Diversity of Ullucus tuberosus (Basellaceae) in the Colombian Andes and notes on ulluco domestication based on morphological and molecular data

Abstract

Ullucus tuberosus (common name ‘ulluco’) is a popular tuber crop of Andean highlands. Until now attention has been focused on ulluco from Bolivia, Peru and Ecuador, but little is known about its diversity in Colombia. Thirty-six accessions of cultivated ulluco preserved in the Gene Bank of the Universidad Nacional de Colombia were studied to assess the genetic diversity and spatial genetic structure of Colombian ulluco. We used morphological characters, molecular markers (total proteins, isozymes and RAPDs) and ploidy level. High morphological variability, especially for tuber shape and colour characters, was found. Eight accessions from north-east Colombian Andes showed some typical character-states of wild ulluco, suggesting that they could be partially domesticated forms. Genetic analysis using RAPD markers indicated that these accessions were very similar to other cultivated ullucos belonging to the same region. The regional structure observed in isozyme and RAPD dendrograms was confirmed by AMOVA results (52.6% among-region variation) and the spatial correlogram, showing the presence of two gene pools of ulluco in Colombia. Our results and the accumulated data suggest that ulluco was introduced to Colombia at least two times. Initially, semi-domesticated forms would have come from the central Andes to north-east Colombian Andes, where the native inhabitants would have completed the domestication process. Again, fully domesticated ullucos might have been introduced to south-west Colombian Andes.