Repeatability, number of harvests, and phenotypic stability of dry matter yield and quality traits of <i>Panicum maximum</i> jacq.

Selection of superior forage genotypes is based on agronomic traits assayed in repeated measures. The questions are how repeatable the performance of individual genotypes is and how many harvests are needed to select the best genotypes. The objectives were to estimate repeatability coefficients of dry matter yield (DMY) and forage quality, their phenotypic stability and the number of harvests needed for an accurate selection. Two randomized complete block design experiments data with 24 genotypes each, undergoing 12 and 16 harvests, over a period of 2 and 3 years, respectively, were used. The DMY repeatability estimates ranged from 0.42 to 0.55, suggesting a low heritability. The mean numbers of repeated measures were 5 and 7 harvests for 0.80 and 0.85 accuracy, respectively. The inclusion of the first two harvests negatively affects the estimates. Repeatability for quality traits ranged from 0.30 to 0.69, indicating low to moderate heritability.

Keywords:
repeated measures; selection efficiency; selection effectiveness

Authorship

Francisco Duarte Fernandes ^**Author for correspondence. E-mail: carlos.lazarini@embrapa.br

Embrapa Cerrados, Empresa Brasileira de Pesquisa Agropecuária, BR-020, km 18, 73310-970, Planaltina, Distrito Federal, Brazil. Embrapa Cerrados, Empresa Brasileira de Pesquisa AgropecuáriaBrazilPlanaltina, Distrito Federal, BrazilEmbrapa Cerrados, Empresa Brasileira de Pesquisa Agropecuária, BR-020, km 18, 73310-970, Planaltina, Distrito Federal, Brazil.

Gustavo José Braga

Allan Kardec Braga Ramos

Liana Jank

Embrapa Gado de Corte, Empresa Brasileira de Pesquisa Agropecuária, Campo Grande, Mato Grosso do Sul, Brazil. Embrapa Gado de Corte, Empresa Brasileira de Pesquisa AgropecuáriaBrazilCampo Grande, Mato Grosso do Sul, BrazilEmbrapa Gado de Corte, Empresa Brasileira de Pesquisa Agropecuária, Campo Grande, Mato Grosso do Sul, Brazil.

Marcelo Ayres Carvalho

Giovana Alcântara Maciel

Claudio Takao Karia

Carlos Eduardo Lazarini da Fonseca

*Author for correspondence. E-mail: carlos.lazarini@embrapa.br

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (2)
Tables (6)

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Figure 1
Mean number of repeated measures for dry matter yield of P. maximum for Exp.1, Exp.2, and the average over four methods for four levels of accuracy.

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Figure 2
Estimated number of repeated measures for total dry matter yield (DMY) of P. maximum for four levels of accuracy with data from 6 different studies by Martuscello et al. (2007Martuscello, J. A., Jank, L., Fonseca, D. M. D., Cruz, C. D., & Cunha, D. D. N. F. V. (2007) Agronomic characters repeatability in Panicum maximum Jacq. Revista Brasileira de Zootecnia , 36(6), 1975-1981. , 2015), Lédo et al. (2008Lédo, F. J. S., Pereira, A. V., Souza Sobrinho, F., Auad, A. M., Jank, L., & Oliveira, J. S. (2008). Estimativas de repetibilidade para caracteres forrageiros em Panicum maximum. Ciência e Agrotecnologia, 32(4), 1299-1303.), Torres et al. (2016Torres, F. E., Teodoro, P. E., Benites, S. B., Oliveira, E. P., Corrêa, C. C. G., & Silva, F. A. (2016). Number of cuts for estimating forage productivity in P. maximum. Bioscience Journal, 32(1), 172-178.), Exp. 1, and Exp. 2.

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Table 1
Estimates of repeatability coefficient (r) and coefficient of determination (R²) of total dry matter yield (DMY) for 12 harvests in Exp.1 and 16 harvests in Exp.2, by analysis of variance (ANOVA), principal component covariance (PCCov), principal component correlation (PCCor) and structural analysis (STCor).

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Table 2
Number of repeated measures of dry matter yield of P. maximum for Exp.1 and Exp.2 estimated by four methods of repeatability coefficient and four levels of accuracy (R²).

