Variabilidade genética e endogamia em duas populações de milho (zea mays) contrastantes para o teor de óleo
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Data
1987-01-01
Autores
Zanotto, Maurício Dutra [UNESP]
Tosello, Geraldo A.
Souza Jr., Claudio L.
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Editor
Universidade de São Paulo (USP), Escola Superior de Agricultura
Resumo
Com o objetivo de se avaliar os efeitos da seleção para maior tamanho do embrião, visando o aumento da porcentagem de óleo e suas interrelações com a produtividade de grãos, estimaram-se os parâmetros genéticos e os efeitos de uma geração de autofecundação, em progênies de meios irmãos e S1 de uma mesma planta S0, de duas populações de milho derivadas do Composto Flint. As progênies foram avaliadas separadamente para cada população, através do delineamento experimental em látices planta do em faixas. As médias das progênies de meios irmãos e S1 para porcentagem de óleo, foram respectivamente 5,31% e 5,19% para a população 01, e 6,21% e 5,63% para a população 02. Para peso de espigas na população 01, as médias foram 4,68 e 2,91, e para a população 02 foram iguais a 4,05 e 2,77 kg/m². Embora as médias das progênies S1 fossem sempre inferiores às médias das progênies de meios irmãos, a análise através do teste F não permitiu, ao nível de 5% de probabilidade, se destectar os efeitos da depressão por endogamia na média das características avaliadas, exceto para porcentagem de óleo na população 02. As estimativas das variâncias genéticas entre progênies S1 foram superiores as estimativas das variâncias entre progênies de meios irmãos com exceção da característica peso de espigas despalhadas na população 01 e da característica altura da espiga na população 02. As estimativas da herdabilidade e dos coeficientes de variação genética foram inferiores aos resultados descritos na literatura para a característica porcentagem de óleo nos grãos para as duas populações utilizadas. A população 01 apresentou estimativa da herdabilidade para peso de espigas despalhadas considerada alta 76,76%, enquanto que esta estimativa na população 02, foi considerada baixa 15,76%. Os coeficientes de correlação genética aditiva entre as características peso de espigas e porcentagem de óleo foram de -0,37 e 0,12 para as populações 01 e 02, respectivamente. Concluiu-se que a seleção efetuada na população 02, para aumento do tamanho do embrião, foi efetiva para elevar a porcentagem média de óleo e também para quebrar a correlação genética negativa entre as características de peso de espiga e teor de óleo, porém restringiu drasticamente a variavilidade para essa característica.
The objective of the present research was to evaluate the percentage increase of oil and productivity of grains and their interrelations in two maize populations, through the estimates of genetic parameters as well as the study of the effects of one generation of inbreeding. Half-sib and S1 progenies from the same plant S0 were obtained and evaluated from two maize populations. The data for plant height and ear height were also considered. The studied populations were derived from Composto Flint. The progenies were evaluated separately for each population in a lattice experimental design planted in a split block arrangement. The half-sib and S1 progenies means for the oil percentage were respectively, 5.31% and 5.19% for populations 01, and 6.21% and 5.63% for the population 02. For ear weight in population 01, the means were 4.68 and 2.91 respectively, for the half-sib and S1 progenies, and for the population 02, equal to 4.05 and 2.77 kg/5m². Although the means of the S1 progenies were always lower than those of the half-sib progenies, the analisys through the F test did not allow, at the 5% level of probability, to detect the effect of inbreeding depression in the means of the characteristics evaluated, except for the oil percentage in the population 02. The estimates of the genetic variancces among S1 progenies were higher than the estimates of the variances among the half-sib progenies, except for the ear weight in population 01 and ear height in population 02. The coefficient of heritability and genetic variation estimated, were lower in someway than those described in the literature when oil percentage is considered in both populations. For ear weight the population 01 showed a high value for the estimates of heritability (h² = 76.76%), on the other hand, the population 02 presented a low value (h² = 15.76%). The coefficient of additive genetic correlation between ear weight and oil percentage were -0.37 and 0.12, for the population 01 and 02 respectively. It was also concluded that, the selection carried out in population 02 in order to increase the embryo size, was effective to improve the average for oil percentage and also to break the negative genetic correlation between ear weight and oil content, however as a consequence of this type of selection a genetic variability reduction was observed for such characteristics.
The objective of the present research was to evaluate the percentage increase of oil and productivity of grains and their interrelations in two maize populations, through the estimates of genetic parameters as well as the study of the effects of one generation of inbreeding. Half-sib and S1 progenies from the same plant S0 were obtained and evaluated from two maize populations. The data for plant height and ear height were also considered. The studied populations were derived from Composto Flint. The progenies were evaluated separately for each population in a lattice experimental design planted in a split block arrangement. The half-sib and S1 progenies means for the oil percentage were respectively, 5.31% and 5.19% for populations 01, and 6.21% and 5.63% for the population 02. For ear weight in population 01, the means were 4.68 and 2.91 respectively, for the half-sib and S1 progenies, and for the population 02, equal to 4.05 and 2.77 kg/5m². Although the means of the S1 progenies were always lower than those of the half-sib progenies, the analisys through the F test did not allow, at the 5% level of probability, to detect the effect of inbreeding depression in the means of the characteristics evaluated, except for the oil percentage in the population 02. The estimates of the genetic variancces among S1 progenies were higher than the estimates of the variances among the half-sib progenies, except for the ear weight in population 01 and ear height in population 02. The coefficient of heritability and genetic variation estimated, were lower in someway than those described in the literature when oil percentage is considered in both populations. For ear weight the population 01 showed a high value for the estimates of heritability (h² = 76.76%), on the other hand, the population 02 presented a low value (h² = 15.76%). The coefficient of additive genetic correlation between ear weight and oil percentage were -0.37 and 0.12, for the population 01 and 02 respectively. It was also concluded that, the selection carried out in population 02 in order to increase the embryo size, was effective to improve the average for oil percentage and also to break the negative genetic correlation between ear weight and oil content, however as a consequence of this type of selection a genetic variability reduction was observed for such characteristics.
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Anais da Escola Superior de Agricultura Luiz de Queiroz. Universidade de São Paulo (USP), Escola Superior de Agricultura, v. 44, n. 1, p. 493-513, 1987.