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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.1996.tde-20220208-033114
Document
Author
Full name
Raimundo Nonato Vieira da Cunha
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1996
Supervisor
 
Title in Portuguese
Potencial genético de populações de milho (Zea mays L.) obtidas de germoplasma exótico
Keywords in Portuguese
GERMOPLASMA VEGETAL
MILHO
POPULAÇÕES VEGETAIS
POTENCIAL GENÉTICO
Abstract in Portuguese
O presente trabalho teve por objetivo avaliar a variabilidade genética de quatro populações de milho obtidas de germoplasma exótico, sendo este último nas proporções de 50%, 50%, 100% e 100% para as populações CEX-1, CEX-2, CEX-3 e CEX-4, respectivamente. Foram avaliadas 1293 progênies de meios irmãos, assim distribuídas: 357 da população CEX-1, 366 da CEX-2, 185 da CEX-3 e 385 da CEX-4. As progênies foram classificadas em dois tipos, dentado e flint, e avaliadas em dois locais (L1: Ponta Grossa, PR; L2: Rio Verde, GO) em experimento em blocos casualizados, com duas repetições no L1 e três no L2. Foram avaliados os seguintes caracteres: peso de espigas, altura de planta, altura de espiga e posição relativa da espiga. As médias para o caráter peso de espigas (kg/ha), no L1, foram: 7275, 7925, 7225 e 6000 para CEX-1, CEX-2, CEX-3 e CEX-4; em porcentagem da média das testemunhas (FT-9043 e XL-370) os valores obtidos foram 68%, 76%, 67% e 64%, respectivamente. As médias no L2 foram 5100, 4775, 6186 e 5825, equivalentes a 75%, 69%, 70% e 68% da produção da testemunha (G-85), respectivamente. As médias para os caracteres altura de planta, altura de espiga e posição relativa da espiga foram equivalentes ou menores que a das testemunhas (FT-9043 e XL-370), no L1, e equivalentes ou maiores que a da testemunha (G-85), no L2. Para o caráter peso de espigas (g/planta), as estimativas da variância genética aditiva variaram de 703,00 a 970,48 no L1, e de 146,64 a 722,64 no L2; os coeficientes de herdabilidade (ao nível de médias) variaram de 0,44 a 0,50 no L1, e de 0,23 a 0,55 no L2. Para os caracteres altura de planta e de espiga, as variâncias aditivas foram relativamente altas nos dois locais, e os coeficientes de herdabilidade (ao nível de médias) mostraram valores entre 0,47 e 0,87. Os coeficientes de correlação genética aditiva e fenotípica entre médias, entre peso de espigas e altura de planta ou altura de espiga foram maiores no L1. Dentre os compostos avaliados, o CEX-3 foi o que apresentou o maior potencial genético para o melhoramento dos caracteres peso de espigas, altura de espiga e altura de planta, em ambos os locais, o que se evidencia pelos maiores coeficientes de herdabilidade, variação genética e índices de variação genética. Em face dos resultados obtidos, pode-se afirmar que a utilização de materiais exóticos constitui-se em uma maneira eficiente de se obter populações base com ampla variabilidade genética para uso em programas de melhoramento.
 
Title in English
Genetic potential of corn populations obtained (Zea mays L.) from exotic germplasm
Abstract in English
The objective of the work here reposted was to evaluate the genetic variability of four corn populations obtained from exotic germplasm corresponding respectively to the proportions of 50%, 50%, 100% and 100% in the populations CEX-1, CEX-2, CEX-3 and CEX-4. A total of 1293 half-sib families were studied, comprising 357 from the population CEX-1, 366 from CEX-2, 185 from CEX-3 and 385 from CEX-4. The progenies were classified as dent or flint types, and evaluated in experiments with randomized blocks in two locations: L1, Ponta Grossa, State of Paraná, and L2, Rio Verde, State of Goiás. Two replications were employed in L1 and three in L2. The following characters were evaluated: ear weight, plant height, ear height and the relative positions of the ear. The averages of the character ear weight (kg/ha) were, in L1, 7275, 7925, 7225 and 6000 respectively for CEX-1, CEX-2, CEX-3 and CEX-4. As a percentage of the controls (FT-9043 and XL-370), the values obtained were 68%, 76%, 67% and 64%, respectively. The averages in L2 were 5100, 4775, 6186 and 5825, corresponding to 75%, 69%, 70% and 68% of the control yield (G-85). The averages of plant height, ear height and position relative of the ear were equivalent or lower than those of the controls (FT-9043 and XL-370), in L1, and equivalent or higher than those of the control (G-85), in L2. For the character ear weight (g/plant) the estimates of the genetic additive variance ranged from 703,00 to 970,48 in L1 and from 146,64 to 722,64, in L2; the coefficients of heritability (at the level of averages) varied from of 0,44 to 0,50 in L1 and from 0,23 to 0,55 in L2. For the characters plant height and ear height the additive variances were relatively high in both locations and the coefficients of heritability (at the level of averages) displayed values between 0,47 and 0,87. The coefficients of additive genetic correlation and phenotypic among averages, among ear weight and plant height or ear height were higher in L1. Among the evaluated composites, CEX-3 presented the higher genetic potential for improvement of characters ear weight, ear height and plant height in both locations, as shown by higher coefficients of heritability, genetic variation and index of genetic variation. Based on the results obtained it can be concluded that the use of exotic materials provides efficient means for obtaining basic populations with wide genetic variability for use in breeding programs.
 
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2022-02-08
 
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