Acta Scientiarum: Agronomy (Apr 2011)
Heterotic parameterizations of crosses between tropical and temperate lines of popcorn = Parametrizações heteróticas de cruzamentos entre linhagens tropicais e temperadas de milho pipoca.
Abstract
We examined the heterotic parameterizations of diallel crosses among10 popcorn inbred lines in two different environments (municipalities of Campos dos Goytacazes and Itaocara, Rio de Janeiro State) and originating from tropical, temperate and subtropical germoplasm. Traits, including grain yield (GY), plant height (PH), ear height (EH), days to silking (FL) and popping expansion (PE), were measured. The inbred lines and the hybrids were evaluated in a randomized complete block design with three replications. The sources of genotypic variation, inbred lines and heterosis had significant effects on all traits. When the sources of heterotic variation were compared separately, estimated mean heterosis was found to be significant for all traits. When inbred lines and specific heterosis was investigated, only popping expansion was not significantly different, demonstrating that heterotic effects are favorable for developing superior hybrids. A direct relation between .i and i V. was made clear, especially for traits that were slightly influenced by the effects of dominance. Additivity was determined to have the best effect for improving popping expansion. The hybrid combinationshad positive estimates of heterosis for the GY but not for PE. The hybrids P1 x P3 and P2 x P4 had the best responses for the GY and PE. The superiority of the combination P1 x P3 shows that the addition of genomes with different edaphoclimatic adaptations is an important factor in obtaining superior hybrids.O presente trabalho teve com objetivo averiguar as parametrizacoes heteroticas de cruzamentos dialelicos entre dez linhagens de milho pipoca oriundas de genotipos tropicais, temperados e semi-temperados, em dois ambientes (municipios de Campos dos Goytacazes e Itaocara, Estado do Rio de Janeiro), em relacao as caracteristicas rendimento de graos; altura media de planta e da insercao da primeira espiga; numero medio de dias para florescimento e capacidade expansao. As linhagens e os hibridos foram avaliados em delineamento em blocos ao acaso, com tres repeticoes. Para as fontes de variacao linhagens eheterose houve significancia, pelo teste F, para todas as caracteristicas. No desdobramento da fonte de variacao heterose, estimativas de heterose media foram significativas para todas ascaracteristicas. Em relacao a heterose de linhagens e especifica, apenas a caracteristica capacidade de expansao nao expressou diferenca significativa, o que confirma que os efeitos heteroticos naosao favoraveis para sintese de hibridos com superioridade. A relacao direta entre .i e i V. ficou claro, especialmente para as caracteristicas pouco influenciadas pelos efeitos de dominancia. O efeito genico aditivo foi confirmado para capacidade de expansao. As combinacoes hibridas revelaram estimativas positivas de heterose para GY, mas nao para PE. Os hibridos P1 x P2 e P3 x P4 tiveram as melhores respostas para GY e PE. A superioridade da combinacao P1 x P3, demonstra que a adicao de genomas com adaptacao edafoclimaticas diferentes e importante para a obtencao de hibridos superiores.
