<b>Repeatability and phenotypic stabilization of <i>Panicum maximum</i> accessions

Abstract

The experiment aimed at determining repeatability coefficients for four methods (analysis of variance, principal components-correlation and covariance matrices and structural analysis), number of harvests necessary to increase accuracy and phenotypic stability of yield characteristics of accessions of Panicum maximum. The experiment was conducted in a completely randomized design with 35 genotypes and three replications. Five cuts were made and material was weighed and dried to obtain total, stem, leaf and dead forage dry matter yields. The repeatability coefficients in the different methods, for the evaluated characteristics, ranged from 0.1867 and 0.6583. The estimates of repeatability coefficients obtained for the evaluated characteristics by analysis of variance were generally smaller than the ones obtained with the other methods. By the principal components (based on the covariance matrix), the estimates were usually larger than those for the other methods. Therefore, it is possible to recommend this method to estimate the coefficient of repeatability for traits evaluated in this study. Considering that levels of 80 or 90% of confidence in the evaluation of the relative superiority of the accessions for all the evaluated characteristics are satisfactory, five harvests are sufficient for the choice of the best accession.

Repeatability estimates and minimum number of evaluations for selection of elephant-grass genotypes for herbage production

“…The repeatability coefficient estimates for the variable plant height were considered of medium magnitude (0.39< r <0.44). Similar results were reported by Martuscello et al (2015), estimating repeatability in Panicum maximum genotypes. According to these authors, this variable is important in the evaluation of forage plants, as it correlates with biomass production and may have specific recommendations according to the desired use, be it in the feeding of grazing animals like goat and sheep, or even for use in cattle feeding.…”

“…For the variables stem diameter and dry matter yield, the pair of harvests seven and eight showed coincidence, culminating in lower r estimates, indicating that the genotypes were not stabilized for these traits. When the measured genotype is not stabilized, the variation in the individuals will contain a fraction of the variance of the genotype with temporary environment, and an increment in the number of measurements would not be beneficial (MARTUSCELLO et al, 2015). Overall, the highest repeatability estimates for the variable dry matter yield were obtained when harvest four was correlated with the others, whereas the lowest estimates were observed with the inclusion of harvests one and two.…”

Study of repeatability and phenotypical stabilization in kale using frequentist, Bayesian and bootstrap resampling approaches

“…In addition to the study of the optimal number of evaluations, phenotypic stabilization study is of great importance in plant selection, since it allows verification of which harvests provide greater efficiency (Martuscello et al, 2015). The evaluation of non-stabilized genotypes may suffer from low repeatability, and in these situations the increase in the number of replications is not always the solution to alleviate the problem (Pereira et al, 2002), as a consequence of the performance of distinct genotypes as a function of the stage of development of the culture (Martuscello, Jank, Fonseca, Cruz, & Cunha, 2007).…”

“…The selection of kale genotypes is based on several harvests (Azevedo et al, 2016a); thus, information on the minimum number of harvests is needed to avoid more evaluations than are necessary, which would entail the waste of labour and financial resources (Cruz, Regazzi, & Carneiro, 2012). To establish how many and which harvests should be contemplated during progeny selection, repeatability and phenotypic stabilization studies can be performed (Martuscello et al, 2015).…”

Productivity of forage cultivars in Northeast of Brazil

“…(Argenta et al, 2017) e P. maximum (Martuscello et al, 2015), sendo que esta última se destaca, principalmente pela elevada produtividade. Assim, a avaliação da produção e seleção de cultivares dessas espécies no agreste certamente contribuiria para o aumento na produtividade animal, uma vez que a forrageira adotada nos sistemas de produção seria aquela de maior adaptação ao meio.…”