Genetic Diversity Of Processed Tomato Germplasm Based On SSR And Morphological Markers

Processed tomatoes are a type of common tomato that can be used as a raw material to make products such as tomato paste and tomato juice.China is the world’s second largest producer of processed tomatoes,with more than 40 years of industrial development,with tomato paste as the main product,as well as processed product types such as chopped,sun-dried and whole pack.However,there are still problems in the selection and breeding of new varieties of processed tomatoes in China,such as a narrow genetic base of germplasm resources,difficulty in breaking through resistance and few excellent germplasm resources.Therefore,in-depth excavation and research on existing germplasm resources of processed tomatoes will help to improve breeding efficiency,select more varieties with rich genetic background and excellent agronomic traits,and promote the sound development of the processed tomato industry in Xinjiang.In this thesis,35 processed tomato germplasm resources preserved by the processing tomato group of Shihezi University were selected for genetic diversity analysis using SSR molecular markers and morphological markers to clarify their relatives and to screen out germplasm resources with excellent comprehensive traits,providing a theoretical basis for the selection of parents in the selection of new varieties.The main findings of this study were listed below.1.Through the analysis of 27 agronomic characters of 35 processed tomatoes,it is obtained that there are great differences between different materials and different characters.The coefficient of variation for all phenotypic traits in this study was above 10%,with an average coefficient of variation of 26.2% and significant polymorphism for each trait,with the largest coefficient of variation for lycopene content at72% and the smallest coefficient of variation for first inflorescence node at 10%.Through comprehensive evaluation,the top five processed tomato germplasm materials were selected for their overall quality,which were DG-8,DG-6,JY-3,WS-2 and JY-1.2.According to the correlation analysis,fruit hardness and lycopene content and first inflorescence node were highly significantly negatively correlated,fruit shape index was highly significantly negatively correlated with the number of ventricles,highly significantly positively correlated with fruit hardness and fruit cross diameter,highly significantly positively correlated with soluble solids content and total soluble sugar content,and highly significantly positively correlated with the number of fruits per inflorescence and the number of flowers per inflorescence.3.By conducting principal component analysis on the traits,the percentage explained by each principal component was counted,and the cumulative contribution of the top 10 principal components reached 78.21%.Therefore,this experiment further extracted the top 10 principal components as new indicators,which were used to replace the 27 trait indicators and establish regression equations to simplify the calculation process and facilitate the progress of subsequent studies.4.Using the morphological data for clustering,the participating germplasm could be distinguished into four major groups at a genetic distance of 10.Cluster I contains 12 germplasm materials,mainly early maturing germplasm,with common leaf shapes,large fruit cross-sectional and longitudinal diameters and high fruit shape indices.Taxon II contains 13 germplasm material,mainly of the large-fruited type,with mostly red ripening colour,moderate hardness,high lycopene content,high soluble solids content and low titratable acid content.Taxon III has three germplasm materials with low lycopene content,a small,nearly round fruit size index,high fruit hardness and low soluble solids content.Taxon IV has 7 germplasm material with a high number of fruits per inflorescence and a concentration of fruit.5.Using SSR molecular markers,10 primers with high polymorphism and clear bands were selected from 100 random primers.61 bands were amplified from 10 pairs of primers,including 51 polymorphic bands,with a polymorphism rate of 83.6%.The Nei genetic distance between the germplasm was calculated using Pop Gene32 software in the range of 0.10-0.85.A systematic clustering map of the 35 processed tomato germplasm was generated using Power Marker software,which showed that the 35 processed tomato germplasm could be classified into five major groups at a genetic distance of 0.60.