Different Fertilizers Applied Alter Fungal Community Structure in Rhizospheric Soil of Cassava (Manihot esculenta Crantz) and Increase Crop Yield

Comparison and analysis of soil microbial communities in organic and conventional paddy fields by farming season

Interest in soil health and biodiversity conservation has become increasingly important. Consequently, studies comparing the chemical and biological characteristics of organic and traditional paddy soils have been increasing. Soil microorganisms are essential in nutrient cycling; however, their diversity is challenging to ascertain because of their environmental sensitivity and complex interactions. Particularly, in domestic rice cultivation, the soil undergoes multiple irrigation and drainage processes during crop growth, providing a diverse ecological environment for soil microorganisms. The objective of this study is to compare the microbial community and diversity between paddy soils in two agricultural systems. We selected organic and conventional paddy fields in Yangpyeong, Gyeonggi Province, and collected monthly samples from August to November 2022 for analysis. Bacteria and fungi were amplified from the 16S rRNA V3V4 region, ITS 3-4 region respectively, For the comparison of microbial diversity, Alpha diversity indices (Chao1, Shannon, Gini-Simpson indices) were analyzed. The results indicated genus-level differences in microbial communities, with the genera Mucor and Sirastachys exclusively present in organic paddy soils, while the genus Ustilaginoidea was exclusively found in conventional paddy soils. Among them, Ustilaginoidea is reported to be a fungus causing false smut disease, causing damage to crop growth and quality. Additionally, the comparison of microbial diversity between the two farming showed no significant differences (p>0.05). In conclusion, When the microbial communities present in both farming systems were examined, organic farming appeared to be more advantageous than conventional farming regarding crop disease and health. This study provides essential soil chemical and microbiological data for understanding the fundamental characteristics of paddy soils in South Korea.

Root exudates influence rhizosphere fungi and thereby synergistically regulate Panax ginseng yield and quality

Root exudates contain a complex array of primary and specialized metabolites that play important roles in plant growth due to their stimulatory and inhibitory activities that can select for specific microbes. In this study, we investigated the effects of different root exudate concentrations on the growth of ginseng (Panax ginseng C. A. Mey), ginsenoside levels, and soil fungal community composition and diversity. The results showed that low root exudate concentrations in the soil promoted ginseng rhizome biomass and ginsenoside levels (Rg1, Re, Rf, Rg2, Rb1, Ro, Rc, Rb2, Rb3, and Rd) in rhizomes. However, the rhizome biomass and ginsenoside levels gradually decreased with further increases in the root exudate concentration. ITS sequencing showed that low root exudate concentrations in the soil hardly altered the rhizosphere fungal community structure. High root exudate concentrations altered the structure, involving microecological imbalance, with reduced abundances of potentially beneficial fungi (such as Mortierella) and increased abundances of potentially pathogenic fungi (such as Fusarium). Correlation analysis showed that rhizome biomass and ginsenoside levels were significantly positively correlated with the abundances of potentially beneficial fungi, while the opposite was true for potentially pathogenic fungi. Overall, low root exudate concentrations promote the growth and development of ginseng; high root exudate concentrations lead to an imbalance in the rhizosphere fungal community of ginseng and reduce the plant's adaptability. This may be an important factor in the reduced ginseng yield and quality and soil sickness when ginseng is grown continuously.

Integrative analysis of metabolome and transcriptome reveals the mechanism of color formation in cassava (Manihot esculenta Crantz) leaves

