| As one of the most important sino maize germplasms, lvda red cob germplasm has formed its regional characteristic, which is high combine ability, long ear, deep kernel and remarkable heterosis with other germplasms. It played an important part in maize breeding and grain production. Since wide spreading of density tolerance cultivars, the defect of lvda red cob germplasm became notable with low density tolerance and non-lodging resistance. Its high combine ability, long ear and deep kernel can be taken good advantage of. Based on that, a genetic improvement and the special characters were studied.This study was composed in three aspects: Introducing B1 M germplasm for genetic improvement of lvda red cob elite inbred lines 8-F, S122, and Dan340 by haploid breeding techniques; Analyze haploid induction rate, doubling rate and genetic compose for improvement lines by SSR; Genetic analyze heterosis and combine ability of the genetic improved lines.The experiments were designed as follows: conduct combinations by lvda red cob elite lines dan 340, S122, 8-F as maternal, exotic inbred line B1 M as paternal, in summer 2011. Each combination were induced with high frequency haploid inducer JS9 for 20 ears, and ascertaining inducing rate at Hainan province in winter, 2011. 3. Treated with concentrations of colchicine to ascertain the inducing rate with 2 times of repetition.Reid gremplasm inbred lines as testers and the improved Lvda red cob DH lines were tested in 7×7 NCII design. The densities were 45 thousand plants per hectare, 60 thousand plants per hectare, 75 thousand plants per hectare, 90 thousand plants per hectare and 120 thousand plants per hectare. By doing analysis of heterosis, density tolerance and the combine ability, main results were as follows:1. There significant differences of inducing rate among hereditary bases. The highest haploid inducing rate showed up in S122×B1M, while the lowest was based on 8-F×B1M.2. Highest haploid doubling rate showed up with colchicine as the agent with the concentration of 0.06%, the combination was with 8-F×B1M.3. The study of genetic composition of DH lines DH1488, DH1510, DH1576 which derived from 8-F×B1M, S122×B1M, S122×B1M, respectively, suggested that genetic contribution rate of 8-F was higher than the B1 M, which was 9.09%; S122 and Dan 340 were lower than the B1 M, whose genetic contribution rate was 36.36% and 45.45%, respectively. Meant that, DH1510 and DH1576 inclined to B1 M, while DH1488 inclined to 8-F.4. Heterosis analyzation results of 49 combinations suggest that improved lvda red cob lines had better heterosis. There was significant difference of heterosis among 3 lvda red cob improved lines in densities. To receive better results, improved lvda red cob lines should be select at Optimum densities.5. The GCA analysis of 3 improved lines showed that the improved lines hadmore GCA effects under 5 densities. Suggested that lvda red cob elite lines 8-F,S122, Dan 340 can be improved by B1 M for GCA. Inbred lines with high GCAeffects could be use in population GCA improvement by accumulating valuablegenes.6. The results of path analysis of main agronomic traits in 5 densities suggest that ear weight, 100 kernel weight had direct effect on single plant yield. Barren ear tip length could apparently affect yield drop, negative affect increased along with plants density, which made barren tip length a main indicator to evaluate inbred lines’ density tolerance. |
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