Genetic parameters and simultaneous selection for root yield, adaptability and stability of cassava genotypes

Abstract

The objective of this work was to estimate genetic parameters and to evaluate simultaneous selection for root yield and for adaptability and stability of cassava genotypes. The effects of genotypes were assumed as fixed and random, and the mixed model methodology (REML/Blup) was used to estimate genetic parameters and the harmonic mean of the relative performance of genotypic values (HMRPGV), for simultaneous selection purposes. Ten genotypes were analyzed in a complete randomized block design, with four replicates. The experiment was carried out in the municipalities of Altamira, Santarém, and Santa Luzia do Pará in the state of Pará, Brazil, in the growing seasons of 2009/2010, 2010/2011, and 2011/2012. Roots were harvested 12 months after planting, in all tested locations. Root yield had low coefficients of genotypic variation (4.25%) and broad-sense heritability of individual plots (0.0424), which resulted in low genetic gain. Due to the low genotypic correlation (0.15), genotype classification as to root yield varied according to the environment. Genotypes CPATU 060, CPATU 229, and CPATU 404 stood out as to their yield, adaptability, and stability.

Genetic parameters and agronomic evaluation of cassava genotypes

“…Possibly, in the present study, the augmented blocks design was not suitable to detect differences for root yield. Farias Neto et al (2013) evaluated ten cassava genotypes in three different locations in the state of Pará, using a randomized complete block design, and identified CVe for root yield of 20.9%, which, in the present work, reached 44.5% for FRY, affecting the detection of genetic variation.…”

“…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). However, researches on estimates of genetic parameters for cassava quantitative traits and of polygenic heritage (Resende, 2002;Ojulong et al, 2008) are still scarce in Brazilian conditions (Barreto & Resende, 2010;Farias Neto et al, 2013). The separation of total variation into inheritable and non-inheritable components is fundamental to define the progress and best strategies for selection.…”

Molecular characterization of 'sweet' cassavas (Manihot esculenta) from a germplasm bank in Brazilian Eastern Amazonia

“…In the North region, there is little adoption of advanced methods of culture, such as mechanized planting and use of erect cultivars in dense plantations, more commonly used in the Southeast region of Brazil. Moreover, plantations are composed of a mixture of landraces, and generally, farmers from each micro region use their preferred materials, which may be an effect of the high genotype x environment interaction detected for cassava (Farias-Neto et al 2013). This may have contributed for the high genetic variability detected in the germplasm bank.…”

Variation in cassava germplasm for tolerance to post-harvest physiological deterioration

“…In studies related to potential rice production, similar proportions were observed between the genotypic variance and the G x E interaction (Colombari Filho et al, 2013), indicating that the effects of the G x E interaction strongly influence the expression of quantitative traits. In contrast, when evaluating the fresh root yield in 10 cassava varieties, Farias Neto et al (2013) reported that most of the variation was due to the environmental effect (79%) over the G x E interaction (18%) and genotypic variation (3%). Furthermore, Oliveira et al (2015) evaluated the effect of drought on genetic parameters and genotypic values for dozens of cassava accessions.…”

“…The AUP-PPD presented a high magnitude (0.72), which would ensure high reliability when selecting the best accessions. In another study related to fresh root yield in cassava, Farias Neto et al (2013) reported success in selecting superior genotypes even when a selective accuracy of moderate magnitude (0.53) was observed. However, those authors noted that an appropriate number of repetitions is essential in field trials for a more efficient and accurate selection, because it can contribute to an increase in the .…”