RESUMO
A análise dialélica propicia estimativas de parâmetros úteis à seleção de genitores e ao entendimento dos efeitos genéticos envolvidos na determinação dos caracteres. O objetivo deste trabalho foi estimar a capacidade geral e específica de combinação multivariada de genótipos de batata em gerações iniciais de seleção. Foram avaliadas 20 famílias clonais de batata (5*4) de nove genótipos, em um esquema dialélico, por duas gerações sucessivas. Os experimentos foram conduzidos na Embrapa Clima Temperado, em Pelotas, RS (31°S, 52°W), na primavera de 2005 e no outono de 2006. Foram avaliados 14 caracteres morfológicos de tubérculo e selecionados os seis mais estáveis ou que melhor repetiram perante as gerações para outras análises. A análise de variância revelou diferença significativa para todos os caracteres. A análise de variância multivariada dialélica com componentes principais mostrou os genótipos "2CRI-1149-1-78", "Eliza", "C-1786-6-96" e "White Lady" com maior capacidade geral de combinação para os caracteres aparência, aspereza, sobrancelha, apontamento, curvatura e achatamento de tubérculo, contribuindo com efeitos aditivos nos cruzamentos. Os cruzamentos "C-1750-15-95"/"Agria", "C-1786-6-96"/ "Asterix" e "Eliza"/"Asterix" destacaram-se em capacidade específica de combinação para sobrancelha, apontamento, curvatura e achatamento de tubérculo, e "2CRI-1149-1-78"/ "Vivaldi", "Eliza"/"BP1" e "Eliza"/"Agria", para aparência, aspereza e sobrancelha de tubérculo.
The diallel analysis provides estimates of useful parameters to parent selection and to the understanding of the genetic effects involved in a trait control. This research was aimed at estimating multivariate combining ability of potato parents in the initial generations of selection. Twenty potato clonal families (5*4) of nine genotypes in a partial diallel design were evaluated for two successive generations. The experiments were conducted at the Embrapa Clima Temperado, in Pelotas, RS (31° S, 52° W), in the spring of 2005 and autumn of 2006. Fourteen morphological tuber traits were evaluated and the six more stable, or those that were best repeated in the generations were selected for further analysis. The analysis of variance revealed significant differences for all traits. The diallel multivariate analysis, using principal components, showed "2CRI-1149-1-78", "Eliza", "C-1786-6-96" and "White Lady" genotypes with higher general combining ability for tuber appearance, smoothness, eye brown, pointing, curving and flatness, contributing with additive effects for crossings. The "C-1750-15-95"/"Agria", "C-1786-6-96"/"Asterix" and "Eliza"/"Asterix" cross combinations were outstanding for specific combing ability for tuber eye brown, pointing, curving and flatness, and "2CRI-1149-1-78"/"Vivaldi", "Eliza"/"BP1" and "Eliza"/"Agria" for tuber appearance, smoothness and eye brown.
RESUMO
The objective of the present study was to correlate the genetic distances (GD) of single cross hybrids with yield, heterosis and specific combining ability (SCA) in the double cross hybrid synthesis. For this, 10 single cross commercial hybrids were used from different companies, and all the possible double hybrids were synthesized by a complete dialell. The hybrids were assessed in 15 locations in the 2005/2006 agricultural season, using the randomized complete block design with three repetitions. DNA was extracted from the single cross hybrids and 20 simple sequence repeat primers were used, nine of which were linked to the quantitative trait loci. It was ascertained that the single hybrids were superior in general to the double cross hybrids and that yield was highly correlated with heterosis and SCA (r = 0.75 and 0.82, respectively). There was no significant correlation between yield and GD (r = 0.25), but this index was at the limit of significance. There was a medium correlation between GD and heterosis (r = 0.40) and GD and SCA (r = 0.38). The intergroup hybrids placed by genetic grouping were generally more productive than intragroup hybrids, and the hybrids with GD greater than 0.84 had the maximum heterosis and SCA. It was concluded that the markers were efficient in placing hybrids in different heterosis groups and were also useful in eliminating the most negative heterosis and SCA.
