Variation in precocity in a macadamia breeding population

Abstract

Genetic improvement of macadamia (Macadamia integrifolia and M. tetraphylla) is still in its early stages. The industry breeding program in Australia is only two to four generations removed from wild germplasm. There are extensive opportunities to improve this crop. Seedling trees have a long juvenile phase and can take up to 6 years to produce fruit. Seedling juvenility impedes the efficiency of the breeding cycle and cultivar juvenility increases the financial risk to the growers. Developing early producing precocious cultivars may reduce these risks and provide farmers with earlier economic returns. Genetic variability of precocity is an important resource that can be used to breed improved macadamias. Experimentation on 39 open pollinated families of diversified genotypes identified significant genetic variation for precocity among 692 progeny. Six progeny from six different families produced flowers at age 3. A total of 101 progeny from 31 families produced flowers and nuts at age 4. Open pollinated families of 'A538', 'A38', 'D4', 'A268', 'A4' and M. jansenii were the most precocious. Genotypes used as parents from Hidden Valley Plantations (HVP) produced the most precocious cultivars. There was a strong correlation between flowering intensity and early yield. The assessment of precocity among genotypes and families will allow the use of a tandem selection strategy, which is aimed to reduce the breeding cycle for selecting high yielding cultivars.