Cassava (Manihot esculenta Crantz) leaves are often used as vegetables in Africa. Anthocyanins possess antioxidant, anti-inflammatory, anti-cancer, and other biological activities. They are poor in green leaves but rich in the purple leaves of cassava. The mechanism of anthocyanin's accumulation in cassava is poorly understood. In this study, two cassava varieties, SC9 with green leaves and Ziyehuangxin with purple leaves (PL), were selected to perform an integrative analysis using metabolomics and transcriptomics. The metabolomic analysis indicated that the most significantly differential metabolites (SDMs) belong to anthocyanins and are highly accumulated in PL. The transcriptomic analysis revealed that differentially expressed genes (DEGs) are enriched in secondary metabolites biosynthesis. The analysis of the combination of metabolomics and transcriptomics showed that metabolite changes are associated with the gene expressions in the anthocyanin biosynthesis pathway. In addition, some transcription factors (TFs) may be involved in anthocyanin biosynthesis. To further investigate the correlation between anthocyanin accumulation and color formation in cassava leaves, the virus-induced gene silencing (VIGS) system was used. VIGS-MeANR silenced plant showed the altered phenotypes of cassava leaves, partially from green to purple color, resulting in a significant increase of the total anthocyanin content and reduction in the expression of MeANR. These results provide a theoretical basis for breeding cassava varieties with anthocyanin-rich leaves.

Magnesium chelatase subunit D is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting starch accumulation in Manihot esculenta Crantz

BACKGROUND

Magnesium chelatase plays an important role in photosynthesis, but only a few subunits have been functionally characterized in cassava.

RESULTS

Herein, MeChlD was successfully cloned and characterized. MeChlD encodes a magnesium chelatase subunit D, which has ATPase and vWA conservative domains. MeChlD was highly expressed in the leaves. Subcellular localization suggested that MeChlD:GFP was a chloroplast-localized protein. Furthermore, the yeast two-hybrid system and BiFC analysis indicated that MeChlD interacts with MeChlM and MePrxQ, respectively. VIGS-induce silencing of MeChlD resulted in significantly decreased chlorophyll content and reduction the expression of photosynthesis-related nuclear genes. Furthermore, the storage root numbers, fresh weight and the total starch content in cassava storage roots of VIGS-MeChlD plants was significantly reduced.

CONCLUSION

Taken together, MeChlD located at the chloroplast is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting the starch accumulation in cassava. This study expands our understanding of the biological functions of ChlD proteins.

Integrated Metabolomic and Transcriptomic Analyses Reveals Sugar Transport and Starch Accumulation in Two Specific Germplasms of Manihot esculenta Crantz

As a starchy and edible tropical plant, cassava (Manihot esculenta Crantz) has been widely used as an industrial raw material and a dietary source. However, the metabolomic and genetic differences in specific germplasms of cassava storage root were unclear. In this study, two specific germplasms, M. esculenta Crantz cv. sugar cassava GPMS0991L and M. esculenta Crantz cv. pink cassava BRA117315, were used as research materials. Results showed that sugar cassava GPMS0991L was rich in glucose and fructose, whereas pink cassava BRA117315 was rich in starch and sucrose. Metabolomic and transcriptomic analysis indicated that sucrose and starch metabolism had significantly changing metabolites enrichment and the highest degree of differential expression genes, respectively. Sugar transport in storage roots may contribute to the activities of sugar, which will eventually be exported to transporters (SWEETs), such as (MeSWEET1a, MeSWEET2b, MeSWEET4, MeSWEET5, MeSWEET10b, and MeSWEET17c), which transport hexose to plant cells. The expression level of genes involved in starch biosynthesis and metabolism were altered, which may result in starch accumulation. These results provide a theoretical basis for sugar transport and starch accumulation and may be useful in improving the quality of tuberous crops and increasing yield.

Control efficiency of hexaconazole-lentinan against wheat sharp eyespot and wheat crown rot and the associated effects on rhizosphere soil fungal community

The use of polysaccharides to induce the systemic immune response of plants for disease resistance has become an effective plant protection measure. Sharp eyespot wheat and crown rot wheat are serious diseases of wheat. In this study, the control effects of hexaconazole and lentinan (LNT) seed dressing of the two wheat diseases were evaluated by field experiments, and the effects of the seed dressing on plant growth, soil enzyme activity, and community diversity in the wheat rhizosphere were discussed. The results showed that the combined seed dressing of hexaconazole at 0.5 a.i. g·100 kg⁻¹ and LNT at 4 a.i. g·100 kg⁻¹ could significantly improve the control effect of the two wheat diseases. The combined treatment of hexaconazole and LNT had little effect on wheat soil enzyme activities. Different seed dressing treatments changed the fungal community structure in the wheat rhizosphere soil, and the combination of LNT and hexaconazole reduced the relative abundance of Rhizoctonia, Cladosporium, Fusarium, Bipolaris, and Gibberella in wheat planting soils. These findings suggested that the combined seed dressing of hexaconazole and LNT could effectively control soilborne diseases of wheat, concurrently could change in rhizosphere fungal community, and reduce in potential soilborne pathogens.

