A half diallel cross between 10 inbred lines of maize (Zea mays L.) was evaluated under two different sowing dates for ten quantitative characters. Sowing date, genotypes, parents and hybrids mean squares were significant for all traits under study. Significant genotypes x sowing date mean squares were obtained for all traits except ear height, ear husk and no. of rows/ear. Significant interaction between hybrids and sowing dates mean squares were obtained for all traits except ear height, ear husk and no. of rows/ ear. General and specific combing ability mean squares were significant for all traits. The magnitudes of the ratios of GCA/SCA revealed that the additive and additive x additive types of gene action were the most important expressions for ear husk, maturity date, no. of rows/ear, tasseling date and silking date. Plant height, ear height, no. of grain/row, 100-kernel weight and grain yield/plant showed GCA/SCA ratios less than unity. The mean squares of interaction between sowing dates and both types of combining ability were significant for tasseling date, silking date, plant height, no. of grains/row and grain yield/plant. The ratio for GCA x D/GCA was higher than ratio of SCA x D/SCA for tasseling date, plant height, no. of grains/row, and grain yield/ plant. The parental inbred line no. 4 seemed to be good combiner for; plant height, ear height, no. of grains/row, 100-kernel weight and grain yield/plant. The parental inbred line no. 10 appeared to be one of the good combiner for; ear husk, no. of rows/ ear, no. of grains/row and grain yield/plant. The cross P1xP8 had the highest values for both SCA and heterotic effects followed by crosses P1xP10, P4xP8, P6xP8 and P6xP10 for grain yield. The five RAPD primers generated 143 scorable bands across 10 inbred lines. These primers produced a total of 32 reproducible fragments, from which 26 (73.06) were polymorphic. The mean of polymorphic bands per primer was 5.2. The lowest genetic similarity (0.333) was obtained between the two inbred lines P2 and P9, while, the highest genetic similarity (0.81) was scored between the two inbred lines P10 and P9. The estimated value for correlation coefficient between genetic diversity (GD), and each of mean performance and heterosis relative to both checks varietes and SCA for grain yield/ plant were significant (r = 0.315, 0.332, 0.334, 0.401), respectively. The correlation coefficient between sub cluster1 (inbred lines P1 and P2) and main cluster 2 (inbred lines P7, P8, P9and P10) was higher (r = 0.56). In the same time the highest values of grain yield and heterosis were obtained from the crossing between inbred line P1 (sub cluster 1) and inbred line P8 (main cluster 2). Also crossing between inbred line P1 (sub cluster 1) and inbred line P10 (main cluster 2) ranked the third for grain yield, specific combining ability and heterosis. While the crosses P6xP8 and P6xP10 derived from inbred line P6 (sub-sub cluster 2) and P8 and P10 (main cluster 2) had the fourth rank for grain yield and heterosis, The results indicated that RAPD marker can be used as a tool for determining the extent of genetic diversity among maize inbred lines and classiting genotypes into different groups. This study showed that GD can be used to precisely predict the yield performance and heterosis value for F1 hybrids. |
