Análise dialética e depressão por endogamia dos caracteres agronômicos e da qualidade da forragem em milho (Zea mays L.)

Abstract

Mayze is increasingly being recommended for ensiling in Brazil, due to its qualitative and quantitative characteristics, besides the acceptance of bovine, bubalines, goats and sheeps, milk production and weight gain in meat production. The recommendation of better cultivars with quality and productive potential is very important for an appropriate silage production. Thus, the purpose of this study was to evaluate the general and specific combining ability, heterosis, varietal effects and inbreeding depression of agronomic traits and forage quality in order to identify commercial maize hybrids useful to originate superior populations and inbred lines with high potential for forage production, that will serve as the basis for the breeding program of maize. The 36 hybrids from a full diallel 9 x 9, with the 9 genotypes (1:Impacto, 2:Cargo, 3:P30B39, 4:P30P34, 5:P30R50, 6:CD304, 7:CD308, 8:2B710, 9:DKB390) without the reciprocals, more 9 S1 generations and two checks were evaluated in a complete randomized block design with three replications during 2009/2010 and 2010/2011 growing seasons. Fifteen characteristics was measured and evaluated: fresh weight, dry matter, grain yield, height of plant, height of ear, leaf percent, ear percent, stem percent, stay green (on both trial) and crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, mineral weight and organic weight (on the first trial). The analysis of variance were applied on the experimental data. After that, diallel analysis according to the Griffing's (1956) and Gardner and Eberhart (1966) methodologies were performed. Results indicate a high potential of genotypes DKB390, Impacto and CD304 for using in intrapopulation breeding programs and also to be used in recurrent selection. Hybrids 2B710 x DKB390, CD304 x DKB390 and Impacto x P30P34 can be used in interpopulation breeding programs and also for obtaining elite inbreed lines. The high levels of inbreeding depression observed for grain yield lead us to indicate interpopulational breeding strategies and synthesis of new elite inbreed lines for increasing yield.