Repeatability estimates in longitudinal data on guava trees

The use of longitudinal measurements is an essential practice both in Psidium guajava L. breeding and in other perennial crops in which covariance structures can be introduced to explain the form of dependence between measurements. Hence, this study aimed to analyze six covariance structures to identify one that best described the correlation between the repeated measurements in time in traits of guava full-sib families. The repeatability coefficient for each trait was estimated and the minimum number of evaluations required for estimates representing the population was determined. The work was performed based on average data of three yield-related variables from nine harvests of a guava tree population evaluated from 2011 to 2018. The best model was chosen based on the Akaike and Schwarz Bayesian information criterion. The autoregressive covariance structure best represented the dependencies among families between crops for all traits. The number of variables of fruits and total yield per plant presented repeatability estimates higher than 0.5 and may be essential traits for indirect selection of others, such as fruit mass, which had an estimated repeatability of 0.24, proving low regularity in the repetition of the character from one cycle to another. It was also possible to define four harvests as the minimum acceptable number of observations necessary on the same individual for these traits; therefore, the repetitions represented the individuals.(AU)

Row-Col and Bayesian approach seeking to improve the predictive capacity and selection of passion fruit

Methods for genetic improvement of semi-perennial species, such as passion fruit, often involve large areas, unbalanced data, and lack of observations. Some strategies can be applied to solve these problems. In this work, different models and approaches were tested to improve the precision of estimates of genetic evaluation models for several characteristics of the passion fruit. A randomized block design (RBD) model was compared to a posteriori correction, adding two factors to the model (post-hoc blocking Row-Col). These models were also combined with the frequentist and Bayesian approaches to identify which combination yields the most accurate results. These approaches are part of a strategic plan in a perennial plant breeding program to select promising genitors of passion to compose the next selection cycle. For Bayesian, we tested two priors, defining different values for the distribution parameters of effect variances of the model. We also performed a cross-validation test to choose a priori values and compare the frequentist and Bayesian approaches using the root mean square error (RMSE) and the correlation between the predicted and observed values, called Predictive capacity of the model (PC). The model with the post-hoc blocking Row-Col design captured the spatial variability for productivity and number of fruits, directly affecting the experimental precision. Both approaches applied to the models showed a similar performance, with predictive capacity and selective efficiency leading to the selection of the same individuals.

Genotypic superiority of Psidium Guajava S1 families using mixed modeling for truncated and simultaneous selection

The purpose of this study was to conduct selection, genetic parameter estimation, and prediction of genetic values for 18 S1 families of guava trees using mixed model methodology and simultaneous selection of traits by means of the additive selection index, multiplicative selection index, and mean rank adapted from Mulamba. All families analyzed were obtained by means of self-fertilization of superior genotypes (full siblings) from the genetic breeding program of guava trees at the Universidade Estadual do Norte Fluminense. An experimental randomized block design with 18 S1 families, three replicates, and ten plants per plot was used. A total of 540 genotypes (individual plants) of guava tree were evaluated. Genetic parameter estimation and selection of the best genotypes based on the genetic value were performed using the statistical procedure, from the Selegen-REML/BLUP program. The analyses of the additive selection index, multiplicative selection index, and the sum of rank adapted from Mulamba were also performed under the Selegen program. During the evaluation by the individual BLUPs, families 1, 12, 4, 6, and 8 contributed to most of the genotypes selected for the traits under evaluation, suggesting their significant potential to generate high quality and high yield genotypes. In the selection indexes via mixed models, the multiplicative index showed higher values for genetic gains (74 %), followed by the mean rank index adapted from Mulamba (19 %), and the additive index (2%).(AU)

Novel approach to the selection of Psidium guajava genotypes using latent traits to bypass multicollinearity

Multicollinearity is a very common problem in studies that employ path analysis in agronomic crops, which generates unrealistic results and erroneous interpretations. This study was aimed at assessing the path analysis in data obtained from guava tree full-sib based on modelling multiple regressions applying latent variables to neutralize the effects of multicollinearity. Seven explanatory variables were measured fruit mass (FM), fruit length (FL), fruit diameter (FD), mesocarp thickness (MT), peel thickness (PT), pulp mass (PM), total number of fruits (NTF) –, plus the main dependent variable, total yield per plant (YIELD). In accordance with the multicollinearity scenario, eleven values were tested with the addition of the constant K to the diagonal of the correlation matrix XX. Path analysis was applied in two models: all the explanatory variables with direct effect on the dependent one and another model with multiple regression with more than one chain and the presence of latent variables. The path analysis in the multivariate methodology of structural equation modelling (SEM), which uses latent variable prediction, provided better results than the traditional and ridge path analyses.(AU)

