What is the weed potential of GM cotton in the Northern Territory

Region: Greater Darwin, Katherine Region | Topic: Horticulture
Nov 2022
Cotton fields

Cotton farming is growing in the Northern Territory (NT) owing to favourable tropical climate and use of contemporary technologies. About 8,000 hectares of cotton was planted in 2021-22 season, more than double the crop from the 2020-21 season. Historically, the NT cotton bales have been shipped to Queensland for processing at a high freight cost to the grower. During transportation, loose cotton bolls can fall off the truck and deposit on the roadside.

Later this year, the first cotton gin for commercial use in the NT is expected to be operational in the Katherine region. This will reduce industry overheads and limit the amount of cotton debris lining the roads. Answering the question of the potential weediness of the cotton debris is of great importance both to industry and the broader community. The Northern Territory Department of Industry, Tourism and Trade (DITT) has responded to the apprehensions that genetically modified (GM) cotton spread around the roadside could potentially turn into a difficult-to-control weed owing to its enhanced fitness derived from resistance against glyphosate (a well-known herbicide).

GM Regulation in Australia

GM cotton has been one of the most adopted transgenic crop commodity globally, since its release more than 25 years ago. In Australia, the Office of the Gene Technology Regulator (OGTR) has prepared a comprehensive Risk Assessment and Risk Management Plan (RARMP) for GM cotton after completing a thorough review of relevant national and international scientific literature and consulting important stakeholders including subject experts, state agencies, and the public at large. OGTR maintains oversight of commercially grown GM cotton, monitors scientific and other literature for any new information relevant to GM cotton, and has the power granted through legislation to assess that information in relation to existing licences, thereby ensuring continued safety of GM cotton production in Australia.

Research findings

DITT has invested in research to test whether GM cotton is more likely than conventional cotton to form weedy or invasive populations in different locations, habitats, seed type, or population density. Both GM and conventional cotton seeds were planted at 12 sites in northern Australia (in Katherine, Kununurra and Broome regions) as part of a multi-year field experiment.

The study found no evidence that the GM trait provides increased fitness which could lead to increased weediness of cotton in northern Australia. Over time, both GM and conventional cotton plants decreased in population.

The results indicated that in terms of germination, establishment, and survival, GM and conventional cottonseeds were identical. Environmental factors, such as nutrient intake, water availability, plant competition, being eaten by insects, grazing and trampling by cattle, and fire all contributed to lower survivability of both GM and conventional cotton plants. In other words, the results proved that GM cotton populations will not be more invasive than conventional cotton.

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