## 3 Results and Discussion
### VOC Extraction and Gas Chromatographic Analyses  
The VOCs produced by _P. kluyveri_ and _S. pyralidae_ were shown to play a significant role in inhibiting _B. cinerea_ growth during in vitro trials (Figure 7). The VOCs produced by _P. kluyveri_ and _S. pyralidae_ were analysed using solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS), identifying a total of 29 compounds, of which seven were consistently present across all replicates. The key compounds included alcohols (isobutanol, isoamyl alcohol, 2-phenylethanol), esters (isoamyl acetate, 2-phenethyl acetate), gamma butylrolactone (\(\gamma\)-decanolactone), and a fatty acid methyl ester (methyl palmitate) (Table 4). These VOCs were produced by the yeast isolates alone or in conjunction with _B. cinerea_. Notably, isoamyl alcohol, 2-phenylethanol, 2-phenethyl acetate, and methyl palmit were also detected when _B. cinerea_ was cultured independently. _Subunyces porralidae_ produced all seven VOCs in monoculture, with isobutanol, isoamyl acetate and 2-phenethyl acetate concentrations slightly elevated in the presence of _B. cinerea_. These VOCs, particularly isobutanol, isoamyl acetate, and 2-phenethyl acetate, are likely contributors to the inhibition of _B. cinerea_, aligning with findings of [PERSON] et al. (2019) who reported isoamyl acetate's antagonistic effects against grey mould on blueberries. Further,  
Figure 7: Growth inhibition activity (expressed as a percentage) of five yeasts (details listed in Table 2) and Captain (Cap), a commercial fungicide against _Botrytis cinerea_ B05.10 (**A**), IWBT-FF1 (**B**), and PPRI 30807 (**C**) based on volatile organic compound production. Values are means of three replicates and the standard deviations are also shown. Different letters indicate significant differences (\(p\leq 0.05\)). The negative control treatments only contained the respective moulds and were the references for determining growth inhibition. [PERSON] et al. [51] demonstrated the antifungal efficacy of isoamyl acetate against _B. cinerea_ mycelial growth, and _Hanseniaspora uvarum_ effectively controlled _B. cinerea_ in strawberries and cherries, with 2-phenylethyl acetate identified as the predominant VOC [52]. Phenylethyl acetate has also shown strong inhibitory activity against _Aspergillus ochraceus_ and _Mucor_ spp. growth [49; 53]. When co-cultured with _B. cinerea_, _S. pynralidae_ produced slightly lower levels of isoamyl alcohol and 2-phenylethylanol, yet these VOCs continued to contribute to its antagonistic effect. [PERSON] et al. [54] reported complete inhibition of _B. cinerea_ growth in vivo by isoamyl alcohol, with additional studies by [PERSON] et al. [31] and [PERSON] et al. [51], linking isoamyl alcohol and 2-phenylethylanol to _B. cinerea_ inhibition. The observed inhibition of _B. cinerea_ may be due to the combined or synergistic effects of VOCs produced by _S. pynralidae_. _Pichia fluyveri_, when cultured alone, produced high concentrations of isoamyl acetate and 2-phenethyl acetate; however, these levels significantly decreased when co-cultured with _B. cinerea_. Lower concentrations of isoamyl alcohol and 2-phenylethylanol were also observed in co-culture, yet these VOCs may still be central to _B. cinerea_ suppression. Previous research on biocontrol yeasts, such as _P. kudriavzevii, P. occidentalis, W. anomalous, H. uvarum_, and _C. intermedia_, demonstrates that VOCs effectively inhibited _B. cinerea_ spore germination and mycelial growth [14; 49; 55; 31]. Ethanol and 2-phenylethylanol are specifically highlighted as potent antifungal agents against _B. cinerea_ and _Alternaria alternata_[56; 57]. Additionally, transcinnamaldehyde has shown to inhibitory effects on _B. cinerea_ mycelial growth and conidia germination, significantly reducing infections in cherry tomatoes [58]. VOCs such as 3-methyl-1-butanol, 2-phenylethanol, 2-ethyl-1-hexanol, 4-methyl-ethyl ester, and ethyl acetate have also been identified as effective in inhibiting _B.