Analysis of volatile compounds by GCMS reveals their rice cultivars

Due to the similarity in the grain and difference in the market value among many rice varieties, deliberate mislabeling and adulteration has become a serious problem. To check the authenticity, we aimed to discriminate rice varieties based on their volatile organic compounds (VOCs) composition by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography mass spectrometry (GC-MS). The VOC profiles of Wuyoudao 4 from nine sites in Wuchang were compared to 11 rice cultivar from other regions. Multivariate analysis and unsupervised clustering showed an unambiguous distinction between Wuchang rice and non-Wuchang rice. Partial least squares discriminant analysis (PLS-DA) demonstrated a goodness of fit of 0.90 and a goodness of prediction of 0.85. The discriminating ability of volatile compounds is also supported by Random forest analysis. Our data revealed eight biomarkers including 2-acetyl-1-pyrroline (2-AP) that can be used for variation identification. Taken together, the current method can readily distinguish Wuchang rice from other varieties which it holds great potential in checking the authenticity of rice.

Metabolomic study on the quality differences and physiological characteristics between rice cultivated in drought and flood conditions

The differences between dry- and flood-cultivated rice and the reason behind low-quality dry-cultivated rice were clarified. The physiological traits, starch synthase activity, and grain metabolomics of 'Longdao 18' were measured and analyzed at four growth stages. The brown, milled, and whole-milled rice rates and AGPase, SSS, and SBE activity were lower after drought treatment than during flood cultivation, while the chalkiness, chalky grain rate, amylose (16.57-20.999%), protein (7.99-12.09%), and GBSS activity were higher. Related enzymatic gene expression showed significant differences. Metabolic results showed pyruvate, glycine, and methionine upregulation at 8DAF and higher citric, pyruvic, and α-ketoglutaric acid content at 15DAF. Therefore, 8DAF-15DAF represented the crucial quality formation period for dry-cultivated rice. At 8DAF, the respiratory pathways used amino acids as signaling molecules and alternative substrates to adapt to energy shortages, arid environments and rapid protein accumulation and synthesis. Excessive amylose synthesis at 15DAF accelerated reproductive growth, promoting rapid premature aging.

Correlation between Irradiation Treatment and Metabolite Changes in Bactrocera dorsalis (Diptera: Tephritidae) Larvae Using Solid-Phase Microextraction (SPME) Coupled with Gas Chromatography-Mass Spectrometry (GC-MS)

The metabolites produced by the larvae of Bactrocera dorsalis (Diptera: Tephritidae) exposed to different doses of irradiation were analyzed using solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), and a metabonomic analysis method of irradiated insects based on GC-MS was established. The analysis revealed 67 peaks, of which 23 peaks were identified. The metabolites produced by larvae treated with different irradiation doses were compared by multivariate statistical analysis, and eight differential metabolites were selected. Irradiation seriously influenced the fatty acid metabolic pathway in larvae. Using the R platform combined with the method of multivariate statistical analysis, changes to metabolite production under four irradiation doses given to B. dorsalis larvae were described. Differential metabolites of B. dorsalis larvae carried chemical signatures that indicated irradiation dose, and this method is expected to provide a reference for the detection of irradiated insects.

Analysis of metabolites and metabolic pathways in three maize (Zea mays L.) varieties from the same origin using GC-MS

Metabolites of the Jinyu 88, Huanong 18, and Demeiya 9 maize varieties from the same origin were isolated and identified by GC–MS, and the specific metabolites and metabolic mechanisms of these three varieties of maize were preliminarily analysed and discussed. The metabolites were extracted with 80% methanol and derived with N,O-bis(trimethylsilyl)trifluoroacetamide. A total of 59 metabolites were identified. The specific metabolites of these three varieties of maize were identified. Four possible unknown-structure metabolites were hypothesized. The results showed that the specific metabolites of JY88 were only involved in fatty acid metabolism. The specific metabolites of HN18 were determined to be involved in fatty acid metabolism, glucose metabolism, and phytosterol metabolism. The specific metabolites of DM9 were observed to participate in glucose metabolism and fatty acid metabolism. The disease resistance of HN18 was higher than that of DM9, and its grain bulk density was higher than that of DM9. JY88 was determined to be significantly different from the other two varieties, and its appearance and disease resistance were worse than those of the other two varieties. The variety with the highest nutritional value was determined to be HN18, and the variety with the lowest nutritional value was JY88. This finding indicated that different maize varieties from the same origin had different metabolites and different metabolic mechanisms, which caused the three maize varieties to exhibit different characteristics and qualities.