Novel approach to the selection of Psidium guajava genotypes using latent traits to bypass multicollinearity

Multicollinearity is a very common problem in studies that employ path analysis in agronomic crops, which generates unrealistic results and erroneous interpretations. This study was aimed at assessing the path analysis in data obtained from guava tree full-sib based on modelling multiple regressions applying latent variables to neutralize the effects of multicollinearity. Seven explanatory variables were measured – fruit mass (FM), fruit length (FL), fruit diameter (FD), mesocarp thickness (MT), peel thickness (PT), pulp mass (PM), total number of fruits (NTF) –, plus the main dependent variable, total yield per plant (YIELD). In accordance with the multicollinearity scenario, eleven values were tested with the addition of the constant K to the diagonal of the correlation matrix X’X. Path analysis was applied in two models: all the explanatory variables with direct effect on the dependent one and another model with multiple regression with more than one chain and the presence of latent variables. The path analysis in the multivariate methodology of structural equation modelling (SEM), which uses latent variable prediction, provided better results than the traditional and ridge path analyses.

Genotypic superiority of Psidium Guajava S1 families using mixed modeling for truncated and simultaneous selection

The purpose of this study was to conduct selection, genetic parameter estimation, and prediction of genetic values for 18 S1 families of guava trees using mixed model methodology and simultaneous selection of traits by means of the additive selection index, multiplicative selection index, and mean rank adapted from Mulamba. All families analyzed were obtained by means of self-fertilization of superior genotypes (full siblings) from the genetic breeding program of guava trees at the Universidade Estadual do Norte Fluminense. An experimental randomized block design with 18 S1 families, three replicates, and ten plants per plot was used. A total of 540 genotypes (individual plants) of guava tree were evaluated. Genetic parameter estimation and selection of the best genotypes based on the genetic value were performed using the statistical procedure, from the Selegen-REML/BLUP program. The analyses of the additive selection index, multiplicative selection index, and the sum of rank adapted from Mulamba were also performed under the Selegen program. During the evaluation by the individual BLUPs, families 1, 12, 4, 6, and 8 contributed to most of the genotypes selected for the traits under evaluation, suggesting their significant potential to generate high quality and high yield genotypes. In the selection indexes via mixed models, the multiplicative index showed higher values for genetic gains (74 %), followed by the mean rank index adapted from Mulamba (19 %), and the additive index (2%).

Macronutrients release by green manure species grown in cerrado/pantanal ecotone / Liberação de macronutrientes por espécies de adubação verde cultivadas no ecótono cerrado/pantanal

Assessing the nutrient release by cover crops species, especially those used in green manure, is important for planning activities aimed at the higher economic return. The use of these species in order to improve the growing conditions in the transition region between the Cerrado and Pantanal biomes, which have particular characteristics, may be a viable alternative. This study aimed to evaluate the amount of biomass produced and macronutrients released in this biomass by different green manure species grown in the Cerrado/Pantanal ecotone. The trial was carried out from April 2013 to June 2014 in the Plant Science sector at State University of Mato Grosso do Sul, Aquidauana-MS (Brazil). Experimental design was completely randomized arranged in time split plot, with four replications. First factor consisted of seven species of green manure, while the second were seven evaluation times (months). The variables evaluated were: dry mass of shoot and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) contents as a function of time. For all variables evaluated there was significant interaction between the green manure species and the collection months. Vegetable cover showed different rates of decomposition and nutrient release. Mucuna aterrima was the species that produced higher amounts of dry mass and nutrient content. After four months of cutting the plants, green manure species do not differentiate between the amounts of released nutrients.

