Abstract:-This experiment was carried out with the objectives of determining repeatability coefficients, the number of harvests necessary to increase accuracy and the genotypic stability of yield characteristics in Brachiaria brizantha cultivars in the northeast region of Brazil in the period from July 2009 to March 2011. The experimental design used was completely randomized with three treatments (Brachiaria brizantha var. Marandu, Xaraés and Piatã) and three replications. Each plot was harvested seven times: five in … Show more
“…Observing the clusters of harvests that provided greater repeatability, we note the same trend observed for TDM, with higher coefficients when harvests between 4 and 6 were grouped, wherein a greater repeatability was obtained with the clustering of harvests 4 and 5 (Table 1). In a similar study, Martuscello et al (2013) obtained repeatability coefficients lower than those of this study, with 0.212 and 0.411 for TDM and LDM, respectively.…”
-The objective of this study was to evaluate the genotypic stability of agronomic traits in hybrids of Panicum maximum. Hybrids originating from the crosses between two sexual parents and cultivars Mombasa and Tanzania were evaluated in an incomplete-block design. Evaluated traits were total dry matter, leaf dry matter, stem dry matter, percentage of leaves, and leaf:stem ratio. These traits were evaluated in six harvests. Overall, higher repeatability was observed for the traits total dry matter and leaf dry matter, especially when harvests 4, 5, and 6, occurring in spring and summer, were evaluated. The leaf dry matter was the trait that provided the greatest repeatability and determination. The repeatability of stem dry matter, percentage of leaves, and leaf:stem ratio had a low magnitude, even when the coefficient was estimated based on the harvests of better stabilization for the other variables. The hybrids achieved genotypic stabilization in the harvests made in the second rainy season. Harvests made in the rainy season provide greater repeatability and determination, and the inclusion of the dry-season harvest is detrimental to the process of selection of low-repeatability traits such as percentage of leaves.
“…Observing the clusters of harvests that provided greater repeatability, we note the same trend observed for TDM, with higher coefficients when harvests between 4 and 6 were grouped, wherein a greater repeatability was obtained with the clustering of harvests 4 and 5 (Table 1). In a similar study, Martuscello et al (2013) obtained repeatability coefficients lower than those of this study, with 0.212 and 0.411 for TDM and LDM, respectively.…”
-The objective of this study was to evaluate the genotypic stability of agronomic traits in hybrids of Panicum maximum. Hybrids originating from the crosses between two sexual parents and cultivars Mombasa and Tanzania were evaluated in an incomplete-block design. Evaluated traits were total dry matter, leaf dry matter, stem dry matter, percentage of leaves, and leaf:stem ratio. These traits were evaluated in six harvests. Overall, higher repeatability was observed for the traits total dry matter and leaf dry matter, especially when harvests 4, 5, and 6, occurring in spring and summer, were evaluated. The leaf dry matter was the trait that provided the greatest repeatability and determination. The repeatability of stem dry matter, percentage of leaves, and leaf:stem ratio had a low magnitude, even when the coefficient was estimated based on the harvests of better stabilization for the other variables. The hybrids achieved genotypic stabilization in the harvests made in the second rainy season. Harvests made in the rainy season provide greater repeatability and determination, and the inclusion of the dry-season harvest is detrimental to the process of selection of low-repeatability traits such as percentage of leaves.
