Wheat is the second most important crop (after rice) in China's Sichuan Province. About 2.3 million ha are planted each year, and this yields about 7.85 million tonnes of grain that is used mainly for making noodles and bread. However, the quantity did not meet the needs of the current population of 89 million people and the Government was anxious to improve grain output. It was important that the province improve the efficiency of its wheat breeding efforts. The quality of the grain was also often inadequate for the products it was needed for. Yellow alkaline noodles, a popular food in Japan, China and elsewhere, look unattractive when made with wheat of the incorrect quality. There was an opportunity to improve relevant attributes through genetic manipulation.
Climatic conditions played a part in limiting the yield (inappropriate rain and periods of cold and low light intensity), but there were other factors. These included disease (principally the fungal disease stripe rust), also the problem of the premature germination of the wheat grains while still on the stalk, which is faced in Australia as well as Sichuan. Known as sprouting, it is promoted by rainfall coming just before the harvest. Certain wheat varieties - white-grained ones - are inherently more susceptible to this problem. Sprouting resistance exists in some varieties but it proved difficult to select for in a breeding program because there were no easy markers for it.
Another problem was the intermittent sterility occurring in some wheat types in Sichuan. This could be related to low light intensity because of a naturally cloudy climate, and to cold periods, but resistance genes for this exist. CIMMYT (the International Maize and Wheat Improvement Centre) had been trying to upgrade the productivity of wheat grown in Sichuan by providing elite germplasm and training. However, some of this germplasm, when grown in Sichuan, suffered from intermittent sterility.
The project worked to strengthen wheat breeding capacity in Sichuan and to develop better wheat varieties for the province, and also to provide a better understanding of wheat improvement for noodle quality and sprouting resistance for similar environments in Australia.
The project was divided into five main parts: the first studied the interaction between genotypes and the environment in Sichuan's wheat. A range of Sichuan, CIMMYT and Australian cultivars were grown at 10 sites for three years. Analysis determined the effects of environment on yield, and how and where breeding materials should be yield-tested in order to make the fastest breeding progress.
The second part identified breeding technologies for wheat varieties that exhibit the processing characteristics necessary for making the noodle and bread products consumed in Sichuan. The third part focused on the diversity and range of stripe rust pathogens and the development of wheat varieties with durable resistance to them, while the fourth part looked for genetic markers to help develop sprouting-resistant lines.
Intermittent sterility was the focus of the fifth sub-project, and researchers worked to develop a cost-effective screening for the problem, using molecular markers.
Analysis of three years of yield trial data for 14 Australian, Chinese and CIMMYT wheat lines grown across 10 sites in Sichuan, together with analysis of 10 years of Sichuan Provincial Trial data has yielded important information concerning the range of wheat-growing environments in the Province and the number of trials and trial sites required to assess varieties. This information will inform long-term breeding strategies and wheat variety deployment across Sichuan.
Investigations into quality characteristics for high-quality fresh white noodles, including both Australian and Sichuan wheats, have provided very useful information concerning relative performance of these lines and which attributes in the Chinese and Australian materials might be suitable for crossing into the relevant adapted germplasm for each country. Taste panel evaluations have indicated that genes controlling grain hardness are linked to noodle texture, while colour preference tests indicate that the market has a preference for a creamy white noodle appearance, whose quantitative parameters using a Minolta colour meter can be used as a selection tool by breeders. Chinese lines with resistance to grain blackpoint have been identified and are being evaluated in Australia, while testing to eliminate lines with high levels of late maturity a-amylase has now been adopted in Sichuan.
Stripe rust, caused by Puccinia striiformis, is currently a major foliar disease of wheat throughout China. The introduction of near-isogenic lines (NILs) and trials conducted in Sichuan by Prof Bob McIntosh during this project indicate that major single genes for resistance are very vulnerable to breakdown in the Sichuan environment. Multiple minor effect genes that give adult plant resistance in the field are much more likely to result in durable resistance and this approach is now being adopted by some Sichuan wheat breeders with the hope that future new varieties will show effective and durable resistance in the Sichuan environment indefinitely. A young Chinese plant pathologist has received training in the assessment of disease severity in the field, conducted in Australia and Sichuan.
Germination of grains in the head following rain at harvest time is a major cause of economic losses in both countries. Markers for major genes conditioning embryo dormancy in Chinese and Australian lines have been identified and published. These markers will assist the selection of lines with resistance to preharvest sprouting. Chromosomal regions conditioning the expression of low polyphenol oxidase activity, a desirable characteristic for noodle colour stability, have been identified and a simple biochemical test is now in use in Chengdu to determine breeding lines carrying this trait.
During the project, trials were conducted to determine the factors which lead to intermittent reproductive sterility in some wheats in Sichuan. Results indicate that lower temperature at flowering was the major factor in the overcast spring conditions of Sichuan, and some locally-derived varieties had much better tolerance to the lower temperatures than materials developed elsewhere. This information is now being widely used for parental selection in breeding programs in Sichuan. Genetic analyses suggest that the very high fertility of the local variety Chuanyu 12 is controlled by two complementary dominant genes. Work to locate molecular markers for gene(s) for intermittent reproductive sterility, using the technologies transferred during the project, are currently under way in Chengdu.
Chinese participants have received training in the application of recently developed breeding technologies, equipping them to produce improved wheat varieties suitable for a range of growing environments and to a plurality of market demands. Chinese colleagues can now state-of-the-art approaches to breeding wheat cultivars with high yielding potential and improved quality in Sichuan growing conditions
Trainees have gained experience in determining flour and noodle sheet colour and measuring dough characteristics on a farinograph. They have also learned techniques for small-scale noodle production, conducting taste panel analysis and measuring embryo dormancy, polyphenol oxidase levels and late maturity a-amylase.
Links:
[1] http://www.aciar.gov.au/country/China
[2] http://www.aciar.gov.au/programarea/Crop Improvement and Management