GENETIC EFFECTS, HETEROSIS AND GENETIC DIVERSITY AMONG COMMERCIAL MAIZE HYBRIDS ADAPTED TO EL BAJÍO IN MÉXICO

Abstract

In this research 13 commercial corn (Zea mays L.) hybrids adapted to El Bajío México, and their 78 crosses resulting from a diallel, were evaluated in order to identify hybrids with a high genetic value (GCA and heterosis), useful for a maize breeding program, and to determine the heterosis and genetic diversity among these hybrids. The experiments were set ut up in three environments, two at Celaya, Gto. (two planting dates) and one at Sandia, N. L., during 1996, under a randomized complete block design with two replications, and two rows as experimental unit. Genetic effects were estimated on grain yield (t ha^-1), plant height (cm), grain moisture (%) and days to flowering (d). The best crosses across environments were: AS910 x AS4450, PP9538 x AS948 and PP9539 x AN453, which yielded 17.5, 17.5 and 17.3 t ha^-1, respectively. The highest heterosis based on the midparent were for hybrids PP9603 x PP9539, PP9539 x AN453 and PP9539 x AN 447, with values of 13.9, 12.8 and 11.1 %, respectively. The highest combinig ability values were registered in the hybrids PP9539, AN447 and AS910, with 1.17, 0.68 and 0.52 t ha^-1, respectively, and the highest heterosis was found in hybrids PP9539 (2.27), A7500 (1.170) and C220 (1.07). The most related hybrids were AS910 and AN450 with a genetic distance of 0.033 and heterosis of –47.7 %; the most diverse hybrids were AN454 and A7500 with a genetic distance of 1.42 and heterosis of 12.3 %.