Taro (Colocasia esculenta (L.) Schott), breeding history, objectives, methods and strategies: a review of fifty years of sporadic efforts

Abstract

Despite its essential role for food security, vast geographical distribution, high nutritional value, and considerable trade, very few improved genotypes of taro (Colocasia esculenta (L.) Schott) are available to farmers. This review present an update on taro’s origin, wild relatives, domestication, diversity, preservation of germplasm, breeding history, objectives, methods and breeding strategies. Poor flowering of cultivars is the main factor limiting hybridization. For decades, it was thought that cultivars were sterile and could not produce seeds due to high ploidy or mutations inhibiting their sexuality. Taro diversity has been explored with different molecular markers, with no congruence between morphological and molecular groupings. Poor correlations between traits measured in seminal and first clonal generation, as well as heterogeneity of planting material, affect accurate phenotyping and slow down breeding cycles. Most efforts have been oriented towards taro leaf blight tolerance. The high diversity found within the pathogen (Phytophtora colocasiae Raciborski) favours the development of horizontal resistance. Breeding programs achievements have been constrained by: (i) Limited project funds oriented towards the development of expensive molecular tools rather than breeding activities, (ii) Absence of long-term commitments from research institutions, and (iii) Poor international cooperation. Encouraging results have been obtained through the exchange of germplasm and will pave the way to future breeding developments, long overdue to farmers, especially in Africa. Future directions to assist breeders are outlined and discussed.