QTL Analysis Of Nitrogen Use Efficiency In Brassica Rapa

Brassica rapais an important Brassica vegetables and oil crops in the nationaleconomy.It is also a kind of variety, adaptability, large cultivated area, the demand forhigh nitrogen plant. The popularity of chemical fertilizers in modern agriculture,including nitrogen fertilizer, greatly improved the crop yield. However, excessiveapplication of nitrogen fertilizer has also brought environmental pollution and thenegative impact of soil degradation. Reasonable application of nitrogen fertilizer toincrease plant uptake of nitrogen use efficiency, reduce environmental pollution and forsustainable development of agriculture has important significance.This highly complex objective requires a deep understanding of the genetic basis of Nassimilation and N use at different stages of plant development, providing theoreticalguidance to scientific fertilization of Brassica rapa. The main structural elements of Nassimilation pathway in higher plants are well known.The problem we have to solve nextstep is to perfect this big metabolic network.Quantitative trait loci (QTL) mapping consistsof identifying (through linked genetic markers) the individual genetic factors influencingthe value of a quantitative trait.We genotyped the R-O-18×L58RILspopulation with372Insertion/Deletion (InDel)markers evenly distributed along the genome and constructed a genetic linkage map.Thenthe QTLs mappingfor nitrogen use ffficiency(NUE)were performed in Brassica rapa. Theresults we got were listed as follows:1. The map comprises a total of372InDels with a total length of968.9cM. The mapdefined herein represents average genetic and physical intervals of2.60cM and606.3Kbpper marker respectively. Therefore, it is currently the first linkage map of a RILspopulation with only InDel markers for B. rapa. The distribution of these markers isuniform，However, there were still four gaps(>15cM):one on A06,one on A04and two onA02.2. Based on the four publicly available B. rapa genetic map，88.9%of thescaffoldwere anchored on to the chromosomes.Using the developed linkage map,12 mroe scaffolds were anchored on to the chromosomes, encompassing1.09%of the B.rapa genome.3. Phenotypic variation analysis shows that the mean values of all traits wereobviouslychanged to some extent underdifferent nitrogen condition.Varianceanalysisshowed that the most of the traitsin the conditions of normal nitrogen (N+) expressa significant differencewith nitrogen stress (N-) except traits of PH, LR,PTL in two placesand LM, BT,FT in Beijing.4. Through QTL mapping，29QTLs were identified in Beijing, with14QTLs innormal N(N+) and15QTLs in N stress (N-);25QTLs were identified in Yunnan, with14QTLs in normal N(N+) and11QTLs in N stress (N-).10locican be detected between thetwo nitrogen treatments at the same locus and trait.14QTL loci were only detected innormal N(N+) and13QTLs were detectedonly in N stress (N-), which might be N supplycondition changed some genes expression and regulation.