Research on heterosis and combining ability of maize lines under different density.

The heterosis and combining ability of yield per plant were analyzed with five maize lines which were selected from one foreign hybrid by means of NCⅡcross design in three densities.The results showed that the yield per plant had high heterosis by 116.4%,77.2%,48.7% respectively,and the heterosis decrease with the increasing of density.Strong heterosis was found in the crosses of self-selected lines×Tangsipingtou and self-selected lines×Ludahonggu groups,and the combination cross from two heteritic patterns occupied 4/6,7/8 and 6/8 of all high heterotic crosses which were selected in three densities.Specific combining ability of the same self-selected line and the general combining ability of self-selected lines and key inbred lines in three densities were different.The general combining ability of yield per plant were significantly positively correlated in 60 000 and 75 000 plant·hm-2.