Potential volatile markers of brown rice infested by the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Volatile Byproducts of Carotenoid Degradation as Biomarkers of Maize Infestation by the Maize Weevil (Sitophilus zeamais) (Motsch.)

Maize (Zea mays) is a major global food crop and a source of industrial raw materials. Effective postharvest storage is important for national food security programs, international trade, and global agriculture economics. The maize weevil (Sitophilus zeamais) is a primary postharvest insect pest that infests maize during storage and leads to significant losses. Using multivariate discriminant analysis of volatile profiles collected from intact and infested maize, we identified two volatile apocarotenoids, 6-methyl-5-hepten-2-one and 6-methyl-5-hepten-2-ol, as indicators of maize weevil infestation in stored maize. Emission of these biomarker compounds rapidly signaled maize weevil infestation and showed a significant correlation with oviposition damage to the stored kernels. The pattern of elevated biomarker emission after weevil exposure was consistent across all seven maize lines examined. These volatile biomarkers can be used for early detection and removal of infested maize and can aid in the control of this pest.

Comparative transcriptomic analysis and volatile compound characterization of Aspergillus tubingensis and Penicillium oxalicum during their infestation of Japonica rice

Volatile organic compounds (VOCs), a byproduct of mold metabolism, have garnered increasing interest because the VOCs can be used to detect food early contamination. So far, the use of VOCs as indicators of rice mildew, specifically caused by Aspergillus tubingensis and Penicillium oxalicum, and the mechanisms of their generation are not well investigated. This study examines the VOCs produced by these molds during paddy storage, utilizing headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). We further elucidate the mechanisms underlying the formation of these VOCs through a comparative transcriptomic analysis. The VOCs characteristic to A. tubingensis and P. oxalicum, identified with a VIP value > 1 in the partial least squares discriminant analysis (PLS-DA) model, are primarily alkenes. Our transcriptome analysis uncovers key metabolic pathways in both molds, including energy metabolism and pathways related to volatile substance formation, and identifies differentially expressed genes associated with alkane and alcohol formation.

Metabolomics analysis of physicochemical properties associated with quality deterioration in insect-infested hawthorn berries

The sliced and dried hawthorn berries are easily infested by insects during storage. This study aimed to determine the effect of insect infestation on the quality of hawthorn berries and assess the change at metabolite level by analyzing physicochemical property and metabolomics profiling. A total of 184 shared differential metabolites were obtained, mainly including flavonoids, fatty acids, carboxylic acids and derivatives, and nitrogenous compounds. Through receiver operating characteristic curve assessment, 9 significant differential markers were screened out to distinguish insect infestation of hawthorn berries. Correlation analysis showed that the color, total organic acids, total phenolics, and total flavonoids were effective indicators for quality evaluation of insect infestation, and uric acid and hippuric acid can serve as biomarkers for the quality deterioration of hawthorn berries during storage. This study demonstrated that insect infestation could decrease the quality of hawthorn berries from macro and micro perspectives.

Evaluation of five medicinal plants for the management of Sitophilus oryzae in stored rice and identification of insecticidal compound

Sitophilus oryzae is a kind of stored grain pest. This is controlled by using natural pesticides, which are more reliable, cost-effective, biodegradable, and eco-friendly than synthetic pesticides. Several plants show different insecticidal activities against various pests on their different parts (leaves, seeds, etc.). In this study, methanolic extracts of Lantana camara (leaves), Carica papaya (seeds), Ricinus communis (leaves), Calotropis gigantea (flowers), and Gliciridia sepium (leaves) were used to identify the best insecticidal activity against the rice weevil by doing mortality tests for one week with four replications under laboratory conditions. Gliciridia sepium leaves showed the highest insecticidal activity (100 ± 0) after seven days, and its extract was fractionated by using column chromatography and yielded 12 fractions. A contact bioassay of each fraction was performed, and fraction-11 showed the highest insecticidal activity against Sitophilus oryzae with a 100 % mortality after four days. Fraction-11 was analyzed by using GC-MS and FT-IR. Results revealed that the major constituent identified in fraction-11 was 4-C-methyl-myo-inositol. Therefore, 4-C-methyl-myo-inositol acts as a natural insecticide against rice weevils.

Early Detection of Fusarium Basal Rot Infection in Onions and Shallots Based on VOC Profiles Analysis

Gas chromatography ion-mobility spectrometry (GC-IMS) technology is drawing increasing attention due to its high sensitivity, low drift, and capability for the identification of compounds. The noninvasive detection of plant pests and pathogens is an application area well suited to this technology. In this work, we employed GC-IMS technology for early detection of Fusarium basal rot in brown onion, red onion, and shallot bulbs and for tracking disease progression during storage. The volatile profiles of the infected and healthy control bulbs were characterized using GC-IMS and gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS). GC-IMS data combined with principal component analysis and supervised methods provided discrimination between infected and healthy control bulbs as early as 1 day after incubation with the pathogen, classification regarding the proportion of infected to healthy bulbs in a sample, and prediction of the infection's duration with an average R2 = 0.92. Furthermore, GC-TOF-MS revealed several compounds, mostly sulfides and disulfides, that could be uniquely related to Fusarium basal rot infection.

The Effects of Genotype × Environment on Physicochemical and Sensory Properties and Differences of Volatile Organic Compounds of Three Rice Types (Oryza sativa L.)

Understanding the effects of genotype, environment and their interactions on rice quality is of great importance for rice breeding and cultivation. In this study, six rice varieties with two indica, two japonica and two indica-japonica types of rice were selected and planted at ten locations in Zhejiang Province to investigate the genotype (G) × environment (E) on physicochemical and sensory properties and the differences of volatile organic compounds (VOCs) among the three types of rice. Analysis of variances showed that apparent amylose content (AC), total protein content (PC), alkali spreading value (ASV), RVA profiles, and appearance (ACR), palatability (PCR), and sensory evaluation value (SEV) of cooked rice and texture of cooled cooked rice (TCCR) were mainly affected by genotypic variation, whereas the smell of cooked rice (SCR) was mainly affected by environment (p < 0.05). The G × E effect was significant for most parameters. The weather in the middle and late periods of filling had important effects on the formation of rice quality, especially on setback (SB) and pasting temperature (PT) (p < 0.01). They were negatively correlated with the texture of cooked rice (TCR) and SEV (p < 0.05). Peak viscosity (PV) and breakdown (BD) were positively related to the sensory evaluation parameters (p < 0.01) and could be used to predict cooked rice quality. A total of 59 VOCs were detected, and indica, japonica and indica-japonica had 9, 6 and 19 characteristic compounds, respectively. The principal component analysis showed that the physicochemical and sensory properties and VOCs of indica-japonica rice were more stable than those of indica and japonica rice at ten locations in Zhejiang Province. It is helpful for rice breeders to understand how the environment affects the physicochemical, sensory properties and VOCs of the three rice types, and it is also important for food enterprises to provide rice products with stable quality.