一个具有主效晚抽穗基因的水稻染色体片段代换系的鉴定、形态分析及Ehd4-2定位

Identification and Morphological Analysis of a Rice Chromosome Segment Substitution Line Carrying a Major Effect Gene for Late Heading Date and Mapping of Ehd4-2

抽穗期是决定水稻品种种植地区和季节适应性的重要农艺性状,鉴定抽穗期基因对水稻生产具有重要意义。本研究采用高代回交和SSR标记辅助选择相结合的方法获得了1个以日本晴为受体亲本、西恢18为供体亲本的含有1个控制晚抽穗表型的主效单基因的水稻染色体片段代换系Z315。Z315携带来自西恢18的5个代换片段,分布于第1、第3、第6和第7染色体上,平均代换片段长度为7.39 Mb。Z315的叶绿素含量、株高、穗长、倒一节间长、倒二叶长、倒三叶长、有效穗数、每穗实粒数和总粒数均显著高于受体日本晴,暗示其代换片段可能携带这些性状的QTL。进一步利用日本晴与Z315杂交产生的F1和F2群体对晚抽穗基因进行遗传分析和分子定位。该晚抽穗表型受1对隐性核基因控制,最终将该基因定位于第3染色体RM14283和RM6349之间,物理距离为233 kb。对该区间进行候选基因预测和测序,发现1个与抽穗相关的编码锌指蛋白的基因LOC_Os03g02160在日本晴和Z315间存在差异,该基因可能与Ehd4等位,称作Ehd4-2。由于染色体片段代换系除代换片段外与受体亲本一致,因此本研究无论对进一步分离其他QTL还是进行基因聚合育种均具有较大利用价值。

Heading date is an important agronomic trait deciding planting area and seasonal adaptability of rice varieties. Identification of genes for heading date is important for rice production. In this study, a novel chromosome segment substitution line（CSSL） named Z315, carrying a single gene for late heading date, was identified by advanced backcrosses between the recipient Nipponbare and donor Xihui 18 and SSR marker-assisted selection. Z315 carried five substitution segments from Xihui 18. They were distributed on chromosomes 1, 3, 6, and 7. The average length of these substitution segments is 7.39 Mb. The chlorophyll content, plant height, panicle length, length of the 1st internode, length of the 2nd and 3rd upper leaf, number of efficient panicles, number of spikilets per panicle and number of grains per panicle in Z315 were significantly higher than those in Nipponbare, suggesting that QTLs（quantitative trait locus） for these traits might be carried on the chromosome substitution segments. Furthermore, F1 and F2 populations from cross of Nipponbare and Z315 were used for genetic analysis and gene mapping for the late heading date. Genetic analysis showed that the late heading date phenotype was controlled by a single recessive nuclear gene, which was mapped between SSR markers RM14283 and RM6349 on chromosome 3, with a physical distance of 233 kb. By gene prediction and candidate gene sequencing, a gene（LOC_Os03g02160） related to heading date was found existing differences between Nipponbare and Z315. The gene encoded zinc finger protein, which might be an allele of Ehd4, named Ehd4-2. The results in the paper have important applications for further dissection of other QTLs in Z315 and breeding for gene pyramiding because chromosome segment substitution lines have the same genetic background besides substitution segments compared with the recipient parent.