Jun Yu

Soil degradation poses a significant threat to agricultural sustainability. The integration of plant growth regulators (PGRs) with cover cropping systems r

Introduction: Tobacco flower buds play a crucial role in enhancing the aroma quality of cigar tobacco leaves (CTLs). By incorporating tobacco flower bud extract into the fermentation process, this study investigates its effects on microbial community dynamics and the volatile aroma compounds in CTLs, aiming to improve cigar flavor and quality during fermentation.Methods: To investigate the effects of tobacco flower bud extract on microbial communities and aroma quality during the fermentation of cigar tobacco leaves, volatile aroma components were evaluated using gas chromatography-mass spectrometry (GC-MS). The microbial community dynamics across different fermentation stages were analyzed using metagenomic sequencing.Results and Discussion: Results revealed that tobacco flower buds contain 23 characteristic aroma compounds, including β-ionone and phenylethanal. Notably, the extract induced a pronounced microbial shift, enriching Aspergillus in unfermented leaves and promoting Staphylococcus dominance (97%–98%) during fermentation. This shift facilitated carbohydrate and protein degradation, significantly reducing nicotine content (P < 0.001), increased total sugar (12.5%–18.75%) and reducing sugar levels (13.04%–27.27%), and optimized the potassium-to-chloride ratio. Aroma analysis demonstrated significant enrichment of carotenoid degradation products (farnesyl acetone, citronellal) and Maillard reaction products (5-methyl-2-furaldehyde) in the FE group, with total aroma content increasing by 11.9% compared to control (FW). Metagenomic functional analysis further indicated that the extract inhibited pathways related to harmful metabolite synthesis (47.0% reduction) and enhanced carbohydrate metabolism (30.6% increasing). This study confirms that tobacco flower bud extract reshapes microbial communities and metabolic networks by simultaneously suppressing harmful microbes and enhancing aroma, providing theoretical support for optimizing cigar fermentation and agricultural waste utilization.

Tobacco (Nicotiana tabacum L.) is a crucial Solanaceae crop globally, but its continuous cultivation can lead to soil degradation. Crop rotation offers numerous benefits, including enhanced soil fertility, improved microbial communities, and pest control. However, how different tobacco planting systems specifically reshape rhizosphere metabolite profiles and regulate microbial diversity remains unclear. Here, we analyzed soil samples from four tobacco cropping systems using non-targeted metabolomics, 16S rRNA and ITS sequencing. The results revealed distinct changes in soil metabolite profiles and microbial communities under different treatments. We identified significant alterations in lipid metabolism, amino acid biosynthesis, and secondary metabolite pathways, which influence soil microbial populations and tobacco plant health. Lipid metabolites, including fatty acids and eicosanoids, were particularly notable for their roles in microbial signaling and plant defense. Furthermore, microbial gene abundance analysis indicated that different treatments fostered unique microbial populations, including increased arbuscular mycorrhizal fungi and saprotrophic fungi, which support nutrient cycling and plant growth. These findings highlight the critical interplay between soil metabolites, microbial diversity, and plant productivity, offering insights into optimizing tobacco cropping systems for improved soil health and sustainable agricultural practices.

