## 4 Discussion  
Using HS-SPME collections and GC-MS analyses, 58 volatile compounds were identified from lychee, of which 44 were terpenoids (Table 1). There were large quantitative and qualitative differences in the blend of volatiles released from distinct plant tissues (B1-B4) and among plants with varying LEM infestation levels (A1-A5). Un transfected field-collected samples obtained from floral buds (B1), open flowers (B2), leaf buds (B3), and new leaf shoots (B4) had 30 unique compounds, mostly terpenoids (Table 1, Figure 2), that were not detected in LEM infested lychee plants. The PCA analysis applied based on the GC-MS data from samples B1 to B4 showed that these plant tissues can be clustered in two groups (Figure 4). The sesquiterpenes \(\alpha\)-zingiberene, \(\alpha\)-curcumene and \(\beta\)-caryophyllene were the most important volatiles separating floral buds (B1), leaf buds (B3) and new leaf shoots (B4) from the open flowers (B2). Although sesquiterpene hydrocarbons were the most abundant compounds detected in these plant tissues, the monoterpene alcohol linalool and its _cis_- and _trans_-linaloal oxides were only detected in open flowers (B2). The monoterpene hydrocarbons \(\alpha\)-thujene, \(\alpha\)-pinene, sabinene and (E)-\(\beta\)-ocimene were present in higher quantities in the floral buds (B1) and open flowers (B2) than in the other plant tissues. The sesquiterpene hydrocarbons \(\beta\)-caryophyllene and \(\alpha\)-zingiberene were mostly detected in leaf buds (B3) and new leaf shoots (B4). In agreement with our findings, previous studies have also found that the most abundant compounds present in lychee samples were terpenoids. [PERSON] et al. (2016) identified 43 volatiles in lychee fruit from nine lychee cultivars and found remarkable qualitative and quantitative differences among cultivars. Nonetheless, lychee cultivars held different terpene profiles that played an important role in discriminating them. For instance, only 11 terpenids were found in 'Xiangli' and 'Jizuili', while 'Guangxi Huaizhi' and 'Guangdong Huaizhi' had 30 and 27 terpenoids, respectively. Linalool, _cis_-rose oxide, \(\alpha\)-terpineol, \(\beta\)-citronello, geraniol, and \(p\)-cymene were identified in all lychee cultivars, while \(\alpha\)-copaene and _cis_-pyran linalool oxide were found only in 'Nuomici' and 'Guiwei', respec  
Figure 11: Preference of LEM to the volatile compound sabinene and its solvent ethanol (control), in a dual-choice experimental unit. Panel shows all eight Sabinene concentrations tested: 3%, 5%, 7%, 10%, 25%, 50%, 75% and 100%. Numbers inside bars represent number of replicates; GLMM: \({}^{*}\)\(p<0.05\); \({}^{**}\)\(p<0.01\), \({}^{***}\)\(p<0.001\); ns, not significant. Bars indicate proportion (\(\pm\)SE) of mites reaching the end section of the slide towards sabinene and ethanol in 24 h.  
tively. Besides terpenoids, they also found ester aldehydes and alcohols in less abundance. By using a solvent-assisted flavor evaporation (SAFE) coupled with gas chromatography-olfactometry/mass spectrometry (GC-O/MS), [PERSON] et al. [45] identified 31 volatiles in lychee fruit with methional, geraniol, furaneol, nerol and linalool pointed as the most abundant compounds. Similarly, [PERSON] et al. [52] reported alcohols and terpenoids as major components of lychee, and [PERSON] et al. [53] reported that nearly all the volatiles from lychee fruit cv. Mauritius and McLean's Red were terpenoids or derivatives. Nerol, citronello1, geraniol, linalool, limone, terpinolene, myrcene, germacrene D, \(\beta\)-ocimene, \(\beta\)-myrcene, \(\alpha\)-muurolene and curcumene were the compounds identified as responsible for the characteristic odor of 'Mauritius' fruit [47; 53]. By using simultaneous distillation extraction (SDE), [PERSON] et al. [48] extracted 13 terpenoids, 3 aldehydes, 1 acid, 2 alcohols and 1 ester from young and old lychee leaves. Major terpenoids found were zingiberene, trans-caryophyllene, \(\alpha\)-sesquiphellandrene, \(\alpha\)-humulene, \(\alpha\)-bergamotene and \(\alpha\)-copaene.