Genetic improvement of cocoyam (Xanthosoma sagittifolium) through mutagenesis

Cocoyam ( Xanthosoma sagittifolium ) is a low input demand crop which is culturally held in high esteem in West Africa due to its food, nutrition and income security status. Its production and productivity in Ghana have been dwindled since the last four decades mainly due to inadequate improved varieties. There is the need for development and release of end-user preferred high yielding adaptable varieties of cocoyam. Wider genetic base is a prerequisite for breeding a very narrow genetic base crop such as cocoyam. Limited genetic diversity in cultivated gene pool threatens its genetic gain through hybridization. A large amount of genetic variability has been induced by various mutagens and contributed to modern plant breeding. This study aimed at identifying suitable irradiation dose range for purposeful mutation induction using gamma radiation, and to select superior mutants for food and income security. The work was carried out at the Biotechnology and Nuclear Agriculture Research Institute (BNARI) of the Ghana Atomic Energy Commission, Kwabenya-Accra, and the CSIR-Crops Research Institute (CSIR-CRI), Fumesua, Ghana. Pre-sprouted corms and cormels of three improved cocoyam varieties ( CRI-Akyede, CRI-Gye me di and CRI-Ma ye yie ) were exposed to 5 Gy, 10 Gy, 15 Gy, and 20 Gy gamma-radiation doses. Variations were observed in cormel yield, shape, dry matter content and cooking quality. The potential of gamma irradiation in broadening the genetic base of cocoyam for breeding was revealed. The highest number of mutants were from the 5 Gy (57.3%) and 10 Gy (38.8%) doses, but most of the useful mutants (54.2%) were from the 5 Gy dose. Genotypic and planting material type responses to the irradiation doses varied. Three superior mutants (2021, 2036, and 2043) were identified. These superior mutants require further testing multilocational for stability and adaptability towards their release as commercial varieties.