Characteristics of rhizosphere and bulk soil microbial community of Chinese cabbage (Brassica campestris) grown in Karst area.

Understanding the rhizosphere soil microbial community and its relationship with the bulk soil microbial community is critical for maintaining soil health and fertility and improving crop yields in Karst regions. The microbial communities in the rhizosphere and bulk soils of a Chinese cabbage (Brassica campestris) plantation in a Karst region, as well as their relationships with soil nutrients, were examined in this study using high-throughput sequencing technologies of 16S and ITS amplicons. The aim was to provide theoretical insights into the healthy cultivation of Chinese cabbage in a Karst area. The findings revealed that the rhizosphere soil showed higher contents of organic matter (OM), alkaline hydrolyzable nitrogen (AN), available phosphorus (AP), total phosphorus (TP), available potassium (AK), total potassium (TK), total nitrogen (TN), catalase (CA), urease (UR), sucrase (SU), and phosphatase (PHO), in comparison with bulk soil, while the pH value showed the opposite trend. The diversity of bacterial and fungal communities in the bulk soil was higher than that in the rhizosphere soil, and their compositions differed between the two types of soil. In the rhizosphere soil, Proteobacteria, Acidobacteriota, Actinobacteriota, and Bacteroidota were the dominant bacterial phyla, while Olpidiomycota, Ascomycota, Mortierellomycota, and Basidiomycota were the predominant fungal phyla. In contrast, the bulk soil was characterized by bacterial dominance of Proteobacteria, Acidobacteriota, Chloroflexi, and Actinobacteriota and fungal dominance of Ascomycota, Olpidiomycota, Mortierellomycota, and Basidiomycota. The fungal network was simpler than the bacterial network, and both networks exhibited less complexity in the rhizosphere soil compared with the bulk soil. Moreover, the rhizosphere soil harbored a higher proportion of beneficial Rhizobiales. The rhizosphere soil network was less complicated than the network in bulk soil by building a bacterial-fungal co-occurrence network. Furthermore, a network of relationships between soil properties and network keystone taxa revealed that the rhizosphere soil keystone taxa were more strongly correlated with soil properties than those in the bulk soil; despite its lower complexity, the rhizosphere soil contains a higher abundance of bacteria which are beneficial for cabbage growth compared with the bulk soil.

Types of vegetables shape composition, diversity, and co-occurrence networks of soil bacteria and fungi in karst areas of southwest China.

BACKGROUND: Microorganisms are of significant importance in soil. Yet their association with specific vegetable types remains poorly comprehended. This study investigates the composition of bacterial and fungal communities in soil by employing high-throughput sequencing of 16 S rRNA genes and ITS rRNA genes while considering the cultivation of diverse vegetable varieties. RESULTS: The findings indicate that the presence of cultivated vegetables influenced the bacterial and fungal communities leading to discernible alterations when compared to uncultivated soil. In particular, the soil of leafy vegetables (such as cabbage and kale) exhibited higher bacterial α-diversity than melon and fruit vegetable (such as cucumber and tomato), while fungal α-diversity showed an inverse pattern. The prevailing bacterial phyla in both leafy vegetable and melon and fruit vegetable soils were Proteobacteria, Acidobacteriota, Actinobacteriota, and Chloroflexi. In leafy vegetable soil, dominant fungal phyla included Ascomycota, Olpidiomycota, Mortierellomycota, and Basidiomycota whereas in melon and fruit vegetable soil. Ascomycota, Mortierellomycota, Basidiomycota, and Rozellomycota held prominence. Notably, the relative abundance of Ascomycota was lower in leafy vegetable soil compared to melon and fruit vegetable soil. Moreover, leafy vegetable soil exhibited a more complex and stable co-occurrence network in comparison to melon and fruit vegetable soil. CONCLUSION: The findings enhance our understanding of how cultivated soil bacteria and fungi respond to human disturbance, thereby providing a valuable theoretical basis for soil health in degraded karst areas of southwest China.

Different composites inhibit Cd accumulation in grains under the rice-oilseed rape rotation mode of karst area: A field study.

