Co-Amended Synergistic Interactions between Arbuscular Mycorrhizal Fungi and the Organic Substrate-Induced Cucumber Yield and Fruit Quality Associated with the Regulation of the AM-Fungal Community Structure under Anthropogenic Cultivated Soil

Root separation modulates AMF diversity and composition in tomato-potato onion intercropping systems

Plant-plant interactions shape arbuscular mycorrhizal fungi (AMF) communities in rhizosphere soil, with tomato/potato-onion intercropping emerging as a promising agro-ecological strategy to optimize resource utilization. However, the role of root separation methods in modulating AMF diversity within intercropping systems remains unclear. Specifically, whether the AMF community in the rhizosphere of tomato and potato-onion intercropping differs from monoculture and how root separation methods modulate these effects. This study evaluates the effects of various root separation methods (no separation, 0.45 μm nylon membrane, 38 μm nylon membrane, and solid separation) on AMF diversity and composition in tomato/potato-onion intercropping and monoculture systems. High-throughput Illumina MiSeq sequencing was used to assess AMF diversity indices (Ace, Chao1, Shannon, and Simpson), and Principal Coordinate Analysis evaluated community structure. Results showed that the non-separation mode achieved the highest Ace and Chao1 indices, indicating greater richness, while intercropping lowered Shannon and Simpson indices. Intercropping significantly reduced Glomerales but increased Paraglomerales, under the non-separation mode. Similarly, it decreased Glomus while increasing Paraglomus in the rhizosphere of both crops. Principal Coordinate Analysis revealed that root separation distinctly altered AMF community structure, reflecting specific barrier effects on AMF interactions. Intercropping increased AMF abundance in the tomato rhizosphere but reduced it in potato-onion as shown by 18S rRNA gene abundance. These findings emphasize that minimizing root separation in intercropping enhances AMF diversity and functionality, providing valuable insights for sustainable agricultural management. Understanding the role of root interactions in shaping AMF communities can help optimizing intercropping strategies to improve soil health and nutrient dynamics.

The influence of urban environmental effects on the orchard soil microbial community structure and function: a case study in Zhejiang, China

The urban environmental effects can have multifaceted impacts on the orchard soil microbial community structure and function. To specifically study these effects, we investigated the soil bacterial and fungal community in the laxly managed citrus orchards using amplicon sequencing. Ascomycota demonstrated significant dominance within the citrus orchard soils. The increased presence of beneficial Trichoderma spp. (0.3%) could help suppress plant pathogens, while the elevated abundance of potential pathogenic fungi, such as Fusarium spp. (0.4%), might raise the likelihood of disorders like root rot, thereby hindering plant growth and resulting in reduced yield. Moreover, we observed significant differences in the alpha and beta diversity of bacterial communities between urban and rural soils (p < 0.001). Environmental surveys and functional prediction of bacterial communities suggested that urban transportation factors and rural waste pollution were likely contributing to these disparities. When comparing bacterial species in urban and rural soils, Bacillus spp. exhibited notable increases in urban areas. Bacillus spp. possess heavy metal tolerance attributed to the presence of chromium reductase and nitroreductase enzymes involved in the chromium (VI) reduction pathway. Our findings have shed light on the intricate interplay of urban environmental effects and root systems, both of which exert influence on the soil microbiota. Apart from the removal of specific pollutants, the application of Bacillus spp. to alleviate traffic pollution, and the use of Trichoderma spp. for plant pathogen suppression were considered viable solutions. The knowledge acquired from this study can be employed to optimize agricultural practices, augment citrus productivity, and foster sustainable agriculture.

Differential Strategies of Ectomycorrhizal Development between Suillus luteus and Pinus massoniana in Response to Nutrient Changes

Ectomycorrhizal fungi employ different strategies for mycelial growth and host colonization under varying nutrient conditions. However, key genes associated with mycorrhizal interaction should be influenced solely by the inoculation treatment and not by nutrient variations. To utilize subtle nutrient differences and rapidly screen for key genes related to the interaction between Suillus luteus and Pinus massoniana, we performed an inoculation experiment using culture bottles containing high- and low-nutrient media. Interestingly, S. luteus LS88 promoted the growth of P. massoniana seedlings without mature ectomycorrhiza, and the impact of LS88 inoculation on P. massoniana roots was greater than that of nutrient changes. In this study, the resequenced genome of the LS88 strain was utilized for transcriptome analysis of the strain. The analysis indicated that a unique gene encoding glutathione S-transferase (GST) in LS88 is likely involved in colonizing P. massoniana roots. In this study, the GST gene expression was independent of nutrient levels. It was probably induced by P. massoniana and could be used as a marker for S. luteus colonization degree.

