## 3 Discussion  
Although the screening of a BCA's sources mainly focuses on the rhizosphere and rhizplane soil, there has been increasing interest over the last few years in using bacterial endophytes as biological control agents [27]. The endophytic strain ETR-B22 isolated from _S. tonkinensis_ was identified as _B. cenocpacia_, which belongs to _B. cepacia_ complex (BCC) [28]. Bcc occupy a surprisingly wide range of ecological niches and have useful biotechnological potential associated with biological control, plant growth promotion and degradative agents of aromatic pollutants [29; 30; 31]. Here, we focused on the broad spectrum of ETR-B22 against plant pathogenic fungi, including nine genera and twelve species. Previous research on biological control agents based on _B. cenocpacia_ has been reported in several plant diseases and reached the stage of commercialization [32]. However, the antifungal activity of _B. cenocpacia_ against _Magnaporthe oryzae_, _A. Aspergillus niger_, _Bipolaris sorokiniana_, _Helmitthosporium torulosum_, _Mycosphaerella fijensis_ and _Phyllosticta zingiberi_ has not been reported. Specifically, ETR-B22 exhibited significant antagonistic activity against _M. oryzae (77.5% suppression), which is a destructive pathogen that threatens cultivated rice. Thus, compared with other _B. cenocpacia_ strains used against plant fungal pathogens that have been reported [33; 34], ETR-B22 exhibits a stronger antifungal effect against a broader spectrum of fungal pathogens. Our study further highlights the potential role of _B. cenocpacia_ ERT-B22 as a biological agent for controlling plant pathogenic fungi. The volatile organic compounds produced by biocontrol bacteria attract wide attention for their antifungal effects against several important fungal phytopathogens. Compared with non-volatile antifungal substances, bacterial VOCs have some significant benefits: they have smaller molecules,  
\begin{table} \begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Compound**} & \multicolumn{6}{c}{**Inhibition Rate (\%)**} \\ \cline{3-8}  & & **Aa** & **An** & **Bc** & **Bs** & **Fs** & **Fo** \\ \hline
1 & Dimethyl trisulfide & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) \\
2 & Allyl benzyl ether & \(66.87\pm 2.91\) & \(34.55\pm 4.14\) & \(86.71\pm 0.58\) & \(67.18\pm 0.59\) & - \\
3 & Methyl benzoate & \(89.42\pm 1.45\) & \(67.15\pm 3.23\) & \(100\pm 0.00\) & \(84.26\pm 0.36\) & \(25.68\pm 0.82\) & \(67.77\pm 0.25\) \\
4 & Benzyl acetate & \(75.76\pm 1.86\) & \(81.19\pm 2.47\) & \(91.28\pm 0.27\) & \(76.27\pm 0.52\) & \(22.57\pm 0.44\) & \(53.85\pm 2.03\) \\
5 & Methyl salicate & \(100\pm 0.00\) & \(76.23\pm 2.92\) & \(100\pm 0.00\) & \(87.19\pm 1.46\) & \(40.42\pm 4.27\) & \(100\pm 0.00\) \\
6 & Benzyl propionate & \(77.91\pm 2.38\) & \(52.28\pm 1.14\) & \(92.23\pm 0.25\) & \(100\pm 0.00\) & \(32.26\pm 1.29\) & \(82.45\pm 1.14\) \\
7 & Nonanoic acid & \(80.82\pm 1.94\) & \(47.18\pm 1.54\) & \(83.28\pm 1.89\) & \(48.03\pm 1.10\) & - & - \\
8 & Indole & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) & \(100\pm 0.00\) \\
9 & Methyl anthranilate & \(82.07\pm 2.47\) & \(76.56\pm 1.20\) & \(88.27\pm 0.72\) & \(79.24\pm 1.23\) & \(55.17\pm 1.14\) & \(70.25\pm 0.77\) \\
10 & 3-5-Di-tert-butylpen & \(78.33\pm 4.05\) & \(71.61\pm 0.71\) & \(87.67\pm 1.39\) & \(75.84\pm 1.67\) & \(53.18\pm 0.73\) & \(68.09\pm 0.95\) \\
11 & 3-Hexen-1-ol, & & \(7.90\pm 2.25\) & - & \(17.94\pm 1.29\) & - & - & - \\
12 & 2-Pentadecanone & - & - & - & \(16.36\pm 1.98\) & - & - \\
13 & Dodecanamide & - & - & - & \(14.95\pm 1.24\) & - & - \\
14 & Benzyl benzoate & - & 24.62 \(\pm\) 1.98 & - & - & - & - \\ \hline \hline \end{tabular}   
* **No.