关键词: 玉米, 雄性不育, 恢复基因, 配合力

Abstract:

【Objective】The study was aimed to determine the type of the male sterile line of maize, Jinyu1A, by molecular biology and cytology approaches, identify restoring and maintaining relationships of maize germplasm resources to the sterile line, and to test its general combining ability (GCA) and specific combining ability (SCA).【Method】The stability of sterility of Jinyu1A was investigated at 4 locations (Ledong, Jinzhong, Xinzhou and Yuncheng) for successive 3 years. Tassel, anther and pollen grains of Jinyu1A was observed and compared with Zheng58. F₁ pollen grains of Jinyu1A×Chang7-2 were observed by I₂-KI staining. The sterility type of Jinyu1A was identified by specific PCR. Jinyu1A was used as the female parent and test-crossed with 158 maize inbred lines. The fertility of F₁ plants was investigated to screen for the suitable restorer and maintainer lines. The fertility of F₂ and BC₁ population plants was investigated. The grain yield general combining ability and specific combining ability of Jinyu1A were estimated by analyzing the data of its F₁ hybrids.【Result】The sterility characters of Jinyu1A were stable in the 4 locations for the 3 years. The appearance of tassel of Jinyu1A was similar to that of Zheng58, but its glumes were closed, anthers were withered and could not exert out of the glumes, and I₂-KI staining showed that the pollen of Jinyu1A was completely sterile. The microscopical observation on the pollen grains of F₁ hybrid plants of Jinyu1A and Chang7-2 showed that 64.4% of the pollen grains could be stained dark by I₂-KI and 35.6% pollen grains were aborted, which indicated that the sterile line belonged to S-type cytoplasmic sterile lines. The cytoplasm of Jinyu1A and Chang7-2 were identified as S-type male sterile type by specific PCR. The nuclear genome of Chang7-2 carries restorer genes, which concealed the phenotype of cytoplasmic male sterility. The specific primers suggested by ZHENG et al. were more applicable for categorizing maize cytoplasm sterile types. Among 158 inbred lines test-crossed with Jinyu1A as female parent, 96 maintainers, 47 restorers, and 15 semi-restorers were identified. There were 3.1%-8.7% sterile plants in F₂ populations derived from fertile F₁ plants of crosses between Jinyu1A and the restorer lines, which indicated that there were minor effect restorer genes in the restorer lines. There was no significant difference in the grain yields of the hybrids between each of Jinyu1A and Zheng58 as females and other 10 inbred lines as males, respectively. However, the F₁ combining ability analysis of these hybrids showed that the general combining ability of Jinyu1A was slightly higher than that of Zheng58.【Conclusion】Jinyu1A was a S-type cytoplasmic male sterile line with stable male sterile characters and completely aborted pollen grains. There are a certain amount of restorer and maintainer type breeding stocks for Jinyu1A in the present maize germplasm resources. F₁ plants of its hybrid with Chang7-2 could produce normal panicles and disperse fertile pollen. The existence of minor effect restorer gene(s) made the pollen dyeability shift to the direction of fertility, which led to the emergence of a few fertile plants in F₂ populations. There was no significant difference in the grain yield between the hybrids with Jinyu1A and Zheng58 each as female parents test-crossed with the same male parents. The general combining ability of Jinyu1A was slightly higher than that of Zheng58, indicating that it could be used in the breeding programs for selecting new maize hybrids and male sterile lines.

Key words: maize, male sterility, restorer gene, combining ability