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Genotype x location x feeding interactions in Nellore cattle calculated through three-mode principal component analysis

Franco, Ingryd Loiola; Mendes Malhado, Carlos Henrique; Souza Carneiro, Paulo Luiz; Martins Filho, Raimundo; Pereira, Derval Gomes; Dias, Carlos Tadeu dos Santos
Fonte: UNIV FEDERAL SANTA MARIA; SANTA MARIA Publicador: UNIV FEDERAL SANTA MARIA; SANTA MARIA
Tipo: Artigo de Revista Científica
Português
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65.89%
The main objective of this study was to apply three-mode principal component analysis to assess the triple interaction (genotype x location x feeding) on direct genetic value for weight at 205 days of age. We used 60 sires with offspring in three regions of northeastern Brazil (Maranhao, Mata and Agreste, and Reconcavo Baiano) and raised on a pasture regime or with supplementation. There was no interaction between genotype and location, but there was a correlation between genotype and direct effect of feeding. The use of sires should be dictated according to the system of rearing of their offspring.

Estabilidade e adaptabilidade fenotípica através da reamostragem "Bootstrap" no modelo AMMI.; Phenotypic stability and adaptability via ammi model with bootstrap re-sampling.

Lavoranti, Osmir José
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/08/2003 Português
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As posições críticas dos estatísticos, que atuam em programas de melhoramento genético, referem-se à falta de uma análise criteriosa da estrutura da interação do genótipo com o ambiente (G x E) como um dos principais problemas para a recomendação de cultivares. Tradicionalmente, a análise dessa estrutura á superficial não detalhando os efeitos da complexidade da interação. Com isso, os ganhos genéticos podem ser diminutos, pela não seleção de genótipos superiores melhores indicados a um ambiente específico. A busca constante por novos métodos e algoritmos, visando eliminar ou minimizar esse problema, tem proporcionado uma inegável evolução científica, com a geração de tecnologias de ponta que envolvem grande capacidade de processamento computacional. Atualmente, a metodologia AMMI (additive main efects and multiplicative interaction analysis) propõe ser mais eficiente que as análises usuais na interpretação e compreensão da interação G x E. Entretanto, os principais pontos negativos dessa metodologia dizem respeito à dificuldade de se interpretar a interação quando há baixa explicação do primeiro componente principal; à dificuldade de se quantificar os escores como baixos, considerando estável os genótipos e/ou ambientes...

Utilização de técnicas multivariadas na análise da divergência genética via modelo AMMI com reamostragem "bootstrap"; Use of multivariate techniques in the analysis of genetic diversity through ammi model with bootstrap resampling

Faria, Priscila Neves
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/10/2012 Português
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Em estudos de divergência genética por métodos multivariados, a distância euclidiana é a medida de distância mais amplamente utilizada e essa distância é a mais recomendada quando as unidades de cálculos são escores de componentes principais, como é o caso da análise AMMI (additive main effects and multiplicative interaction analysis). Tal análise permite a obtenção de estimativas mais precisas das respostas genotípicas e possibilita a análise da divergência genética por métodos aglomerativos. A análise dos modelos AMMI combina, num único modelo, componentes aditivos para os efeitos principais (genótipos e ambientes) e componentes multiplicativos para os efeitos da interação genótipos × ambientes. Os melhoristas de plantas compreendem que a interação genótipos × ambientes é de suma importância para a obtenção de variedades superiores e as estimativas de dissimilaridade atendem aos objetivos do melhorista, por quantificarem e informarem sobre o grau de semelhança ou de diferença entre pares de indivíduos. Entretanto, quando o número de indivíduos é grande, torna-se inviável o reconhecimento de grupos homogêneos pelo exame visual das estimativas de distância. Portanto, é importante proceder à análise de agrupamentos...

