INCREASING yield remains the primary goal of cotton breeding researchers in Australia, who face a daunting task.
It can take 20 to 25 years to develop a new variety for commercial release, which means people like CSIRO cotton breeder Dr Warwick Stiller have to both think strategically and be extremely patient.
"We have to try to identify if there's going to be a problem in 10, 15, 20 years' time, and we need to be trying to investigate solutions for that now," he said.
"If there's a new problem, such as a new disease that shows up in the industry this season, for us to be able to have a variety that might be able to help in the management of that, we needed to have started work 20 years ago."
CSIRO has developed all cotton now grown in Australia, releasing more than 100 new varieties in the past 30 years with commercial partner Cotton Seed Distributors.
They include cultivars resistant to bacterial blight, verticillium wilt, fusarium wilt, and cotton bunchy top.
Dr Stiller, who has led the Cotton Breeding Research Group since 2012, said factors affecting yield included disease and insect resistance, water use efficiency, regional adaptation and the fibre length and strength demanded by international customers.
Analysis of CSIRO data found 48 per cent of all yield gains were directly attributable to new varieties, with 28pc from improved management practices, and 24pc from interaction between the two.
Australian cotton yields are already the highest in the world, adding an extra layer of complexity for plant breeders.
Dr Stiller said it was pointless developing varieties with new traits unless they yielded as well or better than existing varieties, and also included the GM traits required by the industry for resistance to the primary pest Helicoverpa as well as tolerance to various herbicides.
"Despite the fact that these other traits might be important, nobody's going to grow it just for that trait," he said.
"Yield is still the primary thing. It actually is very hard, and takes a long time to be able to identify these traits, do all the research to develop the traits, incorporate it in the germplasm, and then release a variety that is competitive in the marketplace."
The silver lining to this protracted timeline is plant breeders have done much of the groundwork necessary to address increasing climate variability and new challenges thrown up by the spread of the cotton industry into non-traditional growing regions further to the south and north.
This includes secondary pests, such as two-spotted spider mites and silverleaf whitefly, which are likely to become more of an issue in hotter, drier conditions that accelerate their life cycles and population growth.
Dr Stiller said diseases such as black root rot and verticillium wilt had the potential to cause much more damage in the cooler conditions of southern New South Wales and Victoria than in the more traditional warmer growing regions of northern NSW and Queensland.
But much remains unknown about which pests and diseases growers might face in northern Queensland, the Northern Territory and Western Australia.
"Going into a very tropical environment, the diseases and some of the pests are quite different to other growing regions," he said.
"Some are known, but others will emerge that we don't yet know of, because the industry hasn't been established there for long enough.
"That creates a challenge and so we're very much on the lookout for the first sign of when something like that might emerge as a problem so we can start to do something about it."
In other news:
Dr Stiller said the breeding program had made significant progress on developing varieties that would help growers further reduce insecticide use.
The most advanced, with resistance to two-spotted spider mites, were in the variety development phase and could be commercially available in the next five to seven years.
Dr Stiller said it was an exciting time to be involved in cotton breeding, particularly with advances in resistance to diseases, such as black root rot.
"It's something I've been working on for about 20 years," he said.
"We've now had the first couple of years of field trials. And that looks very exciting, particularly for the southern growers, because it is becoming a significant limiting factor for expansion in the south. Part of the reason why it's exciting is because it's taken such a long time, and nobody else around the world has been able to achieve it."
Dr Stiller said new techniques and technologies such as genomic selection and gene editing were revolutionising the way plant breeders operated by improving accuracy and rates of genetic gain.
"It's very complicated and expensive," he said.
"And it's not without its challenges.
We've been working on it for six or seven years now, just in a research phase. We're in the process of starting to use that in a much more applied way, from this season onwards."
