Estimativas de m+a' e d como indicadores do potencial de híbridos de milho para extração de linhagens

• Ano de defesa: 2007
• Autor(a) principal: Viana, Laryssa Ferreira
• Orientador(a): Souza, João Cândido de
• Banca de defesa: Carvalho, Samuel Pereira de, Guimarães, Lauro José Moreira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: UNIVERSIDADE FEDERAL DE LAVRAS
• Programa de Pós-Graduação: DBI - Departamento de Biologia
• País: BRASIL
• Palavras-chave em Português: Milho; Estimativa de m+a'; Heterose; Linhagens
• Área do conhecimento CNPq: CNPQ_NÃO_INFORMADO
• Link de acesso: https://repositorio.ufla.br/handle/1/4347

The purposes of this study were to estimate the contribution of heterozygous loci (d) and the contribution of homozygous loci (m+a´) for morphophisiological characters and to verify the potential of commercial maize hybrids for breeding programs. F1 and F2 generations of ten commercial single cross hybrids were used (DKB 199, 30F90, A2555, DKB 333B, DOW 657, AG 8060, 30F87, DOW 8420, 30K75, AG 7000). From the F1 generation of each hybrid, acquired in the local commerce, the F2=S0 generations were obtained by controlled selfings. The experiments were carried out in Lavras, Vitorinha community and Ijaci county, in the crop season of 2005/06. The cultural practices were those normally used by the maize growers in the region. Treatments were evaluated using a randomized complete block design, with 3 replications, and data taken from five plants per replication. The characters evaluated were: plant and ear height, number of ears, number of leaves above the ear, stalk diameter, ear length, ear diameter, cob diameter, ear weigh and grain weigh. Analysis of variance was performed for place and then a joint analysis of the data were made. Estimate of m+a´ was obtained which corresponds to the average of all lines in the S∞ generation allowing to assess the populations potential in early generations. However, it is necessary to have a higher estimate of m+a´ associated with higher variance between the lines, which is measured through the estimation of d. One option for line extraction is the commercial hybrids, since they present a wide range of adaptation, high production potential and are highly heterozygous associating high average and great variation. In this work larger estimations of m+a´ for grain weight were obtained for the hybrids A2555 and AG7000 which allow to infer that these two hybrids demonstrate a great potential for line extraction. In the average, heterosis responded for 69.36% of grain yield in the F1 generation. The remaining 30.64% were due to parental line means. It was also obtained the correlations between the average of F1 generations of the hybrids and m+a´ and the correlation between the average of F1 generations of the hybrids and d, but for most characters they were not significant, showing that it is not possible to select the populations based on the average of the F1 generations.