Avaliar a liberação de nutrientes por espécies de plantas de cobertura, especialmente aquelas utilizadas na adubação verde é importante para o planejamento das atividades objetivando o maior retorno econômico. O uso dessas espécies afim de se melhorar as condições de cultivo na região de transição entre os biomas do Cerrado e Pantanal que possuem características particulares, pode ser uma alternativa viável. O objetivo deste trabalho foi avaliar as taxas de liberação de macronutrientes de diferentes espécies de adubação verde cultivadas no ecótono Cerrado/Pantanal. O experimento foi realizado entre os meses de abril de 2013 a junho de 2014 no setor de Fitotecnia da Universidade Estadual de Mato Grosso do Sul, Aquidauana-MS. O delineamento experimental adotado foi o inteiramente casualizado disposto em esquema de parcelas subdivididas no tempo, com quatro repetições. O primeiro fator consistiu em sete espécies de adubação verde, enquanto o segundo em sete épocas (meses) de avaliação. As variáveis avaliadas foram: massa seca da parte aérea e quantidades de nitrogênio (N), fósforo (P), potássio (K), cálcio (Ca), magnésio (Mg) e enxofre (S) liberados em função do tempo. Para todas as variáveis avaliadas houve interação significativa entre as espécies de adubação verde vezes os meses de coleta. As coberturas vegetais apresentaram distintas taxas de decomposição e de liberação de nutrientes. Mucuna aterrima foi à espécie que produziu maiores quantidades de massa seca e disponibilizou as maiores quantidades de nutrientes. Após quatro meses de corte das plantas, as espécies de adubação verde não diferiram entre si quanto as quantidades liberadas de nutrientes.

Correlations and genetic parameters in maize hybrids / Correlações e parâmetros genéticos em híbridos de milho

The study of the genetic control of agronomic traits and heritage through estimates of genetic parameters of a population allows inferences about its genetic variability and which can be expected of gain with selection. Know the correlations among traits of interest for selection allows to the breeder know the degree of association among traits of economic importance, given that the selection of certain trait changes the behavior of the other. With the aim to estimate genetic parameters and identify agronomic traits correlated with the grain yield of maize hybrids, an experiment was conducted at the State University of Mato Grosso do Sul - University Unit of Aquidauana (UEMS/UUA). The experimental design was a randomized block with four replications. Treatments consisted of 20 maize hybrids. The traits evaluated were: plant height, first ear height, stem diameter, ear diameter, ear length, number of rows per ear, number of kernels per row, hundred grain weight and grain yield. The hybrids XB9010, P30F53, 20A78HX, XB6012, P3340, AG9010 and XB7253, obtained the highest grain yield and mass of one hundred grains. The population has a genetic variability and potential for selection of all traits. Based on the evaluated genetic parameters, mass of hundred grains can be used at the direct selection of genotypes with high grain yield.

O estudo do controle genético de caracteres agronômicos através de estimativas de parâmetros genéticos de uma população permite inferências sobre sua variabilidade genética e o ganho esperado com a seleção. Conhecer as correlações entre caracteres de interesse para a seleção permite ao melhorista saber o grau de associação entre os caracteres de importância econômica, uma vez que a seleção de determinado caráter altera o comportamento do outro. Com o objetivo de estimar os parâmetros genéticos e identificar quais caracteres agronômicos estão correlacionados com a produtividade de grãos de híbridos de milho, um experimento foi conduzido na Universidade Estadual de Mato Grosso do Sul - Unidade Universitária de Aquidauana (UEMS/UUA). O delineamento experimental utilizado foi o de blocos ao acaso com quatro repetições Os tratamentos consistiram de 20 híbridos de milho. Os caracteres avaliados foram: altura de plantas, altura de inserção da primeira espiga, diâmetro do colmo, diâmetro da espiga, comprimento da espiga, número de fileiras por espiga, número de grãos por fileira, massa de cem grãos e produtividade de grãos. Os híbridos XB9010, P30F53, 20A78HX, XB6012, P3340, AG9010 e XB7253 obtiveram as maiores massa de cem grãos e produtividade. A população possui variabilidade genética e potencial para seleção de todos os caracteres. Com base nos parâmetros genéticos avaliados, a massa de cem grãos pode ser usada na seleção direta de genótipos com alta produtividade de grãos.

Number of cuts for estimating forage productivity in P. maximum / Número de cortes para estimativa da produtividade de forragem em P. Maximum

The evaluation of the coefficient of repeatability (r) allows verify if the superiority or initial inferiority of an individual remains over the measurements, being important for genetic breading programs with forages. Thus, this research aimed to determine the minimum number of cuts for selection with greater efficiency and reliability and to phenotypic stabilization of P. maximum cultivars. The experiment was conducted during the months of September 2011 to October 2012 at the State University of Mato Grosso do Sul. It were used three P. maximum cultivars (Massai, Mombaça and Tanzânia) for evaluation of dry mass of leaves and stems and total dry mass in six cuts. From this cuts, it was estimated the coefficient of r repeatability by methods ANOVA, principal components (correlation and covariance matrices) and structural analysis, as well as the required number of cuts based on pre-established coefficients of determination (0.80, 0.85, 0.90, 0.95 and 0.99). Seven harvests are necessary to discriminate with 85% accuracy in P. maximum cultivars based on the traits dry mass of leaves, dry mass of stems and total dry mass. The exclusion of the first three harvests promotes increase in coefficients of repeatability and determination due to forage production stabilization of P. maximum cultivars.