Interação testecrosses por épocas de semeadura e implicações para o melhoramento de milho; Testcrosses by sowing dates interaction and implications for maize breeding

Aragão, Thiago Ricielli de Paula
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/02/2013 Português
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O cultivo do milho safrinha tem se expandido consideravelmente nos ultimos anos. Porem devido as condicoes ambientais contrastantes entre safra e safrinha, deve ocorrer pronunciada interacao genotipos x safras, indicando que os genotipos selecionados para a safra podem nao ser adequados para a safrinha. Assim, os objetivos deste trabalho foram investigar a magnitude e natureza da interacao genotipos x safras e a necessidade de conduzir programas de melhoramento de milho distintos para o cultivo de safra e safrinha. Foram utilizadas 100 progenies S1fs derivadas do cruzamento entre as linhagens endogamicas L08- 05F e L38-05D, as quais foram retrocruzadas com ambas as linhagens genitoras e, posteriormente, estas foram cruzadas com a linhagem endogamica L02-03D para obtencao de 200 testecrosses (100 RC1 TC e 100 RC2 TC ). Os testecrosses obtidos foram avaliados nos ambientes de safra e safrinha em dois anos agricolas no municipio de Piracicaba/SP no delineamento ?¿-latice com duas repeticoes por ambiente por ano. Os caracteres analisados foram producao de graos (PG), prolificidade (PROL), acamamento e quebramento de plantas (ACQ), altura de planta (AP) e de espiga (AE), posicao relativa da espiga (PRE), florescimento masculino (FM) e feminino (FF) e intervalo entre florescimentos (IF). Diferencas entre as medias nas duas safras foram significativas para todos os caracteres...

Interpretação da interação genótipos x ambientes em feijão-caupi usando modelos multivariados, mistos e covariáveis ambientais; Interpreting genotype x environment interaction in cowpea using multivariate, mixed models, and environmental covariates

Carvalho, Leonardo Castelo Branco
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/04/2015 Português
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Várias metodologias têm sido propostas com o intuito de medir a influência que a interação GxE exerce sobre os mais diversos caracteres de interesse e, dentre essas, as abordagens via modelos mistos utilizando REML/BLUP têm sido mencionadas como vantajosas. Ainda, o uso de informações ambientais pode ser útil para encontrar os fatores que estão por trás da real diferença entre os genótipos. O objetivo do estudo foi avaliar a resposta da produtividade de grãos em feijão-caupi frente às variações espaciais, e as variáveis ambientais mais relevantes para a interação GxE. Foram avaliados 20 genótipos em 47 locais entre os anos de 2010 a 2012 sob delineamento DBC. Após a análise conjunta, os padrões de adaptabilidade dos genótipos foram testados pelas metodologias GGE Biplot e MHPRVG e a estratificação ambiental foi feita via Análise de Fatores sobre a matriz dos efeitos aleatórios GGE. A importância das variáveis ambientais na produtividade foi verificada pela associação entre os efeitos da matriz GGE e cada variável ambiental. Após decomposição SVD, os componentes principais foram plotados em Covariáveis-Biplots. Os efeitos de genótipos e da interação tripla apresentaram elevada significância (p ≤ 0...

Modelos de normas de reação para estudo da interação genótipo x ambiente; Reaction norms models for study of genotype by environment interaction

Cardoso, Leandro Lunardini
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
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65.98%
O objetivo desse estudo foi avaliar diferentes modelos estatísticos com diferentes pressuposições para definir o melhor modelo que descreva a presença de interação genótipo x ambiente no ganho de peso pós-desmama ajustado (GPD345) de bovinos Hereford, mediante o estudo de normas de reação ao ambiente, obtidas por regressão aleatória, usando uma abordagem bayesiana. Quatro modelos hierárquicos de normas de reação (MHNR) e um modelo animal padrão (MA) foram empregados por meio do programa INTERGEN. O MHNRk utiliza as soluções de grupos contemporâneos estimadas previamente pelo modelo animal padrão (MA) e as considera como nível ambiental e o de uma única análise, MHNRS, que estima simultaneamente esses dois conjuntos de incógnitas considerando nas duas metodologias a variância residual homogênea (hm) e heterogênea (ht). Pelo critério de informação da "deviance", o MHRNshm foi que apresentou melhor ajuste aos dados, seguido pelo MHNRsht, MHNRKhm, MHNRkht e o pior ajuste foi obtido pelo MA, já pelo Fator de Bayes os MHNR homoscedásticos foram os que melhor ajustaram-se aos dados. Pela ordenada preditiva condicional o MA, foi melhor em relação aos MHNR. As herdabilidades nos MHNR foram crescentes nos gradientes ambientais em GPD345 de -60; 0 e +60 kg. As correlações genéticas entre o nível e inclinação das normas de reação foram de alta magnitude caracterizando efeito de escala em interação GxE. Os modelos hierárquicos de normas de reação são eficientes para descrever as alterações nos componentes de variância em função do ambiente ao qual o genótipo está exposto bem como para descrever a presença de interação genótipo x ambiente na característica GPD345 em bovinos Hereford.; The objective of that study was to evaluate different statistical models with different presuppositions to define the best model than it describes the presence of genotype by environment interaction in the characteristic weight post weaning gain (GPD345) of Hereford cattle...

