Australia-China linkage for improved rice cold tolerance

The principal objective of this policy linkage and impact assessment project is to maintain and extend the scientific connections between Chinese and Australian rice research programs, particularly those focusing on tolerance to low temperatures.
Low temperatures during rice crop establishment and reproductive growth cause significant limitations to rice yields and production in Australia and China, and the development of varieties with enhanced levels of cold tolerance is rated the highest priority objective of the NSW DPI rice breeding program.
Additionally, tolerance to low temperatures is a critical foundation for the development of alternative irrigation strategies for rice production, which are aimed at reducing total water use and increasing water productivity.
We conducted an international workshop of Australian and Chinese scientists to review the current status of rice cold tolerance research and to discuss the potential for cooperative projects on cold tolerance. The workshop was to provide the basis for discussion with the objective of initiating joint activities on cold tolerance research.
The workshop was held from December 3rd to 8th, 2006, and the international participants are listed in Table 1. Participants from China were funded by from the project, and scientific critical mass was further enhanced by the addition of three participants from Korea and Japan funded by the Rural Industries Research and Development Corporation
Table 1. International participants to the Rice Cold Tolerance Workshop held at Yanco, December 3-8, 2006

Location
Participant
Address
Comments
Yunnan province, China
Dr Tan Xuelin
Rice Research Institute, Yunnan Agricultural University, Kunming
Rice researcher
Yunnan province, China
Dr Zhao Xiaochun
Rice Research Institute, Yunnan Agricultural University, Kunming
Now located at Sydney University, Cobbity
Heilongjiang province, China
Dr Zhang Fengming
Heilongjiang Academy of Agric. Sciences
Rice Breeder
Beijing
Prof. Wang Huaqi
Upland Rice Research Centre, China Agricultural University, Beijing
Aerobic rice development program
Beijing
Dr Zhikang Li
China Academy of Agricultural Science
Rice Molecular Breeding
Yunnan province, China
Dr Ye Changrong
School of Land and Food Sciences, University of Queensland
From China but now at University of Queensland
Korea, IRRI
Dr K.K. Jena
National Institute of Crop Science, RDA Suweon, Republic of Korea
IRRI representative in Korea
Miyagi Prefecture, Japan
Dr Kuniaki Nagano
Furukawa Agricultural Experiment Station
Rice Breeder
Hokkaido, Japan
Dr Yutaka Sato, Crop Cold Tolerance Research Team
National Agricultural Research Center for Hokkaido Region
Biotechnologist and Team Leader

The foremost outcomes from this meeting are summarised as follows:

Ongoing linkage to rice cold tolerance research in Yunnan province is essential due to the extensive genetic diversity available and the existence of reliable cold tolerance screening facilities at high altitude sites with the area available to test large populations
Development of a relationship with the Upland Rice Research Centre at China Agricultural University is warranted to interact in the development of aerobic rice. While this was not the main focus of the workshop, aerobic rice is important for water-limited areas of China and for future Australian rice production. Aerobic rice requires cold tolerance because there is no protection from standing water. Aerobic rice suffers a small yield penalty in China if adapted cultivars are used. The penalty is likely to be much greater in Australia, however, because humidity is so low. It is unlikely that cultivars could be directly transferred from successful programs in China or Brazil, but knowledge of traits which confer adaptation to aerobic conditions and access to relevant germplasm will be essential.
Germplasm exchange with research programs in the far north of China will be initiated. Production in Heilongjiang Province has increased dramatically from around 100,000 ha in 1949 to 2 million ha in 2006 with a predicted area of 3 million ha within the next decade. This production is entirely japonica rice and varieties are developed using cold-water screening. Unique germplasm characteristics such as the extensive use of semi-erect panicle types also merit investigation.
Cold tolerance is primarily associated with temperate rice production areas and japonica rice is used extensively for its adaptation to cooler regions. At the conclusion of the workshop Dr Jena (IRRI representative, Korea) proposed that a Temperate Rice Research Consortium (TRRC) be developed to continue and improve the liaison between producers of japonica rice. Seed funding for this initiative is to be provided by the Rural Development Administration of South Korea. All participants at the workshop supported the concept, and cold tolerance was seen to be a significant focus of the TRRC.

