| Litchi(Litchi chinensis Sonn)is a subtropical evergreen fruit tree of the genus Sapindaceae.Litchi flowers are abundant and each variety has its own unique fragrance.In order to study the volatile substances in different developmental stages of litchi flowers and the differences in floral aromas between varieties,this study selected 5 litchi varieties of ‘Chen Zi’,‘Shui Mi’,‘Jian Ye’,‘Zhu Mu Ru’ and ‘Da Zhao’.Male flowers and female flowers in the unopened,half-opened and full bloom stages were collected.The volatile substances in the litchi flowers were detected by HS-SPME and GC-MS.The main results are as follows: 1.A total of 43 volatile substances were detected in the litchi samples tested,which were mainly divided into 7 categories,namely terpenes,alcohols,benzene rings,alkanes,esters,aldehydes,ketones.Among them,the relative content and type of terpenes are the highest,with the highest 95.83%.α-Zingiberene and Humulene were detected at all developmental stages of the tested variety..α-Zingiberene is the highest content of volatile matter in litchi flowers.It has the highest content in the ‘Chen Zi’ female flower,which is 75.75%,but the content is very low at 0.6 different stages of ‘Shui Mi’.The Humulene is relatively low in the percentage of flowers in each variety.2.There were obvious differences between the variety and the state: β-myrcene,(E)-β-farnesene,δ-Selinene,δ-Elemene,germacrene,α-Zingiberene,and their relative percentages were higher.Among them,β-myrcene was only detected in two varieties of ‘Zhu Mu Ru’ and ‘Chen Zi’;(E)-β-farnesene was not detected in ‘Shui Mi’,but other four varieties existed;δ-Selinene is detected only in the two varieties of ‘Shui Mi’ and ‘Jian Ye’;δ-Elemene and Germacrene are higher in ‘ Shui Mi’,but detected in the ‘Chen Zi’ male flower in full bloom.3.The above six terpenoids with large differences among varieties showed different accumulation patterns in fruits.Among them,α-Zingiberene was detected in flowers and rich in content,but it was only detected in two fruit varieties,‘Chen Zi’ and ‘Shui Mi’.(E)-β-farnesene was not detected only in the ‘Shui Mi’litchi flowers,but was not detected in the fruits of the four litchi varieties.δ-Elemene andδ-Selinene were only detected in the flowers and fruits of ‘Shui Mi’.4.By analyzing the changes in the relative expression of TPS gene in different states of different litchi varieties,the results showed that the expression patterns of Lc TPS1,Lc TPS5 and Lc TPS10 were similar.The expression levels of Lc TPS1,Lc TPS5 and Lc TPS10 were higher in male flowers than female flowers,and the expression levels in half-open and fullbloom were higher than those in unopened stage.In addition to the ‘Jian Ye’ female flowers and the ‘Zhu Mu Ru’ male flowers,Lc TPS7 has the highest content of female flowers and male flowers in other varieties.The unopened stages of α-Zingiberene in ‘Chen Zi’and ‘Da Zhao’were higher than that of half-opened and full bloom stages;The relative percentages of Germacrene in the unopened ‘Chen Zi’ female flowers and male flowers and the unopened ‘Da Zao’ female flowers were higher than the half-opened stage,which was consistent with the trend of relative expression of Lc TPS7 in different litchi flowers.Therefore,it is speculated that Lc TPS7 may be involved in the synthesis of α-Zingiberene and Germacrene. |
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