| Maize is the major grain crop and industrial crop for diet and fodder in China. Dwarf compact type in maize with the characteristics of lodging resistance and fertilizer tolerance, and suitable mechanized production, plays an important role in the yield improvement and the income increasement. Germplasm resource is very important material basis for crop breeding. However, available dwarf genes for breeding is unitary and the genetic basis is narrow. Therefore, it is vital to explore and utilize new dwarf resources for further dwarf corn breeding. In this study, the dwarf mutant K125d was set as the material and the homologous inbred lines K211 was set as control to investigate the differences of the agronomic and economic traits and the sensitivity to GA3. Meanwhile, the genetic model of dwarf trait was analyzed by using genetic mating design with 7 inbred lines and K125d, and the preliminary mapping of the target gene was determined by using SSR makers. The results will provide the basis for further research and application. The main results are listed as follows:1. Compared to inbred line K211, the growth period of K125d was extremely significant longer, the ear height was extremely significant lower, the plant height was reduced by 53.07%; the leaves were intensively over lapped, leaf number and leaf width were extreme significantly increased, however, the leaf angle was extreme significantly decreased, which benefited to establish the ideotype; the yield per plant was reduced by 34.41%, however, no differences were found in ear length and ear rows that implied the yield might be potentially improved; K125d showed the irregular cells with the asymmetrical length and size, that the average length was shortened by 30% by observation of the stalk vertical section. These results indicated that the dwarf phenotype of K125d was caused by the shortened stem cells resulting in shorter internode length.2. K125d was reciprocal crossed with K.211 and 7 inbred lines including dwarf, middle and high plant height type. The obtained F1, BC1, BC2 and F2 population showed the same results in the 2 different environment. The F1 population was high plant height without cytoplasmic inheritance effects; the separation ratio of high to dwarf plants in 6 BC1 populations were 1:1 fitted with Chi-square test except K123d with br2 gene type,6 BC2 populations were high plant height, and the separation ratio of high to dwarf plants in F2 population were 3:1. The results demonstrated that the plant height of K125d was controlled by a single recessive nucleus gene, temporarily named d125.3.The K125d/K236 F2 was established as gene mapping population. A total of 611 pairs of SSR primers were used for polymophism screening between the parents K125 and K236, and also high and dwarf gene pools,10 pairs of SSR primers were screened out. The 10 pairs of primers were further used to amplificate 255 recessive dwarf plants of K125d/K236 F2 population by the Agarose gelelectrophoresis for detection. The amplificated results were conducted for linkage analysis by mapping software MAPKAKER 3.0. We found that the target gene for K125d was linked to SSR markers umc2569 and umc1278 on chromosome 1L, with genetic distances of 6.6 and 5.1cM respectively, approach the recessive dwarf gene brl and br2.4.K125d seedlings were exposed to five different concentrations of GA3. The results showed that K125d dwarf phenotype can be recovered by low concentrations of 25uM GA3, and the elongation of leaf sheath was significant, but no difference was observed among treatment concentrations of GA3. These results suggest that the transport pathway of GA3 in dwarf mutant of K125d seedlings is normal and the K125d phenotype belongs to GA-sensitive mutation. Besides, as br1 and br2 are both dwarfing genes with GA3 insensitive characteristics, also the F1 plants which were produced by K123d (br2 Type) crossing with K125d performed normal height, and the separation ratio of heigh and dwarf plants is 1:1 in BC populations, associated with the 9:7 separation ratio in the F2 populations, suggested that the d125 gene for K125d was non-allele of both br2 and brl. |
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