| Chinese olive(Canarium album(Lour.)Raeusch),a evergreen fruit tree of the Burseraceae family and Canarium genus,is a characteristic fruit tree in Fujian Province with high economic value.In this study,mature fruits of 48 accessions collected from Chinese olive planting areas in Fujian were used as experimental materials to determine the content of lignin,soluble sugar,total phenol and flavonoid,and to study their correlation.The relationship between sugar,total phenol,flavonoid metabolism and lignin metabolism was analyzed using metabolomics,and the key metabolites of lignin synthesis were initially identified.The lignin of typical varieties of processing and fresh Chinese olive was analyzed by ultraviolet scanning and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance(2D-HSQC NMR)techniques.The differences in lignin composition between fresh and processing Chinese olive were analyzed,and the lignin metabolism pathway was determined to provide a research basis for elucidating the mechanism of the formation of quality differences in Chinese olive fruit and variety breeding.The main research results are as follows:1.The fruit quality indicators of 48 Chinese olive accessions were measured.The results showed significant differences in physiological indicators such as weight,horizontal and vertical diameter,fruit shape index,color difference,edible rate,and moisture content among the 48 Chinese olive varieties.The variety with the largest single fruit weight was ‘Huiyuan’ with an average weight of 13.81 g,while the smallest was‘Yangshibendizhong’ with an average weight of 4.15 g.The variety with the highest fruit shape index was ‘Qilichi’ with an average index of 2.19,while the variety with the lowest fruit shape index was ‘Huiyuan No.2’with an average index of 1.32.The variety with the highest color difference was ‘Matouzhong’ with an average color difference of 120.20°,while the variety with the lowest color difference was ‘Xiaxiben No.2’with an average color difference of 98.28°.The variety with the highest edible rate was ‘Pingyang No.2’ with an average rate of 84%,while the varieties with the lowest edible rate were ‘Zhejiangpingyanglan’,‘Dianbaiertoujianlan’ and ‘(Minqing)Changying’,all with an average rate of 72%.The variety with the highest moisture content was ‘Sanlenglan’with an average content of 85%,while the variety with the lowest moisture content was ‘(Minqing)Changying’ with an average content of76%.Among the 48 samples,significant differences were observed in the contents of flavonoids,total phenols,fructose,glucose,sucrose,lignin,cellulose,and hemicellulose in the fruit.The fruit of ‘Longxicun No.5’had the highest content of flavonoids(3.32 mg/g)and total phenols(19.9mg/g).The fruit of ‘Baihecun’ had the highest content of fructose(12.99mg/g),while ‘Xiaxiben’ had the highest content of glucose(10.64 mg/g)and sucrose(156.81 mg/g).The lignin content in the Chinese olive fruit peel and flesh is significantly higher than the cellulose and hemicellulose content.Among all the fruit flesh,the lignin content of ‘Xiaosanleng’ is the highest,at24.17 mg/g,and the highest cellulose content is found in ‘Lingfeng’,with an average of 0.395 mg/g.The highest hemicellulose content is found in‘Zilaiyuan’,with an average of 0.098 mg/g.The peel lignin content of‘Xiaxiben No.2’ is the highest,with an average of 53.20 mg/g,the highest cellulose content is found in ‘Pingyang No.2’,with an average of 0.491mg/g,and the highest hemicellulose content is found in‘(Minqing)Changying’ and ‘Xiaosanleng’,with an average of 0.194 mg/g.It can be seen that the content of lignin,cellulose,and hemicellulose in the Chinese olive fruit peel is significantly higher than that in the flesh.The correlation analysis showed that the content of fruit flesh lignin was significantly positively correlated with fruit peel cellulose,fruit flesh hemicellulose,fruit peel lignin,fruit peel hemicellulose,flavonoids and total phenols,and significantly negatively correlated with moisture content.The content of fruit peel lignin was significantly correlated with cellulose,fruit flesh hemicellulose,fruit flesh lignin,fruit peel hemicellulose,flavonoids and total phenols,and significantly negatively correlated with color difference and moisture content.Therefore,it is speculated that the metabolism of lignin in Chinese olive fruit is closely related to other metabolisms.2.Based on non-targeted metabolomics technology,the metabolites of three Chinese olive varieties,‘Meipu No.2’,‘Zilaiyuan’ and ‘Huiyuan’,were determined.The results showed that a total of 1050 metabolites belonging to 14 categories were detected in the positive and negative ion modes among the three varieties,with lipids,phenylpropanoids,and organic acids being the categories with the most significant differences in metabolites among the three varieties.By analyzing the metabolites of the phenylpropanoid pathway in the three varieties,it was found that the relative contents of pinosylvin,pinosylvin 2,syringin,5-hydroxy pinosylvinol,agmatine,verbascoside in ‘Meipu No.2’ were significantly higher than those in ‘Zilaiyuan’ and ‘Huiyuan’;the relative contents of2-hydroxy cinnamic acid,p-coumaric acid,and ferulic acid in ’Huiyuan’were significantly higher than those in ‘Meipu No.2’ and ‘Zilaiyuan’;the relative content of pinosylvin in ‘Zilaiyuan’ was significantly higher than that in ‘Meipu No.2’ and ‘Huiyuan’;the relative content of anethole in‘Zilaiyuan’ and ‘Huiyuan’ was significantly higher than that in ‘Meipu No.2’.The correlation analysis showed that scopolamine was highly positively correlated with flesh lignin(r=1.000**);verbascoside was significantly positively correlated with peel lignin(r=0.998*);p-coumaric acid was significantly negatively correlated with flesh lignin(r=-0.998*);indicating that p-coumaric acid,verbascoside,and scopolamine are key differential metabolites that affect lignin synthesis in Chinese olive.3.A method for the separation and purification of lignin from Chinese olive fruits was established,and the lignin from three cultivars‘Meipu No.2’,‘Zilaiyuan’ and ‘Huiyuan’,was analyzed using ultraviolet scanning and 2D-HSQC NMR techniques.The results showed that the main connecting method of the lignin structural units in the three cultivars was β-O-4’,followed by the β-β’ connecting method,which was associated with the content of syringyl structural units,while the β-5’connecting method was not found.The lignin in Chinese olive fruits was mainly composed of S-type lignin,followed by H-type and G-type lignin.The relative content of H,G,and S lignin in ‘Meipu No.2’ was 28.22%,19.31%,and 52.47%,respectively;in ‘Zilaiyuan’,it was 27.27%,18.16%,and 54.56%,respectively;and in ‘Huiyuan’,it was 14.15%,9.52%,and76.33%,respectively.The G/S ratios in ‘Huiyuan’,‘Meipu No.2’,and‘Zilaiyuan’ were 0.13,0.37,and 0.33,respectively,indicating that the differences in the connecting methods of structural units and the composition of different types of lignin components can affect the texture and quality of Chinese olive fruits. |