Effect of in situ vermicomposting combined with biochar application on soil properties and crop yields in the tomato monoculture system

Vermicompost and biochar have been widely used to improve soil conditions. However, little information is available regarding the efficiency and effectiveness of in situ vermicomposting with biochar (IVB) in monoculture soils. In this study, we estimated the effects of IVB on soil physiochemical and microbial properties, crop yields, and fruit quality under the tomato monoculture system. The soil treatments considered were (i) untreated monoculture soil (MS, control), (ii) MS plus 1.5 t/ha biochar applied to soil surface (MS+1.5BCS), (iii) MS plus 3 t/ha biochar applied to soil surface (MS+3BCS), (iv) MS mixed with 1.5 t/ha biochar (MS+1.5BCM), (v) MS mixed with 3 t/ha biochar (MS+3BCM), (vi) in situ vermicomposting (VC), (vii) VC plus 1.5 t/ha biochar applied to VC surface (VC+1.5BCS), (viii) VC plus 3 t/ha biochar applied to VC surface (VC+3BCS), (ix) VC mixed with 1.5 t/ha biochar (VC+1.5BCM), and (x) VC mixed with 3 t/ha biochar (VC+3BCM). In general, soil pH varied from 7.68 to 7.96 under VC-related treatments. The microbial diversity was much higher in bacterial communities (OTU: 2284-3194, Shannon index: 8.81-9.91) than in fungal communities (OTU: 392-782, Shannon index: 4.63-5.71) in VC-related treatments. Specifically, Proteobacteria was the dominant bacterial phylum, followed by Bacteroidota, Chloroflexi, Patescibacteria, Acidobacteriota, Firmicutes, and Myxococcota. It is worth noting that IVB-related treatments could increase the relative abundance of Acidobacteria and reduced the relative abundance of Bacteroidetes. In addition, the VC+1.5BCM treatment exhibited the greatest yield (9377.6 kg/667m2) and simultaneously showed higher fruit quality (vitamin C, 28.94 mg/100g; soluble sugar, 20.15%) as compared to other treatments. Our results suggested that in situ vermicomposting with biochar can improve soil properties and enhance both crop yields and fruit quality under the tomato monoculture system.

Deciphering the Synergies of Reductive Soil Disinfestation Combined with Biochar and Antagonistic Microbial Inoculation in Cucumber Fusarium Wilt Suppression Through Rhizosphere Microbiota Structure

Application of reductive soil disinfestation (RSD), biochar, and antagonistic microbes have become increasingly popular strategies in a microbiome-based approach to control soil-borne diseases. The combined effect of these remediation methods on the suppression of cucumber Fusarium wilt associated with microbiota reconstruction, however, is still unknown. In this study, we applied RSD treatment together with biochar and microbial application of Trichoderma and Bacillus spp. in Fusarium-diseased cucumbers to investigate their effects on wilt suppression, soil chemical changes, microbial abundances, and the rhizosphere communities. The results showed that initial RSD treatment followed by biochar amendment (RSD-BC) and combined applications of microbial inoculation and biochar (RSD-SQR-T37-BC) decreased nitrate concentration and raised soil pH, soil organic carbon (SOC), and ammonium in the treated soils. Under RSD, the applications of Bacillus (RSD-SQR), Trichoderma (RSD-T37), and biochar (RSD-BC) suppressed wilt incidence by 26.8%, 37.5%, and 32.5%, respectively, compared to non-RSD treatments. Moreover, RSD-SQR-T37-BC and RSD-T37 caused greater suppressiveness of Fusarium wilt and F. oxysporum by 57.0 and 33.5%, respectively. Rhizosphere beta diversity and alpha diversity revealed a difference between RSD-treated and non-RSD microbial groups. The significant increase in the abundance, richness, and diversity of bacteria, and the decrease in the abundance and diversity of fungi under RSD-induced treatments attributed to the general suppression. Identified bacterial (Bacillus, Pseudoxanthomonas, Flavobacterium, Flavisolibacter, and Arthrobacter) and fungal (Trichoderma, Chaetomium, Cladosporium, Psathyrella, and Westerdykella) genera were likely the potential antagonists of specific disease suppression for their significant increase of abundances under RSD-treated soils and high relative importance in linear models. This study infers that the RSD treatment induces potential synergies with biochar amendment and microbial applications, resulting in enhanced general-to-specific suppression mechanisms by changing the microbial community composition in the cucumber rhizosphere.

