QTL Mapping Of Drought Tolerance And Low Nitrogen Tolerance And Evaluation Of Polymerization Effects Of Favorable Alleles In Rice

In recent years,with the constant change of global climate,abiotic stresses frequently occur,which have seriously threatened the production of rice,and drought was one of the most important factors that lead to the decrease of rice yield.Rice drought tolerance is quantitatively inherited controlled by multiple genes or QTL,thus comprehensively understanding genetic mechanism of rice resistant to drought could considerably facilitate to drought tolerance and further improve the effectiveness of breeding.In addition,for the sake of rice high production,more fertilizers were applied to field and gave rise to a big environment problem.Hence,it is indispensable to improve rice cultivals for the adaption of poor soil and improve the use efficiency of rice absorbed nutrition from soil.Cultivating green super rice（GSR）with drought tolerance and low nitrogen tolerance is an important way to ensure high yield.In this study,huanghuazhan（HHZ）as the recurrent parent crossed with eight donors and 2000 BC₁F₁ plants were obtained.314 traits-specific BC₁F₃ plants were got in the first round of high yield,drought resistance,salt tolerance and submerge tolerance.Finally,497 BC₁F₅ plants were obtained in the second round of tolerance screening and progeny tests.Then dissection of QTL mapping for drought tolerance and low nitrogen tolerance.Vertifying the stable QTL which expressed in multiple conditions,then screening QTL from different allele for pyramiding and phenotypic evaluation.The main research results were summarized as follows:1.Analysis of genomic variation in HHZ ILs（introgression lines）:497 ILs and their parents were carried out on genome resequencing studies.The average sequencing depth of the ILs was 3.16X,and the average sequencing depth of nine parents was 25X.41,754 high quality SNPs were acquired and two sets of genotypes were generated by eliminating and screening,one contains 7,388 SNP bin genotypes,the other contains 4,613 SNP bin genotypes for QTL mapping.At the same time,the genetic similarity analysis between eight donors and HHZ showed that Teqing was the lowest of 42.2%and OM1723 was the highest of 65.1%.2.The QTL analysis for drought tolerance related trait by selection breeding population:totally 206 ILs in three populations（HHZ5,HHZ12 and HHZ17）,which were screened from eight ILs populations.We obtained 57 DT-ILs by drought screening and selected six ILs（M73,M75,M79,M387,M498,M505）which performed better than others based on phenotypes and QTL genotpypes under drought condition.DT-QTL detection by MSDA（Mendelian’s segregation distortion analysis）in combined multiple populations.Nine QTL were detected and were distributed on chromosome 2,3,5,6,8,12 and six of which were previously reported.3.The QTL analysis for low nitrogen tolerance related trait by selection breeding population:The eight selection breeding populations were combined,and QTL for yield and yield related traits of interconnect breeding population under three nitrogen conditions（low nitrogen,the ratio of low nitrogen and normal nitrogen,normal nitrogen）in three seasons by GWAS（genome wide association study）approach-GLMM（generalized linear mixed model）.A total of 52 QTL were identified and distributed on 1¹2 chromosomes.Among these QTL,five of which were previously reported.Additionally,qGY1,qSF8-2 and qTGW2-1 were detected in different seasons,and further fine mapping of qTGW2-1,the physical location of about 200kb and a new InDel marker CLN9 was developed simultaneously.4.Screening of LNT-and DT-QTL pyramiding lines by SNP marker assisted selection:six excellent ILs were selected from the three breeding populations（HHZ5,HHZ12 and HHZ17）as the pyramiding parents,and four pyramiding groups were arranged.Five important QTL were selected from breeding populations under drought and low nitrogen stress conditions and verified in the field.Finally qDT3.9,qDT5.4,qDT6.3,qGY1 and qSF8-2were true.Using 3,162 KASP SNP markers provided by Huazhi biotechnology company to screen polymorphism.Screening progeny QTL pyramiding lines based on two KASP SNP markers flanking each target QTL.Eventually screening 235 F₂ pyramiding lines from four pyramiding populations and 12 F₃ pyramiding lines harboring different QTL were screening by the verification in drought,low nitrogen and normal conditions.These 12 F₃ lines performed significantly higher than HHZ under three conditions and could be used in rice tolerance breeding as valuable donors.