HETEROSIS IN MAIZE SINGLE CROSSES DERIVED FROM A YELLOW TUXPENO VARIETY IN BRAZIL

Most maize (Zea mays L.) crosses in tropical regions use the heterotic pattern of Tuxpeno dent and Caribbean flint. Crosses between related lines are not used for commercial production. Related inbred lines are used in either double or three-way hybrids with other unrelated lines to develop superior hybrids. This study was conducted to determine th e combining ability among 11 related inbred lines from a Tuxpeno popul ation. The 11 inbred lines were crossed in a diallel series and were e valuated at six locations. A combining ability analysis was made for g rain yield. The average yield across environments for the 55 single cr osses (44.8 q/ha) was not comparable to that of the single-cross hybri d (56.5 q/ha), included as check. General combining ability (GCA) effe cts and specific combining ability (SCA) effects were highly significa nt (P < 0.01). Variation due to GCA, however, accounted for 68% of the variation among crosses, indicating that additive genetic effects wer e more important than nonadditive effects. Highly significantly positi ve GCA effects were observed for lines 6 (2.44 q/ha) and 7 (6.40 q/ha) and highly significantly negative GCA effects for lines 5 (1.63 q/ha) , 10 (2.64 q/ha), and 11 (4.01 q/ha). Significantly positive SCA effec ts were observed with line 4 x line 11, line 5 x line 9, and line 5 x 11 crosses. Lines 6 and 7 may have potential use as parents for three- way or double-cross hybrids.