Tobacco Fusarium root rot is caused by various Fusarium species, with eleven species reported, among which F. oxysporum and F. solani are main responsible in China (Yang et al., 2024). Notably, Fusarium concentricum has not been previously reported until now at a global level in tobacco. In June 2022, tobacco (Nicotiana tabacum L.) root rot symptoms were observed in tobacco fields (approximately 1500 m2) in Xuanen County, Enshi City, Hubei Province (29.99°N, 109.44°E). About 20% of tobacco plants showed symptoms including dwarfing of plants, chlorosis in the lower leaves and black roots or root rot, and some plants had died. The roots of twenty diseased tobacco plants were randomly collected from this field and subjected to surface sterilization with 75% ethanol for 5 min and 1% sodium hypochlorite for 5 min, followed by rinsing with sterile distilled water. The roots were then cut into small pieces (around 0.5 cm), placed onto potato dextrose agar (PDA) medium, and incubated at 28℃ in darkness for 3 to 5 days. Three representative isolates 40-LD, 41-LD and 42-LD with typical Fusarium spp. characters were obtained using single-spore purification method (Xiao et al. 2023). After 4 days of culture at 28°C on PDA, the colonies were circular, and by the next day, they began to produce red pigment. On the seventh day, the pigment turned purple, and the mycelium appeared cottony and wool-like. On PDA, microconidia were obovate to fusoid, with the size of 4.6 to 8.7×1.6 to 2.9 μm (n=50), 0 or 1 septate. Macroconidia observed on synthetic low nutrient medium (SNA) were falcate, with the size of 13.6 to 41.7×2.9to 4.8 μm (n=50), 3 to 5 septa. The morphological characteristics of the fungi were consistent with the description of Fusarium species(Liu et al. 1998). The internal transcribed spacer region (ITS) of rDNA, the elongation factor 1α (TEF-1α), and RNA polymerase II second largest subunit (RPB2) of the isolates were amplified using primers ITS1/ITS4(Kim and Choi 2020), EF-1H/EF-2T (Wang et al. 2013) and RPB2-5F/RPB2-7CR(Qiu et al. 2023). The obtained ITS (PQ056894), TEF-1α (PQ118393), and RPB2 (PQ329359) sequences showed 99.6% (490/514 bp), 99.7% (667/667 bp), and 100% (940/940 bp) similarity to F. concentricum NFMJ-1 (GenBank accession nos. ON184033, ON212051 and ON212052, respectively)(Xiao et al. 2023). A maximum likelihood phylogenetic tree, constructed by concatenating ITS, TEF1-α and RPB2 sequences using ACOPTools v2 software, showed the three isolates and F. concentricum were clustered into one branch. Pathogenicity was assessed by coculturing potted tobacco plants with 42-LD-infected wheat grains (Shen et al. 2023). Strain 42-LD was inoculated onto sterilized wheat grains and cultured at 28℃ for 7 days. Subsequently, the roots of ten healthy seedlings of Yunyan 87 at the 4-leaf stage were wounded with sterile scissors and then transplanted into sterile soil containing 30 wheat grains infected with 42-LD. In contrast, the wheat grains without 42-LD inoculation were used as controls. All seedlings were placed in a greenhouse at 25°C with 16 h of light and 8 h of darkness. Seven days later, all seedlings inoculated with 42-LD showed symptoms of yellowing and wilting of leaves, blackening of roots, and slow plant growth, while control plants showed no symptoms. The pathogenicity test was repeated three times. The pathogens reisolated from the root and stem of the infected plants were morphologically and molecularly identified as F. concentricum. This is the first report on F. concentricum inducing tobacco root rot in China. This finding implies that F. concentricum may pose a potential threat to tobacco production and thus reduce the income of tobacco farmers. Consequently, it is essential to develop appropriate prevention and control measures for this pathogen to ensure the sustainability of cultivation in our region.

Introduction: Cigar wrapper leaves (CWLs) plays a crucial role in reflecting cigar overall quality. Originating from the Qinba region of China, Fangxian Huangjiu (FHJ) is distinctive from other varieties of Huangjiu.Methods: To investigate the effects of FHJ on enhancing the aroma and quality of CWLs, as well as the consequent alterations in microbial communities, Gas Chromatography-Mass Spectrometry (GC-MS) coupled with Odor Active Value (OAV) analysis was utilized to evaluate the volatile aroma components of CWLs.Results and Discussion: The results indicated that the total amount of aroma compounds in CWLs reached 3,086.88 ug/g, increasing of 270.50% and 166.31% compared to the unfermented and naturally fermented groups, respectively. Among them, β-ionone and 4,7,9-megastigmatrien-3-one from the FHJ fermentation group significantly influenced the sensory characteristics of CWLs. Metagenomic results demonstrated that FHJ fermentation enriched the abundance of both shared and unique microbial species in CWLs, while also increased the diversity of differential microbial species. Addition of FHJ effectively altered the microbial community structure of CWLs from a dominance of Staphylococcus to a prevalence of Staphylococcus, Aspergillus, Pseudomonas, and Acinetobacter. The interactions among these diverse microorganisms collectively contribute to the enhancement of the intrinsic quality of CWLs. This paper provides a theoretical basis for improving the quality of CWLs by FHJ and exploring the changes of microbial community structure and interaction between CWLs and FHJ.

Hydrogen sulfide (H₂S) has emerged as a novel endogenous gas signaling molecule, joining the ranks of nitric oxide (NO) and carbon monoxide (CO). Recent research has highlighted its involvement in various physiological processes, such as promoting root organogenesis, regulating stomatal movement and photosynthesis, and enhancing plant growth, development, and stress resistance. Tobacco, a significant cash crop crucial for farmers’ economic income, relies heavily on root development to affect leaf growth, disease resistance, chemical composition, and yield. Despite its importance, there remains a scarcity of studies investigating the role of H₂S in promoting tobacco growth. This study exposed tobacco seedlings to different concentrations of NaHS (an exogenous H₂S donor) − 0, 200, 400, 600, and 800 mg/L. Results indicated a positive correlation between NaHS concentration and root length, wet weight, root activity, and antioxidant enzymatic activities (CAT, SOD, and POD) in tobacco roots. Transcriptomic and metabolomic analyses revealed that treatment with 600 mg/L NaHS significantly effected 162 key genes, 44 key enzymes, and two metabolic pathways (brassinosteroid synthesis and aspartate biosynthesis) in tobacco seedlings. The addition of exogenous NaHS not only promoted tobacco root development but also potentially reduced pesticide usage, contributing to a more sustainable ecological environment. Overall, this study sheds light on the primary metabolic pathways involved in tobacco root response to NaHS, offering new genetic insights for future investigations into plant root development.

