Genetic parameters and agronomic evaluation of cassava genotypes

Rodrigo De Souza Silva,José Edson Sampaio,Elisa Ferreira Moura,João Tomé De Farias Neto

doi:10.1590/s0100-204x2016000700006

Abstract

Abstract: The objective of this work was to estimate genetic parameters and predict genetic values for the selection of cassava (Manihot esculenta) genotypes in the state of Pará, Brazil. The trial was performed with 56 genotypes in two growing seasons (2012/2013 and 2013/2014), in the municipality of Igarapé-Açu, in the state of Pará, using the augmented blocks design with two control treatments. The evaluated traits were: plant shoot weight (PSW), number of roots per plant (NRP), number of rotten roots per plant (NRRP), fresh root yield (FRY), harvest index (HI), and starch content in the roots (SCR). The restricted maximum likelihood (REML) and best linear unbiased prediction (BLUP) methods were used. There was genetic variability among genotypes for PSW, NRP, HI, and SCR. Broad-sense heritability estimates were low for PSW and SCR, but were moderate for NRP and HI. However, the heritabilities of the average of genotypes were higher for PSW and SCR. The genetic gains of the five best genotypes varied from 6.0 to 11.08% (PSW), 15.81 to 27.10% (NRP), 9.82 to 12.14% (HI), and 1.90 to 2.20% (SCR). There is genetic variability among cassava genotypes, and the possibility of genetic gains based on selection is moderate for this region in the state of Pará.

Highlights

Cassava (Manihot esculenta Crantz) is mainly cultivated by small farmers in tropical and subtropical countries, because its roots are an important source of carbohydrates (Howeler et al, 2013)
Significant differences were observed in the mixed analysis using unbalanced data for plant shoot weight (PSW), number of roots per plant (NRP), harvest index (HI), and starch content in the roots (SCR) between genotypes (Table 2), indicating genetic variation and the possibility of genetic gains
There was no significant difference for number of rotten roots per plant (NRRP) and fresh root yield (FRY)

Summary

Introduction

Cassava (Manihot esculenta Crantz) is mainly cultivated by small farmers in tropical and subtropical countries, because its roots are an important source of carbohydrates (Howeler et al, 2013). The Amazonian region probably represents a stock of its genetic resources. The genetic resources of the species are being kept in active germplasm banks distributed all over different regions of Brazil and are mainly represented. The conservation of cassava germplasm is essential to reduce genetic erosion and to supply part of the genetic diversity for genetic breeding programs (Fukuda et al, 2005). A fundamental action in the process of genetic breeding is the genotypic prediction of the most promising genotypes, which depends on the estimation of genetic parameters, as well as on the correlations among traits under selection (Resende et al, 2001; Oliveira et al, 2015)

Objectives

Methods

Results