A diallelic cross

between 16 tropical and subtropical populations was formed

at Iguala, Gro., in the winter nursery 2002 - 2003. Crosses

and parents were evaluated during the 2003 growing season

at INIFAP Bajío Experimental Station, in Celaya, Gto,

Mexico. The objective was to identify the best populations to

support the heterotic structure in our breeding program and as

sources to derived new inbred lines. Data were analyzed

using the Gardner and Eberhart model, in which variance

components can be separated to estimate additive and nonadditive

genetic effects. Results showed that despite the

heterotic response involved in the formation of the

populations, the “tropical x subtropical” heterotic pattern was

expressed in specific combinations such PABG T x Sint “B”

IG and Sint PABG I ACG x Sint “A” IG, with grain yields of

12.5 and 12.4 t/ha respectively. These crosses presented

maximum values of specific heterosis which can be used for

developing high-yielding hybrids through reciprocal

recurrent selection. Tropical population Sint “A” IG

presented the highest varietal effect, and because of its good

adaptation in the subtropic is considered an outstanding

germplasm to be incorporated in the Bajío Maize Breeding

Program. The best value of varietal heterosis, which is an

indicator of General Combining Ability, was observed in

PABG I GH “A” synthetic which can be used as tester. More

detailed analysis will permit to take advantage of the

germplasm involved to benefit maize breeding programs.

Keywords: Heterotic patterns, hybridization, diallelic crosses, Tropical x Subtropical germplasm.