“…The superiority of the repeatabilitycoefficient estimates obtained by the Principal Components method based on the covariance matrix have been reported in many forage species: Penissetum purpureum (CAVALCANTE et al, 2012); Panicum maximum (MARTUSCELLO et al, 2007;LÉDO et al, 2008); Brachiaria brizantha (MARTUSCELLO et al, 2013), as well as in fruits, like banana (LESSA et al, 2014).…”
Section: Resultsmentioning
confidence: 87%
“…It is essential to utilize methodologies that maximize efficiency in the phenotypic selection and that minimize the costs with financial and human resources. Several authors have obtained the estimate of the repeatability coefficient in many forage species, such as Pennisetum purpureum (DAHER et al, 2004;VIANA et al, 2009;OLIVEIRA et al, 2011;CAVALCANTE et al, 2012), Panicum maximum (MARTUSCELLO et al, 2007;LÉDO et al, 2008), Brachiaria brizantha (MARTUSCELLO et al, 2013), Medicago sativa (FREITAS et al, 2011), and also other perennial cultures like sugarcane (FERREIRA et al, 2005), coffee (CECON et al, 2008), banana (LESSA et al, 2014, and guaraná (NASCIMENTO FILHO et al, 2009).…”
In forage-plants breeding, the selection of superior genotypes has been undertaken through successive harvests in previously established intervals. However, this process involves many steps, the evaluation of many traits, and a great spending with costs and labor. Thus the estimate of the repeatability is essential in improvement of perennials, it allows predicting genotypic value of the individual, the minimum number of evaluations in the selection of genotypes and minimizes resources and time in the selection of promising individuals. The objective of this study was to estimate the repeatability coefficient for morphological traits in elephant grass and determine the number of evaluations needed for phenotypic selection more efficient. The experimental randomized block design with 53 genotypes and two replications. The repeatability coefficients were estimated for variables plant height, number of tillers, stem diameter and dry matter yield, using the methods of Anova, Principal Components and Structural Analysis. We observed significant differences between genotypes (P <0.01) for all variables. The main components provide larger estimates of repeatability when compared to other methods. Estimates of the repeatability coefficients are of high magnitude average for the variables plant height (0.44) number of tillers (0.44) and stem diameter (0.63) and low magnitude for dry matter production (0.27). The Principal Components method requires five, five, two and eleven measurements for plant height, number of tillers, stem diameter and dry matter yield, respectively, with 80% reliability.
“…Therefore, several studies have been conducted to estimate the repeatability (ρ̂) of characteristics of interest in forage plants including Urochloa spp. (Basso et al, 2009;Souza Sobrinho et al, 2010;Teixeira et al, 2011;Martuscello et al, 2013;Matias et al, 2016;Coêlho et al, 2018;Figueiredo et al, 2019), Megathyrsus maximus (Martuscello et al, 2007;Braz et al, 2015;Martuscello et al, 2015;Coêlho et al, 2018;Ferreira et al, 2019), Medicago sativa L. (Botrel et al, 2000;Ferreira et al, 2010), Pennisetum purpureum Schum. (Shimoya et al, 2002;Rodrigues et al, 2020), and Lolium multiflorum Lamarck (Rios et al, 2019).…”
The objective of this study was to verify the repeatability of the expression of forage characters in intraspecific hybrids of Paspalum notatum Flügge to aid early selection. Across five harvests, plant height, tiller population density, leaf dry matter, stem dry matter, inflorescence dry matter, total dry matter, and growth habit were quantified for five parents, 189 hybrids, and a commercially available cultivar as a control (n = 195). Analysis of variance, principal components analysis, and structural analysis methods were used to determine the repeatability coefficients. The repeatability coefficients (ρ̂) for all evaluated characteristics generated by the different methods were between 0.05 (ANOVA II) and 0.95 (PCACov). For most of the characteristics studied, repeatability coefficients and determination coefficients were considered high. The repeatability coefficients estimates obtained for the eight characteristics evaluated with the ANOVA I and II methods were almost always lower than those obtained by PCA and structural analysis methods. Based on the covariance matrix, the principal component method generated higher estimates than those produced by ANOVA or structural analysis. Assuming a minimum 80% reliability to verify the relative superiority of the hybrids across all assessed traits, the five harvests proved adequate for selecting the optimal plant materials to advance to the next phase of the breeding program. However, reliable early selection for leaf dry matter, leaf:stem ratio, and total dry matter required a minimum of two harvests. The genetic parameters (h 2 and CVg) showed a favorable scenario for direct selection to increase forage production.
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