Overview of the Australian macadamia industry breeding program

Macadamia (Macadamia integrifolia Maiden and Betche and M. tetraphylla L.A.S. Johnson) is an Australian-native, evergreen nut tree adapted to the subtropics. It is the basis of an international industry producing highly valued kernels. Australia is the world leader in production, with about 6 million trees planted on 17,000 ha. Industry funding for an Australian breeding program commenced in 1996, and over 3500 hybrid seedlings were produced and field-planted from 1998 to 2003. Industry participation has involved use of grower properties for progeny field trials, review of outcomes by an industry steering group and consultation with industry on the important traits in new cultivars. Key selection traits are cumulative nut yield per tree to age 8, tree height, canopy width, kernel recovery and nut quality. Quantitative selection methods were used to identify elite selections for commercial testing and for use as parents. The mean cumulative nut-in-shell yield to age 8 for the top 20 seedlings planted from 2000-2003 was 39% higher than the best five cultivars in the same trials. A second generation of hybrid seedlings is being produced using these elite selections, with 2296 seedlings planted from 2011 to 2014. We discuss strategies to improve breeding efficiency and future plans for a husk spot disease nursery, use of wild species and rootstock screening