Mating system in an experimental garden composed of cassava (Manihot esculenta Crantz) ethnovarieties

Crossing patterns were investigated in an experimental garden of ethnovarieties of Manihot esculenta (Euphorbiaceae) in Piracicaba, Sao Paulo, Brazil. A model of evolutionary dynamics for cassava presupposes genetic recombination by means of crossing within cassava gardens as a source that amplifies genetic diversity. Quantitative analysis of mating system parameters was performed using progeny arrays assayed for eight allozyme markers. The multilocus outcrossing rate (tm) estimate (0.915 ±0.04) revealed that outcrossing was prevalent, but that a low level of self-pollination also occurred. The multilocus outcrossing rate ranged from 0.69 to 1.00 among eight varieties. The high value found for the outcrossing rate indicates that the ethnovarieties studied are preferentially allogamous. Genetic recombination occurred through crossing within the cassava garden, in agreement with an assumption of the model of evolutionary dynamics for this species.