| In present paper, the difference, heterosis, combining ability, heritability, parent-offspring correlation of the maize grain, genotypic correlations between iron content and agricultural characters, economic characters and quality characters were analyzed with 30 maize inbred lines and 120 crosses made from 16 maize inbred lines selected randomly according to Griffing's diallel methodⅣ. The materials were sown in two seasons (spring and summer). The results showed that:1. The iron content in the 30 inbred lines ranged from 14.98mg/kg to 26.83mg/kg (Table 4.) The highest was the minimum 1.79 times. The coefficient of variation was 15.48%, and the variation was larger. The F test indicated that the difference of iron content among inbred lines was remarkable. During spring sowing, the iron content ranged from 12.39 mg/kg to 24.43mg/kg, and the average iron content was 18.53 mg/kg. The highest was the lowest 1.97 times. During summer sowing, the iron content ranged from 14.18 to 27.25 mg/kg, and the average iron content was 20.00mg/kg. The highest was the lowest 1.92 times. The coefficient of variation was 13.85%. Iron content of combinations during summer sowing was generally higher than those during springsowing (table 6). Combined variance analysis for two seasons (table5) indicated that the difference of the maize grain iron content among combinations was extremely remarkable, meanwhile effect of seedtime, interaction effect between the geneotype and seedtime were extremely remarkable. The result explained that there was real heredity difference among the genotypes. Moreover, seedtime and interaction between the genotype and seedtime had greater influence to iron content of maize grain.2. Combined varicance analysis for combining ability of iron content over two seedtimes (table 8) showed that GCA, SCA, seedtime and interactions of GCA and SCA with seedtime were significant or highly significant. The results indicated that there were real differences among genotypes of GCA, SCA of iron content, moreover seedtime and interactions between them had greater influence to GCA and SCA. Therefore, in the iron-rich maize breeding, through identification of stability of GCA and iron content of hybrid in different environments, breeders can select out of parents with high GCA and iron-rich maize hybrids with strong stability and wide adaptability.3. Analysis of general combing ability (table 9) showed that effect values of GCA ranged from -2.09 to 2.67. Effect values of GCA of 7 inbred lines were positive number. Effect values of GCAof P15, P13, P5 and P10 were positive significant or highly significant, and P15 and P13 had higher effect values of GCA. Analysis of specific combing ability (table 10) showed that effect values of GCA ranged from -3.56 to 4.50. Effect values of SCA of 57 crosses were positive number, among which 14 crosses were positive significant or highly significant. Effect values of GCA of P15,P13,P5 and P10 were positive significant or highly significant, and P15 and P13 had higher effect values of GCA. Positive top five crosses in order were 2×7, 8×14, 4×10, 5×12 and 5×9. In Majority of the crosses with high SCA, at least one of the parents had high GCA. However, in some crosses with high SCA, the parents have less effect values of GCA. Therefore, in breeding of high iron maize hybrid, parents with high GCA should be selected and be widely tested to identify crosses with high SCA. The phenotypic values of iron content of parents were highly significantly correlated to their GCA (correlation coefficient r=0.70). Therefore it is possible to forecast the GCA effect values of parent with their phenotypic performance.4. Analysis of heterosis of iron content (table 7) showed that there were 119 crosses with positive value of over-low parent heterosis among 120 crosses during sprng sowing. Mid-parent heterosis and over-high parent of most crosses were negative, and their average was negative, but there were some crosses that their mid-parent heterosis and over-high parent were positive. The results indicated over-low parent hterosis was main in iron content of hybrid heterosis, meanwhile there were mid-parent heterosis and over-high parent heterosis. Therefore, in breeding of hybrid maize, it is possible to impove iron content of maize hybrids through choosing right parents and using mid-heretosis and over-high hretosis.5. Variances and geneticl parameters of iron character of maize kernel were estimated through stochastic model. The results (table 11) showed broad sense geneticl abilitys of iron character during spring sowing and summer sowing were 50.48% and 62.76%, respectively. Environmental decision degrees in spring and summer were 49.52%,37.24%. This indicated that iron character was mainly controlled by heredity. Meanwhile influence of seedtime to iron character was very great, especially spring sowing. In spring and summer, ratio of additive variances and non-additive variances were 0.85, 0.51, respectively. The results indicated heredity of iron character relyed mainly on non-additive effect while additive effect subsidiary, morover there was greater non-additive effect during summer sowing. During spring sowing and summer sowing, narrow sense geneticl abilitys of iron character were 23.17% and 21.14%, respectively. The change between them was very small. The result indicated additive effect of iron character exhibited steadily, but change of non-additive was greater.6. Analysis of parent-offspring correlation (table 12) showed that iron content of the hybrid was great significant positively correlated with those of their female parents, male parents, high-value of parents, mid-value of parents and the difference between high-parents and low-parents, and was significant positively correlated with low-value of parents. Therefore, in breeding of hybrid maize, it is possible to increase iron content of maize hybrids through choosing inbred lines with high iron content, higher values of mid-parents and difference of iron content between parents.7. Analysis of genotypic correlations between the maize grain and agricultural, economic charaters (table 13) showed that phenotypic and genotypic correlations between iron content and ear hight were greatly significant and negative. The result indicated hybrids with lower ear hight had higher iron content. Phenotypic and genotypic correlations between iron content and axis weight were highly significant and positive. The results indicated hybrid with greater axis weight had higher iron content. Phenotypic and genotypic correlations between iron content and yield/plant were positive significant or highly significant. The results indicated hybrid with higher yield had higher iron content. Analysis of genotypic correlations between iron content and quality characters of the maize grain (table 14) showed that phenotypic and genotypic correlations between iron content and protein were highly significant and positive. The result indicated maize hybrid with higher protein content had higher iron content. Therefore breeding variety with the two indexs was possible. Genotypic correlations between iron content and starch, oil were weakly negative and positive. The results indicated it was possible to improv iron content of hybrid without affecting content of starch and oil.
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