Genetic diversity in sweet cassava from the Brazilian Middle North Region and selection of genotypes based on morpho-agronomical descriptors

This work had as objective the morpho-agronomic characterization of germplasm of cassava (Manhiot esculenta Crantz) from the Brazilian Region Middle North and the selection of genotypes. The germplasm collection was carried out in autochthonous fields. 10 genotypes of which, 8 were ethno-varieties and 2 modern varieties (BRS Dourada and BRS Gema de Ovo), were collected. A completely randomized blocks design was used and the experiment was carried out in January of 2013 in Chapadinha-MA, Brazil. The morphological and agronomical characterizations were carried out at eight months after planting and at the harvesting time, respectively. The frequency of genotypes in each descriptor class and the entropy level for each descriptor were calculated. There was high phenotypic difference in the germplasm for most of the characters evaluated. Lowest entropy levels corresponded to the descriptors sinuosity of foliar lobe, margins of stipules, pubescence of apical bud, growing habit and color of stem epidermis. Highest entropy and consequently higher variability were noticed in petiole color, color of stem cortex, plant kind and peduncle presence. The genotypes Rampa and Turiacu have higher productive and marketing value, thus are excellent alternatives for adoption and cultivation in the Middle North Region. The work proved to be a prominent approach in the screening and selection of promising and contrasting cassava genotypes. Cassava genetic resources occurring in the Brazilian Middle North Region represent a valuable resource in breeding programs of this crop. Key words: Characterization, genotypes selection, M. esculenta.