What was it all about?

Macadamia (Macadamia integrifolia Maiden & Betche and Macadamia tetraphylla L.A.S. Johnson) is an Australian native, evergreen nut tree adapted to the subtropics. Australia is also the home of the wild macadamias growing in northern New South Wales and southern Queensland.

This project, which ran from 2009 to 2013, made use of this valuable native resource to develop new cultivars for a more profitable Australian industry.

Key industry stakeholders, including marketers, growers, agribusiness representatives and pest consultants were consulted to guide the objectives of the breeding program.

Characteristics most desired by stakeholders included…

• Increased yield
• Resistance to husk spot
• Desirable consumer characteristics
• Resistance to fruit spotting bugs
• Small tree size.

Elite selections developed from the breeding program were assessed on these characteristics and the most promising were used to produce the second generation. Almost 2,000 seedlings were evaluated for yield, kernel recovery, tree height and tree canopy width.

Top candidates were further assessed using detailed agronomic and field observations on nut quality, disease and insect susceptibility, nut drop pattern and other key traits.

Researchers created a second generation of seedling populations using controlled hand pollinations to combine the elite first generation selections.

A total of 3,555 seedlings using 79 parents were created in this project and have been planted in trials at Nambour and Bundaberg. These trials will be evaluated for eight years and the resulting elite selections will be clonally propagated for regional testing prior to industry release.

Four rootstock trials were conducted in which 12 cultivars were propagated as seedling or cutting rootstocks and grafted to combinations of the same 12 cultivars as scions. Non-grafted cuttings on their own roots were also included.

Scion was found to be more important than rootstock in determining yield and tree size. Rootstock had virtually no influence on kernel recovery. After 12 years, the cumulative nut in shell yield for Beaumont cuttings was 13 per cent higher than the industry standard H2 seedling rootstock.

The researchers recommended further trials of Beaumont, at this stage.

The project has successfully re-invigorated the seedling production phase of breeding after a 10 year break. Industry was to benefit from the first release of new cultivars from 2017 onwards.

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To learn more about the macadamia varieties produced by this investment, including information on how to access them, head to the Macadamia Innovation website.