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.

Keywords: AM-fungal community composition; Glomus-AM symbiosis; cucumber yield; fruit quality; garlic substrate; mycorrhizal inoculation.

Figure 1

Arbuscular mycorrhizal (AM) root colonization (A), fusarium wilt incidence % (B), extraradical hyphal (ERH) density (C), and spore density (D) among treatments. Non-amendment, control; GS, garlic stalk addition; AMF, mycorrhizal Inoculation; GS+AMF, combine garlic stalk and AMF addition. Shared letters above bars denote no significant difference among treatments, as indicated by LSD’s (p < 0.05; means ± SE, n = 3).

Figure 2

The nutrient uptake analysis in the final harvest of cucumber fruits examined during the spring cultivation of 2018. Different letters indicate the significant differences (p < 0.05) by means comparisons (means ± SE, n = 3).

Figure 3

The relative abundance of major identified taxonomic genera of AMF across all treatments. The treatments NA-NM, NA+AM, GS-NM and GS+AM represent the applied soil amendments. Non-amendment and non-mycorrhizal inoculation, non-amended mycorrhizal Inoculation, garlic stalk amended with non-mycorrhizal inoculum and Garlic stalk amended with mycorrhizal inoculum, respectively.

Figure 4

A Venn diagram displaying the degree of overlap or OTUs based co-occurrence of AMF (at the 3% evolutionary distance) among the four treatments. NA-NM: Non-amended Non-mycorrhizal inoculation; NA+AM: Non-amended Mycorrhizal Inoculation; GS-NM: Garlic stalk amended with Non-mycorrhizal inoculum; GS+AM: Garlic stalk amended with mycorrhizal inoculum. Total number of OTUs in each group (A), overlapping fashion among all soil samples (B), and specific and shared OTUs (C) among treatments.

Figure 5

Clustering analysis of AMF communities (A), and principal component analysis (B) of the different soil samples based on OTU abundance.

Figure 6

Heat map analysis revealed the relationship between top abundant AMF taxa and cucumber productivity. (Pearson correlation *: p < 0.05; **: p < 0.01; ***: p < 0.001).