during the WoNS process and an approved target for biocontrol) forms monocultures across the northern regions of Australia. The exotic rust fungus, Puccinia xanthii, illegally or accidentally introduced in the mid-1970s to Australia, has been highly effective in controlling Noogoora Burr in south-eastern Queensland, but has failed to have a major impact in tropical northern Australia (Morin et al., 1996).