Genetic relatedness between cassava (Manihot esculenta Crantz) and M-flabellifolia and M-peruviana based on both RAPD and AFLP markers

The taxonomy of the genus Manihot is still uncertain and the genetic origin of cassava (M. esculenta Crantz) continues to be controversial. We studied the degree of genetic relatedness between cassava and two naturally occurr ing species (M. flabellifolia and M. peruviana) which are probably involved in the evolution of cassava, using RAPD and AFLP molecular markers. Thirty -three clonal accessions of cassava of known genetic diversity and 15 acces sions of the wild species M. flabellifolia and M. peruviana were analyzed u sing 92 polymorphic RAPD bands and 73 polymorphic AFLP bands. The genetic m arkers were unable to differentiate the two wild species, which confirms th eir botanical similarity. Half of the total number of amplified bands were monomorphic in all of the genotypes evaluated. The mean genetic similarity (Jaccard) between cassava and the species M. flabellifolia/M. peruviana was 0.59. A grouping analysis (neighbor-joining method) with RAPD markers of c ultivated cassava, M. flabellifolia/M. peruviana and the other wild species located the genotypes of cassava and M. flabellifolia/M. peruviana at one extremity and the three Mexican species (M. aesculifolia, M. michaelis and M. chlorostica) at the other. An intermediate position between these groups was occupied by two wild species (M. glaziovii and M. reptans) native to c entral and northeastern Brazil. These results are consistent with the hypot hesis that the species M. flabellifolia and M. peruviana gave rise to the c ultivated species.