Arbuscular Mycorrhizal Fungi and Dry Raw Garlic Stalk Amendment Alleviate Continuous Monocropping Growth and Photosynthetic Declines in Eggplant by Bolstering Its Antioxidant System and Accumulation of Osmolytes and Secondary Metabolites

Vegetable production under plastic sheds severely threatens regional eco-sustainability via anthropogenic activities (excessive use of agrochemicals, pesticides) and problems associated with replanting. Long-term successive cropping across growing seasons induces continuous cropping stress, whose effects manifest as diminished plant growth. Therefore, it is imperative that we develop environmentally sustainable approaches, such as replacing agrochemicals with vegetable waste like dry raw garlic stalk (DRGS) or use biofertilizers like arbuscular mycorrhizal fungi (AMF) (e.g., Diversispora epigaea). In this study, the influence of AMF on the growth, biochemical attributes, antioxidant defense system, phytohormones, accumulation of osmolytes, phenols, and mineral elements in eggplant grown on DRGS-amended soils under continuous monocropping (CMC) was studied. The results showed that inoculation with AMF or the DRGS amendment could improve the pigments' content, photosynthesis, and antioxidant defense system; augmented phytohormones synthesis (except for ABA), and increased the leaves' mineral nutrients. These parameters were enhanced most by the combined application of AMF and DRGS, which also increased the concentration of osmolytes, including proline, sugars, and free amino acids in eggplant when compared with the control. Furthermore, either AMF and DRGS alone, or in combination, ameliorated the induced stress from continuous cropping by reducing the incidence of Fusarium wilt and production of ROS (reactive oxygen species); lipid peroxidation underwent maximal reduction in plants grown under the combined treatments. The AMF, DRGS, and AMF + DRGS exhibited a lower disease severity index (33.46, 36.42, and 43.01%), respectively, over control. Hence, inoculation with AMF coupled with DRGS amendment alters the photosynthetic attributes in eggplant through the upregulation of its antioxidant system and greater accumulation of osmolytes, which led to the improved growth and yield of eggplant.

Colonization of Listeria monocytogenes in potting soils as affected by bacterial community composition, storage temperature, and natural amendment

This study aimed to characterize the bacterial community of commercial potting soils with or without Listeria monocytogenes inoculation at 5-35 °C using 16S metagenomic sequencing and evaluate the effect of natural amendments on the reduction L. monocytogenes in non-sterile potting soils. An increase in the expected operational taxonomic units of each sample with or without L. monocytogenes was proportional to the increasing storage temperatures after 5 days. Biodiversity was distinct among all potting soils for Shannon and inverse Simpson indices, with the highest diversity being observed in a soil sample stored at 35 °C for 5 days with L. monocytogenes. An increase in richness and diversity of soil bacterial community structure positively correlated with less survival of the invading L. monocytogenes. Particularly, garlic extract was demonstrated as a promising soil-amendment substrate, reducing L. monocytogenes by ≥ 4.50 log CFU/g in potting soils stored at 35 °C.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00925-9.

The Formation of Fruit Quality in Cucumis sativus L

Cucumber is one of the most widely grown vegetables in China and an indispensable fresh fruit in the diet. With the development of society, the demand of people for cucumber quality is higher and higher. Therefore, cultivating high-quality cucumber varieties is one of the main goals of cucumber breeding. With the rapid development of biotechnology such as molecular marker, cucumber quality control network is becoming clear. In this review, we describe the formation mechanism of cucumber fruit quality from three aspects: (1) the commercial quality of cucumber fruit, (2) nutritional quality formation, and (3) flavor quality of cucumber fruit. In addition, the determinants of cucumber fruit quality were summarized from two aspects of genetic regulation and cultivation methods in order to provide ideas for cucumber researchers and cultivators to improve fruit quality.

