| The study includes two parts,’the genome-wide association study of salt tolerance traits in rice germination stage’ and ’preliminary studies of two leaf-color mutants’.Rice is one of the most important food crops in the world,and is the model organism of monocotyledon.However,soil salinization is one of the major abiotic stresses limiting crop growth and yields.Up to date,Salt-affected soils account for 20%of the total area of rice cultivation.What is worse is that salt-affected irrigated land area of China is expanding and spreading.Therefore,it is of great theoretical significance and practical value to search for salt tolerance genes,increase crop yields under salt stress and develop salt-tolerant rice varieties.Salt-tolerance traits at the germination stage are complex traits controlled by multiple genes.In this study,121 rice accessions were treated with 150 mM NaCl solution,and the salt-tolerance traits were determined.We performed GWAS with salt-tolerance traits and 35,033 developed SNPs in our laboratory.There were seven reported salt stress-related genes and six candidate genes that may be associated with salt stress.At the same time,five most salt-tolerant cultivars and six most sensitive cultivars were screened through estimation of breeding values.The main results are as follows:1.A total of 148 associated sites were detected in this experiment.18 loci were detected according to the relative root number(RNR),59 loci were detected by relative root length(RLR),12 loci were detected by relative bud length(SLR),58 of relative germination potential(GER),and 3 loci were detected by relative germination rate(GPR).At the same time,both the relative root length(RLR)and the relative shoot length(SLR)detected the same sites.By website annotation and consulting the literature,we have detected 7 genes related to salt stress in rice,which were NADP-ME2,RSS1,OsGLYII2,DST,OsBADHl,OsGR3,OsSOSl.What’s more,there were three new distinct peaks,which locateed on Chr.l,Chr.7,Chr.ll.By analyzing the linkage region beside the associated sites and website annotation,it was found that there are 12 genes in the LD region on the Chr.1 around the association site,but the salt-tolerance candidate genes have not yet been determined and further verification is needed.it was found that LOC_Os01g52030 on the first chromosome is a gene that encodes a containing A20 and AN1 domain stress related protein.There are four series genes encoding OsFBLD-F-box,LRR and FBD domain protein on the seventh chromosome,whose effect values were significant and may play an important role in the salt tolerance of rice.The two genes of LOC_Osllg34750(OsABC1-14)and LOC_Os11g34830(OsABCl-15)on the eleventh chromosome belonging to the family of ABC1(Activity of bcl complex).They all encode a protein kinase,and ABC1 family genes are easily induced by abiotic stresses and may involve in the response process of salt stress in rice.2.Breeding value is the result of an additive effect calculation between all markers.The mixed linear model was used to calculate the breeding values for RLR,RNR and GER traits and then ranked in descending order.Considering the direction of breeding values,we selected varieties with higher breeding values throughout the genome,the cultivars in the top 5 salt-tolerant varieties with high breeding values(’IR36’,’Chuanmi 2’,’Wenzhouzhu’,’Zaoshu 691’,’Mandalu’)may carry more salt-tolerance genes and excellent allelic variation.At the same time,the cultivars in the bottom 6 salt-sensitive varieties with low breeding values(’IR20’,’Shannong 13’,’Lianmi 15’,’Gu Dong’,’Ai jiaohong’ and ’Asu XX’)were screened.The greater the RNR,RLR,GER breeding values,the stronger the resistance to salt stress.The extreme salt-tolerant varieties screened out in this experiment can be used as potential breeding parents for genome selection.The biosynthetic pathway of chlorophyll contains a series of complex and conservative enzymatic reactions that are essential for the photosynthesis and growth-related metabolic processes of plants.In this study,an albino mutant was used as the material,which laid the foundation for studying the regulation network of chlorophyll biosynthesis,chloroplast differentiation and cell death.The main results are as follows:On the basis of previous studies,the three-dimensional structure of OsPPR6 protein in the wild type and the mutant were further observed.It was found that the three-dimensional structure of the wild type was significantly different with osppr6 mutant.The 23 S and 16S rRNAs in the mutant were significantly reduced by chloroplast RNA analysis.RT-PCR analysis of the chloroplast development genes showed that the transcripts of ycf3(photosystem I loaded protein)in the osppr6 mutant were not completely spliced.It was speculated that OsPPR6 is important to transcript splicing of ycf3 and chloroplast early biosynthesis. |
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