QTL Mapping And Genetic Analysis For Free Amino Acid In Tea Plant

Tea plant（Camellia sinensis（L.）O.Kuntze）is an important economic crop,which originated in China.Amino acids are an key components of tea,and have a great effect on tea quality and flavor.The genetic mechanism of amino acids trait is not clear as it being controlled by quantitative traits loci（QTL）.Therefore,great efforts should be paid to conduct QTL Mapping and elucidate the genetic mechanism of associated traits,which can accelerate the development of new molecular technologies to promote breeding process.In this study,we used an F₁ population constructed by the cross of two C.sinensis varieties with great genetic and phenotypic variation to conduct QTL analysis for amino acids traits.Single nucleotide polymorphisms（SNP）were identified within theanine synthetase（TS）and glutamine synthetase（GS）genes,and subsequently mapped onto the genetic map.The main results are as follows:1.The contents of amino acids were analyzed in parents and F₁ progenies across two years.The result showed that total amino acids（AA）and each of amino acids in femal parent were higher than that in male parent.The majority component of amino acids in F₁ progenies was theanine（THN,57%-75%）,followed by glutamic acid（Glu,7%-14%）,glutamine（Gln,4%-14%）,Arginine（Arg,2%-12%）,and aspartic acid（Asp,3%-5%）.Transgressive inheritance was observed in several F₁ progenies.The phenotypic values of components,including THN,AA,Glu,Gln,Asp in the F₁ population were approximately normal distribution,while Arg deviated slightly.Significant positive correlation was observed between each pair of traits.The highest correlation coefficient was between AA and Glu（r=0.732,p<0.01）,followed by AA and THN（r=0.661,p<0.01）.2.By using composite interval mapping method,a totoal of nineteen QTL for amino acids traits were detected on the genetic map.The QTL distributed on seven linkage groups（LG01,LG03,LG04,LG07,LG08,LG09,LG10）.Of them,six QTL were found on LG01,four on LG03,three on LG07,two on LG04 and LG09,one on LG08 and LG10,respectively.There were two QTL for AA,Asp,Glu and Gln,while four QTL for Arg.The explained phenotypic variance of each QTL varied from 11.1%-20.2%.Seven QTL were identified for THN,distributed on five linkage groups（LG01,LG04,LG03,LG09,LG10）.Among them,the smallest phenotypic variance was 8.4%,the largest was 11.7%.3.SNP in the TS and GS gene were identified in the parents and F₁ population by sequence alignment.A total of three SNP were found in TS,and SNP735 was verified to be heterozygous.However,there was no SNP detected in GS.SNP735 was subsequently transformed into derived cleaved amplified polymorphic sequence（d CAPS）marker and used for genotyping of polymorphism in the F₁ population.The results showed that the segregation ratio of alleles was close to 1:1.In addition,the d CAPS marker was then mapped between Marker4551 and Marker7860 on LG03 of genetic map.