Maize breeders studied the combining ability of different maize plants for grain yield and agronomic traits. They crossed 18 inbred lines with 2 testers to create 36 testcrosses, and compared them to commercial hybrids. The inbred lines and testers showed wide diversity in traits like plant height, ear height, and number of ears per plant. Some crosses performed better than the commercial hybrids, especially one involving line 4 and tester 2. The inheritance of traits like grain yield and number of ears per plant was influenced by both additive and non-additive gene effects. The environment had a greater impact on traits controlled by additive genes.