On a modelling environmental indexes.

Pereira, Dulce
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Aula Formato: 111789 bytes; application/pdf
Português
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The paper deals with the structuring the Genotype x Environmental Interaction in an analysis of series of experiments. The analysis of regression is one of the most appropriate methods in this problem. As in regression analysis we should have two sets of variables, one characterizing genotypes while the second characterizing environments. The so-called adjusted means for genotypes constitute usually observations of dependent variable. The problem is how to model the environmental indexes being the observation of independent variable. In the paper we examine two approaches to modelling the environmental indexes, one is based on so called adjusted means for environments while second method uses iterative (called zig zag) algorithm for estimation of considering indexes.

A note on a modelling environmental indexes

Mejza, S.; Mexia, João T.; Pereira, Dulce G.
Fonte: Printed by Ipskamp Partners, Enschede Publicador: Printed by Ipskamp Partners, Enschede
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
75.83%
The paper deals with the structuring of the Genotype x Environmental Interaction in an analysis of series of experiments. Regression analysis is one of the most often applied statistical techniques for this purpose. In regression analysis we should have two sets of variables, one characterizing genotypes while the second characterizing environments. The so-called adjusted means (or some other genotype characteristics) for genotypes usually constitute observations of the dependent variable. The problem is how to model the environmental indexes, these being the observation of independent variable. In the paper we examine three approaches to modelling the environmental indexes; two are based on socalled adjusted means for environments, while the third method uses iterative (”zig-zag”) algorithm for estimation of the considered indexes.

Factor analysis and SREG GGE biplot for the genotype × environment interaction stratification in maize

Fritsche-Neto,Roberto; Miranda,Glauco Vieira; DeLima,Rodrigo Oliveira; Souza,Heraldo Namorato de
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2010 Português
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The objective of this study was to evaluate the use of SREG GGE biplot methodology and factor analysis to stratify the genotype×environment interaction in maize. Forty-nine early maize hybrids were evaluated in nine environments. The experimental design used was a 7×7 square lattice with two replicates. Each plot consisted of two 5m long rows spaced 0.90m apart. Grain yield data were used to perform the analysis. The results indicated the existence of two mega-environments in the State of Minas Gerais, Brazil, for early maize hybrids. The stratification of the environment by factor analysis was more selective to join the similarity the according with cultivar performance. However, this approach did not identify specific genotype x environment interactions, which is possible through SREG GGE biplot analysis.

Correlation and path analysis in components of grain yield of cowpea genotypes

Almeida,Wener Santos de; Fernandes,Francisco Ronaldo Belém; Teófilo,Elizita Maria; Bertini,Cândida Hermínia Campos de Magalhães
Fonte: Universidade Federal do Ceará Publicador: Universidade Federal do Ceará
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 Português
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This study aimed at verifying the effect of genotype x environment interaction on the relative contribution of yield components and final production of different cowpea genotypes. For this, data of yield components of 22 cowpea genotypes were evaluated in four environments in the State of Ceará. A one-way ANOVA tested the variability between genotypes and the Scott-Knott test compared the mean values of the genotypes. The correlations were estimated by a path analysis. A differentiated response from the genotypes to each environment was observed for all traits examined, indicating the need to perform the test for each situation separately. The number of pods per plant is the yield component with great potential of genetic gain in additional cycles of selection of more productive genotypes. The number of pods per plant and the number of grains per pod were the yield components with greater direct effects on the productivity.

