Analysis Of Combining Ability And Heterosis For Seed Vigor And Yield-related Characters Of Maize

Seed vigor is a more promising seed quality character reflecting potential seed germination, field emergence under different conditions than standard germination. High vigor seeds have higher growth advantage and potential productivity. Studies on Inheritance law of seed vigor and yield-related traits was to provide theory reference for genetic improvement and high yield breeding in maize seed vigor. Currently, the genetic analysis of concerned characters in maize seed vigor and heterosis was rarely reported. The study was conducted by seven inbred lines for female parents and five for male parents as materials which were from incomplete diallel cross to form 35 crosses growing simultaneously with parents. A total of 30 indicators including seed vigor , physiology and biochemistry , and agronomic characters indicator, etc. Analyses were made for combining ability, population genetic parameter estimation, heterosis and its correlation. The main results were as follows.1. Results on combining ability analysis. General combining ability (GCA) of traits related to seed vigor and agronomic traits was significantly different among different parents and different traits of the same parent. Specific combining ability (SCA) was also existing significant differences on various combination in the same traits of the same inbred line. But SCA of inbred lines with low GCA was high. GCA in Parents P₇ (K1516), P₁ (SD9311) and P₈ (990) was high, which had the same results both in comprehensive characters of indoor germination experiment and in field properties determination. However, GCA of physiological and biochemical indicators in P4 (Ji 533), P₁ (SD9311) and P₈ (990) was high. In the SCA analysis, P₇ (K1516) / P₁0 (986) had the hightest in SCA of vigor index of field trial, P6 (Wan 9086) / P₁1 (24858-2) was the lowest. The hightest SCA of yeild was P5 (Xun 0566) / P₁2 (PH4CV), and P6 (Wan 9086) / P₁1 (24858-2) was the lowest. In all, the high SCA in seed vigor index and yield was not consistent.2. Results on genetic parameter estimation.. Because of high narrow heritability of conductivity and malonaldehyde, you could achieve the desired effect in early generation selection. Broad heritability of soluble sugar and soluble protein content were high, but its narrow heritability was low. They were affected greatly by non-additive effect of genes. Narrow heritability in vigor index of indoor standard germination was high, so it was suitable to select on early generation. But narrow heritability of germination tendency and germination rate was low, so early generation selection was not suitable. Each index of field measurement in seed vigor had low narrow heritability. Therefore each character was not suitable to select on early generation. Narrow heritability of 100-grain weight, grain length, ear length and ear rows were high, so early generation selection was suitable. Although narrow and broad heritability of ear diameter, ear height, axis diameter and bald top length of ear were high, these traits had negative effect on yield, which were comprehensively considered. Narrow heritability of yield and single panicle weight were low, so it was suitable to select on later generation.3. Results on analysis of heterosis. Experimental Analysis on each index of the herterosis was obvious, which indicated that use of heterosis can significantly improve the status of seed vigor, yield and its related agronomic characters. The mean value of mid-parent heterosis in all characters mostly was positive except for Conductivity and bald top length of ear. Positive heterosis had a high proportion. In the analysis of yield characters, positive heterosis in bald top length of ear accounted for 63%, other characters were 90%. Positive heterosis of all characters of indoor germination test were over 70%, and field measurement was the same as indoor germination test, except seedling emergence occupying 49%. The variation of mid-parent heterosis in physiological and biochemical indicators was larger. The combinations of first three yield over-standard heterosis were P₇ (K1516) / P₈ (990) (22.27%), P₄ (Ji 533) / P9 (Xin 7 hong) (16.95%) and P2 (A3519) / P10 (986) (16.39%). This study also showed that in terms of a certain trait, parents in all combinations showed positive heterosis, more likely to present strong heterosis combinations.4. Results on correlation analysis. Vigor index of field measurement and yield had a very significant positive correlation (p<0.01), and indoor germination vigor index with yield had a significant positive correlation (p<0.05). Other indicators of seed vigor and yield had no significant correlation. The correlation among field activity index and dehydrogenase activity, peroxidase activity, indoor germination energy, germination percentage, germination index and vigor index was significant positive (p<0.05), but the correlation between field activity index and MDA content was very significant negative (p<0.01). Yield and single panicle weight, row grains, plant height, grain length, ear diameter, 100-seed weight and ear length had a very significant positive correlation (p<0.01), and correlation coefficient was 0.989, 0.859, 0.804, 0.767, 0.759, 0.669, 0.664, respectively.