Estimativas de parâmetros genéticos visando o melhoramento do café robusta (Coffea canephora Pierre ex A. Froehner)
Data
2013
Autores
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Editor
Escola Superior de Agricultura “Luiz de Queiroz” - Universidade de São Paulo
Resumo
O presente estudo objetivou estimar parâmetros genéticos visando quantificar a variabilidade genética de uma população de café robusta (Coffea canephora Pierre ex A. Froehner) introduzida da Costa Rica e analisar o seu potencial genético para o desenvolvimento de futuras cultivares clonais para o estado de São Paulo. Outro intuito foi verificar a possibilidade de submeter essa população à seleção recorrente, tornando-a, assim, fonte de alimentação e sustentação de programas de melhoramento genético do café robusta. O experimento foi composto por 25 tratamentos, sendo 21 progênies de C. canephora e quatro cultivares de C. arabica, plantados em Mococa (SP). O delineamento experimental utilizado foi em látice balanceado 5x5 quadruplicado, com seis repetições e uma planta por parcela. Foram realizadas doze colheitas e após a sexta colheita as plantas foram podadas. Em 2004, foi realizada uma seleção fenotípica dessa população a fim de clonar os melhores indivíduos. Essa seleção resultou em novo experimento, instalado em Campinas, seguindo o delineamento de blocos ao acaso, com três repetições, 28 clones e quatro plantas por parcela, sendo realizadas cinco colheitas consecutivas. As análises estatísticas e biométricas foram realizadas considerando os modelos lineares mistos (procedimento REML/BLUP), por meio do software Selegen, cujos componentes de variância são estimados pelo método da máxima verossimilhança restrita (REML) e os valores genotípicos preditos pela melhor predição linear não viesado (BLUP). As análises mostraram que, na população em estudo, observou-se elevada variabilidade genética, passível de ser explorada tanto para a extração de clones quanto para a seleção recorrente. As adversidades climáticas severas fizeram com que a seleção fosse prejudicada. Nessa situação é preferível não considerar o período afetado e analisar os dados após a recuperação das plantas. A seleção baseada em seis colheitas forneceu estimativas de parâmetros e ganhos genéticos similares aos obtidos na seleção baseada em duas colheitas de alta produção. Os ganhos genéticos esperados nas duas formas de propagações foram elevados e a seleção clonal proporcionou maiores ganhos do que a sexual. No experimento clonal foi possível identificar materiais com potencial produtivo e que poderão vir a ser recomendados para o cultivo no estado de São Paulo. Apesar de a interação genótipos x colheitas ter sido do tipo complexa, devido ao veranico ocorrido, esta não afetou significativamente o ordenamento dos melhores clones e nem comprometeu as estimativas dos parâmetros genéticos. Os coeficientes de variação experimental e genético bem como seu valor relativo deverão ser analisados conjuntamente com o número de repetições e a acurácia seletiva. A seleção recorrente deverá ser conduzida concomitantemente com o programa de seleção clonal, a fim de evitar o esgotamento da variabilidade genética e o comprometimento do programa de melhoramento genético visando o desenvolvimento de cultivares clonais. Tendo em vista que a população inicial foi constituída por um pequeno número de progênies, é aconselhável o monitoramento do tamanho efetivo populacional e do grau de endogamia ao longo dos ciclos de seleção recorrente.
