Noogoora burr (Xanthium occidentale)

Background | Enhancing biocontrol in northern Australia | Key People| Collaborators | Publications

Worldwide, Noogoora burr is an annual weed of 11 major agricultural crops in 28 countries, and is listed one of the 10 most noxious weeds in the USA (Hocking and Liddle, 1995). It is a major problem to the livestock industry because it competes with palatable plants, seedlings are toxic to stock, burrs reduce wool values and it poses quarantine issues. In far northern Australia it continues to invade previously un-infested catchments and is currently perceived to be a major threat by pastoralists and government agencies. Noogoora burr is a weed across northern Australia, mostly of riparian areas.

Background

Noogoora burr was one of the first weeds to be systematically targeted by biological control and there were two major phases in the Australian program: 1929-1940; 1953-1975. Three agents have been released: a seed-feeding fly in the 1930s, and two stem-borers in the 1960s. None have resulted in significant impact. A fourth insect, a gall-forming moth (Epiblemma strenuana) was released against parthenium in 1982 and also attacks Noogoora burr, on which it causes some damage. However, Noogoora burr infestations along eastern Australia have been largely brought under control by the rust Puccinia xanthii which was accidentally or illegally introduced into Australia in 1975. The rust fungus though has not controlled infestations in the far north (including the Northern Territory and Western Australia).

An eradication program was terminated in the Kimberley in the early 1990's, and the remaining populations contained within a quarantine zone. NT Department of Infrastructure, Planning and Environment have also considered Noogoora burr to be an important weed and contracted CSIRO in 1999 to review past biological control attempts and to determine the potential of renewing it. This report highlighted that the best bet for successful biological control is to find a rust strain that is better suited to climatic conditions in northern Australia (especially warmer summer minima).

Enhancing biocontrol in northern Australia

Achievements of 2006-08 project

Field surveys for exotic isolates of Puccinia xanthii were undertaken in 2007 in Venezuela, Mexico and Dominican Republic, areas that climatically match those of northern Australia where the rust fungus has not been highly effective (van Klinken & Julien, 2003). Rust-infected material from 12 sites in Dominican Republic and Mexico was imported into the CSIRO Black Mountain Containment Facility in Canberra.

Pathogenicity tests revealed that Noogoora burr and other Xanthium spp. from Australia were resistant to these exotic rust isolates. In contrast, plants inoculated with Australian rust isolates developed disease symptoms. This was expected based on a previous study which showed that Xanthium spp. comprised in the ‘Noogoora burr complex’ were susceptible to an Australian isolate of P. xanthii.
Closer examination of Xanthium specimens collected in the Dominican Republic and Mexico confirmed that they were morphologically and genetically different (based on chloroplast and ribosomal DNA sequence data) to Australian accessions of Noogoora burr and other Xanthium spp.

A diagnostic microsatellite marker to differentiate between exotic and Australian rust isolates was successfully developed to provide a tool for monitoring exotic isolates, should any be released in Australia. Primers were designed to amplify eight microsatellites (Simple Sequence Repeats) DNA loci isolated and characterised from genomic DNA of P. xanthii. Genetic variation at these loci was observed across 29 single-telium isolates from Australia, Hungary, Brazil, Argentina, Mexico and Dominican Republic. Allelic variation at some loci was useful in discriminating between isolates from Australia and tropical America.

Baseline data on Noogoora burr populations and prevalence of biocontrol agents (P. xanthii and the moth Epiblemma strenuana) were collected by collaborators from the Department of Natural Resources, Environment and the Arts (NRETA) 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 isolates of P. xanthii, should any be released in the future in Australia.  

Conclusion

Genetic differences between Xanthium accessions from tropical America and Australian Noogoora burr accessions most likely explain why the latter were not infected by the tropical American isolates of P. xanthii.

A more extensive follow-up project is required to deliver on the original goal of introducing additional isolates of P. xanthii better adapted to the climate of tropical northern Australia. The establishment of an outdoor experimental garden consisting of northern Australian accessions of Noogoora burr in tropical America would be required to source pathogenic rust isolates.

Key People

Collaborators

DAFWA - Department of Agriculture and food, Western Australia

Australian Government, DAFF – Department of Agriculture, Fisheries and Forestry

Background | The Project | Key People| Collaborators | Publications