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

Abstract

Monotonous cucumber double-cropping systems under plastic greenhouse vegetable cultivation (PGVC) previously intensified by long-term anthropogenic activities and manipulative treatments leads to a crop productivity reduction and soil biota disturbances. In this study, the role of the indigenous arbuscular mycorrhizal strain (AM: Glomus versiforme L.) and organic substrate (GS: Garlic stalk) application were assessed for plant microbe interaction and crop productivity feedback in a greenhouse (2016–2018) under a cultivated Anthrosol characterized as a replanted degraded soil. We found that repetitively adding AM inocula with organic substrates (GS) improved the cucumber growth and physiology. The useful trait of AM symbiosis with C-amended organic substrates preferentially manifested as increased root colonization, hyphal density proliferation, AM sporulation, root activity, and suppressed Fusarium incidence. The post AM development further prevailed the synergistic interaction, and the co-inoculation effect resulted in an increase in fruit nutrition uptake, seasonal cucumber yield and fruit quality attributes. Illumina MiSeq analysis of the 18S rRNA gene amplicons revealed that the dominant AM genera that are particularly enriched with the Glomus taxon may be important ecological drivers associated with plant productivity and fruit quality characteristics. These results suggest that the AM-organic substrate association might be a pragmatic option for use as an economic and efficient biological resource and as a newly-sustainable plant microbe mediator to enhance the regional ecosystem services and plant productivity of the anthropogenic PGVC of this region.

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

“…Unfortunately, such allelopathic interaction via crop residue addition has not been dynamically reported. To correlate with our previous study [ 6 ], we infer that, during decomposition in the vicinity, the garlic substrate did not exert allelotoxic or deleterious effects on cucumber growth and physiology, because its planted organs or biomass inputs possess different allelopathic potential depending on their mode of action [ 26 ]. Phytotoxic activity from various garlic tissues, such as root exudates and bulb extract/root extracts, have been verified to have a strong allelopathic potential and they produced a greater adverse and dose-dependent effect on receiver crops [ 22 , 34 ].…”

“…Soil microbial communities are primarily limited by C-deficient environments, especially in exhaustive cropping systems, and the C-amended garlic substrate could result in the proliferation of microbial growth to provide abundant carbon resources. The incorporated garlic substrate in cucumber-planted soil may increase the C-rich substrate availability for copiotrophic microbes, which could also be ecologically important to mediate microbial processes, resulting in the maintenance or improvement of the microbial taxonomic and functional diversity [ 6 ]. Therefore, the greater quantity of a dominant microbial group of Acidobacteria , as associated with the ratio of garlic substrate, may also be due to the consumption of surplus carbon sources.…”

“…Recent studies revealed that changes in microbial communities could influence plant performance and crop health [ 6 , 26 , 27 ]. Key soil environmental factors and microbial species could be a major determinant of positive feedback effects during soil–plant–microbe interactions [ 18 ].…”

“…Regrettably, the global PGVC development is becoming increasingly problematic and eco-susceptible for sustainable vegetable production [ 6 ]. The conventional management system of PGVC crops has been accelerated by long-term anthropogenic activities, such as single crop repetition, the excessive use of synthetic fertilizers and hostile plant protection measures.…”

“…Thus, continuous cropping in this growing system disrupts the soil micro-ecological environment and alters the soil microbial structure, which consequently affects the aboveground plant growth [ 12 , 17 ]. Rhizosphere soil harbors significantly more microbial abundances of copiotrophic communities (fast-growing microbes) than bulk (root-free) soil, which substantially alter soil microbiomes [ 6 ]. Rhizosphere microbes can influence the aboveground plant biomass of the host plant through their influence on nutrient cycling, biological functions and pathogen status, thus acting as a bottom-up force [ 13 ].…”