Adaptability and stability of sweet sorghum cultivars

Souza,Vander Fillipe de; Parrella,Rafael Augusto da Costa; Tardin,Flávio Dessaune; Costa,Márcia Regina; Carvalho Júnior,Geraldo Afonso de; Schaffert,Robert Eugene
Fonte: Crop Breeding and Applied Biotechnology Publicador: Crop Breeding and Applied Biotechnology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2013 Português
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The objective of this study was to evaluate the phenotypic stability and adaptability of 25 sweet sorghum cultivars of Embrapa Maize and Sorghum. The experiments were conducted in five Brazilian environments, three in the state of Minas Gerais, and the others in Sinop, Mato Grosso and Pelotas, Rio Grande do Sul. Fresh biomass yield (FBY), and total soluble solids (TSS) of the juice were evaluated in a randomized complete block design with three replications. Analysis of variance showed significant genotype by environment interaction for both traits. According to the Annicchiarico methodology analysis, genotypes CMSXS634, BRS506, and CMSXS646 were the most stable and adapted for FBY and TSS concomitantly; CMSXS634 being more adapted to favorable environments and CMSXS646 being more adapted to unfavorable environments.

Genotype-environment interaction for quantitative trait loci affecting life span in Drosophila melanogaster.

Vieira, C; Pasyukova, E G; Zeng, Z B; Hackett, J B; Lyman, R F; Mackay, T F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/2000 Português
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The nature of genetic variation for Drosophila longevity in a population of recombinant inbred lines was investigated by estimating quantitative genetic parameters and mapping quantitative trait loci (QTL) for adult life span in five environments: standard culture conditions, high and low temperature, and heat-shock and starvation stress. There was highly significant genetic variation for life span within each sex and environment. In the analysis of variance of life span pooled over sexes and environments, however, the significant genetic variation appeared in the genotype x sex and genotype x environment interaction terms. The genetic correlation of longevity across the sexes and environments was not significantly different from zero in these lines. We estimated map positions and effects of QTL affecting life span by linkage to highly polymorphic roo transposable element markers, using a multiple-trait composite interval mapping procedure. A minimum of 17 QTL were detected; all were sex and/or environment-specific. Ten of the QTL had sexually antagonistic or antagonistic pleiotropic effects in different environments. These data provide support for the pleiotropy theory of senescence and the hypothesis that variation for longevity might be maintained by opposing selection pressures in males and females and variable environments. Further work is necessary to assess the generality of these results...

Epistasis and genotype-by-environment interaction of grain protein content in durum wheat

Bnejdi, Fethi; Gazzah, Mohamed El
Fonte: Sociedade Brasileira de Genética Publicador: Sociedade Brasileira de Genética
Tipo: Artigo de Revista Científica
Português
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Parental, F1 , F 2 , BC 1 and BC 2 generations of four crosses involving four cultivars of durum wheat (Triticum durum Desf.) were evaluated at two sites in Tunisia. A three-parameter model was found inadequate for all cases except crosses Chili x Cocorit 71 at site Sidi Thabet and Inrat 69 x Karim at both sites. In most cases a digenic epistatic model was sufficient to explain variation in generation means. Dominance effects (h) and additive x additive epistasis (i) (when significant) were more important than additive (d) effects and other epistatic components. Considering the genotype-by-environment interaction, the non-interactive model (m, d, h, e) was found adequate. Additive variance was higher than environmental variance in three crosses at both sites. The estimated values of narrow-sense heritability were dependent upon the cross and the sites and were 0%-85%. The results indicate that appropriate choice of environment and selection in later generations would increase grain protein content in durum wheat.

Interação genótipo x ambiente em soja com ênfase na estratificação ambiental para a região central do Brasil; Genotype by environment interaction in soybean with emphasis in the environmental stratification for central region of Brazil

