A major review of research relating to cotton biotechnology, plant breeding, weed and disease control, water use efficiency and farming systems has been held in conjunction with the Australian Cotton Conference on the Gold Coast.

The pre-Conference research review, sponsored by Monsanto and Cotton Seed Distributors (CSD), was attended by around 200 industry researchers, growers, consultants and agronomists.

CSD general manager, Adam Kay, said the review discussed research in progress as well as numerous issues for future deliberation, with prominent themes being maintenance and continual enhancement of the industry’s stewardship of both biotechnology and best management practices.

Kristen Knight from Monsanto highlighted the importance of extracting the best from biotechnology, while concurrently preserving its benefits and protecting the risk of resistance emerging in the field.

She particularly emphasized the importance of compliance with regulatory requirements, regular monitoring for insect pests, and enhancing refuge efficiency and best management practices.

James Neilsen from CSIRO and the Cotton CRC stressed the importance of soil type in influencing the way that cotton plants respond to moisture deficiencies.

He said that understanding how cotton responds to moisture stress on different soil types will assist in developing more robust water management strategies for a wider range of cotton growing regions, and may also contribute to the development of better genotypes.

Steve Yeates, also representing CSIRO and the Cotton CRC, noted that new technology BollgardÒ cotton needs careful management close to cut-out as it is then less able to compensate for water stress.

He advocated further research aimed at optimizing irrigation scheduling of BollgardÒII crops for yield and water use efficiency.

CSIRO plant breeder, Dr Greg Constable, defined water use efficiency as bales of cotton produced for each megalitre of total water use by cotton from all sources: soil storage, rainfall and irrigation.

Recent research found water use efficiency in the Namoi, Gwydir and Macintyre valleys at about 1 bale per megalitre, suggesting that 1.25b/Ml was achieveable, although since then instances of 2b/Ml have been recorded.

Michael Bange and Greg Constable highlighted the importance of fibre quality issues such as length, micronaire and nep levels, noting the influence of the environment, crop management, stress and variety on these factors.

Their take-home message was to focus on varietal selection, minimizing water stress, managing for uniform growth and boll set, and correct defoliation timing as essential elements in assuring maximum fibre quality.

A new industry decision support tool, FIBREpak, has been developed to assist growers and consultants maximize yields without degrading fibre quality. CSIRO’s research strategy is to develop varieties with specific fineness and maturity for each region, then advise on how the crop should be managed to optimize micronaire.

Dr Constable said modern testing methods are being developed to differentiate fibre fineness and maturity as better indicators of ultimate yarn properties than micronaire.

Following the rapid adoption of Roundup ReadyÒ technology, the Australian cotton industry is placing increased emphasis on preventing and delaying  the evolution of glyphosate resistance in weeds.

Jeff Werth from QDPI&F said research models indicate that when glyphosate is used alone, resistance is possible after 12-17 years. However, if used in conjunction with one other weed control method, resistance can be delayed to 30 years, prolonging the benefits of glyphosate tolerance as a weed management tool.

The phased introduction of Roundup Ready FlexÒ cotton by Monsanto this season (pending APVMA approval) will allow over-the-top glyphosate applications well into flowering.

Monsanto’s Craig Dunn said this will enable growers to tailor their in-crop herbicide applications to target weed development instead of the stage of cotton growth, leading to more effective weed control.

Hs said customizing herbicide application to environmental conditions will reduce the risk of off-target drift and maximize herbicide efficiency.

CSIRO plant breeder, Greg Constable, said three BollgardÒ Roundup Ready FlexÒ varieties would be released in 2006, followed by a number of others in the following two years. Each are expected to contain a generally improved combination of yield, fibre quality and disease resistance.

Two major diseases were discussed at the Forum: fusarium and black root rot. CSD pathologist, Dr Stephen Allen, said fusarium has now been reported in the Darling Downs and Theodore regions in Queensland, and in the Macintyre, Macquarie, Gwydir, St George, Bourke and Walgett regions on NSW.

He said fusarium has a tendency to increase in severity with plentiful rainfall in the October to November period and is known to increase and spread via the common use of cereal rotations.

Improved farm hygiene, the use of less susceptible varieties, particularly those with high F-ranks, and selecting later planting dates can help alleviate the threat of fusarium, Dr Allen said.

Dr David Nehl from the NSW Department of Primary Industries said black root rot has emerged as a widespread and chronic disease of cotton in major growing regions, but there are no practical eradication methods, making prevention via farm hygiene a key objective. 

Contaminated soil movement via farm machinery and vehicles is a significant contributor to transfer of the pathogen within and between farms.

The researchers also note that the use of high-retention transgenic varieties of cotton may enable extension of the sowing window to optimise disease avoidance with less risk of compromising yield potential.

Several leads are currently under investigation for developing better disease control, including the impact of crop rotations on spore concentration and disease, the use of novel biofumigation (green manure) crops, and the relationship between soil types and disease severity.

A further avenue of research is the use of non-toxic chemicals, such as acibenzolar-S-methyl (Bion®, Syngenta Crop Protection), that activate a degree of resistance in the plant prior to infection by the pathogen. This enhanced form of resistance is referred to as systemic acquired resistance.

Recent research, investigating the impact of BionÒ applied as a seed treatment (jointly funded by Cotton Seed Distributors), showed a decrease in the severity of black root rot in 13 of 19 field trials conducted in 2005-06.