| Eight inbred lines of super sweet corn according to the Griffing diallel methodⅡwere designed experiment and hybrid combination. Specific primer was designed and the gene sh2 of inbred lines were determined; To aim the weakness of super sweet corn breeding at present, such as thick pericarp, bad tenderness and low sugar content, combining ability and genetic parameter of seventeen characters--pericarp thickness, total soluble sugar, reducing sugar, net ear weight, spike length, the length of bare, ear diameter, ear row number, kernels per row, plant height, ear height and stem diameter were studied. Furthermore, according to the value of SCA for net ear weight,pericarp thickness and total soluble sugar, the heterotic groups and heterotic patterns of eight inbred lines were researched. The main results as follow:1. According to the reported sequence, specific primers were designed and the genes of inbred lines were tested. The result showed that eight inbred lines were controlled by the gene sh2.2. The pericarp thickness changed as curve during the development process of kernel. That was to say, after pollinating, the pericarp thickness gradually increased with the development of kernel, until the milk stage arrived at maximum. Then the pericarp cell arrangement became thin with dehydration. There was extremely significant deviation among different materials of the same genotype. The result indicated that the pericarp thickness of kernel was mainly influenced by nuclear background. The pericarp thickness had deviation in spring and autumn in Guangzhou. Generally, the pericarp thickness of autumn was regarded as the standard.3. The total soluble sugar changed as curve in the development process of kernel. After pollinating, the sugar content changed with the development of kernel grout following two tendencies: (1) the sugar content increased gradually first and arrived at maximum at milk stage, then decreased gradually; (2) the sugar content decreased gradually first, then increased and arrived at max in the milk stage, and decreased gradually in the last. In Guangzhou, after 16～20 days of pollinating, the sugar content of super sweet corn reached the peak. The optimum harvest date is 16～20 days after pollinating.4. According to the result of general combining ability and the analytic variance of specific combining ability, eight inbred lines were evaluated synthetically. The result was shown that T-19 was an outstanding inbred line on the yield and high quality treats; T-14 and T-8 had the higher value of GCA effect on yield; T-4 had the high value of GCA effect on high quality treats.5. Usually when parents were the inbred lines which had high value of GCA, crosses always had high value of SCA. The result was shown that there was the consistency between hybrid combinations SCA and GCA of parents. From the synthetic evaluation about the value of SCA on yield, high quality and agronomic treats, T-8×T-4 had an excellent synthetic combination on the high value of SCA which had high yield, agronomic treats, total soluble sugar and pericarp thickness. T-5×T-14 and T-8×T-1 had the high value of SCA on yield and pericarp thickness; T-19×T-8 had the high value of SCA on yield and total soluble sugar.6. The analysis of correlation of general combining ability for all traits indicated that there was significant positive correlation between pericarp thickness and reducing sugar; there was little correlation between total soluble sugar and pericarp thickness; there was significant positive correlation between net ear weight and ear diameter; there was very significant positive correlation between ear row number and ear diameter; there was significant positive correlation between plant height and ear height; there was significant negative correlation between ear diameter and stem diameter; there was no significant correlation between kernel per row and others treats.7. According to the calculating of heredity of 17 treats in 8 inbred lines, the order of the generalized heredity of all treats was showed as following: reducing sugar>kernel per row>net ear weight>plant height>pericarp thickness>tassel length>total soluble sugar>fusule>scattering>tassel branch number>ear diameter>ear row number>ear length>the half of spike leaf vein>stem diameter>ear height>the length of bare. The order of the narrow heritability of all characters was showed as following: ear diameter>ear height> ear row number> ear length>stem diameter>total soluble sugar>fusule>scattering>tassel branch number>pericarp thickness>net ear weight>plant height. Traits of ear length, ear row number, ear diameter, ear height, stem diameter had high generalized and narrow heritability which was mainly controlled by additive genes and selected in early generation. Traits of total soluble sugar, pericarp thickness and net ear weight had high generalized heritability and low narrow heritability which were controlled by dominant and epistasis genes and could be selected in late generation. The generalized and narrow heritability of the length of bare were low, so the length of bare was influenced by environment and the selecting rate was low.8. Based on the SCA effect of net ear weight, the 8 inbred lines were clustered into 5 heterotic groups which were A, B, C, D, E. A×B was the best heterotic pattern. According to the SCA effect of pericarp thickness, the 8 inbred lines were clustered into 3 heterotic groups which were 1, 2, 3 .1×3 was the best heterotic pattern. Based on the SCA effect of total soluble sugar, the 8 inbred lines were clustered into 4 heterotic groups which were L,M,N,O. L×M was the best heterotic pattern.
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