Ensuring the safe production of food and oil crops in soils with elevated cadmium (Cd) content in karst regions is crucial. We tested a field experiment to examine the long-term remediation effects of compound microorganisms (CM), strong anion exchange adsorbent (SAX), processed oyster shell (POS), and composite humic acids (CHA) on Cd contamination in paddy fields under a rice-oilseed rape rotation system. In comparison to the control group (CK), the application of amendments significantly increased soil pH, cation exchange capacity (CEC), and soil organic matter (SOM) content while markedly decreasing the content of available Cd (ACd). During the rice cultivation season, Cd was predominantly concentrated in the roots. Relative to the control (CK), the Cd content in each organ was significantly reduced. The Cd content in brown rice decreased by 19.18-85.45%. The Cd content in brown rice following different treatments exhibited the order of CM > POS > CHA > SAX, which was lower than the Chinese Food Safety Standard (GB 2762-2017) (0.20 mg/kg). Intriguingly, during the oilseed rape cultivation season, we discovered that oilseed rape possesses potential phytoremediation capabilities, with Cd mainly accumulating in roots and stems. Notably, CHA treatment alone significantly decreased the Cd content in oilseed rape grains to 0.156 mg/kg. CHA treatment also maintained soil pH and SOM content, consistently reduced soil ACd content, and stabilized Cd content in RSF within the rice-oilseed rape rotation system. Importantly, CHA treatment not only enhances crop production but also has a low total cost (1255.230 US$/hm2). Our research demonstrated that CHA provides a consistent and stable remediation effect on Cd-contaminated rice fields within the crop rotation system, as evidenced by the analysis of Cd reduction efficiency, crop yield, soil environmental change, and total cost. These findings offer valuable guidance for sustainable soil utilization and safe production of grain and oil crops in the context of high Cd concentrations in karst mountainous regions.

Sensitive or tolerant functional microorganisms under cadmium stress: suggesting potential specific interaction network characteristics in the rhizosphere system of karst potato.

The heavy metal cadmium (Cd) pollution in Chinese karst soils threatens food security, and microorganisms play an important role in regulating the migration and transformation of Cd in the soil-plant system. Nevertheless, the interaction characteristics between key microbial communities and environmental factors in response to Cd stress in specific crop environmental systems need to be explored. In this study, the soil (ferralsols)-microbe-crop (potato) system was taken as the object to explore the potato rhizosphere microbiome, using toxicology and molecular biology approaches, to explore the potato rhizosphere soil properties, microbial stress characteristics, and important microbial taxa under Cd stress. We hypothesized that different members of fungal and bacterial microbiome would regulate the resilience of potato rhizosphere and plants to Cd stress in the soil environment. Meanwhile, individual taxa will have different roles in the contaminated rhizosphere ecosystem. We found that soil pH was the main environmental factor affecting fungal community structure; urea-decomposing and nitrate-reducing functional bacteria as well as endosymbiotic and saprophytic functional fungi gradually decreased. In particular, Basidiomycota may play a key role in preventing the migration of Cd from the soil to plants (potato). These findings provide important candidates for screening the cascade of Cd inhibition (detoxification/regulation) from soil to microorganisms to plants. Our work provides an important foundation and research insights for the application of microbial remediation technology in the karst cadmium-contaminated farmland.

Systematic analysis and expression profiles of TCP gene family in Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) revealed the potential function of FtTCP15 and FtTCP18 in response to abiotic stress.

BACKGROUND: As transcription factors, the TCP genes are considered to be promising targets for crop enhancement for their responses to abiotic stresses. However, information on the systematic characterization and functional expression profiles under abiotic stress of TCPs in Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) is limited. RESULTS: In this study, we identified 26 FtTCPs and named them according to their position on the chromosomes. Phylogenetic tree, gene structure, duplication events, and cis-acting elements were further studied and syntenic analysis was conducted to explore the bioinformatic traits of the FtTCP gene family. Subsequently, 12 FtTCP genes were selected for expression analysis under cold, dark, heat, salt, UV, and waterlogging (WL) treatments by qRT-PCR. The spatio-temporal specificity, correlation analysis of gene expression levels and interaction network prediction revealed the potential function of FtTCP15 and FtTCP18 in response to abiotic stresses. Moreover, subcellular localization confirmed that FtTCP15 and FtTCP18 localized in the nucleus function as transcription factors. CONCLUSIONS: In this research, 26 TCP genes were identified in Tartary buckwheat, and their structures and functions have been systematically explored. Our results reveal that the FtTCP15 and FtTCP18 have special cis-elements in response to abiotic stress and conserved nature in evolution, indicating they could be promising candidates for further functional verification under multiple abiotic stresses.