Abstract

S6-19

The Dynamics of the Sweet-Bitter Differentiation in Cassava Varieties as Unravelled by Molecular Polymorphism

Narvaez-Trujillo A., T. Lozada and G. Second¹

1.     Lab. Plant Molecular Systematics.  Pontificia Universidad Catolica del Ecuador. Av. 12 de octubre y Roca. Quito, Ecuador. anarvaez@puceuio.puce.edu.ec

A written report attests that in Ecuador, sweet and bitter cassava were considered as different crops two centuries ago.  This is still the case in several Amerindians, or mixed blood communities, in the main area of cultivation of bitter cassava, where sweet cassava (probably recently introduced) is considered as a legume, grown next to house.  AFLP and SSR markers were used to study traditional varieties from various Amerindian communities in French Guiana (bitter) and Ecuador (sweet), compared with those of a “caboclo” community in the upper Rio Negro (Brazil) area (mostly bitter) and a collection representative of the core collection in CIA.  This study shows that: 1) Amerindian varieties from French Guiana and Ecuador are found mostly at the two extremes of the first axis of variation in a multivariate analysis of the polymorphism and 2) the “caboclos” varieties and the collection assembled in modern times are found intermediate although more related to the Amerindian bitter or sweet varieties, respectively.  We interpret this pattern of variation as expressing a progressive historical merging of sweet and bitter varieties in a continuum: the more recent traditionally bred varieties tend to be hybrids derivative between sweet and bitter varieties.