Identification Of QTL For Low Nitrogen,Phosphorus And Potassium Deficiency In Rice By Using Back Cross Recombinant Inbreed Lines(BRILs)Population

Rice(Oryza sativa L.),an extremely important grain crop,fills approximately half of the population of the universe and is the main source of daily human consumption.In this study,we performed three experiments and analyze QTLs for low nitrogen,phosphorus and potassium(NPK)deficiency tolerance in rice.(1)QTL mapping was performed to examine the genetics of low nitrogen(N)tolerance,a series of high-performance genotype backcross recombinant inbreed lines(BRILs)(BC₁F₆)consisting of 117 families was used to determine QTLs for root and shoot traits at the seedling level.Under the two levels of nitrogen and their ratio,a total of fourteen(14)QTLs were recorded,with significant LOD values for six traits.These 14 QTLs are located on the six chromosomes such as Ch01,Ch02,Ch03,Ch04,Ch09,and Ch11.Only one QTL(q SFW1)from these QTLs has the positive additive effect,4 QTLs(q SFW9,q RFW1,q RFW11,and q SDW9)were identified under the normal nitrogen condition(N+),4 QTLs(q SFW11,q RFW1,q RFW3,and q RFW11)were identified under nitrogen deficiency(N-)conditions,and remaining 6 QTLs(q SL4,q RL9,q SFW-1 q RFW-1,q RFW-2,and q SDW-3)were mapped under N+/N-ratio.Out of14 QTLs,q RFW-3 under N-and q SDW-3 under N+/N-ratio is pioneer QTLs.For these variables in the analog region,shoot fresh weight and shoot dry weight were directly related to each other.QTLs were placed on the same chromosome 9.(2)QTLs are analyzed with 120 backcross recombinant inbred lines(BRILs)for phosphorus(P)deficiency tolerance.To understand the genetic regulation of P deficiency tolerance,we used high-quality SNPs bin markers to trace some of the major loci accompanying phosphorous deficiency.Depending on this map,50 loci,included four new loci,q SL-3,q RL-11,q SDW-1,q RDW-1 with phenotypic variance 23.26%,12.06%,and 9.89%of P deficiency-related seedling traits were identified.No meaningful QTLs were observed for root length below P+,shoot fresh weight P-and root length,and shoot fresh weight for P+,P-and ratio respectively.Root fresh and root dry weight remained intimately associated with each other and QTLs for these parameters were placed on the identical chromosome 1 in the same location.Surprisingly,the pioneers of our research are three pleiotropic regions,and these areas will speed up map-based cloning to speed up the collection of MAS for the development of low phosphorus-resistant cultivars.(3)A potassium(K)deficiency tolerance QTL analysis was conducted to explore the genetic mechanism of six seedling characteristics under two K conditions,LK and normal K(NK),and their relative trait ratio(LK/NK).For chromosomes1,2,3,4,5,7,and 11,a maximum of 17QTLs was found with a significant LOD value for all variables below two levels of potassium K;6 in K+,7 in K-and 4 in the K+/K-ratio.For root length,shoot fresh weight,and shoot dry weight under K+,root length and root fresh weight K-and shoot length and shoot fresh weight for K+/K-and their ratio,no significant QTL had been found.Mainly three novel QTLs were described:q RL1,q RL-2,and q RDW-11 with 9.77,2.96,1.42 phenotypic variation associated with potassium deficiency seedling traits...