Contribution Evaluation of Heterosis Effect to Chinese Maize Breeding

Twenty maize single cross hybrids and thirty-two parents in different period utilized widely on maize production in China were chose as the materials in the study by split plot design over 3 sites.It was made for contribution of inbred lines yield,heterosis and planting density to hybrids yield.The results showed that yield of hybrids and parents increased gradually with the varieties replacement;yield of the earlier varieties showed decreasing in high plant density,while yield and plant density increased accordantly in present varieties;heterosis of maize hybrids presented the trend of down-up-down with the varieties replacement,the heterosis was lower in present hybrids.It found that there was conflicting evidence to support the heterosis was the principal contribution to yield increase,the contribution of maize yield increase owed to the increase of parents yield and plant density.