A half diallel cross between 9 inbred lines of maize (Zea mays L.) was evaluated under two different nitrogen rates for six quantitative characters in RCBD with three replications. Nitrogen rates, genotypes, parents and hybrids mean squares were significant for all traits under study except, mean squares for parental inbred lines for ear height at high nitrogen rate and 100-kernel weight at both nitrogen rates and in the combined analysis. Significant genotypes x nitrogen rates interaction mean squares were obtained for days to 50% tasseling, ear height and grain yield/ plant, revealing that the performance of genotypes were differed from rate of nitrogen to another.Significant interaction mean squares between hybrids and nitrogen rates were obtained for days to 50% tasseling, ear height and grain yield/ plant. General and specific combing ability mean squares were found to be 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 days to 50% tasseling at low rate of nitrogen fertilization, ear height at both nitrogen rates as well as the combined analysis. No. of rows /ear at high nitrogen rate as well as the combined analysis showed GCA/SCA ratios was found to be high than unity. The mean squares of interaction between nitrogen rates and both types of combining ability were significant for days to 50% tasseling and ear height. The ratio for SCA x D/SCA was higher than ratio of GCA x D/GCA for ear height. The parental inbred line no. P4 seemed to be the best general combiner for grain yield/plant and some of its components in the combined analysis of both nitrogen rates. The parental inbred line no. 3 appeared to be one of the good combiner for; days to 50% tasseling. For grain yield/ plant, the crosses P1xP4, P1xP5, P1xP6, P1xP9, P2xP3, P2xP4, P2xP5, P2xP6, P2xP8, P3xP4, P3xP5, P3xP6, P3xP7, P3xP8, P4xP5, p4xP6, P4xP8, P5xP7, P5xP8, P6xP7, P7xP8, P7xP9 and P8xP9 had the highest values for both SCA. Also, the three hybrids P3xP4, P4xP5 and P4xP6 were out yielded significantly the check hybrid S.C. G. 155. The nine RAPD primers generated 397 scorable bands across 9 inbred lines. These primers produced a total of 66 reproducible fragments, from which 39 (59.09%) were polymorphic. The mean of polymorphic bands per primer was 4.3. The lowest genetic similarity (0.55) was detected between P1 and P5 also, obtained between P8 and P9. While, the highest genetic similarity was (0.90) scorded between the two parental inbred lines P4 and P9. Non considerable values for correlation coefficients between genetic diversity (GD), and each of mean performance and heterosis relative to check variety S.C. G 155 for grain yield/ plant were positive (r = 0.06 and 0.03), respectively. The results indicated that RAPD marker can be used as a tool for determining the extent of genetic diversity among maize inbred lines. The results indicated that RAPD marker can be used as a tool for determining the extent of genetic diversity among maize inbred lines and for genotypes into different groups but when used a large number of primers to detect the variation over all DNA or used a new marker like SSR or AFLP. |
