| Summary: | <p style="margin-bottom: 0cm; font-style: normal; font-weight: normal; line-height: 120%; text-decoration: none;" lang="pt-BR" align="JUSTIFY"><span style="color: #000000;"><span><span style="font-size: small;">With the objective of identifying the best commercial hybrids to extract maize lines, a top cross scheme of 49 endogamic partial lines (S<sub>3</sub>) was carried out with the IA33 tester. The resultant hybrids were evaluated for grain yield, in Campinas, Mococa, and Palmital (S&atilde;o Paulo State, Brazil), in two agricultural years (2005/2006 and 2006/2007), <span style="color: #292526;">in a randomized block design,</span> with three replications, in two experiments (TC1 and TC2). Individual and group variance analysis and a grouped analysis of the experiments with common treatments were carried out, for each place. The top cross hybrids were grouped according to the line origins. Afterwards, orthogonal contrasts were carried out by using the Student&rsquo;s t test, in order to compare the hybrid groups. It was verified that the use of commercial hybrids to extract lines is an interesting strategy. In general, it was also verified that the top cross hybrid groups, whose lines originated from the AG1051, Master, and XL357 hybrids, obtained high yield, with a higher potential for lines extraction. </span></span></span></p> <p style="margin-bottom: 0cm; font-style: normal; font-weight: normal; line-height: 120%; text-decoration: none;" lang="en-US" align="JUSTIFY"><span style="color: #000000;"><span><span style="font-size: small;">KEY-WORDS: <em>Zea mays</em> L.; top cross hybrids; partially endogamic lines (S<sub>3</sub>).</span></span></span></p><br><p style="margin-bottom: 0cm; font-style: normal; font-weight: normal; line-height: 120%; text-decoration: none;" lang="pt-BR" align="JUSTIFY"><span style="color: #000000;"><span><span style="font-size: small;">O presente trabalho teve por objetivo identificar os melhores h&iacute;bridos comerciais para extra&ccedil;&atilde;o de linhagens de milho. Para isto, foram realizados cruzamentos, em esquemas top crosses, de 49 linhagens parcialmente endog&acirc;micas (S<sub>3</sub>), com o testador IA 33. Os h&iacute;bridos resultantes foram avaliados, quanto &agrave; produtividade de gr&atilde;os, em Campinas, Mococa e Palmital (Estado de S&atilde;o Paulo), em dois anos agr&iacute;colas (2005/2006 e 2006/2007), utilizando-se o delineamento de blocos ao acaso, com tr&ecirc;s repeti&ccedil;&otilde;es, em dois experimentos denominados TC1 e TC2. Efetuaram-se an&aacute;lises de vari&acirc;ncia individuais e conjuntas e, tamb&eacute;m, uma an&aacute;lise agrupada do TC1 e TC2, com tratamentos comuns, por local. Os h&iacute;bridos top crosses foram agrupados de acordo com a origem das linhagens. Posteriormente, foram realizados contrastes ortogonais, para comparar os grupos de h&iacute;bridos, pelo teste t de Student. Constatou-se que a utiliza&ccedil;&atilde;o de h&iacute;bridos comerciais, para extra&ccedil;&atilde;o de linhagens, &eacute; uma estrat&eacute;gia interessante. Verificou-se, tamb&eacute;m, que, em geral, os grupos de h&iacute;bridos top crosses, cujas linhagens foram oriundas dos h&iacute;bridos AG1051, Master e XL357, obtiveram elevada produtividade, tendo, portanto, maior potencial para extra&ccedil;&atilde;o de linhagens. </span></span></span></p> <p style="margin-bottom: 0cm; font-style: normal; font-weight: normal; line-height: 120%; text-decoration: none;" lang="pt-BR" align="JUSTIFY"><span style="color: #000000;"><span><span style="font-size: small;">PALAVRAS-CHAVE: <em>Zea mays </em>L.; h&iacute;bridos top crosses; linhagens S<sub>3</sub>.</span></span></span></p>
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