Tropical root and tuber crops breeding in the Pacific: a review of 35 years of efforts

The tropical root and tuber crops (aroids, cassava, sweet potato and yams) represent major contributions to food security in the Pacific Islands Countries (PICs) but are also cash crops for local and export markets. Conventional breeding is complex as the flowering ability of cultivars is erratic; they are predominantly allogamous, highly heterozygous with variable ploidy levels. Breeding is based on phenotypic recurrent selection with comprehensive characterisation and elimination of numerous hybrids evaluated across successive clonal generations for major agronomic traits. Over the last three decades, the PICs breeding programmes have been project-driven but have successfully delivered improved clones. The results obtained for Colocasia esculenta, Xanthosoma sagittifolium, Ipomoea batatas, Dioscorea spp., and Manihot esculenta, are reviewed. For each species, the technical bottlenecks and research priorities are identified and perspectives for further genetic improvement are discussed.