The Validation Of QTL Related To The Timing Of Spring Bud Flush And Localization Candidate Gene In Tea Plant(Camellia Sinensis(L.)O.kuntze)

Tea plant?Camellia sinensis?L.?O.Kuntze?is an important economic crop with a long history of cultivation in China.According to the statistics of 2017,the planting area is more than about 293 hectares.As a woody crop with young sprouts as the object of harvest,the timing of spring bud flush of tea plant is conducive to environmental adaptation and cultural value.In tea producing areas with warm winter,the early-growing tea varieties have longer growing times and longer spring tea harvesting periods.Therefore,more prominent economic values can be created.Previously,it was reported two QTL?qTBF01-1 and qTBF01-2?related to the timing of spring bud flush based on'Longjing 43'×'Baihaozao',Located in tea tree LG01 linkage group,and a total of about 30%of phenotypic variation is explained.However,QTL effects of woody plants may vary greatly among different ages,environments and combinations,and the effect estimates are susceptible to population size.Therefore,the above QTL needs further verification.In this study,in order to determine its stability and applicability,the above QTL were validated by expanding the mapping population,at different plant ages,cultivation sites,and cross combinations.In addition,this study also mapped several candidate genes that may affect the germination period of tea plants.The main results are as follows:?1?In the previous study,genotype analysis and phenotype observation were performed on 157 individual strains remaining in'Longjing 43'×'Baihaozao'F₁population and combining the data from the previous 170 individual plants to form a larger population?n=327?.The results show that the PVE score of two QTLs is reduced by more than 30%.Then a random sampling of the'Longjing 43'×'Baihaozao'F₁ population?n=327?confirmed that the QTL effect was significantly affected by the population size.When the population reaches 150,the QTL with a detection effect of more than 10%can be basically guaranteed,but an accurate estimate of the QTL effect value cannot be achieved.The highest estimate may be 2-3 times higher than the minimum estimate.?2?Using MQM mapping,the above two QTL can also be detected in the crossing of'Wuniuzao'×'Longjing 43',but the effect of qTBF01-1 is relatively small.For'Longjing43','Baihaozao'and'Wuniuzao',QTL analysis of the three parent maps found that the above two QTL were only separated in'Longjing 43'and were not detected in the other two parents.It shows that the selection of parents is crucial for the detection and application of QTL.?3?In two cross populations of'Longjing 43'×'Baihaozao'?n=327?and'Wuniuzao'×'Longjing 43'?n=173?,the above QTL can be detected in different ages or in different cultivation environments.It was found that the PVE value had a large change of 26.2 to40.5%by IM mapping.The results indicated that QTL exists stably,but its expression is significantly affected by the environment or plant ages.?4?The DNA sequences closest to the two QTL markers was compared with the whole genome sequence of tea plant through local BLAST alignment,and 28 genes were found in the corresponding Scaffold sequence.This study also developed SSR markers through possible 8 candidate genes about CsFT,CsMADS-BOX1 related to the dormancy release of tea plants and their homologous genes,and genotype analysis and linkage localization were performed for a part of'Longjing 43'×'Baihaozao'population?n=56?.As a result,7 candidate genes were located,but none of them mapped to the confidence interval of the above two QTLs.The genotypes of individual genes showed a certain correlation with the timing of spring bud flush,but were not stable in different years.