COMBINING ABILITY AMONG 15 EARLY CYCLE MAIZE POPULATIONS IN BRAZIL

Early maturity maize (Zea mays L.) populations are used in short growi ng season areas, and their use is gradually increasing in tropical are as. The objective of this study was to determine the genetic potential of 15 early maturity maize populations in a diallel crossing system. The 15 parents, 105 diallel crosses among parents, and selfed generati on of parents were evaluated in a triple lattice design at 13 location s in Brazil. The combined analyses of variance for grain yield, time t o tassel, and plant height indicated highly significant (P < 0.01) dif ferences for entries, parents, heterosis, parent heterosis, specific h eterosis and for the first-order interactions with environments. Avera ge heterosis was highly significant for grain yield, significant (P < 0.05) for time to tassel, and not significant for plant height. Mean y ield ranged from 3187 to 5213 kg/ha for populations, and ranged from 3 041 to 6017 kg/ha for the population crosses. Population Pool 17 had t he largest inbreeding depression effects, whereas population CMS 52 ha d the smallest inbreeding depression effects. The highest specific cro ss for grain yield was for Across 8528 x Pool 18. None of the populati on crosses was superior to the hybrid checks for the three traits. No association was found between endosperm type and heterosis. The result s suggest that either the populations themselves or the synthetic comp osites of selected populations can be used for breeding purposes.