水稻单片段替换系群体的建立及QTL定位

Development of Single Segment Substitution Lines (SSSLs) and Mapping of QTLs in Rice (Oryza sativa L.)

水稻中许多重要的农艺性状属数量性状 ,由多基因 (QTL)控制。研究QTL的遗传特性和遗传效应对于培育高产和稳产的水稻品种具有十分重要的意义。本研究以 6个优良的品种为供体亲本 ,以华粳籼 74为轮回亲本 ,通过微卫星标记辅助回交选择培育了一批单片段替换系 ,随后利用所培育的单片段替换系进行了QTL分析和基因定位。主要结果有 :1、利用 2 5 8个微卫星标记对 6个供体亲本和轮回亲本间的多态性进行了筛选。 6个供体亲本与轮回亲本间的多态率在 32 98%至 6 0 78%之间 ,平均 4 7 81% ,粳型供体亲本比籼型供体亲本的多态性要高。2、随着回交代数的增加 ,植株所含的替换片段数逐渐减少。在BC2 F1、BC3F1、BC3F2 和BC3F3代 ,平均每个植株携带有 12 5 0、 5 98、 1 6 9和 1 4 6个替换片段。替换片段的平均长度也随回交和自交代数的增加而逐渐变短。在BC2 F1、BC3F1、BC3F2 和BC3F3代 ,替换片段的平均长度分别为 2 5 4 3cM、2 2 38cM、 2 0 78cM和 18 15cM。回交世代替换片段变短的速率 (11 99% )比自交世代变短速率(7 15 % )要快。在BC2 F1、BC3F1、BC3F2 和BC3F3代 ,轮回亲本基因组的恢复率分别为 82 2 4 %、92 5 5 %、 98 0 4 %和 98 5 2 %。3、在BC3F2 和BC3F3代 ,共选育出 111个单片段替换系 ,其?

Most traits of agronomic importance in rice are quantitative in nature and are controlled by polygenes, called quantitative trait loci (QTL) Understanding the nature and effect of QTLs are important for rice breeding to achieve higher yield and stability. Single segment substitution lines (SSSLs) were developed through simple sequence repeats (SSR) marker facilitated backcrossing methods for Hua Jing Xian 74 (HJX74) with the donor segment from six elite germplasm, and were subjected to analysis of QTLs and mapping of genes. Salient findings of the research are as follows: 1 Complete genome survey was carried out with 258 usably polymorphic SSR markers. Polymorphism of the donors with the recurrent parent varied between 32 98 and 60 73% with an average of 47 81%. Japonica donors were more polymorphic than indica donors. 2 Number of substitution segments per plant decreased with the advancement of backcross generations. In BC 2F 1, BC 3F 1, BC 3F 2 and BC 3F 3 the average number of substitution segment per plant was 12 5, 5 98, 1 69 and 1 46, respectively. Average size of substitution segments also decreased with the number of times plants were backcrossed and selfed. In BC 2F 1, BC 3F 1, BC 3F 2 and BC 3F 3, average size of the segments was 25 43, 22 38, 20 78 and 18 15cM, respectively. The rate of reduction of segment size was more in backcross (11 99%) than selfing (7 15%) generations. Percent recovery of recurrent parent genome in BC 2F 1, BC 3F 1, BC 3F 2 and BC 3F 3 was 82 24, 92 55, 98 04 and 98 52%, respectively. 3 A total of 111 SSSLs comprising of 42 unique types were developed in BC 3F 2 and BC 3F 3. The estimated length of the segments in SSSLs ranged from 2 00 to 64 80cM with an average of 21 75cM, and 6 05 to 48 90 cM with an average of 20 95cM in BC 3F 2 and BC 3F 3, respectively. No substitution segments were recovered from chromosome 11. Total length of all substitution segments was 2367 5cm that covered 704 50cM (39 25%) of the entire rice genome. 4 A total of 234 QTLs for 22 traits were detected in 52 SSSLs through t test (P≤0 001) in BC 3F 3 generation. Number of QTL per trait varied from 3 to 19 with an average of 4 5. Similarly, number of QTL per SSSL varied from 2 to 15 with an average of 10 64. Additive effect and P values of the QTLs varied with traits as well as SSSLs; additive effect as low as -0 02 (0 79%) was detected for grain width. Presence of QTLs of opposite effect (positive or negative) was detected for various traits with loci RM237, RM322, RM225 and RM481. 5 Mapping of QTLs for 16 traits was done through overlapping substitution segment mapping in seven SSSLs. Duplicate substitution line was used to confirm location of QTLs on segments. 6 Correlatedness in expression of complex traits like plant height, number of grains per panicle and grain shape was tested through additive effect of the QTLs detected for those traits, and correlation of such QTLs were analyzed. 7 Gene for heading date, purple apiculus, plant height and grain length: width ratio was mapped. Gene affecting late heading ( Hd-8 ) in rice was found as monogenic dominant and was tightly linked to PSM155 on chromosome 8. Gene producing purple apiculus ( Pa-6 ) appeared as monogenic dominant and was closely linked to RM253 on chromosome 6. Gene affecting plant height ( Ph-1-3 ) was mapped to the long arm of chromosome 1 and was tightly linked to PSM331. Gene controlling grain length: width ratio ( Rlw-8-2 ) was mapped to the distal end of chromosome 8 and was tightly linked to RM447. The slender shape of rice grain appeared as a monogenic recessive trait. The gene ( Rlw-8-2 ) was reported here for the first time at this locus. Effective development and successful utilization of single segment substitution lines for analysis of QTLs and mapping of genes established the suitability of the SSR marker facilitated backcross breeding approach for SSSL development and analysis of QTLs in rice.