Genetic Analysis Of Phosphorus-deficiency Tolerance In Wheat

Wheat(Triticum aestivum L.)plays an important role in grain crops.The growth of the world population causes food problem.Meanwhile,the deficiency of soil phosphorus(P)limits the increase of wheat production.The comprehensive analysis and improvement of wheat genetic in phosphorus-deficiency tolerance are the basis for seeking sustainable development and meeting production demand.In this study,a recombinant inbred line population(RIL,H461×CM 107)and 707 Chinese wheat landraces from 10 agro-ecological regions of China were cultured in applied P(AP)and no applied P(NP)nutrient solution with three replications.Twelve and fifteen traits were evaluated in seedling stage for RIL population and wheat landraces,respectively.The best linear unbiased prediction(BLUP)were carried out for all traits to eliminate the environmental impact.Then those data were combined with molecular markers for linkage analysis or association analysis to identify significant QTL and associated DArT markers.And public databases were used to annotate candidate genes around above markers to integrate the important sites of low phosphorus tolerance.The main results are described as follows:1.The phenotypic analysis of P-deficiency tolerance traits in RIL population at seedling stage was carried out.Significant positive correlations were found among all traits in both treatments,except for root/shoot ratio and root diameter which had complex correlations with other traits.The analysis of mean values showed that all traits decreased under NP treatment comparing with AP treatment,except for root/shoot ratio and root diameter.Then 4345 DArT markers and 12 P-deficiency tolerance traits were used to linkage analysis.The results showed that 8 and 9 significant quantitative trait loci(QTL)were respectively detected under AP and NP treatment(LOD≥4.00),and they could respectively explain 10.60%-16.60% and 10.80%-17.00% phenotypic variation.Among them,eight QTL had pleiotropic effects.2.In Chinese wheat landraces population,the analysis of correlations and mean values showed same trends with RIL population.The variance analysis showed that all the traits showed significantly different between two P treatments and genotypes.According to the analysis of Shannon–Weaver diversity index(H′),root tips had lowest H′ in AP and NP,while H′ of other traits were 0.63-0.86 and 0.74-0.87,respectively.The principal component analysis showed that the first three principal components could explain 82.98% phenotypic variation.And the top ten and last ten P-deficiency tolerance wheat genotypes were selected basing on S value.3.GWAS was performed with 52303 DArT markers and 15 traits,using two mixed linear models(MLM: K+Q;K+PCA).The results showed that 180 significant markers were detected under both models(-lg(P)≥ 4.72),including 111 significant associated markers under AP treatment for total length,shoot length,maximum root length,shoot fresh weight,root fresh weight,shoot dry weight,root dry weight,fresh root/shoot ratio,dry root/shoot ratio,total root length,total root surface area,total root volume,root tip and root forks,and 69 significant associated markers under NP treatment for shoot fresh weight,root fresh weight,shoot dry weight,root dry weight,fresh root/shoot ratio,dry root/shoot ratio,total root length,total root surface area,root diameter,total root volume,root tip and root forks.Among them,23 significant markers were associated with more than one trait.4.The intervals of significant markers detected in two populations were compared with the Chinese Spring reference sequence to predict candidate genes.Thirteen genes were predicted in the linkage analysis,and 36 genes were predicted in the association analysis.The linkage analysis data were annotated to 10,12,and 12 genes in Arabidopsis,maize and rice,respectively.The association analysis markers were annotated to 21,25 and 28 genes in Arabidopsis,maize and rice,respectively.5.Compared with previous studies,14 loci have been verified to be consistent with previous studies.Further analysis,seven important loci responding to phosphorus starvation were found in the linkage analysis.Among them,Qrt.sicau-7B.NP had been reported,and gene TaPDR which respond to stress was predicted from Qrt.sicau-3D.NP.In association analysis,one site which respond to phosphorus-deficiency stress(near marker A32484)was significantly associated with six traits.Four important sites controlling root development were found: sites near marker A66452,B17945,B765 and B22995 were significantly associated with 7,5,4,and 4 traits,respectively.Among them,sites neared B765 and B22995 could explain 11.52% and 8.66% phenotypic variation,respectively.The A66452 and B17945 marker sites have been reported in previous studies,while B765 and B22995 marker loci have not been reported.And a phosphorous starvation regulated Chitinase family gene(POM1 and TIDP3736)was found on the 5A chromosome,which will be used as a candidate gene for subsequent functional study.