## 2 Results
### Identification of Volatile Compounds  
GC-MS analysis is a popular and powerful technique to identify volatile compounds, and headspace solid-phase microextraction (HS-SPME) is more rapid, sensitive, efficient and solvent-free than conventional methods, including steam distillation and solvent extraction. Hence, a combined method of HS-SPME-GC-MS was carried out in this study to investigate the volatile components in different fruit tissues of R-HJH and wild-type HJH. The fruits were separated into two parts, i.e., flavedo and albedo. Supplementary Figure S1 shows the total ion chromatograms (TICs) of all samples. A total of 122 compounds that had more than 90% similarity with authentic standards of the NIST database were successfully identified in the volatile oil from the flavedo and albedo of R-HJH and wild-type HJH. Among these 122 volatile components, D-Imonene was the most abundant volatile component in all samples, followed by \(\upbeta\)-mrycene, \(\upgamma\)-terpinene and linaol.  
The results showed that the contents of different volatile components varied among the different tissues of the two species (Table 3). In the flavedo samples, the content of most volatile components decreased significantly in R-HJH compared to wild-type HJH, with a 33.4-86.5% reduction. The most significantly decreased volatile component was \(\upgamma\)-terpinene. The content of \(\upgamma\)-terpinene in the flavedo of R-HJH was decreased to approximately one-eighth that in wild-type HJH (124.34 \(\pm\) 18.61 \(\upmu\)g/mg vs. 917.96 \(\pm\) 78.94 \(\upmu\)g/mg). The content of limonene, which was the predominant compound, was reduced to less than one-third that in wild-type HJH. However, the amount of dodecannal in the flavedo was not significantly different between R-HJH and wild-type HJH (88.59 \(\pm\) 17.96 \(\upmu\)g/mg vs. 91.55 \(\pm\) 7.81 \(\upmu\)g/mg). In terms of the albedo, the volatile components of R-HJH showed a decreasing trend, which was consistent with that in the flavedo. Approximately 94%  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{
\begin{tabular}{c} **Total** \\ **Carotenoids** \\ \end{tabular} } & \multirow{2}{*}{**B-Carotene**} & \multirow{2}{*}{**Lutein**} & \multirow{2}{*}{**Zexanthin**} & \multirow{2}{*}{**Iycopene**} & \multirow{2}{*}{**B-Cryptoxanthin**} & \multirow{2}{*}{**\(\upGamma\)-Carotene**} & \multirow{2}{*}{**Phytoene**} \\ \cline{1-1} \cline{6-10} R-HJH Albedo & & & & & & & & \\ \hline HJH Albedo & & & & & & & & \\ \hline R-HJH & & & & & & & & \\ juice sacs & & & & & & & & \\ \hline HJH & & & & & & & & \\ juice sacs & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Carotenoids (\(\upmu\)g/g DW) in the albedo and the juice sacs of R-HJH and their corresponding wild type HJH.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **HJH** & **R-HJH** \\ \hline naringin & 55.81 \(\pm\) 2.48 & 38.76 \(\pm\) 1.82 \\ rhoifolin & 10.37 \(\pm\) 0.29 & 5.72 \(\pm\) 0.15 \\ isoimperatorin & 0.95 \(\pm\) 0.01 & 0.35 \(\pm\) 0.01 \\ bergapten & 0.33 & 0.24 \(\pm\) 0.01 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The content of flavone and coumarin (mg/g) in the whole fruit of R-HJH and HJH.  
of the volatile components notably declined in R-HJH compared to wild-type HJH, with a 32.1-87.1% reduction. The \(\alpha\)-pinene and D-limonene contents in the albedo of R-HJH decreased to one half that of wild-type HJH. \(\beta\)-myrcene, \(\alpha\)-muroulene and \(\gamma\)-muroulene were detected in the albedo of wild-type HJH but not in the albedo of R-HJH.