| Seed vigor is an important agronomic trait in rice(Oryza sativa L). The seed germination vigor under normal and low temperature, which is closely related with direct seeding and agriculture mechanization, determines field emergence of rice and the grain quality and yield. Therefore, it is of significance to study the genetic mechanism of low and normal temperature germinability in rice for cultivating high-vigor rice varieties. In this study, the quantitative trait loci(QTLs) for seed viogr under 15℃ and 30℃ were identified with 229 single segment substitution line(SSSL). The main results are as follows:1. The 229 SSSL were derived from 24 donor parents, especially the W5, W6 and W17 which showed better germinability than the recipient parent HJX74 under 15℃, 18℃ and30℃. The average length of substituted segments is 21.11 c M, and the genome coverage percent is 74.9%. The germination rate and germination index under normal and low temperature showed continuous distribution in the early and late season in 2015, suggesting they are typical quantitative traits.2. Fourty-four SSSL showed significant difference to the recipient parent HJX74 on low temperature germination index(LTGI) in the early and late seasons in 2015. A total of24 QTLs controlling LTGI were detected on 11 chromosomes except the chromosome 3 by substitution mapping method. The average length of all QTLs is 15.47 c M. The average additive effect of all QTLs ranged from-3.56 to 1.57, and the average additive effect percentage ranged from 24.6 to 12.0%. Among all the QTLs, q LTGI2-2, q LTGI4, q LTGI6-1,q LTGI7-1, q LTGI7-2 and q LTGI11-1 were stably detected for two seasons, q LTGI2-3,q LTGI8-1 and q LTGI12-1 are novel QTLs, and q LTGI2-4, q LTGI6-2, q LTGI11-2 are major QTLs with positive effect.3. Fifty-two SSSL showed significant difference to the recipient parent HJX74 on low temperature germination rate(LTGR) in the early and late seasons in 2015. A total of 29 QTLs controlling LTGR were detected on 12 chromosomes by substitution mappingmethod. The average length of all QTLs is 15.64 c M. The average additive effect of all QTLs ranged from-0.22 to 0.27, and the average additive effect percentage ranged from-46.6 to 70.1%. Among all the QTLs, q LTGR1, q LTGR4-1, q LTGR6-1, q LTGR6-2,q LTGR7-1, q LTGR7-2, q LTGR7-3, q LTGR11-2 and q LTGR12-1 were stably detected for two seasons, q LTGR2-2, q LTGR4-1, q LTGR8-2, q LTGR9-2 and q LTGR12-1 are novel QTLs, and q LTGR2-3, q LTGR3-1, q LTGR4-2, q LTGR5-2, q LTGR11-2 are major QTLs with positive effect.4. Fourty-four SSSL showed significant difference to the recipient parent HJX74 on normal temperature germination index(GI) in the early and late seasons in 2015. A total of24 QTLs controlling GI were detected on 11 chromosomes except the chromosome 10 by substitution mapping method. The average length of all QTLs is 11.85 c M. The average additive effect of all QTLs ranged from-6.98 to 8.97, and the average additive effect percentage ranged from-11.6 to 14.6%. Among all the QTLs, q GI2-3, q GI3, q GI4-1,q GI4-2, q GI6-1, q GI6-2,q GI7-1 and q GI7-2 were stably detected for two seasons, q GI1-1,q GI2-1, q GI2-2, q GI3, q GI8-1, q GI9-3 and q GI12 are novel QTLs, and q GI8-1 is major QTL with positive effect.5. Fourty-four SSSL showed significant difference to the recipient parent HJX74 on normal temperature germination rate(GR) in the early and late seasons in 2015. A total of22 QTLs controlling GR were detected on 11 chromosomes except the chromosome 10 by substitution mapping method. The average length of all QTLs is 13.19 c M. The average additive effect of all QTLs ranged from-0.2 to 0.22, and the average additive effect percentage ranged from-41.3 to 46.4%. Among all the QTLs, q GR3, q GR4-1, q GR4-2,q GR7-1, q GR8-4, q GR9-1, q GR9-2 and q GR11-2 were stably detected for two seasons,q GR2-1, q GR3, q GR8-1, q GR8-3, q GR9-2 and q GR12 are novel QTLs, q GR2-2, q GR3,q GR5-2, q GR6, q GR7-3, q GR8-3 and q GR11-2 are major QTLs with positive effect.6. Based on the above four phenotype traits, a total of 99 QTLs were mapped on 29 chromosome regions, including eight regions detected four kinds of QTLs, ten regions detected three kinds of QTLs, eight regions detected two kinds of QTLs. Among all the regions, five regions were only detected under low temperature and two regions were only detected under normal temperature.In this study, a number of QTLs controlling seed vigor under normal and low temperature were mapped, which help us to dissect the molecular basis of rice seed vigor. It also provide foundation on map-based cloning of the elite genes and breeding direct seeding rice varieties with high vigor by molecular design breeding method. |
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