Farmers' unconscious incorporation of sexually-produced genotypes into the germplasm of a vegetatively-propagated crop (Oxalis tuberosa Mol.)

摘要

Clonal propagation and sexual reproduction have diametrically opposite effects on the genetic diversity of crops, permitting, respectively, the conservation of existing genotypes or the creation of new diversity. Oxalis tuberosa Mol. ("oca") exhibits a heteromorphic self-incompatibility system and is traditionally propagated clonally but is capable of sexual reproduction. In this study we investigated the influence of sexual reproduction on the in situ genetic diversity of a vegetatively propagated crop, taking oca as a model plant. The occurrence of sexual reproduction in natural conditions and its use by farmers were studied through surveys and interviews, while the effect of sexual reproduction on the in situ genetic diversity was evaluated using microsatellite analysis. Plantlets issuing from sexual reproduction were encountered in five of the nine visited communities. The interviews indicated that six out of the nine interviewed farmers were likely, albeit unconsciously, incorporating clonal lineages issuing from sexual reproduction into their varieties. The microsatellite analysis indicated a strong effect of such incorporations on the genetic diversity of the plant varieties. Assignment tests confirmed the allogamy of oca. "Complex varieties", made up of individuals exhibiting genetically differentiated genotypes, were most likely the result of recent crossing. Unconscious incorporation of new genotypes into the cultivated oca germplasm is therefore highly likely, raising the question of its potential occurrence in other vegetatively propagated crops. These findings could have an important effect on the adaptive potential of oca, especially in light of the genetic erosion that threatens the crop.