The successful of development hybrids depends largely on the identification of the best parents to ensure maximum combining ability. This study was conducted to estimate genetic variability and combining ability for grain yield and its components of seven inbred lines of maize (Zea mays L.) across two irrigated seasons, 2016 and 2017, Gezira, Sudan. The experiment was arranged in a randomized complete block design with three replicates. The traits measured were days to 50% tassel, plant height, ear height, ear length, ear diameter, hundred kernels weight and grain yield. Significant differences were observed among the parents and crosses for most of studied traits in both seasons. The crosses showed high genetic variability and tall plants than their parents which suggested some degree of hybrid vigor. The TEEI 5 followed by TEEI 10 and TEEI 11, indicating earliness for flowering time among the two seasons, and the earliest crosses were obtained by (TEEI 1 x TEEI 5) and( TEEI 1 x TEEI 5) followed by (TEEI 1 x TEEI 29) and (TEEI 1 x TEEI 20) . The highest yielding hybrids had long ears and better shape, e.g., (TEEI 1 x TEEI 20) and (TEEI 11 x TEEI 21).The top ranking crosses for grain yield across locations were (TEEI 4 x TEEI 11) (1929.6 kg/ha) followed by (TEEI 4 x TEEI 21) (1717.1kg/ha) and (TEEI 1 x TEEI 5) (1665.1 kg/ha). The inheritance of most traits was controlled by non-additive gene action except ear height and grain yield. The best combiner for grain among the two seasons was TEEI 4. Also the best crosses through the two seasons were given by (TEEI 4 x TEEI 11) followed by (TEEI 4 x TEEI 21) and (TEEI 5 x TEEI 29). The ratio of GCA to SCA variance for the most traits was less than one, suggesting that the inheritance was due to non-additive gene effect with the exception of grain yield being more than one, indicating that inheritance of this trait was due to GCA effects, and was largely controlled by additive gene action in the base material. From these results it is recommended that parent TEEI 4 to be used in recurrent selection, while, crosses (TEEI 4 x TEEI 11), (TEEI 4 x TEEI 21) and (TEEI 5 x TEEI 29) to be tested in multi-locations trials for commercial utilization.
Key word: maize , combing ability , Sudan.