In a long terms programme was evaluated the general combining ability (GCA) of 42 progenies S1-S2 and 13 progenies S1-S5 from the same source breeding population for line development. Testing of the top crosses with one tester has shown a low relationships between yield of S1- S2 per se and hybrid yield. The r values were 0,104 and 0,296 respectively for S1 and S2 lines. From 13 progenies tested in 17 experiments during 5 years only 4 lines maintained constant, superior GCA from S1 to S5 generation of selling. It was established specific interaction of genotype x environment for values of GCA, importance of lines from different heterotic groups as testers and a variation of hybrid performance among ear-to-row progenies S5 derivates from S3 generation. The presented results support the efficiency of visual selection for grain and ear traits of inbreeds and late testing of S5.