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Table 3
Phenotypic stabilization - estimates of repeatability (r) and coefficients of determination (R²) of dry matter yield for different groups of 12 successive harvests for Exp. 1 and 16 successive harvests for Exp. 2 in P. maximum using ANOVA and principal component analysis (PCA).

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Table 4
Estimates of repeatability coefficient (r) and coefficient of determination (R²) of P. maximum leaf quality traits for 7 harvests, by analysis of variance (ANOVA), principal component covariance (PCCov), principal component correlation (PCCor) and structural analysis (STCor).

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Table 5
Number of repeated measures for quality traits of P. maximum estimated by four methods of repeatability coefficient and four levels of accuracy (R²).

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Table 6
Phenotypic stabilization in P. maximum - estimates of repeatability and determination coefficients of quality traits for different groups of 7 harvests using ANOVA and PCA.

Figure 1 Mean number of repeated measures for dry matter yield of P. maximum for Exp.1, Exp.2, and the average over four methods for four levels of accuracy.

Figure 2 Estimated number of repeated measures for total dry matter yield (DMY) of P. maximum for four levels of accuracy with data from 6 different studies by Martuscello et al. (2007Martuscello, J. A., Jank, L., Fonseca, D. M. D., Cruz, C. D., & Cunha, D. D. N. F. V. (2007) Agronomic characters repeatability in Panicum maximum Jacq. Revista Brasileira de Zootecnia , 36(6), 1975-1981. , 2015), Lédo et al. (2008Lédo, F. J. S., Pereira, A. V., Souza Sobrinho, F., Auad, A. M., Jank, L., & Oliveira, J. S. (2008). Estimativas de repetibilidade para caracteres forrageiros em Panicum maximum. Ciência e Agrotecnologia, 32(4), 1299-1303.), Torres et al. (2016Torres, F. E., Teodoro, P. E., Benites, S. B., Oliveira, E. P., Corrêa, C. C. G., & Silva, F. A. (2016). Number of cuts for estimating forage productivity in P. maximum. Bioscience Journal, 32(1), 172-178.), Exp. 1, and Exp. 2.

Table 1 Estimates of repeatability coefficient (r) and coefficient of determination (R²) of total dry matter yield (DMY) for 12 harvests in Exp.1 and 16 harvests in Exp.2, by analysis of variance (ANOVA), principal component covariance (PCCov), principal component correlation (PCCor) and structural analysis (STCor).

Table 2 Number of repeated measures of dry matter yield of P. maximum for Exp.1 and Exp.2 estimated by four methods of repeatability coefficient and four levels of accuracy (R²).

¹Methods of estimation: ANOVA - Analysis of Variance; PCCov - Principal Component Covariance; PCCor - Principal Component Correlation; STCor - Structural Correlation.

Table 3 Phenotypic stabilization - estimates of repeatability (r) and coefficients of determination (R²) of dry matter yield for different groups of 12 successive harvests for Exp. 1 and 16 successive harvests for Exp. 2 in P. maximum using ANOVA and principal component analysis (PCA).

Table 4 Estimates of repeatability coefficient (r) and coefficient of determination (R²) of P. maximum leaf quality traits for 7 harvests, by analysis of variance (ANOVA), principal component covariance (PCCov), principal component correlation (PCCor) and structural analysis (STCor).

¹OM - Leaf Organic Matter; CP - Leaf Crude Protein; NDF - Leaf Neutral Detergent Fiber; ADF - Leaf Acid Detergent Fiber; Lig-KMnO₄ - Leaf Lignin in potassium permanganate; Lig-H₂SO₄ - Lignin in sulfuric acid; OMD - In vitro organic matter digestibility.

Table 5 Number of repeated measures for quality traits of P. maximum estimated by four methods of repeatability coefficient and four levels of accuracy (R²).

¹Methods of estimation: ANOVA - Analysis of Variance; PCCov - Principal Component Covariance; PCCor - Principal Component Correlation; STCor - Structural Correlation.

Table 6 Phenotypic stabilization in P. maximum - estimates of repeatability and determination coefficients of quality traits for different groups of 7 harvests using ANOVA and PCA.

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Repeatability, number of harvests, and phenotypic stability of dry matter yield and quality traits of <i>Panicum maximum</i> jacq.

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[1] *Author for correspondence. E-mail: carlos.lazarini@embrapa.br