The overall aim of the project is to improve and stabilise farmer returns from growing wheat in dry, rainfed environments in NW China by developing higher-yielding wheat germplasm that makes more effective use of water and soil resources.

Objective 1: To develop new germplasm for NW China bred for high transpiration efficiency (TE).
In NW China, the dryland winter-wheat crop relies heavily on effective use of water stored in the deep, loess subsoil. All the water extracted from the subsoil is transpired, so wheat cultivars with high TE should perform well.
During 2008-09, protocols for screening for high TE using the surrogate measure carbon isotope discrimination (CID) were implemented in China following training from the Australian project leader. Genotypic variation in TE within commercially-relevant Chinese germplasm was assessed by measuring CID of Australian varieties and of entries in the crossing blocks of the Chinese partner institutes. Encouragingly useful genotypic variation was identified and this information has been used to develop a strategy for selecting for improved TE within crosses involving Chinese wheats with appropriate agronomic fit. At NWAFU, a porometer was purchased to aid in evaluating alternative strategies of screening for improved TE.

Objective 2: To develop new germplasm for NW China incorporating dwarfing genes sensitive to gibberellic acid (GA) and bred for long coleoptiles.
Long coleoptile length is an important trait in dryland farming because it allows farmers to sow their seed deeper, into moist soil to promote successful crop establishment. The most widely-deployed dwarfing genes strongly limit the growth of the coleoptile because they are GA-insensitive. Alternative, GA-sensitive dwarfing genes are available to facilitate breeding long-coleoptile wheats of agronomically-appropriate height.
During 2008-09, screening of Chinese germplasm for dwarfing-gene status was initiated using (1) CSIRO-developed molecular-markers diagnostic for GA-insensitive dwarfing genes Rht1 and Rht2 and molecular markers for one GA-sensitive dwarfing gene, Rht8, known to be deployed in China, (2) seedling assays of sensitivity to GA and (3) phenotyping of plant height. This information has been used to choose candidate Chinese winter-wheat and spring-wheat parents for use in crosses with alternative dwarfing-gene donors sourced from Australia.
Screening of tall and semi-dwarf Chinese wheats for coleoptile length was also initiated at the partner institutes in NW China.

Objective 3: To develop new germplasm for NW China bred for high early vigour.
The spring-wheat crop in NW China has a very short season and rapid dry matter production should translate into higher grain yield in this short-season wheat environment.
Progress on this objective has been limited to training activities conducted by the Australian project leader and the generation of fresh seed of Chinese germplasm and of germplasm sourced from Australia.

Objective 4: To develop new germplasm for NW China and Australia incorporating root traits for more effective water use.
In NW China, the loess soils are deep and can store large amounts of water. Some of the wheats from this region probably have the capacity for deep root growth that allows them to access more of the soil water store. In this project we are comparing Chinese, Australian and synthetic bread wheats to identify wheats with the deepest root growth for use in crossing.
Screening for root growth using 'cigars' of rolled germination paper, as practiced at CSIRO, has replaced a 'glass-plate' protocol previously used at NWAFU. Screening of Chinese germplasm is revealing useful genotypic variation in root elongation and root number. Both these traits are likely to be important for efficient exploration of the subsoil.

Objective 5: In Australia, to develop breeder-friendly protocols and germplasm that pyramids high leaf transpiration efficiency with greater early vigour.
Computer-simulations indicate that large and consistent yield gains of about 15% are likely in all regions of Australia by pyramiding high TE and greater early vigour together. In project research being conducted in Australia, breeder-friendly protocols are being developed to most-effectively breed and select for this combination of traits.
During 2008-09, new field-based protocols for screening early vigour were tested among progeny of a typical commercial cross in Australia, involving GA-insensitive parents. Techniques using digital photography and spectral reflectance were compared. Initial indications are that both techniques yield similar information, but that digital photography is less-dependent on sunny weather conditions. Evaluation of surrogate measures of TE, to replace the relatively-expensive CID technique, was also initiated. A second, large population of breeding lines varying for TE, vigour and dwarfing-gene type was advanced in the field and evaluated for variation in key agronomic traits of flowering time, height and disease resistance.

