QTL Mapping Of Nue Related Traits And Genetic Analysis Of A Yellow Leaf Gene YL In Rice (Oryza Sativa L.)

This research project has two parts:'QTL mapping of NUE related traits' and 'Genetic analysis of a yellow leaf gene YL in Rice(Oryza sativa L.)'.The food demanding is getting larger and larger with the rising of the world population.Therefore.More and more fertilizer was applied into the soil.The inefficient using of fertilizer brought great pollution to the environment.Now improving the nitrogen-use efficiency(NUE)is the most effective way to solve this problem.A recombinant inbred lines(RILs)population of 178 lines derived from a cross of Asominori(japonica)/IR24(indica)was used to construct a molecular linkage map was employed to identify the quantitative trait loci(QTLs)and genetic analyze of growth traits under low-nitrogen tolerance in the field condition.The used traits for QTL mapping contain plant height,tiller number,panicle number and corresponding ratio under two nitrogen levels.1.Constructing of molecular genetic map785 SSR markers covering with all 12 chromosomes of rice was detected polymorphism.172 SSR markers were selected out(the ratio of polymorphism was 21.91%)and distribution averagely in the whole 12 chromosomes.There markers covered 2139.8 cM on rice genome with 12.44 cM.2.QTLs mapping of the growth traitsThe software of Windows QTL Cartographer v2.5 was used to calculate QTL.The QTLs of targeted traits and corresponding additive effect and phenotypic variance were detected by composite interval mapping method.Under the help of the rice genetic map.Using composite interval mapping with a LOD threshold of 2.5,we got 11 QTLs associated with targeted traits.They were distributed on 8 chromosomes and can be regarded as presumed QTLs loci for subsequent research.We detected 8 QTLs which related with plant height.The LOD values from 2.66 to 5.55.The QTL in 2014,qRPH,located on chromosome 1.The value of LOD was 3.17,additive effect was 1.75%.It could explain for 8.29%of phenotypic variance in the population.The QTL in 2015,qRPH,located on chromosome 1.The value of LOD was 5.55,additive effect was 1.77%.It could explain for 11.8%of phenotypic variance in the population.In addition.There were another one QTL in 2014,qRPH,located on chromosome 5.The value of LOD was 2.99,additive effect was 1.13%.It could explain for 8.5%of phenotypic variance in the population.The QTL qRPH was repeatedly detected in chromosome 1.We detected 7 QTLs which related with panicle number.The LOD values from 2.96 to 4.08.The QTL in 2014,qRPN,located on chromosome 1.The value of LOD was 3.53,additive effect was 4.83%.It could explain for7.97%of phenotypic variance in the population.The QTL in 2015,qRPN,located on chromosome 4.The value of LOD was 3.1,additive effect was 4.46%.It could explain for 11.3%of phenotypic variance in the population.We detected 6 QTLs which related with tiller number.The LOD values from 2.24 to 4.12.The QTL in 2015,qRTN,located on chromosome 2.The value of LOD was 2.67,additive effect was 6.52cM.It could explain for9.61%of phenotypic variance in the population.However.There were no QTL that over the threshold.Leaf,a crucial organ for photosyhthesis,provides the basis of crop yield formation.The leaf color mutants can be used not only as a trait marker in breeding,but also as one of the prerequisites in chloroplast development and cultivation of new germplasms with higher photosynthetic efficiency.A yellow leaf mutant,named as yl,was isolated from the progeny of 60Co-y-rays treated indica cultivar 9311.We demonstrated that the YLC1 gene is associated with the chlorophyll synthesis,providing a basis for further study on chloroplast pigment synthesis and chloroplast development.1.The yl mutant exhibited a stable yellow leaf phenotype during the seedling stage.As compared with the wild-type,the content of chlorophyll a,chlorophyll b and carotenoid were reduced by 77.3%,69.1%and 68.4%respectively in yl leaves.The yl mutant showed less grain number per panicle,less seed setting rate and fewer 1000-grain weight than the wild-type plants,which were reduced by 13.3%,12.9%and 14.0%,respectivelty.2.Genetic analysis showed that yellow leaf phenotype of the yl mutant was caused by a single recessive gene.The gene was isolated using an F2 mapping population derived from the cross of the yl mutant and Ningjing 4.The YL gene was located in a 14.5-kb region on the long arm of chromosome 9,which contained 3 ORFs.Sequence analysis revealed that the yl mutant had nucleotide changes(2130CTA?G)in the fifth exon of the 3rd ORF,which led to frame shift and early termination in the process of translating protein.Therefore the YL gene was a novel allele of the YLC1 gene.