A avaliação do coeficiente de repetibilidade permite verificar se a superioridade ou a inferioridade inicial de um indivíduo mantém-se ao longo das medições, sendo importante para programas de melhoramento genético com forrageiras. Assim, esta pesquisa teve como objetivo determinar o número mínimo de cortes para a seleção com maior eficiência e confiabilidade e para a estabilização fenotípica de cultivares de P. maximum. O experimento foi conduzido durante os meses de setembro de 2011 a outubro de 2012 na Universidade Estadual de Mato Grosso do Sul. Foram utilizadas três cultivares de P. maximum (Massai, Mombaça e Tanzânia) para avaliação da massa seca das folhas, colmos e total em seis cortes. A partir de destes cortes, estimou-se o coeficiente de repetibilidade pelos métodos da ANOVA, componentes principais (matriz de correlação e covariância) e Análise estrutural, bem como o número de cortes necessários com base em coeficientes de determinação pré-estabelecidos (0,80, 0,85, 0,90, 0,95 e 0,99). Sete cortes são necessárias para discriminar com precisão de 85% cultivares de P. maximum com base nos caracteres massa seca de folhas, colmos e total. A exclusão das três primeiras colheitas promove aumento da repetibilidade e determinação coeficientes devido à estabilização da produção de forragem de cultivares de P. maximum.

Genetic divergence among maize hybrids in cerrado-pantanal ecotone / Divergência genética entre híbridos de milho no ecótono cerrado-pantanal

In maize breeding programs can arise difficulties in relation to combination capacity studies for determination of heterotic groups, which are highly correlated with genetic divergence among the parents. The aim of this study was to estimate the genetic divergence measured for nine quantitative morphological traits in eleven single-cross hybrids of maize cultivated in the Cerrado-Pantanal ecotone. The experiment was conducted at Universidade Estadual de Mato Grosso do Sul ­ University Unit of Aquidauana. The experimental design was a randomized blocks with four replications. At harvest time, it were measured the following traits: plant height, ear insertion height, ear length, ear diameter, stem diameter, number of kernels per rows, number of rows per ear, weight of hundred grains and grain yield. In the application of hybrids cluster technique was adopted the Mahalanobis's generalized distance as dissimilarity measure, and for establishment of similar groups was applied the Tocher's method. The results indicated the existence of genetic variability among tested hybrids. The greatest genetic divergence was observed among the pairs MAXIMUS and XB6012, implying in heterotic gains. Crossings of lines extracted from hybrids 2B587HX and XB6012 with lines obtained from the other hybrids provide greater heterosis. The traits grain yield and ear insertion height were those who more and less contributed, respectively, for genetic divergence among hybrids.

Em programas de melhoramento em milho podem surgir dificuldades quanto a estudos de capacidade de combinação para determinação de grupos heretóticos, que estão altamente correlacionados com a divergência genética entre os genitores. O objetivo deste trabalho foi estimar a divergência genética mensurada para nove descritores morfológicos quantitativos em onze híbridos simples de milho cultivado no ecótono Cerrado-Pantanal. O experimento foi conduzido na área experimental da Universidade Estadual de Mato Grosso do Sul, Aquidauana (MS). O delineamento experimental utilizado foi o de blocos casualizados com quatro repetições. No momento da colheita, foram mensurados os seguintes descritores: altura de planta, altura de inserção da primeira espiga, diâmetro da espiga, diâmetro do colmo, número de grãos por fileira, número de fileiras por espiga, massa de cem grãos e rendimento de grãos. Na aplicação da técnica de agrupamento de híbridos foi adotada a distância generalizada de Mahalanobis como medida de dissimilaridade, e para o estabelecimento de grupos similares foi aplicado o método de Tocher. Os resultados indicaram a existência de variabilidade genética entre os híbridos testados. A maior divergência genética foi observada entre os pares MAXIMUS e XB6012, implicando em ganho heterótico. Cruzamentos de linhagens extraídas dos híbridos 2B587HX e XB6012 com linhagens obtidas a partir dos demais híbridos proporcionaram maior heterose. Os descritores rendimento de grãos e altura de inserção da espiga foram os que mais e menos contribuíram, respectivamente, para a divergência genética entre os híbridos.