2017 ASHS Annual Conference

While indigenous to Australia, macadamia is an iconic Hawai’i crop. Hawai’i initiated the commercial production of the crop, developed grafting to support vegetative propagation of the crop, selected superior cultivars that remain the predominate source of germplasm in commercial orchards throughout the world, and lead world production until the mid-1990s. It is therefore important to improve understanding of the domestication history of the crop in Hawaii to add to the history of the crop, and improve conservation and use of genetic resources. This paper describes archival, field and genetic research undertaken to improve this knowledge and results from this research. Published research suggests the Hawai’ian germplasm derived from three introductions of the genus into Hawaii in the late 19^th century. However, there is archival evidence of at least two additional importations of germplasm, one in the early- and one in the mid-20^th century. The first cultivars were selected from seedling orchards following the development of grafting technology. Archival research supported identification of the location of remnants of these old seedling orchards that were subsequently sampled for DNA testing to identify genetic relationships. Chloroplast analysis of these samples and the Hawaiian cultivars identified that the original introductions were predominantly from a small wild population in the northern range of M. integrifolia, in contrast to previous reports that suggested a southern origin. There is also evidence of that the inedible M. ternifolia was introduced into Hawai’i in the late 20^th century. These results suggest the genepool of Hawaiian macadamia is limited and addition of diversity to breeding populations could assist selection response. The remnant seedling orchards are also significant cultural records of the development of the crop. Further research will explore the diversity of the remnant orchards, and remnants of the other introductions to improve knowledge of germplasm structure and relative importance of the different introductions.