Ground Cover North : Ground Cover 062 June-July 2006 - North
Old weed may turn the salinity tide Researchers have turned to a common weed, sea barley grass, for genes to improve salt and waterlogging tolerance in bread wheat BY EAMMON CONAGHAN n Improved tolerance to both waterlogging and dryland salinity has been achieved by introducing into the wheat genome all seven chromosomes from a native plant called sea barley grass (Hordeum marinum). Project leader Dr Tim Colmer, from the Cooperative Research Centre for Plant-based Management of Dryland Salinity (Salinity CRC) in Perth, explains that sea barley grass is a wild relative of wheat that grows quite happily in ground almost as salty as seawater. “In fact, for many years it has been seen as an indicator of salinity,” Dr Colmer says. “It is also tolerant to waterlogging which is a major constraint to wheat production in southern Australia. “In WA alone, waterlogging adversely affects 1.8 million hectares of crops and pastures each year.” Using genetics to mitigate the impact of environmental stress has not been a straightforward matter. Too frequently scientists have found that stress-tolerance traits require many inter-dependent genes that are dispersed throughout a genome on a number of chromosomes (so-called multi-gene traits). Funded by the GRDC, Dr Colmer and his team sought a way around the genetic complexity by first searching for a suitable stress-tolerance profile in wild relatives of wheat and then determining which accessions could be crossed with wheat. Sea barley grass was chosen after tests on about 30 wild relatives of wheat. Ironically, the Australian researchers went to a seed bank in Sweden to conduct the search only to identify a species naturalised in Australia. The chosen germplasm was then supplied to Dr Rafiq Islam, a highly skilled cytogeneticist at the University of Adelaide. He used the technically demanding ‘wide- hybridisation’ technique to stably incorporate all seven sea barley chromosomes into bread wheat’s already supersized genome. “The resulting hybrid has 56 chromosomes and is known as an ‘amphiploid’,” Dr Islam says. “The term reflects the presence of a full set of chromosomes from two different parental species. “The same technique was used to produce triticale, which combines wheat and rye genomes. Using the same naming convention, the new amphiploid is called ‘tritordeum’ – a combination of Triticum and Hordeum.” Dr Colmer says the tritordeum plants produce slightly smaller grain of a lower quality than wheat, so the crop will probably be harvested as a feed grain rather than as bread or noodle wheat. However, future generations may show improvements in grain size and quality. In glasshouse tests, a tritordeum variety based on Chinese Spring wheat was found to express levels of waterlogging tolerance in between its wheat and grass parents. The tolerance was primarily achieved as a result of improved root aeration. Field trials to precisely define salt- tolerance characteristics are scheduled to start with the 2006 winter sowing season. In the meantime, ongoing efforts to improve grain quality are under way, primarily by trimming back on the amount of sea barley grass DNA residing within the wheat genome. “Lines containing just one grass chromosome pair have already been created for five of the seven grass chromosome pairs,” Dr Islam says. “So far, none of these ‘disomic addition lines’ have expressed the waterlogging tolerance trait. Ongoing efforts are focusing on the two remaining chromosomes – that’s numbers three and six.” Nonetheless, the project has demonstrated that wild species can be crossed with wheat and that, according to Dr Colmer, is “a huge step forward. We’re now working to see whether it could eventually become a new cereal in itself. “The long-term goal is to retain the salt and waterlogging tolerance of the cross, but not sea barley’s other qualities. That’s potentially 10 years down the track.” He thinks the work is important because it aims to give growers productive and economic options for mild to moderately saline-affected land – land that can no longer be cropped with current cereal cultivars. On some areas of salt-affected land, Dr Colmer envisages salt-resistant wheat being grown in an alley-type system with saltbush. He says that the discovery will not remediate land, but rather provide some opportunity to earn a return on land that might otherwise remain unimproved. In the long term he hopes the research will eventually lead all the way to the development of a high-quality wheat variety that can be grown on saline land. Seaweed production from salt farm dams: Page 25 GETTING INTO GENES PROVES A SMART MOVE FOR SCHOOLS BY GIO BRAIDOTTI n A program raising the level of community understanding of crop genetics through high school workshops has been recognised with the CRC Association award for excellence in innovation in education, training and public outreach. The award went to the ‘Get Into Genes’ workshop, which is a joint initiative between the Molecular Plant Breeding Cooperative Research Centre (MPBCRC) and the Australian Centre for Plant Functional Genomics (ACPFG). Devised and run by MPBCRC’s Dr Amanda Able and Dr Heather Bray, with Ms Belinda Barr from the ACPFG, the initiative recruits the centre’s postgraduate students to provide secondary schools with hands-on experience of agricultural uses for DNA technology and to demystify genetic engineering. “Secondary schools are required to teach gene technology in the context of practical applications, but that generally results only in a high awareness of forensic science,” Dr Bray says. “What we wanted to do was teach biotechnology in the light of its value to agriculture and the development of improved plant varieties.” The workshops introduce students to plant breeding and genetics. They handle wheat and barley plants, extract DNA and perform diagnostic experiments related to salt tolerance. “In the first term in Adelaide, 600 of South Australia’s 4000 biology students had access to the workshop,” Dr Bray says. She says the program is now established in Adelaide and is in the process of being made available nationally. The two-hour workshop is offered free to secondary schools and no special facilities are required. More information: Dr Heather Bray, 08 8303 7414 Salinity GROUND COVER JUNE -- JULY 2006 8 KEY POINTS n Tolerance to two environmental stresses has been transferred from sea barley grass to experimental wheat lines and commercial cultivars n Salt and waterlogging tolerance traits were transferred into wheat by incorporating all seven grass chromosome pairs n The genome transfer resulted in feed-quality grain and effor ts are under way to improve quality by whittling back on the sea barley DNA Dr Tim Colmer, from the Salinity CRC, has managed to cross a salt-tolerant weed with wheat, to produce the first real chance of growing grain on salt-affected farmland. PHOTO: EVAN COLLIS GRDC Research Codes UWA340 & UWA368 More information: Dr Tim Colmer, 08 6488 1993, firstname.lastname@example.org; Dr Rafiq Islam, 08 8303 7282, email@example.com Heather Bray (right) with two students from Lucindale High School during a Get Into Genes workshop.
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