| Yield traits are important indicators which determine a rice variety. Panicle number, grain yield per plant, plant height and biomass yield are important yield traits. They are also quantitative traits which controlled by polygene. At the same time, Nitrogen is crucial plant macronutrient for crop growth and is a key limitation that restrict crop yield. However, using large dosage of fertilizer nitrogen is lead to low fertilizer use efficiency, enormous energy dissipation, decreased quality of rice, nitrogen pollution to the environment and other issues. Screening of resistant to low-nitrogen main parents of rice and analyzing the QTLs of yield-related traits is an important approach to resolve above mentioned problems. It not only has important practical significance for improving nitrogen use efficiency, reducing production costs, increasing rice yields, but also has great theoretical significance for revealing the molecular genetic mechanism of yield traits. Introgression lines (ILS) contain one or a few chromosome fragments from donor parent, and eliminate the interference of genetic background. ILS are the important experimental materials for identify and fine mapping of QTL.In this study, combined with high-generation backcrossing and marker-assisted selecting, 66 ILS were established in use of Shuhui 527(indica.) and Chugeng 12( japonica.) as the recurrent parent and donor parent. The ILS were planted in field under two treatments of normal and low-nitrogen fertilizer application. Then, this research also detected and analyzed effects of QTL about panicle number, grain yield per plant, plant height and biomass yield under different treatments. The main results are as follows:1. The polymorphic between Shuhui 527 and Chugeng 12 as the receptor and donor parents were detected with 350 pairs of microsatellite markers, and 64 pairs of markers were selected for ILS screening. These 64 markers covered the entire rice genome. The percent of polymorphism was 18.29%. The average interval distance between adjacent markers was 19.24 cM.2. In this study, 66 ILS with Shuhui 527 genetic background were established after the field screening and detection of molecular marker. These ILS distribute on 11 chromosomes of rice, but not uneven. Most ILS were on chromosome 1, and there were no introgression fragments on chromosome 12. The total length of all substituted segments is 1392.74 cM and average length was 20.48 cM. 3. 24 QTLs for 4 important yield traits of rice under two treatments have been detected in 66 ILS by using QTLIciMapping 2.0 software and RSTEP-LRT method. PIN = 0.05 and POUT = 0.10 were the significant level of selecting markers. LOD≥2.5 and LOD≥3.0 were thresholds to determine the QTL. 11 QTLs which detected under the normal treatment contained 8 QTLs for panicle number, 1 QTL for grain yield per plant, 2 QTLs for plant height. 13 QTLs which detected under low nitrogen treatment contained 5 QTLs for panicle number, 2 QTLs for grain yield per plant, 2 QTLs for plant height, 4 QTLs for biomass yield. 24 QTLs located on chromosome 1-8. Two QTLs for plant height were detected repeatedly in the two kinds of treatments. Qph-1, qpn-1, qby-2 and qby-4 identified in the present research are same with the previous studies, the other 20 QTL s are the new study.4. Under the low nitrogen treatments, qpn-2b was a QTL of panicle number with the highest (49.301%) variation explained and additive effect of 0.826. Qyd-1 was a QTL of grain yield per plant with the highest (12.687%) variation explained and additive effect of 3.091 under the low nitrogen treatments. Qph-1a was a QTL of plant height with the highest (25.593%) variation explained and additive effect of 4.313 under the low nitrogen treatments. Qby-4 was a QTL of biomass yield with the highest (20.779%) variation explained and additive effect of 7.599 under the low nitrogen treatments.ILs with Shuhui 527 genetic background were established in the present research, and QTLs of 4 important yield traits under two treatments have been analyzed. This study lays a certin foundation for using molecular marker-assisted to screen rice chromosomal segment substitution lines and low nitrogen tolerant main rice.
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