Identification Of Nitrogen-efficient Rice Varieties And Genome-wide Association Analysis

Elemental nitrogen(N)is a massive element required for crop growth,and N deficiency is a key limiting factor in crop yield formation.Application of N fertilizer can significantly increase crop yield,but excessive application can have multiple adverse effects on the entire ecosystem.Therefore,elucidating the genetic basis of crop N use efficiency and breeding crops that can still produce high yields under low N conditions are critical for the sustainable development of future agriculture.In order to select N-efficient germplasm of rice and screen N-efficient molecular markers and candidate genes,this experiment was conducted to identify seven phenotypic values related to N use efficiency of rice natural population under low and normal N conditions,namely,effective spike number(PN),longest spike length(MPL),full grain weight(FGW),plant height(PH),number of solid grains(GN),number of grains per spike(EGN)and 1000 grain weight(1000 GW).A comprehensive evaluation of the N-efficient ability of the germplasm was conducted by statistical analysis,and the N-efficient materials were selected;the N-efficient association markers were obtained by association analysis,and the candidate genes were initially screened for further research on the mechanism of N uptake and utilization in rice.1.Genetic diversity and genetic distances were first estimated for 202 rice microcore germplasm resources,and the variety structure was determined and subpopulation classification among individual varieties was inferred.The genetic relationships among subpopulations were statistically analyzed.Based on the genetic distances,we further determined the neighbor-joining clusters and classified the 202 rice microcore germplasm resources into four major rice subgroups: Indica,Japonica,Aus,Intermediate.2.There were highly significant correlations among most traits.Nitrogen efficient traits were identified in 202 rice germplasm using yield traits under low and normal N conditions,and finally 47 double efficient types of rice,25 high N efficient types,35 low N efficient types and 95 double low efficient types were identified.3.Genome-wide association analysis(GWAS)of N-efficient utilization parameters was used to obtain a number of significant association markers for N-efficient utilization in rice.Association analysis between target traits and SNP markers was performed using 202 rice natural populations using mixed linear model(MLM)in EMMAX software.At the significant level of-Log(p)>5,180 SNPs were detected that were stably associated with N-efficient utilization parameters,explaining 8.7%-30.1%of phenotypic variation,and 43 candidate genes for N-efficiency in rice were initially screened.