Branquinho, Rodrigo Gomes
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Agronomia (EAEA); Escola de Agronomia e Engenharia de Alimentos - EAEA (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Agronomia (EAEA); Escola de Agronomia e Engenharia de Alimentos - EAEA (RG)
Tipo: Dissertação Formato: application/pdf
Português
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The objective of this study was to establish a consistent environmental stratification for the region of soybean cropping in Central Brazil, based on genotype by environment (GE) interaction analysis. For this, yield data from variety trials conducted by Embrapa Cerrados in partnership with others Brazilian institutions, during seven growing seasons (2002/03 to 2008/09), were used. The study covered six experimental sets that were related to the genotypes of three maturity groups (early, medium and late), and two commercial groups (soybean conventional and transgenic RR), totaling 559 trials analyzed. The statistical treatment of data was performed in two stages: first, analyses of variance were performed for each experiment, from which the estimates of treatment mean (combination of genotype and environment) were obtained. In the second stage the joint and GE interaction analyses were performed. Thus, the yield mean of each genotype in each environment were submitted to the AMMI analysis (Additive Main effects and Multiplicative Interaction model), that led to choose a model with only one principal component (AMMI1). As result of this analysis, the genotypes and environments were jointly represented in a scatter plot called biplot (graph that display the rows and columns of a matrix; in this case...

Efeito da intera????o gen??tipo x ambiente na qualidade fisiol??gica de sementes de soja (Glycine max (L) Merrill); Effect of the genotype x environment interaction in soybean seed production

KRENSKI, Antonio
Fonte: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR Publicador: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR
Tipo: Dissertação Formato: application/pdf
Português
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65.86%
Soybean production depends on the technology applied associated with scientific know how and availabilities destined to the productive sector. Seed companies associated with plant breeding companies have contributed a lot of with the soybean production in Brazil. The Brazilian production that will be harvest in 2005/2006 will have to reach 58,7 million tons before the previous one of 51,1 million tons, however the sown area have to fall 6,4 percent for 21,9 million hectares. According to IBGE the estimate of bigger production is based on the expectation of better climate conditions during soybean production in this year. To preserve the genetic and physiological maximum potential of one cultivar it is necessary to know its adaptation in environments where the seeds will be produced, to identify, to correlate the genotypes, to determine its productive capacity, in the physiological and sanitary level. The goal of this work was to evaluate the performance of five soybean genotypes from different maturity groups in six environments (contrasting latitudes and altitudes), with intention to determine variations in the seed quality. Among different environment tested Abelardo Luz was the best place to produce soybean seeds. S??o Miguel do Igua??u and Maracaju were high restrictive to soybean seed production. Genotypes from different maturation groups have different seed quality performance in different environment.; A capacidade produtiva da soja est?? associada aos avan??os cient??ficos e disponibilidades tecnol??gicas destinadas ao setor produtivo. O setor sementeiro...

Breeding wheat lines for southern Australia according to three climatic mega-environments

Bell, C.; Eagles, H.
Fonte: Australian Society of Agronomy Publicador: Australian Society of Agronomy
Tipo: Conference paper
Publicado em //2003 Português
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One hundred and sixty-one wheat variety evaluation trials from southern Australian for the years 1994, 1995 and 1996 were analysed. Using this and long-term climate data, we show that, on the basis of differences in genotype by environment interaction, the South Australian and Victorian wheat belt may be separated into 3 mega-environments. These are: a Wimmera type environment with 200 to 300mm rainfall between sowing and anthesis and an average maximum temperature of less than 26°C between anthesis and harvest; and for the same respective crop developmental phases a Mallee type environment with less than 200mm rainfall, and an average maximum temperature of greater than 26°C; and a high rainfall environment with more than 300mm rainfall, and less than 26°C. These 3 mega-environments elicit different response patterns of genotypic performance.

Adaptabilidade e estabilidade de produção de trigo mole; interação, genótipo x ambiente