The overall aim of the project is to improve and stabilise farmer returns from growing wheat in dry, rainfed environments in NW China by developing higher-yielding wheat germplasm that makes more effective use of water and soil resources.

Objective 1: To develop new germplasm for NW China bred for high transpiration efficiency (TE).
During 2009-10, genotypic variation in TE within commercially-relevant Chinese germplasm was assessed by measuring carbon isotope discrimination (CID) of entries in the crossing blocks of Chinese partner institutes in comparison with CID of Australian varieties sown alongside. This information is being used to implement a strategy for selecting for improved TE within crosses involving Chinese wheats with appropriate agronomic fit. At NWAFU, Shaanxi, and NAAFS, Ningxia, crosses have been made among Chinese parents and also between Chinese and Australian parents. Progeny from these crosses are being advanced for selection and field testing.

Objective 2: To develop new germplasm for NW China incorporating dwarfing genes sensitive to gibberellic acid (GA) and bred for long coleoptiles.
Screening of Chinese germplasm for dwarfing-gene status continued during 2009-10. Information from this screening and from screening in 2008-09 was used to choose candidate Chinese winter-wheat and spring-wheat parents that were used in crosses with alternative dwarfing-gene donors sourced from Australia. Progeny from these crosses are being advanced for selection and field testing.
Screening of tall and semi-dwarf Chinese wheats for coleoptile length was also conducted at the partner institutes in NW China.

Objective 3: To develop new germplasm for NW China bred for high early vigour.
Further training in screening for this trait was conducted by the Australian project leader during the visit to Australia of Chinese project staff in November 2009. Field assessment for early vigour in Chinese germplasm is being conducted on spring-2010 sowings by NAAFS project staff. Data from this assessment will be used to direct a crossing strategy incorporating GA-sensitive dwarfing sources.

Objective 4: To develop new germplasm for NW China and Australia incorporating root traits for more effective water use.
Screening of Chinese germplasm for root growth traits using 'cigars' of rolled germination paper has revealed useful genotypic variation in root elongation and root number. Crosses have been made among Chinese parents and progeny from these crosses are being advanced for selection and field testing.
Dr Zhang Hong, from NWAFU, Shaanxi, returned there in April 2010 after 12 months at CSIRO, Canberra, where he conducted studies on root traits using large breeding populations and mapping populations of wheat derived from Chinese and Australian parents. This work linked closely with work being done under the ACIAR-funded project "Indo-Australia project on root and establishment traits for greater water use efficiency in wheat" (CIM/2006/071). Dr Zhang's research indicated that there are multiple genomic regions associated with important root traits such as root number and root elongation. It was also found that repeatability for root traits was high in genetically fixed lines but moderately low at early generations. This information is being used to direct selection strategies for root traits in this ACIAR project and in project CIM/2006/071.

Objective 5: In Australia, to develop breeder-friendly protocols and germplasm that pyramids high leaf transpiration efficiency with greater early vigour.
During 2009-10 a large population of breeding lines varying for TE, vigour and dwarfing-gene type was sown in replicated field trials in three environments in SE Australia. As well as growth and yield, lines were evaluated for variation in TE and vigour and other key traits such flowering time and height.
Substantial variation was observed among lines in both early vigour and TE, assayed by measuring CID. Above ground biomass at the three leaf stage varied ca. 2.5-fold. Leaf-level TE varied ca. 1.3-fold, a large range for wheat. Early vigour had some dependence on seed size and was also influenced by other factors such as tiller number and leaf width. Greater early vigour was not correlated with leaf thickness. Conversely, an increase in TE tended to involve thicker leaves and an increase in chlorophyll concentration. Early vigour and TE were only weakly related, indicating that they could be selected independently and pyramided in this population.

