Retrotransposon molecular markers resolve cocoyam (Xanthosoma sagittifolium) and taro (Colocasia esculenta) by type and variety

Abstract

Retrotransposon-based molecular markers were applied for the first time within the genera Xanthosoma and Colocasia to assess intraspecific variability among 27 accessions of cocoyam (Xanthosoma sagittifolium) and taro (Colocasia esulenta). Retrotransposons were isolated and sequenced; long terminal repeat (LTR) primers were designed to obtain inter-retrotransposon amplified polymorphism (IRAP) fingerprints. A set of six chosen LTR primers yielded 433 reproducible bands across 20 X. sagittifolium samples. Out of the 433 bands, 400 fragments (92 %) were polymorphic. In seven C. esculenta accessions, the six primers amplified a total of 354 reproducible, informative data points, of which 285 (80.5 %) were polymorphic. Cluster analysis placed all the accessions in two groups according to their species. The accessions of X. sagittifolium were further divided into two subgroups corresponding to their ploidy level. Moreover, the genetic variability accessed by IRAP markers allowed separation of X. sagittifolium and C. esculenta accessions according to their type and botanical variety respectively. The results suggest that retrotransposon activity continued after Xanthosoma speciation. The data and approach provides a basis for better germplasm management, future systematic studies and genetic improvement, as well as for exploration of the role of retrotransposons in cocoyam and taro polyploid formation and genome dynamics.