Twenty five hybrids were obtained by five inbred lines selected from European germplasm BRC crossed with 5 inbred lines with different germplasm according to NCⅡ design.Heterosis and combining ability of the combinations in different densities were analyzed.The results showed that the heterosis of yield per plant of F1generation was widespread,and the variation trend was reduced with density increasing.The GCA of inbred line BRC-1 was higher than the other lines in the density of 60 000 plant/ha;the inbred ...