The domestication syndrome in vegetatively-propagated field crops.

BACKGROUND: Vegetatively propagated crops are globally significant in terms of current agricultural production, as well as for understanding the long-term history of early agriculture and plant domestication. Today, significant field crops include sugarcane (Saccharum officinarum), potato (Solanum tuberosum), manioc (Manihot esculenta), bananas and plantains (Musa cvs.), sweet potato (Ipomoea batatas), yams (Dioscorea spp.) and taro (Colocasia esculenta). In comparison to sexually-reproduced crops, especially cereals and legumes, the domestication syndrome in vegetatively-propagated field crops is poorly defined. AIMS AND SCOPE: Here, a range of phenotypic traits potentially comprising a syndrome associated with early domestication of vegetatively-propagated field crops is proposed, including: mode of reproduction, yield of edible portion, ease of harvesting, defensive adaptations, timing of production and plant architecture. The archaeobotanical visibility of these syndrome traits is considered with a view to the reconstruction of the geographical and historical pathways of domestication for vegetatively-propagated field crops in the past. CONCLUSIONS: Although convergent phenotypic traits are identified, none are ubiquitous and some are divergent. In contrast to cereals and legumes, several traits seem to represent varying degrees of plastic response to growth environment and practices of cultivation, as opposed to solely morphogenetic 'fixation'.