Domestication of indigenous fruit and nut trees for agroforestry in the solomon islands

Abstract

To counter deforestation and food insecurity, techniques to domesticate some of the culturally important indigenous nut tree species of Melanesia have been developed in the Solomon Islands. This process started with determining which species the local communities consider to be important. Barringtonia procera (Cutnut) and Inocarpus fagifer (Tahitian chestnut) were chosen as important model species fitting critical niches in the farming systems. The second step was to determine the factors which affect the rooting ability of cuttings of both species, to ensure that a robust and simple method was developed, appropriate for use by village communities on different islands. Both species were found to be easily propagated by juvenile, single-node, leafy, stem cuttings using a leaf area of 50cm2, 0.8% IBA as a rooting stimulant and forest/river soil as the rooting medium in a non-mist polythene propagator. This was supplemented by an attempt to induce physiological youth in the ontogenetically mature crowns of fruiting trees, so that early fruiting cultivars could be developed. While this was not entirely successful, the results provide pointers for future studies. The next step was to characterise the phenotypic variation for dry matter partitioning between different components of the nuts. This study found highly significant (P = 0.001) and continuous intraspecific variation in all the measured traits within each village population. This study was then complemented by a survey of molecular marker variation, which revealed significant genetic diversity within (87%) and between (13%) five surveyed populations of Barringtonia procera. Trees selected for their large kernels were found to be unrelated, so providing the opportunity to develop superior cultivars without severely narrowing intraspecific genetic diversity. Based on the above research, farmers in the Solomon Islands have been trained in tree domestication techniques and encouraged to select their best trees for domestication and planting on their own land. This approach towards participatory domestication is part of an initiative to develop an indigenous nut industry, with a focus on the processing and marketing of indigenous nuts, including the extraction of Canarium kernel oil. © 2010 Taylor & Francis Group, LLC.