Analyses of heterosis and combining ability of the yield traits of five elite inbred lines with tropic germplasm

Four male inbred lines from different heterosis groups were crossed with 5 inbred lines with tropic germplasm according to NCⅡ design to compose 20 crosses.Field trials were carried out using split plot design in 2008 and 2009.Eight ear traits including ear length,ear diameter and so forth were measured to analyze heterosis and combining ability.The results are as follows: 1) in terms of heterosis over mean of parents on all traits investigated and heterosis over better of parents on all traits except for row number per ear differences among crosses were significant or highly significant.2) the mean of parents had close relations with heterosis over mean and better of parents on all traits except grain depth,hence it's reliable to forcast the F1 heterosis based on the mean of parents.3) gene additive action was more important in the variation of ear traits since δ2GCA was 1.14～26.50 times of δ2SCA,and the patterns of tropic lines×Ludahonggu or Tangsipingtou group were two better models.4) the traits with higher heritability in narrow sense such as row number per ear,ratio of grain weight and ear length should be selected in earlier generations.