Grain yield of B73 × Mo17-type maize hybrids from different periods of breeding

Hybrid maize is produced using inbred lines that originate from genetically different (divergent) sources (heterotic groups). Inbred lines from at least two different sources that produce heterotic F1 progeny make up a heterotic pair. Thus far, a large number of heterotic pairs differing in their heterotic potential for grain yield and other traits have been identified. The BSSS × Lancaster heterotic pair is often used in the temperate zone to develop medium-late to late maize hybrids beloning to FAO maturity groups 500 to 700.The lines B73, Mo17 and derived lines are typical representatives of the BSSS × Lancaster heterotic pair. In order to determine the contribution of breeding to the increase of grain yield in B73 × Mo17 hybrids, lines had been introduced from America (the original versions of B73 and Mo17) or developed at the Institute of Field and Vegetable Crops in Novi Sad between 1980 and 2000 and represent three different cycles of selection. B73- and Mo17-type inbreds were used to study the combining abilities for grain yield of the lines and hybrids and assess the contributions of the selection cycles to grain yield increases in the lines and hybrids. With both types of germplasm, s the lines from the third cycle of selection had the highest grain yields. Based on the coefficient of linear regression, the increase of yield in the hybrids from the third selection cycle compared with the first cycle was found to be over 124 kg cycle with B73, and 677 kg cycle with Mo17 inbreds