Coco, João António Chamorrinha
Fonte: Repositório Comum de Portugal Publicador: Repositório Comum de Portugal
Tipo: Dissertação de Mestrado
Publicado em //2013 Português
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A irregularidade das condições ambientais que caracteriza o clima mediterrânico de Portugal condiciona a cultura do trigo mole (Triticum aestivum L.). Neste contexto, a resposta dos genótipos ao ambiente a que estão sujeitos e a respetiva interação genótipo x ambiente (G x E) constituem desafios relevantes nos programas de melhoramento genético, tanto na fase de seleção de material segregante como na de obtenção de novas variedades. O presente trabalho teve como objetivo avaliar a adaptabilidade e estabilidade de produção de 15 genótipos de trigo mole, em dois ambientes distintos, Elvas e Mirandela, com base na análise de dados obtidos em ensaios de campo que decorreram entre 2000/01 e 2008/09. A análise aos parâmetros fenológicos revelou uma maior duração do ciclo até ao espigamento e menor duração do período de enchimento do grão em Mirandela, comparativamente a Elvas. A produção de grão média foi significativamente maior em Mirandela do que Elvas. Para os parâmetros massa do hectolitro e peso de mil grãos observou-se a mesma tendência mas com diferenças pouco acentuadas entre os dois locais. Para avaliar a interação genótipo x ambiente e consequentemente a adaptabilidade e a estabilidade dos genótipos aplicou-se o método proposto por Finlay e Wilkinson (1963). A análise foi realizada com base nos coeficientes de regressão de cada genótipo em relação ao índice ambiental...

Stability of F7:8 snap bean progenies in the Northern and Northwestern regions of Rio de Janeiro State

Vilela,FO; Amaral Júnior,AT; Gonçalves,LSA; Barbé,TC; Gravina,GA
Fonte: Associação Brasileira de Horticultura Publicador: Associação Brasileira de Horticultura
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 Português
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The objective of this experiment was to assess the genotypes by environment interaction for eight morphoagronomic traits in thirty F7:8 snap bean superior lines and evaluate the pod yield stability. The experiments were carried out in the cities of Bom Jesus do Itabapoana, Campos dos Goytacazes and Itaocara, located in the Northern and Northwestern regions of Rio de Janeiro State, Brazil. Experiments were designed in randomized blocks with two replications, using the traditional method (Yates & Cochran, 1938) and the methods proposed by Plaisted & Peterson (1959), Wricke (1965), Kang & Phan (1991) and Lin & Binns (1988), as well. Only the average fiber content in pods revealed no significant genotype x environment interaction, whereas most of the traits showed simple interaction, including pod yield. The results obtained using the methods of Plaisted & Peterson (1959) and Wricke (1965) agreed to a far extent and had a moderate estimate (0.6131) in relation to the traditional method. Both methods highlighted genotypes with pod yield close to the general average, i.e., around 7,546.46 kg ha-1. Kang & Phan's (1991) algorithm was more efficient in optimizing the stability estimates obtained using the methods of Plaisted & Peterson (1959) and Wricke (1965) than the traditional method. Lin & Binns' (1988) procedure revealed the most stable...

Long-term selection experiment with Afrikaner cattle 2: Genetic parameters and genotype x environment interaction for calf growth traits

Beffa,L.M.; van Wyk,J.B.; Erasmus,G.J.
Fonte: South African Journal of Animal Science Publicador: South African Journal of Animal Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2009 Português
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A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) was analyzed. The direct heritability estimates were moderate for birth weight (0.4), but low (0.1 to 0.2) for the other traits, similarly maternal heritabilities were low (0.1 to 0.2). Permanent environmental effects due to dam were moderate (0.3) for weights at 205 days, weaning and at 12 months, and was still an important effect at 18 months. Relatively large negative (-0.4) direct-maternal genetic correlations were indicated for weaning and yearling weights. There were indications that all post-weaning weight traits evaluated were closely related giving rise to their joint inclusion in joint multivariate analysis. There were no indications of line x environment interactions...

Long-term selection experiment with Afrikaner cattle 4: Cow fertility and calf survival

Beffa,L.M.; van Wyk,J.B.; Erasmus,G.J.
Fonte: South African Journal of Animal Science Publicador: South African Journal of Animal Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2009 Português
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A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at the Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over six generations of selection (40 years) were analyzed. The average incidence of calving success (the presence or absence of a calf) was 68%. Heritability and repeatability (in parenthesis) estimates for calving success and calving date were 0.08 ± 0.02 (0.10 ± 0.02) and 0.09 ± 0.02 (0.17 ± 0.02), respectively. Favourable genetic trends were shown (-0.8 ± 0.09 days/generation for calving date). Correlation estimates of sires' EBV between measures of fertility and growth were all unfavourable. A significant interaction was manifested for calving success and was due to the markedly poorer performance (10 percentage units) of the S line cows in the NS environment. The interaction serves to reinforce the commonly held principle that cattle...