The overall aim of the project is to improve and stabilise farmer returns from growing wheat in dry, rainfed environments in NW China by developing higher-yielding wheat germplasm that makes more effective use of water and soil resources. Partners in the project are wheat researchers from CSIRO Plant Industry, Canberra and wheat scientists from North-West Agriculture and Forestry University (NWAFU), Yangling, Shaanxi and the Ningxia Academy of Agricultural and Forestry Sciences (NAAFS), Yinchuan and Guyuan, Ningxia.
This report covers activities carried out in the third year of the project. The bulk of these activities involved screening progeny from crosses involving elite Chinese parents for traits identified at CSIRO as important for enhancing yield in dry, rainfed environments. The aim is to advance selected lines for testing in field trials in the next two years of the project.

Objective 1: To develop new germplasm for NW China bred for high transpiration efficiency (TE).
A large number of crosses have been made among Chinese parents differing in TE and also between Chinese and Australian parents. During 2010-11, a small number of key crosses were chosen for agronomic fit and progeny from these crosses sown in short rows in the field. From among these rows, moderately large sets of lines are being selected that are uniform for height and flowering time but which contrast in the expression of TE. The aim during the last two years of the project is to evaluate the impact of selecting for high TE in several field environments in NW China.

Objective 2: To develop new germplasm for NW China incorporating dwarfing genes sensitive to gibberellic acid (GA) and bred for long coleoptiles.
Screening of Chinese germplasm for dwarfing-gene status has confirmed that almost all wheats bred for rainfed production in NW China are either 'tall' wheats or they carry the Rht8 dwarfing gene. This gene has a relatively minor effect on plant height. Alternative dwarfing-gene donors sourced from Australia have been used in crosses and back-crosses with elite Chinese parents. Dwarfing genes Rht4, Rht13, Rht14 and Rht18 have been the main genes targeted. These genes are more effective than Rht8 in reducing plant height but are not extreme. Progeny from these crosses are being advanced for selection and field testing.
Long coleoptiles are a highly-valued character in the dry, rainfed environments of NW China. Screening for coleoptile length among progeny from crosses of Chinese wheats and between Chinese and Australia-sourced wheats continued at the partner institutes in NW China using protocols introduced during the first year of the project.

Objective 3: To develop new germplasm for NW China bred for high early vigour.
Field assessment for early vigour in Chinese germplasm was conducted on spring-2010 sowings by NAAFS project staff. Data from this assessment is being used to direct a crossing strategy to combine early vigour and GA-sensitive dwarfing genes into elite Chinese cultivars. At NWAFU, selections have been made among progeny rows to develop sets of lines contrasting for vigour for field testing during the last two years of the project.

Objective 4: To develop new germplasm for NW China and Australia incorporating root traits for more effective water use.
During the first two years of the project, screening of Chinese germplasm for root growth traits using 'cigars' of rolled germination paper revealed useful genotypic variation in root elongation and root number. Progeny from crosses among elite Chinese parents are now being screened using the 'cigar' technique and also in PVC tubes filled with soil. The latter have been built to specifications obtained during the visit of Chinese scientists to Canberra in November 2009.

Objective 5: In Australia, to develop breeder-friendly protocols and germplasm that pyramids high leaf transpiration efficiency with greater early vigour.
During 2010-11 a large population of breeding lines varying for TE, vigour and dwarfing-gene type was again sown in replicated trials in SE Australia. The extremely wet 2010 season presented difficulties in agronomic management and also interpretation of results for dryland production. Data from 2009 and 2010 trials has been used to truncate the population for more detailed studies in 2011-12.
Glasshouse studies were used to closely investigate the utility of a widely-used leaf chlorophyll meter, the 'SPAD' meter, to assess variation in photosynthetic capacity. High photosynthetic capacity is an important component of high TE, but selection for early vigour may limit photosynthetic capacity and therefore limit TE gain. Some of the observations on the utility of SPAD measurements made in 2010-11 were unexpected and will be pursued further in 2011-12.