The principal activity of this project during the period covered by this report was the completion of a study tour to five locations in China. Participants in the study tour included Dr Laurie Lewin, rice industry consultant, Dr Peter Snell, Rice Breeder, Mr Russell Ford, Manager, Rice Research Australia and delegate to the RIRDC Rice Research Committee, and Mr Leigh Vial, rice grower and delegate to the RIRDC Rice Research Committee.
The visit encompassed five locations in China, including Yunnan Agricultural University, Kunming, Guangxi Academy of Agricultural Sciences, Nanning, China Agricultural University, Beijing, Liaoning Academy of Agricultural Sciences, Shenyang and Heilongjiang Academy of Agricultural Sciences, Harbin.
The study tour highlighted the importance of Yunnan as the centre of origin of japonica cold-tolerant rice, and the novel genes for cold tolerance which exist in the genetic background of traditional varieties. Following the visit the strategy for the future is to develop collaborative projects which seek to identify new genes for adaptation to low temperature and their mechanism of action such that new varieties can have multiple sources of cold tolerance.
Much work has been carried out on developing cold-tolerant varieties in a number of improvement programs world-wide, however pedigree analysis reveals that many varieties are built on the same sources of cold tolerance, thus combining varieties may be fruitless if the original gene/s for tolerance are present in each of the parents.
A shift in emphasis to the identification of cold tolerance genes in landraces gathered from high altitude areas in Yunnan is warranted. Although ambitious, new research should be brought to bear on uncovering the genetic basis for cold tolerance in landraces and traditional varieties from cold, high altitude areas, so that these genomic regions can be transferred into other genetic backgrounds to provide robust tolerance at all growth stages.
A total of 740 varieties from the Oryza rufipogon collection in Nanning, Guangxi Province, have been screened for cold tolerance at both the seedling stage and at the reproductive stage, resulting in 4 varieties showing seedling stage tolerance and 2 varieties with reproductive stage tolerance. A backcrossing program has been initiated to transfer tolerance from the wild background into the Australian variety Millin, with regular screening throughout development. This project has not received direct funding and thus is of lower priority with efforts proceeding in the background. Given the location of the institute in the southern part of China where production of indica types predominates, cold tolerance accords lower research priority. Ideally future research should be directed at elucidating the mechanism and genomic location of O.rufipogon cold tolerance genes in comparison with those of Yunnan O.sativa landraces.
There is a need to further explore the origins and mechanisms of cold tolerance in varieties utilised throughout the Liaoning and Heilongjiang provinces and develop the linkages between research institutions. The Heilongjiang Academy of Agricultural Sciences has a cold water screening facility at Harbin in which groundwater at 7C is mixed with surface irrigation water to obtain the desired temperature for screening segregating material.
Finally, further collaborative linkages are warranted with the comprehensive rice breeding program of China Agricultural University aimed at aerobic growing conditions. This research focuses on the development of varieties tolerant of water-limited conditions at all growth stages. Although not specifically aimed at cold tolerance, strategically these are high priority traits to build into future varieties as the Australian Rice Industry faces the prospect of generally lower and less reliable rainfall.
Technology to firstly identify genomic regions identified as contributing to cold tolerance and then to facilitate the efficient transfer of such regions will be increasingly important. Diversity Array Technology (DArT) is one means of obtaining an immediate representation of the genome, and by associating genotype with phenotype, regions associated with cold tolerance can be identified. Sequencing the DArT clones identified with specific positive regions allows identification of the location within the genome and suggests candidate genes for additional study. Further, these areas can be tracked with DArT analysis throughout subsequent crosses and back-crosses made to transfer the traits into varieties with appropriate adaptation and grain quality attributes. Elements of this work are being carried out with segregating populations varying for cold tolerance already developed at Sydney University, however additional funding is necessary to advance the work and enhance the linkages with Yunnan Agricultural University.