Genetic variability of landraces of cassava in geographical regions of Brazil

The management practices used in authoctonous agriculture with landraces of cassava (Manihot esculenta Crantz) play an important role in the in situ conservation of genetic resources. The objective of this work was to analyze the genetic variability present in 141 landraces of cassava, collected in gardens of different geographical regions of Brazil using isozyme techniques visualized by starch gel electrophoresis. Eleven enzymatic systems were analised. Of the 15 polymorphic loci evaluated the observed mean heterozigosity was 0.354. GST estimates presented a value of 8.80% for the genetic variability between regions. In cluster analysis, three distinct groups were observed: the first group was formed by the gardens of the Amazon; the second group consisted of gardens of Sao Paulo State; and the third group was formed by the gardens of the Xingu region. Most of the genetic variability of cassava landraces was restricted within the geographical regions, which confirmed the evolutionary dynamic model for this species.