Dwarfing of breadfruit (Artocarpus altilis) trees: Opportunities and challenges

Breadfruit [Artocarpus altilis (Parkinson) Fosberg)] is a traditional staple crop grown for its starchy fruit throughout the tropics. It has long been recognized for its potential to alleviate hunger in the region. However, being a tree of 10 – 30m, breadfruit is vulnerable to wind damage. Owing to the continuing trend of global climate change, the success of the species as a sustainable crop for delivering local food security is compromised by the likelihood of more intense tropical windstorms in the island nations. Tree height also forms a major constraint to disease management and fruit harvesting. These imperatives have driven an increasing interest in developing breadfruit varieties with short stature. While a great diversity of breadfruit cultivars with varying nutritional and agronomic characteristics exists, the genetic resource showing dwarfing traits is largely uncharacterised. Historically, there has been no intentional breeding for breadfruit cultivars. The long growth cycle, predominantly vegetative propagation and lack of genome information create challenge for crop improvement through traditional breeding. In this review, we highlight the current knowledge of plant dwarfism and its application in agricultural practices and genetic improvement for dwarf phenotype, and present options and tools for breadfruit dwarfing with special reference to natural genetic variability for dwarfing rootstocks, plant growth regulators, potential of mutagenesis and its combination with the currently established in vitro propagation protocol in breadfruit. The role of genetic transformation, high-throughput mutant detection by using Targeting-Induced Local Lesions IN Genomes (TILLING) and tools of next generation sequencing is also discussed