Introduction: Microbial succession and metabolic adjustment during cigar tobacco leaf (CTL) fermentation are key factors to improve the quality and flavor of CTLs. However, the interactions in the above processes remain to be further elucidated.Methods: Bacillus altitudinis inoculants were added to the CTLs, and metagenomics and metabolomics were used to analyze the effects of the inoculants on regulating microbial succession, metabolic shift, and aroma production during fermentation.Results and discussion: The addition of the inoculants reinforced the CTL macromolecule transformation and facilitated the aroma production efficiently, and the total aroma production was increased by 43% compared with natural fermentation. The omics analysis showed that Staphylococcus was a main contributor to fatty acid degradation, inositol phosphate metabolism, energy supply (oxidative phosphorylation), nutrient transport (ABC transporter and phosphotransferase system [PTS]), and aroma production (terpenoid backbone biosynthesis, phenylalanine metabolism, and degradation of aromatic compounds). Furthermore, Staphylococcus was positively correlated with TCA cycle intermediates (citric acid, fumaric acid, and aconitic acid), cell wall components, peptidoglycan intermediates (GlcNAc-1-P and UDP-GlcNAc), and phytic acid degradation products (inositol). The characteristics collectively showed Staphylococcus to be the most dominant in the microbial community at the genus level during microflora succession. The addition of the inoculants supplemented the nutritional components of the CTLs, enhanced the metabolic activity and diversity of bacteria such as Corynebacterium, improved their competitive advantages in the microflora succession, and facilitated the richness of microbial communities. Additionally, a metabolic shift in nicotine degradation and NAD + anabolism from Staphylococcus to Corynebacterium in fermentation with inoculants was first observed. Meanwhile, the significantly correlative differential metabolites with Staphylococcus and Corynebacterium were a metabolic complement, thus forming a completely dynamic fermentation ecosystem. The results provided evidence for CTL fermentation optimization.

Background: Hydrogen sulfide (H₂S) is a novel signaling molecule involved in the growth and development of plants and their response to stress. However, the involvement of H₂S in promoting the growth and development of tobacco plants is still unclear. Results: In this study, we explored the effect of pre-soaking or irrigating the roots of tobacco plants with 0.0, 2.0, 4.0, 6.0, and 8.0 mM of sodium hydrosulfide (NaHS) on endogenous H₂S production, antioxidant enzymatic and cysteine desulfhydrase activities, seed germination, agronomic traits, photosynthetic pigments contents, and root vigor. The results revealed that exogenous NaHS treatment could significantly promote endogenous H₂S production by inducing gene expression of D/L-CD and the activities of D/L-CD enzymes. Additionally, a significant increase in the agronomic traits and the contents of photosynthetic pigments, and no significant difference in carotenoid content among tobacco plants treated with 0.0 to 8.0 mM of NaHS was observed. Additionally, a significant increase in the germination speed, dry weight, and vigor of tobacco seeds, whereas no significant effect on the percentage of seed germination was observed on NaHS treatment. Furthermore, NaHS treatment could significantly increase the activity of superoxide dismutase (SOD) and peroxidase (POD) enzymes, which reduces damage due to oxidative stress by maintaining reactive oxygen species homeostasis. Conclusions: These results would aid in enhancing our understanding of the involvement of H₂S, a novel signaling molecule to promote the growth and development of tobacco plants.

Since its discovery as a third unique gaseous signal molecule, hydrogen sulfide (H₂S) has been extensively employed to resist stress and control pathogens. Nevertheless, whether H₂S can prevent tobacco bacterial wilt is unknown yet. We evaluated the impacts of the H₂S donor sodium hydrosulfide (NaHS) on the antibacterial activity, morphology, biofilm, and transcriptome of R. solanacearum to understand the effect and mechanism of NaHS on tobacco bacterial wilt. In vitro, NaHS significantly inhibited the growth of Ralstonia solanacearum and obviously altered its cell morphology. Additionally, NaHS significantly inhibited the biofilm formation and swarming motility of R. solanacearum, and reduced the population of R. solanacearum invading tobacco roots. In field experiments, the application of NaHS dramatically decreased the disease incidence and index of tobacco bacterial wilt, with a control efficiency of up to 89.49%. The application of NaHS also influenced the diversity and structure of the soil microbial community. Furthermore, NaHS markedly increased the relative abundances of beneficial microorganisms, which helps prevent tobacco bacterial wilt. These findings highlight NaHS's potential and efficacy as a powerful antibacterial agent for preventing tobacco bacterial wilt caused by R. solanacearum.