Genetic Diversity Analysis Of Cultivated Tomatoes And Construction Of S.Pimpinellifolium LA2093 Introgression Lines

With the expansion of tomato(Solanum lycopersicum L.)cultivation scale and the rising variety of customer’s demand,the breeding of new tomato varieties is becoming more and more important.Rich germplasm resources are the basis for creating new varieties.Therefore,it is necessary to collect germplasm resources extensively,evaluate and screen for existing germplasm resources,and create new germplasm.The genetic diversity analysis of existing germplasm resources is extremely important for the selection and effective utilization of germplasm resources.Simultaneously,The construction of introgression lines is an effective way to create new tomato germplasm.In this study,in order to analysis the genetic diversity of cultivated tomatoes and use wild tomato to create new germplasm resources,the following studies were mainly carried out:(1)Genetic diversity among 96 cultivated tomatoes from home and abroad were analyzed 41 molecular markers.And ten phenotypic traits were then used to further analyze the genetic diversity of 88 cultivated tomatoes and a batch of excellent germplasm resources were obtained by selection.(2)The excellent cultivated tomato ’Jina’(S.lycopersicum)from the previous result was selected as the recipient parent,and wild tomato LA2093(S.pimpinellifolium)was used as the donor parent.The genetic linkage map was constructed in the BC1F1 generation.Based on this map,a set of introgression lines containing the segment from LA2093 with the genetic background of ’Jina’ was constructed by backcross,selfing and molecular marker-assisted selection.Then the BC3F1 population was used to detect QTLs related to inflorescence-related traits in tomato.The main findings are as follows:1.The results of genetic diversity analysis based on the molecular marker showed that,the genetic distance between 96 cultivated tomato germplasm resources ranged from 0.012 to 0.728.Through the analysis of cluster and genetic structure,96 cultivated tomatoes were divided into three groups.The two division results are similar.Based on the phenotypic traits,the coefficient of variation of different traits ranged from 21.79%to 99.03%in 88 cultivated tomatoes.Material variation is abundant.The correlation analysis showed that there were correlation among 10 phenotypic traits,especially for the fruit traits was extremely significant.Through the principal component analysis,we extracted three principal components,and the cumulative contribution rate reached 71.65%.Cluster analysis showed that 88 cultivated tomatoes were divided into three groups when the Euclidean distance was 4.877.The two results indicated that some cultivated tomatoes from different countries have a similar genetic background.There is no direct relationship between the taxonomic division of cultivated tomato germplasm resources and their geographical origin.Through the cluster analysis of molecular markers and phenotypic traits,three tomato varieties with good comprehensive traits and distant genetic distance from other cultivated tomatoes were selected,named ’Jina’,’Double Color Small Tomato’ and ’Huang Luomanri’.2.The excellent cultivated tomato ’Jina’(S.lycopersicum)was used as the recipient parent,and the wild tomato LA2093(S.pimpinellifolium)was used as the donor parent.A total of 189 co-dominant polymorphic markers which contained 168 InDel markers and 21 SSR markers were screened from 597 InDel markers and 200 SSR markers.The polymorphism ratio was 23.71%.These polymorphic primers were used to genotype 141 individual plants in the BC1F1 population.Then a genetic map of 158 polymorphic markers which contained 137 InDel markers and 21 SSR markers was constructed through Joinmap4.0.There are 12 linkage groups in the map,which correspond to 12 chromosomes of tomato.And the average genetic distance is 7.87 cM in this map.3.The excellent cultivated tomato ’Jina’(S.lycopersicum)was used as the recipient parent,and the wild tomato LA2093(S.pimpinellifolium)was used as the donor parent.Through hybridization,three-time backcrossing and marker-assisted selection,a set of introgression lines were constructed.Those introgression lines have the genetic background of cultivated tomato ’Jina’ with the segment from LA2093.From the genetic map constructed by the BC1F1 population,96 InDel and SSR molecular markers which uniformly distributed on the 12 chromosomes were selected to track the infiltrated segments of LA2093.Subsequently,14 single-segment introgression lines,26 double-segment introgression lines and 10 three--segment introgression lines were obtained in the BC3 generation.A total of 96 introgression segments were obtained,and the average length of a single introgression segments was 35.68 cM.Each introgression line contained an average of 5.6%of the donor gene in 50 introgression lines.They overlapped and covered 100%of the wild tomato genome.After the genome-wide detection of each generation,the proportion of LA2093 segments in the donor genome was reduced by theoretical values of 50%,25%,and 12.5%to 42.0%,21.3%,and 5.6%in BC1,BC2,and BC3 generations.The efficiency of the selection has been greatly improved.4.Using the BC3F1 population which was constructed with wild tomato LA2093(S.pimpinellifolium)as the donor parent and the cultivated tomato ’Jina’(S.lycopersicum)as the recipient parent,6 QTLs were detected for 3 agronomic traits including the node blow the first inflorescence,the node of interval inflorescence and number of flowers per inflorescence by WinQTLcart2.5 software with the method of composite interval mapping method.These QTLs were mapped on chromosomes 1,2,4,6,9,and 12,respectively.Among them,there were 3 QTLs related to the node of interval inflorescence,2 QTLs related to the node below the first inflorescence,and 1 QTL related to the number of flowers per inflorescence.The contribution rate for a single locus was about 4.33%to 47.93%.