Coleção nuclear para o Banco Ativo de Germoplasma regional da mandioca (Manihot esculenta Crantz) da Embrapa Amazônia Ocidental

Abstract

Manioc (Manihot esculenta Crantz) is the fifth most important food produced in the world. Its center of domestication is in southwestern Amazonia. After the initial domestication, divergent selection pressures yielded two groups of varieties: sweet and bitter. The variation generated in farmers’ fields serves as a source of enrichment for germoplasm banks of the species. Efficient use requires morphologic and genetic characterization. Generally, molecular markers directly reflect genetic variation in germplasm at the DNA level, without interference from the environment, and offer valuable information to assess genetic diversity. The Embrapa manioc germplasm bank contains 470 accessions that were analyzed with 10 microsatellite loci to assess genetic diversity and structuring within the bank. Through the bayesian analysis it was possible to find four clusters of the genetic structure of the 470 accessions, and the grouping in K = 2 corresponded roughly to the bitter and sweet manioc groups. However, for geographic structuring none of the K = 2, 3, 5, 7 identified interpretable geographical groups. Data from the genotyped SSR were implemented by the Powercore software, which indicated a core collection with 56 accessions that was able to capture the maximum of allelic variation (113). The Shannon index was 1.74 in the core collection and 1.53 in the germplasm bank. The analysis of molecular variance showed that almost 100% of the genetic diversity is within the two groups CN and BAG.