Non-targeted screening and trimethylamine determination in Tilletia foetida-infected wheat using HS-SPME-GC-MS

Common bunt disease of wheat in China is caused mainly by Tilletia foetida. However, reliable approaches for determining disease-associated biochemical markers are rarely reported. Here, a headspace-solid-phase microextraction coupled with headspace GC-tandem mass spectrometry (HS-SPME-GC-MS) was used to screen volatile substances in infected wheat, and an optimal chemical marker was selected to establish analytical methods for disease determination. Non-targeted screening of 13 volatile compounds unique to diseased wheat allowed a metabolite with rotten fish-like smell, trimethylamine (TMA), to be selected as the inspection marker. Subsequently, two analytical methodologies, HS-SPME-GC-MS and headspace gas chromatography with flame ionization detection (HS-GC-FID), were established to determinate the TMA content in wheat. The linear relationship, recovery and reproducibility of the methods were validated. The limit of detection (LOD) was 0.02 µg/kg for the former method, 5000-fold lower than that for the latter. When analysing samples, HS-SPME-GC-MS showed excellent sensitivity and allowed for the determination of 0.05% infected kernels among whole wheat grains. Therefore, TMA determination using HS-SPME-GC-MS is an effective alternative method to detect wheat common bunt disease occurring at extremely low infection rate.