The Origin Of Pink-fruited Mountain Ash In Tuoliang Mountain And Determination Of Fruit Composition

Previous studies disclosed that both Sorbus pohuashanensis and S.discolor can be the female parents of the pink-fruited mountain ash,which were found in the sympatric area of S.pohuashanensis and S.discolor in northern China.But there is no definite conclusion to if the pink-fruited mountain ash was consequences of the interspecific hybridization between S.pohuashanensis and S.discolor.In this study,S.pohuashanensis,S.discolor and the pink-fruited mountain ash in Tuoliang mountain were chose to explore the origin of the pink-fruited mountain ash by comparing morphological and molecular biological methods(fragments of chloroplast genome,low-copy fragments of nuclear genome and n SSR)in order to obtain a deep insight of the evolution of the pink-fruited mountain ash and its phylogenetic relationship with S.pohuashanensis and S.discolor.In addition,chemical extraction and liquid chromatography were used to determine the nutrients,medicinal substances and their basic composition of the fresh pink fruits to lay a foundation for the development and utilization of its resources.Results are as follows:1 Analysis of comparative morphologyThe pink-fruited mountain ash showed intermediately morphological characteristics between S.pohuashanensis and S.discolor,slightly more similar to S.pohuashanensi.In addition to the color of fruits could clearly distinguish the three Sorbus,pubescent on the winter buds,twigs and leaf blades could clearly discriminate S.discolor from S.pohuashanensis and pink-fruited mountain ash.Quantitative traits indicated that morphological quantitative traits of most of the pink-fruited mountain ash were between the corresponding quantitative traits of S.pohuashanensis and S.discolor.The principal component analysis showed that the pink-fruited mountian ash trees were scattered between S.pohuashanensis and S.discolor,with a slight phenotypically close to S.pohuashanensis.2 SSR markers of nuclear genomeThe gene flow between S.pohuashanensis and S.discolor was obvious as high as 0.609 based on 15 SSR markers.The results of PCo A revealed that all the individuals of S.discolor were clearly clustered together,while the the individuals of S.pohuashanensis were also clustered but relatively scattered and the pink-fruited mountain ash were clustered together with part of the individuals of S.pohuashanensis.The genetic component of the pink-fruited mountain ash was from both S.discolor and S.pohuashanensis disclosed by the results of STRUCTURE analysis,confirmed that the pink-fruited mountain ash were likely to be the product of interspecific hybridization.3 Analysis of cpDNA fragmentsThere were 20 variation sites in 4 cpDNA fragments,and a total of 20 haplotypes were identified in the pink-fruited mountain ash,S.discolor and S.pohuashanensis.There were 1 haplotype in S.discolor,13 haplotypes in S.pohuashanensis,and 10 haplotypes in pink-fruited mountain ash.In addition to 6 individuals of pink-fruited mountain ash had its private haplotpes,4 individuals of the pink-fruited mountain ash shared haplotypes with S.discolor and S.Pohuashanensis.This implied that S.discolor and S.pohuashanensis both can be the female parents of the pink-fruited mountain ash.4 Analysis of low-copy fragment of nuclear genomeThere were 23 variation sites in the 5 low-copy fragments in the pink-fruited mountain ash,S.discolor and S.pohuashanensis.The consistency of S.discolor was relatively high being identified only one haplotype H1,and highly homozygous without heterozygous loci.The diversity of S.pohuashanensis and the pink-fruited mountain ash were higher than that of S.discolor.Among them,there were 8 haplotypes of S.pohuashanensis: H2–H7,H14–H15.The pink-fruited trees contained 8 haplotypes: H3,H8–H15.The same as S.pohuashanensis,some individuals of the pink-fruited mountain ash were homozygous,and some individuals were heterozygous.In addition,specific haplotypes were identified in the pink-fruited mountain ash.5 hybridogenous origin of the pink-fruited mountain ashComprehensive analysis of morphological analysis and cpDNA fragments,low-copy nuclear genes and SSR marker of nuclear genome showed that the pink-fruited mountain ash was the result of interspecific hybridization between S.discolor and S.pohuashanensis,and both S.discolor and S.pohuashanensis can be female parents.There were 4 mating types of hybrid origins of 10 pink-fruited mountain ash trees.(1)Natural simple hybridization between female parent?S.discolor and male parent–S.pohuashanensis leaded to first filial generation F1?1 pink-fruited mountain ash;(2)Natural simple hybridization between female parent? S.pohuashanensis and male parent–S.discolor leaded to first filial generation F1?1 pink-fruited mountain ash;(3)2 pink-fruited mountain ash trees originated from multiple hybridization between the female parent of S.pohuashanensis and the male parent of S.discolor integrated with backcross with S.pohuashanensis;(4)The female parents of 6 pink-fruited mountain ash trees were undefined6 Determination of fruit composition of the pink-fruited mountain ashCompared with the other two Sorbus,the content of soluble sugar,vitamin C and flavonoids in the fresh fruits of the pink-fruited mountain ash were significantly higher,while the other substances were relatively lower.Therefore,the pink-fruited mountain ash can be recommended for research on health care products,food additives,animal fodder,and medicines.