Molecular characterization of accessions of a rare genetic resource: sugary cassava (Manihot esculenta Crantz) from Brazilian Amazon

Abstract

Sugary cassava (Manihot esculenta) represents a type of cassava that accumulates sugar in its root due to a deficiency to convert sugar into starch. This type of cassava is usually found in the Brazilian Amazon. The genetic variability of a group of 39 accessions of sugary cassavas sampled in the States of Amazonas and Para in Brazil and conserved in two germplasm banks was investigated with eleven microsatellite loci. All eleven loci were polymorphic, with 5.91 alleles per locus. Analyses indicated that 14 of the 39 accessions had the same multiloci profile and represented four genotypes, with 4.03 × 10−7 of probability of identity. Duplicates were discarded and 29 genotypes were used in the genetic analyses for groups. Structure analysis divided the 29 genotypes into two groups (K = 2), where group 1 contained only genotypes sampled in the northeast of the State of Para and group 2 contained genotypes sampled in the State of Amazonas, west of Para and one genotype from the northeast of Para. AMOVA indicated high differentiation among the two States (ΦST = 0.374**) and among the two groups detected by Structure (ΦST = 0.45**). Genetic parameters indicated higher genetic diversity among genotypes of group 2. Results showed that there are two genetic groups of sugary cassavas conserved in the germplasm banks of Brazil and they must be investigated in order to identify different sources of mutations associated with starch conversion route.