Genetic gain in oil productivity from breeding program of Cajuput (Melaleuca cajuputi subsp. cajuputi) in Indonesia

A long-term breeding program of cajuput (Melaleuca cajuputi subsp. cajuputi) in Indonesia has aimed to increase oil productivity and quality through imposing selection for oil yield and 1,8-cineole content. This study examined the realized genetic gain for the two key variables of oil yield, oil concentration and leaf biomass. Data were collected from a trial based on seeds collected from two unimproved, and two improved sources with selection intensities (IS) of 1.1 (10% of trees selected) and > 2.5 (<1% of trees selected). The trial was laid-out in a randomized complete block design with five replications. It was measured at 10 years of age. The leaf oil concentration of the IS >2.5 seed source was significantly higher than for the other sources; a realized genetic gain ranging from 14% to 31%. However, although not significant, this seed source had the lowest leaf biomass. The correlation between gains in oil concentration and leaf biomass was weak and not significant (r = 0.15); while the correlation between oil yield and leaf biomass was very strong and highly significant (r = 0.96). These results highlight the importance of carefully incorporating leaf biomass as a selection criterion in cajuput breeding programs aimed at increasing oil yield.