Genetic diversity for chemical, agronomical and molecular characters in accessions of cassava (Manihot esculenta Crantz) originated from the Amazon, Center-South and Northeast regions.

Abstract

This study aims to characterize the genetic diversity of 90 accessions of cassava, from the IAC and ESALQ Germplasm Banks, originated from the Amazon, Central-South and Northeast regions, with agronomical, chemical and molecular (microsatellites) markers. An experiment will be conducted in a randomized block design with three replications and each plot will comprise five plants. The agronomical characters assessed will be root yield, plant height, harvest index and root number. The project aims to determine the carotenoids profile of each accession with the purpose of verifying the possible grouping of genotypes for each region for this character, as well as to characterize the starch content and composition of the amylose/amylopectin fraction, and to characterize the content of cyanogenic compounds and thereby provide information of great interest for cassava breeding programs. The agronomical and chemical data will be analyzed with univariate statistical analysis (F test, test of means) and multivariate (cluster analysis and principal components), using the mean Euclidean distance and UPGMA method for the cluster analysis. For the molecular analysis 18 microsatellite loci will be tested, with the aim to estimate the genotypic and allelic frequencies, levels of genetic diversity and number of alleles per locus, percentage of polymorphic loci, average observed and expected heterozygosity, Wright´s inbreeding index and Nei´s diversity indices, which will provide information on the distribution of genetic variability within and among geographical regions. An analysis will also be held from binary data (presence/absence of bands) for obtaining a dendrogram using the accessions or varieties to check for possible duplicates and their grouping according to their origins, using the Jaccard similarity coefficient and the UPGMA method.