A review of the program that gives Australian wheat and barley breeders access to international germplasm that is vital to crop improvement has reported a benefit:cost return of 20:1.

This recent assessment of the CAIGE program, which equates to an annual benefit in dollar terms of about $18 million, reflects the value of international collaborations that are critical to lifting crop yields in the face of climate and other evolving production challenges.

CAIGE, which stands for CIMMYT Australia ICARDA Germplasm Evaluation, was formally established in 2007 as a mechanism for selecting, importing and evaluating bread wheat germplasm from the International Maize and Wheat Improvement Centre (CIMMYT).

Prior to this, seed from CIMMYT bread wheat nurseries was brought into Australia and quarantined. Little was known about the material, and it was  accessed by Australian wheat breeders on an ad hoc basis.

Even so, this material had a significant impact on Australian wheat production from the 1970s onwards, although over time the yield gains achieved through the introduction of CIMMYT material into Australian wheat cultivars became steadily less pronounced.

The CAIGE program was established to address this. It was based on results of an International Adaptation Trial (IAT) that comprised contrasting pairs of genotypes for a range of biotic and abiotic stresses. It became clear from this trial that Australian grain growers were missing out on access to important new diversity.

The program initially oversaw the selection, importation, quarantine, distribution, evaluation, management and communication of data for CIMMYT bread only. However, this was extended to bread wheat, durum wheat and barley from the International Center for Agricultural Research in the Dry Areas (ICARDA) and durum wheat from CIMMYT in 2014.

The CAIGE program has steadily evolved over the years as the needs of the Australian breeding community have changed. The new CAIGE program, supported by GRDC until 2027, has refocused the acquisition and evaluation of materials to focus on traits of high importance for the Australian wheat industry, such as tolerance to prevalent diseases or abiotic stresses. There is an annual consultative process that surveys stakeholder trait priorities. Shipments of materials from CIMMYT and ICARDA now reflect this changed process with greater emphasis given to high-value traits where access to more genetic diversity would be beneficial.

A breeder reference group, comprising one representative of all participating breeding companies, the CAIGE core group and GRDC, oversees the strategy. A steering committee ensures that the work plan is implemented effectively. An annual research meeting of all stakeholders is held in March and a quarterly newsletter keeps collaborators up to date with developments.

Table 1: Bread and durum wheat lines imported and evaluated since 2012.

Note: CR is crown rot, YS is yellow spot, ST is Septoria tritici, SN is Septoria nodorum, RLN is root lesion nematode and Tox A is an effector screen for SNB and YS.

Table 2: Barley lines imported and evaluated since 2012.

Note: SFNB is spot form net blotch, NFNB is net form net blotch, BLR is barley leaf rust, BSR is barley stem rust, SB is spot blotch and PM is powdery mildew.

Over the past 10 years, 5747 bread wheat, 2631 durum wheat and 2057 barley materials have been imported and subsets tested around Australia in 196 different trials (Tables 1 and 2). Materials have been selected by Australian wheat and barley breeders at the international centres for traits of specific interest to Australia.

This involves visual field assessments at the international centres, augmented by access to CIMMYT and ICARDA breeder data to refine the imported set. CIMMYT and ICARDA breeders assemble sets for importation based on consultation with CAIGE staff and Australian wheat breeders.

Once the imported material is released from quarantine, it is multiplied for inclusion in yield trials in the following season. All bread wheat materials are concurrently screened for rust resistance, and barley for several diseases.

The materials selected for national testing in yield trials are reduced further, based on preliminary disease evaluation and the provision of additional data from CIMMYT and ICARDA. Most yield trials are provided in-kind by participating commercial partners, augmented by a small number of public trials.

More-intensive disease testing is conducted concurrently with yield testing so that both yield and disease resistance data is available to crop breeders by February each year.

Trial designs and analyses are provided by the University of Wollongong under the GRDC-supported ‘Biometrics and Bioinformatics for the Australian Grain Industry’ project.

All information, including pedigrees, CIMMYT and ICARDA breeder data and local yield, disease and quality data, is accessed through the CAIGE website (caigeproject.org.au). This is underpinned by a relational database, the Breeding Management System, that facilitates data interrogation.

The CAIGE team in Mexico at the Norman E. Borlaug Experiment Station in Sonora. From left to right: Richard Trethowan, Dan Mullan, Ian Edwards, Marie Appleby, Fernanda Dreccer, Allan Ratty and Tom Kapcejevs. Photo: CAIGE

Prior to 2018, this data was freely available online. Now, data provided by commercial partners as in-kind contributions is password protected and available only to CAIGE partners.

The CAIGE program has evaluated 10,435 lines since 2012 and many of these materials have been retained by commercial companies for further testing and crossing.

The yield performance of recent materials is shown in Table 3. Here, the numbers of lines from each category (Australian, CIMMYT or ICARDA) appearing among the top 10 per cent of entries in multi-environment trials are given for bread wheat.

Clearly, high-yielding materials from both international centres have been identified and accessed by Australian breeders. While the CAIGE materials are a source of potential new diversity for yield, particularly in bread and durum wheat, the international nurseries are also sources of new diversity for disease resistance.

The frequency of wheat materials with high levels of rust resistance is high (Tables 4 and 5). Lines with resistance to all other diseases tested have been found and many lines carry multiple resistances, making them attractive as parents for Australian commercial companies.

Barley materials tend not to be as competitive with the Australian cultivars for yield, although potential new diversity for yield has been discovered. Instead, the barley lines carry effective levels of disease resistance that provide commercial barley breeders with useful new diversity (Table 6).

The CAIGE program not only coordinates the flow of information between CIMMYT, ICARDA and Australia, but builds and strengthens relationships among scientists. These connections and shared experiences continue to strengthen the importance of CAIGE to Australian grain growers.

Table 3: Number of lines by year and germplasm source that were evaluated,  in the top 10% for yield.

Table 4: Disease resistances in CAIGE bread wheat – percentage in each resistance class.

R = resistant, RMR = resistant to moderately resistant,  MR = moderately resistant, MS = moderately susceptible, S = susceptible, VS = very susceptible.

Table 5: Disease resistances in CAIGE durum wheat – percentage in each resistance class.

R = resistant, RMR = resistant to moderately resistant,  MR = moderately resistant, MS = moderately susceptible, S = susceptible, VS = very susceptible.

Table 6: Disease resistances in CAIGE durum wheat – percentage in each resistance class.

Note: SFNB is spot form net blotch, NFNB is net form net blotch, BLR is barley leaf rust, SB is spot blotch and PM is powdery mildew.
R = resistant, RMR = resistant to moderately resistant,  MR = moderately resistant, MS = moderately susceptible, S = susceptible, VS = very susceptible.

Richard Trethowan: Wheat leader
Mark Dieters: Barley leader
Julie Nicol: CAIGE coordinator
Amit Singh: CAIGE database manager

References
Brennan J.P. and K.J Quade. 2004. Analysis of the Impact of CIMMYT Research on the Australian Wheat Industry. Economic Research Report No. 25, NSW Department of Primary Industries, Wagga Wagga.

Brennan, John P. 2007. Beyond semi-dwarf wheat yield increases: Impacts on the Australian wheat industry of on-going spillovers from the International Maize and Wheat Improvement Centre. Australian Journal of Agricultural and Resource Economics 51(4):385-401. December.

Mathews K.L., Richard Trethowan, Andrew Milgate, Thomas Payne, Maarten van Ginkel, Jose Crossa, Ian DeLacy, Mark Cooper and Scott C. Chapman. 2011. Indirect selection using reference and probe genotype performance in multi-environment trials. Crop and Pasture Science, 62:313-327.