Understanding the components that shape the rhizosphere community is vital for sustainable disease management. This study evaluated an integrated Verticillium wilt management in eggplant and its influence on the soil microbiome. Six treatments; Self-rooted (control; CLA) and sole grafted (CLB) eggplants, Brassica + Self-rooted plant (BrA), and Brassica + Grafted plants (BrB), with Biochar (10 t/ha) + Brassica + Self-rooted plant (BBrA) and Biochar (10 t/ha) + Brassica + Grafted Plant (BBrB) were used. Soil microbiome was characterized using high-throughput sequencing. The grafted treatments significantly reduced the Verticillium abundance, disease index and improved the yield of eggplant compared with CLA (18.13 t/ha), with BBrB (41.54 t/ha) as the best treatment. Results showed that treatments CLB, BrB, and BBrB stimulated more beneficial microbes, especially Arthrobacter, Bacillus, and Sphingomonas for bacteria; and Mortierella, Tausonia, and Chaetomium for fungi. Treatment BBrB was biomarked by phylum Chloroflexi (o_SBR1031), Acidobacteria, Planctomycetes, and Patescibacteria, but only Chloroflexi (o_SBR1031) was found in BrB, and none of them in CLB and treatment BBrB also contained more biomarkers than other treatments. Similarly, the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis revealed that treatment BBrB contained more genes (17.5%) regulating disease resistance followed by BrB (17.3%) and CLB (16.6%) treatments. In conclusion, grafting with Brassica (biofumigation) under a biochar regime could reduce eggplant Verticillium wilt. This study expands knowledge on how soil microbiota can be enhanced using integrated disease management practices to exploit sustainable food production.

It is demonstrated that intercropping improves soil fertility, but its effect on deep soil is still unclear. The major objective of this study was to determine the distribution of arbuscular mycorrhizal fungi (AMF) and soil aggregates and their interrelationship across soil depths in intercropping systems. A three-year positioning experiment based on a two-factor experimental design at two N application levels (N0 and N2) and different cropping systems (maize/soybean intercropping and corresponding monocultures) was started in 2017. Soil samples were collected from 0–15 cm and 15–30 cm for analyzing soil aggregates and from 0–15 cm, 15–30 cm, 30–5 cm, and 45–60 cm for determining the AMF composition. It was observed that intercropping improved the macro-aggregate (> 5 mm) content at 0–15 cm and 15–30 cm depths for maize soil and only 0–15 cm depth for soybean soil without N treatment. The application of N decreased the macro-aggregate content in the intercropping soil at 0–15 cm and 15–30 cm depths. Moreover, intercropping significantly improved the AMF diversity of maize and soybean soils across soil depths, while the application of N reduced the AMF diversity of soil across depths. The structural equation modeling analysis indicated that the intercropping system influenced the stability of soil aggregates and promoted the formation of large aggregates by altering soil nutrients and the diversity of AMF. The results further revealed the reasons behind soil fertility improvement by adopting crop diversification.

The suppressiveness of soils to inhibit pathogens mostly require rich microbiome harbouring plant growth-promoting microbes in the soil, especially rhizosphere. The present study evaluates the suppressiveness of the rhizosphere of a grafted eggplant under biochar amendment and its effects on the microbial communities involved. This study used four treatments consisting of grafted (CB) and self-rooted (CA) eggplants, with 10 t/ha biochar addition each (as BB and BA). Results revealed that BB significantly suppressed the incidence of Verticillium wilt by more than 70% and improved the yield of eggplant compared with the control. Treatment of CB and BB showed significant effects on the community structure and abundance of bacteria and fungi. The bacteria diversity and richness of CB and BB were higher than those of the BA and CA, respectively. For bacteria, the analysis showed the genus Bacillus to be abundant in the rhizosphere of both CB and BB, while genera Humicola, Chaetomium, Mortierella, and Tausonia were the dominant fungi, suggesting they may play an active part in disease suppression. Based on Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis, the results showed that CB and BB harbored more genes responsible for disease resistance than CA and BA. In summary, grafting with the addition of biochar was effective in suppressing Verticillium wilt of eggplant and can be given as a recommendation to eggplant growers to alleviate Verticillium wilt.