Garlic Substrate Induces Cucumber Growth Development and Decreases Fusarium Wilt through Regulation of Soil Microbial Community Structure and Diversity in Replanted Disturbed Soil

Garlic substrate could influence plant growth through affecting soil microbiome structure. The relationship mechanism between changes in soil microbial communities, disease suppression and plant development, however, remains unclear, particularly in the degraded soil micro-ecological environment. In this study, garlic substrates as a soil amendment were incorporated with different ratios (1:100, 3:100 and 5:100 g/100 g of soil) in a replanted disturbed soil of long-term cucumber monoculture (annual double cropping system in a greenhouse). The results indicated that higher amount of C-amended garlic substrate significantly induced soil suppressiveness (35.9% greater than control (CK) against the foliar disease incidence rate. This inhibitory effect consequently improved the cucumber growth performance and fruit yield to 20% higher than the non-amended soil. Short-term garlic substrate addition modified the soil quality through an increase in soil organic matter (SOM), nutrient availability and enzymatic activities. Illumina MiSeq sequencing analysis revealed that soil bacterial and fungal communities in the garlic amendment were significantly different from the control. Species richness and diversity indices significantly increased under treated soil. The correlation-based heat map analysis suggested that soil OM, nutrient contents and biological activators were the primary drivers reshaping the microbial community structure. Furthermore, garlic substrate inhibited soil-borne pathogen taxa (Fusarium and Nematoda), and their reduced abundances, significantly affecting the crop yield. In addition, the host plant recruited certain plant-beneficial microbes due to substrate addition that could directly contribute to plant–pathogen inhibition and crop biomass production. For example, abundant Acidobacteria, Ascomycota and Glomeromycota taxa were significantly associated with cucumber yield promotion. Firmicutes, Actinobacteria, Bacteroidetes, Basidiomycota and Glomeromycota were the associated microbial taxa that possibly performed as antagonists of Fusarium wilt, with plant pathogen suppression potential in monocropped cucumber-planted soil.

Changes in the Soil Microbiome in Eggplant Monoculture Revealed by High-Throughput Illumina MiSeq Sequencing as Influenced by Raw Garlic Stalk Amendment

The incorporation of plant residues into soil can be considered a keystone sustainability factor in improving soil structure function. However, the effects of plant residue addition on the soil microbial communities involved in biochemical cycles and abiotic stress phenomena are poorly understood. In this study, experiments were conducted to evaluate the role of raw garlic stalk (RGS) amendment in avoiding monoculture-related production constraints by studying the changes in soil chemical properties and microbial community structures. RGS was applied in four different doses, namely the control (RGS0), 1% (RGS1), 3% (RGS2), and 5% (RGS3) per 100 g of soil. The RGS amendment significantly increased soil electrical conductivity (EC), N, P, K, and enzyme activity. The soil pH significantly decreased with RGS application. High-throughput Illumina MiSeq sequencing revealed significant alterations in bacterial community structures in response to RGS application. Among the 23 major taxa detected, Anaerolineaceae, Acidobacteria, and Cyanobacteria exhibited an increased abundance level. RGS2 increased some bacteria reported to be beneficial including Acidobacteria, Bacillus, and Planctomyces (by 42%, 64%, and 1% respectively). Furthermore, internal transcribed spacer (ITS) fungal regions revealed significant diversity among the different treatments, with taxa such as Chaetomium (56.2%), Acremonium (4.3%), Fusarium (4%), Aspergillus (3.4%), Sordariomycetes (3%), and Plectosphaerellaceae (2%) showing much abundance. Interestingly, Coprinellus (14%) was observed only in RGS-amended soil. RGS treatments effectively altered soil fungal community structures and reduced certain known pathogenic fungal genera, i.e., Fusarium and Acremonium. The results of the present study suggest that RGS amendment potentially affects the microbial community structures that probably affect the physiological and morphological attributes of eggplant under a plastic greenhouse vegetable cultivation system (PGVC) in monoculture.