The objective of this research was to estimate genetic parameters to quantify the variability of a population of robusta coffee (Coffea canephora Pierre ex A. Froehner) introduced into Brazil from Costa Rica in 1974 aiming at determining its genetic potential for the development of clonal or seedling cultivars for the state of São Paulo, Brazil. The feasibility has also been studied to submit this population to recurrent selection, making it a continuous source of improved base material in support of varietal improvement of robusta. An experiment consisting of 21 open pollinated seedling progenies of robusta and four cultivars of arabica was established in Mococa (SP) in 1975. Yield was observed for twelve harvests and after the sixth harvest the plants were pruned. The experimental lay out was a balanced 5x5 quadruple lattice design, with six replicates and one plant per plot. In 2004 a phenotypic selection of this population for yield was carried out aiming at cloning the best individuals. These 28 clones were planted in an experiment in Campinas in 2005, following a completely randomized block design, with 28 treatments (clones), three replications and four plants per plot. In total, yields were collected over five harvests. Statistical and biometrical analyzes were performed considering the linear mixed models (REML/BLUP), through software Selegen, where the variance components are estimated by restricted maximum likelihood (REML) and genotypic values predicted by best linear unbiased prediction (BLUP). The analyzes showed that the population had high genetic variability, which can be exploited for the extraction of both clones and seedling progenies, used for recurrent selection. Selection was impaired by severe adverse weather conditions. In such situations it is preferable not to consider the affected period and analyze the data after recovery of the plants. Due to the moisture stress that occurred in the clonal trial, genotype x environment interaction was complex. However this did not affect the ranking of superior clones nor compromised the genetic parameter estimates. Selection for yield based on six yield resulted in genetic parameters and genetic gains similar to those obtained by selection based on two high yielding harvesting periods. The expected genetic gains both for clones as for open pollinated progenies were high. However, clonal selection resulted in higher genetic gains for yield than the seedling selection. In the clonal experiment it was possible to identify materials with high yield potential that may become to be recommended for cultivation in São Paulo State. The experimental, genetics and relative coefficients of variation, should be analyzed together with the number of replications and selective accuracy. Recurrent selection should be conducted concurrently with the clonal selection program in order to avoid depletion of genetic variability and to impairthe breeding program aiming at the development of clonal cultivars. Considering that the initial population was composed of a small number of progeny, it will be important monitoring adequately the effective size and the inbreeding coefficient during recurrent selection cycles.
The objective of this research was to estimate genetic parameters to quantify the variability of a population of robusta coffee (Coffea canephora Pierre ex A. Froehner) introduced into Brazil from Costa Rica in 1974 aiming at determining its genetic potential for the development of clonal or seedling cultivars for the state of São Paulo, Brazil. The feasibility has also been studied to submit this population to recurrent selection, making it a continuous source of improved base material in support of varietal improvement of robusta. An experiment consisting of 21 open pollinated seedling progenies of robusta and four cultivars of arabica was established in Mococa (SP) in 1975. Yield was observed for twelve harvests and after the sixth harvest the plants were pruned. The experimental lay out was a balanced 5x5 quadruple lattice design, with six replicates and one plant per plot. In 2004 a phenotypic selection of this population for yield was carried out aiming at cloning the best individuals. These 28 clones were planted in an experiment in Campinas in 2005, following a completely randomized block design, with 28 treatments (clones), three replications and four plants per plot. In total, yields were collected over five harvests. Statistical and biometrical analyzes were performed considering the linear mixed models (REML/BLUP), through software Selegen, where the variance components are estimated by restricted maximum likelihood (REML) and genotypic values predicted by best linear unbiased prediction (BLUP). The analyzes showed that the population had high genetic variability, which can be exploited for the extraction of both clones and seedling progenies, used for recurrent selection. Selection was impaired by severe adverse weather conditions. In such situations it is preferable not to consider the affected period and analyze the data after recovery of the plants. Due to the moisture stress that occurred in the clonal trial, genotype x environment interaction was complex. However this did not affect the ranking of superior clones nor compromised the genetic parameter estimates. Selection for yield based on six yield resulted in genetic parameters and genetic gains similar to those obtained by selection based on two high yielding harvesting periods. The expected genetic gains both for clones as for open pollinated progenies were high. However, clonal selection resulted in higher genetic gains for yield than the seedling selection. In the clonal experiment it was possible to identify materials with high yield potential that may become to be recommended for cultivation in São Paulo State. The experimental, genetics and relative coefficients of variation, should be analyzed together with the number of replications and selective accuracy. Recurrent selection should be conducted concurrently with the clonal selection program in order to avoid depletion of genetic variability and to impairthe breeding program aiming at the development of clonal cultivars. Considering that the initial population was composed of a small number of progeny, it will be important monitoring adequately the effective size and the inbreeding coefficient during recurrent selection cycles.
Descrição
Tese de doutorado defendida na Escola Superior de Agricultura “Luiz de Queiroz” - Universidade de São Paulo
Palavras-chave
Genética quantitativa, Modelos mistos, REML/BLUP, Seleção recorrente e clonal
Citação
MISTRO, J. C. Estimativas de parâmetros genéticos visando o melhoramento do café robusta (Coffea canephora Pierre ex A. Froehner). 2013. 152 f. Tese (Doutorado em Ciências) - Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo, Piracicaba. 2013.