Health and wealth from the Brassica genome

The mapping of the DNA sequence common to canola and an important family of vegetables is set to improve the health of humans and livestock, says Southern Cross University’s Professor of Plant Genomics Graham King.

Professor Graham King, scientific director for Southern Cross Plant Science, was part of a large team of international crop scientists who recently mapped the genome sequence for the 10 chromosomes shared between canola (Brassica napus) and Chinese cabbage, a type of Brassica vegetable (B.rapa).

The paper, ‘The genome of the mesopolyploid crop species Brassica rapa’, is published in the latest edition of Nature Genetics.

Professor King was involved in key stages of the landmark project to ensure links were established between the DNA sequence and the underlying genetic maps of the canola and Chinese cabbage chromosomes.

He said the Brassica DNA sequence will boost research aimed at increasing farming profits while enhancing the value of canola and vegetables to human and livestock health.

“As with the Human genome project completed a decade ago, the Brassica genome sequence provides scientists with a comprehensive roadmap of all the genes needed to specify a Brassica plant,” said Professor King.

“This means we can be far more precise in our identification of genes that contribute to key agronomic characteristics, such as quality, optimisation of fertiliser use, pest resistance and adaptation to climate change,” he said.

“Therefore we can work with breeders to generate improved cultivars that maintain and utilise natural genetic diversity within the Brassica gene pool.”

Compared with wheat, which was domesticated more than 5000 years ago, canola (Brassica napus) is believed to have arisen relatively recently through the cross-hybridisation of two species, one represented by vegetables such as cabbage, kale and broccoli; the other, Brassica rapa, represented by turnips, brocoletto and Chinese cabbage.

“The diversity amongst brassicas is quite remarkable. There is huge potential to tap into this variation for improved cultivars,” said Professor King.

Professor King said the rapid increase in the acreage of canola in the past 40 years arose from the work of breeders and geneticists in Canada who identified lines that had reduced levels of erucic acid, previously associated with causing health problems when used as animal feed.

Oilseed brassica crops contribute more than $2 billion annually to the Australian economy. Canola is used as a healthy cooking oil and in a range of processed foods including breads and spreads; while in Europe it is also widely used in biodiesel. There is considerable scope to use it as a renewable source for polymer processing for non-edible products. After the oil is extracted from the seeds the high quality protein is used as livestock feed.

Nutricious brassica vegetables such as broccoli, cauliflower, cabbage, Chinese cabbage and pak choi are widely eaten in Australia. Vegetable brassicas are rich in natural plant chemicals called glucosinolates. Certain glucosinolates have been found to contribute to an anti-carcinogenic diet by inducing detoxification enzymes in mammalian cells and reducing the rate of tumour development. There is extensive genetic variation for glucosinolate composition within the Brassica gene pool.

Glucosinolates and other secondary sulphur metabolites are also valued in agricultural production because it is thought they contribute to bio-remediation of contaminated soils.

“There is increasing demand for canola across the world as economies grow and seek food high in calories and protein. The recent widespread use of canola oil in Europe for biodiesel is also pushing up demand,” said Professor King.

In addition, canola plays a crucial role in Australian farming systems as a cash crop and through its rotational benefits to subsequent cereal crops.

The Grains Research & Development Corporation (GRDC) invests over $4 million a year in brassica pre-breeding and breeding research and development, with additional resources invested in areas such as farm practices and agronomy.

“The GRDC will continue to invest in research and development and related activities to ensure the continued success of the Australian canola industry,” said managing director, John Harvey.

“However we are a small player by international standards, investing around two per cent of the global effort in grains R&D,” he said. “Therefore it makes sense to work with international partners where we can return a benefit to the Australian grains industry. The multinational Brassica rapa genome sequencing project is an international collaboration with sequencing, database development and management tasks shared among a wide international consortium.”

Professor King has used DNA analysis to investigate the origins of the domestication of cauliflower, as well as narrowing down likely candidates for the progenitors of the hybridised canola species.

Professor King has been involved in Brassica research for over 20 years, initially focussing on vegetables such as cauliflowers and broccoli. He recently moved to Southern Cross University in New South Wales from Rothamsted Research in the UK, where he led research on oilseed biology and genetics and led a national genetic improvement network that brought together breeders and academics. For two years he chaired the multinational steering committee that drove the Brassica genome project, and has played a key role in co-ordinating other platform resources and information sharing. Earlier this month he was an invited keynote speaker at the bi-annual Australian Research Assembly on Brassicas, this year held at Wagga Wagga.

Professor King is looking forward to working with colleagues in Australia, including Associate Professor David Edwards and Dr Jacqueline Batley at the University of Queensland, who led the Australian contribution to the genome project.

Brassica Genome Sequencing Consortium

The multinational Brassica rapa Genome Sequencing Consortium is comprised of member scientists from Australia, Canada, China, France, Germany, Japan, Korea, The Netherlands, United Kingdom and the United States.

The Brassica genome assembly and other resources are now available in the public domain at www.brassica.info
Photo: Golden fields of canola (Brassica napus).