DIALLEL CROSSES AND GENERAL AND SPECIFIC COMBINING ABILITY IN GRAIN YIELD AND COMPONENTS IN MAIZE

Diallel crossing was performed among eight maize inbred lines (1-IPA 2, 2- IPA 7,3- IPA 21, 4-IPA 12, 5- 71-5, 6-IPA6, 7- IPA3 and 8- IPA- 14) in the field of Field Crops Department, College of Agriculture, University of Baghdad, during spring and fall seasons in 1999 and 2000. The objective was to evaluate several inbred lines and their hybrids, and estimating gene action in grain yield and yield components of maize . In the first season (spring 1999), inbred lines were propagated, while in the fall 1999, a set of 28 hybrids were developed. Hybrid yield trials were conducted during spring and fall seasons in 2000, using a randomized complete block design with three replications . Significant differences and heterosis were found among several studied characters. The plants of the crosses (2x8) and (2x7) produced higher number of ears/plant in spring season , while the crosses (2x8) and (7x2) gave higher number of ears/plant in fall season . The crosses (8x5) and (6x5) in spring season, (7x4) ,(4x2) and (1x3) in fall season, produced higher number of grains /ear. Higher grain yield (99.33 g./plant) was produced from the cross (5x8) in spring season , while in the fall season, the cross (1x3) produced highest grain yield (181.60 g/plant). Higher degree of dominance (6.19) was found in grain yield, while higher broad sense heritability (96%) was found in the number of grains year and grain yield. However, highest narrow sense heritability (41%) produced in the grain weight. The cross (1x3) could be a promising hybrid in the fall season in central Iraq.