| In this research, the P-carotene contents of 31 maize inbred lines were detected by column chromatography spectrophotometry, and eight inbred lines were selected as parents. According to Griffing's Method 1,64 combinations were produced by using eight maize inbred lines as parents from a complete diallel cross. The combinations, which were planted in Yuanjiang of Yunnan in autumn of 2007 and in Ya'an of Sichuan in spring of 2008, were evaluated by the P-carotene content. The P-carotene content in seed was analyzed by the high performance liquid chromatography (HPLC). The genotypic difference of theβ-carotene content, combining ability, heritability, heterosis, parent-offspring correlation, the correlation betweenβ-carotene content and main agricultural characters and combining ability analysis on P-carotene content of main agronomic characters were studied. The results were as follows:1. In Yuanjiang of Yunnan province, theβ-carotene contents of maize inbred lines ranged from 0.5998 to 4.0844μg/g, with an average of 1.4639μg/g, the coefficient of variation was 0.8033. The P-carotene contents of hybrids ranged from 0.2432 to 3.6350μg/g, with an average of 1.4301μg/g, the coefficient of variation was 0.5126. In Ya'an of Sichuan province, theβ-carotene contents of maize inbred lines range from 0.2317 to 6.4307μg/g, with an average of 2.0676μg/g, the coefficient of variation was 1.0390. Theβ-carotene contents of hybrids ranged from 0.4329-5.3553μg/g, with an average of 1.8388μg/g, the coefficient of variation was 0.6614. Dongdan54-3-1-1-1×9636, Dongdan54-3-1-1-1×5311 and 9636×R08 were the combinations, which had high P-carotene contents and little differences in the two environments.2. The variance analysis of combining ability showed that the difference of the general combining ability was significant, but the special combining ability and the reciprocal cross effect were not significant, which indicated that there were differences of GCA between different samples. Analysis of general combing ability showed that effect values of GCA ranged from-0.6522 to 1.5195, The GCA values for 9636,5311,Dongdan54-3-1-1-1,698-3 were positive and higher than those of the other parents significantly at 0.01 level. In all the inbred lines,9636 had the highest effect value,5311 and Dongdan54-3-1-1-1 had higher effect value,48-2 had the lowest effect value.3. Variances and genetic parameters ofβ-carotene contents of maize kernel were estimated through stochastic model. The results showed additive effects and dominance effects were 1.0647 and 0.0077 respectively, indicating that the additive effect is the main effect that affected theβ-carotene content in maize seed. Broad heritability and narrow heritability was 79.45% and 78.88% respectively, narrow heritability was larger, indicated that selecting in early generations was more reliability.4. The Parent-offspring correlation of theβ-carotene content between parents and their F1 generation was significant at 0.01 level, both in the crosses and the reciprocal crosses at the two different regions. There was no significant difference in theβ-carotene content between the cross and the reciprocal cross.The Paired Test was adopted to analyze the difference ofβ-carotene contents between the cross combinations and the reciprocal cross combinations at the two regions. It was concluded that there was no significant difference between the cross combinations and the reciprocal cross combinations at the two different experimental regions, which indicated that the genetic effect of the P-carotene content was not influenced significantly by the cytoplasm background.According to theβ-carotene content, the highest 15 combinations were found from the 56 combinations, theβ-carotene content in those 15 combinations ranged from 1.9090 to 3.8723μg/g. Among the highest 15 combinations, the highest combination was 9636×698-3, High×High combinations accounted for 66.7%, High×Low combinations accounted for 33.3%, and there was no Low×Low combination. According to the lowest 15 combinations, the range of theβ-carotene content was 0.4559-1.0133μg/g, the lowest combination in the lowest 15 combinations was Mo17×48-2. The Low×Low combinations accounted for 73.3%, the High×Low combinations accounted for 26.7%, and there was no High×High combination.5. The Paired Test was adopted to analyze the significance of difference ofβ-carotene content between Ya'an and Yuangjiang, there was a significant of difference ofβ-carotene content between the two regions. The result suggested that environment had an important effect on the content ofβ-carotene which indicated that the contents ofβ-carotene of one combination in two environments were different from each other; theβ-carotene contents planted in Ya'an were higher than those of the combinations planted in Yuanjiang.If the combination had highβ-carotene content in Ya'an of Sichuan, it also had higher content in Yuanjiang of Yunnan, the content ofβ-carotene of all combinations in two environments had similar tendency. Analyzing the composition of the combination, it was found that the combinations rich inβ-carotene content were influenced by environment, and obviously contained at least one of the inbred lines 5311 or 9636 as parent except for 48-2×Dongdan54-3-1-1-1.6. Analyzing the combining ability of main agronomic characters, it was found that 9636,R08 and 698-3 had high GCA of yield per plant in the two environments, they might produced high yield combinations.Combinations had been classified by positive or negative of the GCA effect value, whith indicated that the number of combinations which had positive or negative of the GCA effect value of main agronomic characters was much different, but there was a similar in two regions, positive and negative effect value had large amplitude.9636×Huangzaosi and 48-2×Mo17 were the best combinations in both Ya'an and Yuangjiang. Effect value of reciprocal cross had been classified by positive or negative of effect value, which indicated that the number of combinations which had positive or negative of reciprocal cross effect value of main agronomic characters was much different, positive and negative effect value had large amplitude.9636×48-2, Dongdan54-3-1-1-1×Mo17 were the best combinations in two regions. |
