Characterisation of Breadfruit (Artocarpus altilis) Plants Growing on Lakoocha (A. lakoocha) Rootstocks

Abstract

Breadfruit (Artocarpus altilis) is a traditional fruit tree of 15–30 m tall in Oceania. The species is a staple crop for food security in the tropics. Tree loss from tropical windstorms, together with transition toward high-density planting has driven an interest in the dwarf phenotype of the species. Information on dwarfing rootstocks for breadfruit is currently limited. The aim of this study was to assess the performance of breadfruit growth with lakoocha (Artocarpus lakoocha) as rootstocks. We compared the phenotype of breadfruit trees on lakoocha rootstocks with those on self-graft and non-graft within 21 months after grafting. These led to the discovery of a rootstock-induced dwarf trait in breadfruit species. Breadfruit scions on lakoocha rootstocks displayed a reduction in tree height, stem thickness, and internode length, with fewer branches and leaves, resulting in about 32% of the standard height at the end of 21 months after grafting. These suggest lakoocha rootstocks have the potential to control breadfruit tree vigor. Non-structural carbohydrate analysis showed the composite trees exhibited lower hexose concentration in both scion stems and roots, but higher sucrose level in scion stems, and higher starch level in roots. The significance of these parameters in rootstock dwarfing is discussed.