## 3 Results and Discussion
### Correlation Analysis between E-Nose and HS-SPME/GC-MS  
HS-SPME/GC-MS mainly focuses on the identification and quantification of a single substance and is highly sensitive and accurate. However, its high operating cost and required personnel input limit its widespread practical application in agriculture [49]. E-nose is economical, fast, non-destructive, and capable of batch analysis. According to the results of HS-SPME/GC-MS, the content of volatile compounds in _C. fimbrata_-infected sweetpotatoes changed greatly from 40 to 72 h due to the proliferation of _C. fimbrata_. Therefore, a correlation analysis between E-nose and HS-SPME/GC-MS from 40 to 72 h was performed, and the results are shown in Figure 7. Table S1 showed the reported sensitive substance of the sensor array in E-nose. Sensors S1 (r = 0.62, \(p<0.05\)) and S3 (r = 0.63, \(p<0.05\)), which were reported to be sensitive to organic solvents, showed high correlations with aldehydes. S5 (r = 0.72, \(p<0.05\)), S8 (r = 0.94, \(p<0.05\)), and S9 (r = 0.61, \(p<0.05\)), which were reported to be sensitive to alkanes, also showed correlations with alkanes in this study. S11 was reported to be sensitive to volatile organic compounds, and its correlation with aldehydes, alkanes, alkenes, ketones, and esters was 0.85, 0.80, 0.72, 0.68, and 0.71, respectively, in the present study. S6 was reported to be sensitive to alkanes, but we found that it also had a high correlation with aldehydes (r = 0.97, \(p<0.05\)) and alcohols (r = 0.85, \(p<0.05\)). Although the volatile compounds, including ammonia, amine series, and organic sulfur, were not detected by HS-SPME/GC-MS, sensors S2 and S12 showed responses to these substance in sweetpotatoes. Simultaneously, S2 and S12 had a high correlation with other volatile compounds in sweetpotatoes. The correlations between S2 and aldehydes, aldehydes, alkanes, alkenes, ketones and esters were 0.89, 0.78, 0.76, 0.71, and 0.73, respectively. The correlations between S12 and aldehydes, aldehydes, alkanes, alkenes, ketones, and esters were 0.83, 0.82, 0.71, 0.69, and 0.73, respectively. S4, S7, and S10 had low correlations with various volatile compounds. These three sensors were reported to be sensitive to freon and hydrogen, but these two volatile compounds were not detected by HS-SPME/GC-MS. So, then, the sensors (S4, S7, and S10) showed low correlations with freon and hydrogen in the present work.  
Figure 6: Response of 12 sensors to volatile compounds in sweetpotatoes.  
Our results indicated that the sensors of E-nose were not only responsive to the specific gases provided by the company standard but were also responsive to other volatile components. The response signals of the sensors showed good correlations with volatile compounds detected by HS-SPME/GC-MS in this study, so that the detection results of E-nose could reflect the changes in volatile components in C. _fimbriata_-infected sweetpotatoes accurately. In addition, compared with a single sensor, E-nose, which is composed of a sensor array, can reflect the changes in sweetpotato volatile components more accurately and comprehensively, which further enhances the reliability of the detection results.