Knowledge about the combining ability, genetic diversity and heterosis of germoplasm from a maize breeding program is essential for hybrids and varieties development. The objetives of this study were (1) To identify commercial hybrids with high genetic value (GCA and heterosis) useful for initiating a maize breeding program to produce and improved hybrids, varieties and synthetics; (2) To demonstrate that is feasible to create a maize breeding program from commercial hybrids. Estimates of general (GCA) and specific combining ability (SCA) were obtained using the method IV of Griffing (1956) and the genetic distances were estimated according to the method suggested by Troyer (1988). The best crosses were AS910 X AS4450 and PP9538 X AS948 having a yield of 17.538 and 17.463 t/ha respectively; the same crosses had the highest values of SCA. The crosses with the highest values of heterosis over the midparent were PP9539 X AN453 and PP9603 X PP9539 with 11,35 and 11,13 percent respectively. The highest positive values of GCA effects were obtained from hybrids PP9539 and AN447 with 1.168 and 0.684 t/ha respectively;. and the hybrids with the best heterosis were PP9539 ( 2.269 ) and A7500 ( 1.170 ). The most related hybrids were AS910 and AN450 with a genetic distance of 0,033 and heterosis of -47,68 percent whereas the most diverse were AN454 and A7500 with a genetic distance of 1.418 and heterosis of 12,26 %.
Combining ability and genetic diversity under low-temperature conditions at germination stage of maize (Zea mays L.)