Ammonium fertilization increases the susceptibility to fungal leaf and root pathogens in winter wheat

Nitrogen (N) fertilization is indispensable for high yields in agriculture due to its central role in plant growth and fitness. Different N forms affect plant defense against foliar pathogens and may alter soil-plant-microbe interactions. To date, however, the complex relationships between N forms and host defense are poorly understood. For this purpose, nitrate, ammonium, and cyanamide were compared in greenhouse pot trials with the aim to suppress two important fungal wheat pathogens Blumeria graminis f. sp. tritici (Bgt) and Gaeumannomyces graminis f. sp. tritici (Ggt). Wheat inoculated with the foliar pathogen Bgt was comparatively up to 80% less infested when fertilized with nitrate or cyanamide than with ammonium. Likewise, soil inoculation with the fungal pathogen Ggt revealed a 38% higher percentage of take-all infected roots in ammonium-fertilized plants. The bacterial rhizosphere microbiome was little affected by the N form, whereas the fungal community composition and structure were shaped by the different N fertilization, as revealed from metabarcoding data. Importantly, we observed a higher abundance of fungal pathogenic taxa in the ammonium-fertilized treatment compared to the other N treatments. Taken together, our findings demonstrated the critical role of fertilized N forms for host-pathogen interactions and wheat rhizosphere microbiome assemblage, which are relevant for plant fitness and performance.

Optimal NPK Fertilizer Combination Increases Panax ginseng Yield and Quality and Affects Diversity and Structure of Rhizosphere Fungal Communities

Soil microorganisms affect crop rhizospheres via the transformation and transport of nutrients, which has important influences on soil fertility, carbon sequestration, and plant yield and health in agroecosystems. There are few reports on the effects of fertilizer application on the growth of Panax ginseng (C. A. Mey.) or the structure of its rhizosphere microbial communities. In this study, an orthogonal experimental design was used to explore the effects of nine different combinations of nitrogen (N), phosphorus (P), and potassium (K) fertilizers with different amounts and proportions on ginseng growth and accumulation of ginsenosides and the structure of rhizosphere soil fungal communities. Soil without fertilization was the control. With the combined application of NPK, ginseng growth and development increased. The fertilization scheme N₃P₁K₃, with N fertilizer at 50 g·m⁻², P fertilizer at 15 g·m⁻², and K fertilizer at 60 g·m⁻², had the most comprehensive benefit and significantly increased ginseng rhizome biomass and ginsenoside contents (Rg1, Re, Rf, Rg2, Rb1, Ro, Rc, Rb2, Rb3, and Rd). Amplicon sequencing showed that NPK application increased the diversity of fungal communities in ginseng rhizospheres, whereas richness was bidirectionally regulated by proportions and amounts of NPK. Ascomycota was the dominant fungal phylum in ginseng rhizosphere soil, and relative abundances decreased with combined NPK application. Combined NPK application increased the relative abundance of potential beneficial fungi, such as Mortierella, but decreased that of potentially pathogenic fungi, such as Fusarium. Correlation analysis showed that potential beneficial fungi were significantly positively correlated with ginseng rhizome yield and ginsenoside contents, whereas the opposite relation was observed with potential pathogenic fungi. Thus, in addition to directly increasing crop growth, precise NPK application can also increase crop adaptability to the environment by shaping specific microbial communities. The results of this study suggest that the combined effects of biotic and abiotic processes on agricultural production determine crop yield and quality.