Streptomyces-triggered coordination between rhizosphere microbiomes and plant transcriptome enables watermelon Fusarium wilt resistance.

The use of microbial inoculant is a promising strategy to improve plant health, but their efficiency often faces challenges due to difficulties in successful microbial colonization in soil environments. To this end, the application of biostimulation products derived from microbes is expected to resolve these barriers via direct interactions with plants or soil pathogens. However, their effectiveness and mechanisms for promoting plant growth and disease resistance remain elusive. In this study, we showed that root irrigation with the extracts of Streptomyces ahygroscopicus strain 769 (S769) solid fermentation products significantly reduced watermelon Fusarium wilt disease incidence by 30% and increased the plant biomass by 150% at a fruiting stage in a continuous cropping field. S769 treatment led to substantial changes in both bacterial and fungal community compositions, and induced a highly interconnected microbial association network in the rhizosphere. The root transcriptome analysis further suggested that S769 treatment significantly improved the expression of the MAPK signalling pathway, plant hormone signal transduction and plant-pathogen interactions, particular those genes related to PR-1 and ethylene, as well as genes associated with auxin production and reception. Together, our study provides mechanistic and empirical evidences for the biostimulation products benefiting plant health through coordinating plant and rhizosphere microbiome interaction.

Fumigation practice combined with organic fertilizer increase antibiotic resistance in watermelon rhizosphere soil.

Chemical fumigants and organic fertilizer are commonly used in facility agriculture to control soil-borne diseases and promote soil health. However, there is a lack of evidence for the effect of non-antibiotic fumigants on the distribution of antibiotic resistance genes (ARGs) in plant rhizosphere soils. Here, the response of a wide spectrum of ARGs and mobile genetic elements (MGEs) to dazomet fumigation practice in the rhizosphere soil of watermelon was investigated along its branching, flowering and fruiting growth stages in plastic shelters using high-throughput quantitative PCR approach. Our results indicated that soil fumigation combined with organic fertilizer application significantly increased the relative abundance of ARGs and MGEs in the rhizosphere soil of watermelon plant. The positive correlations between the relative abundance of ARGs and MGEs suggested that soil fumigation might increase the horizontal gene transfer (HGT) potential of ARGs. This result was further confirmed by the enhanced associations between ARG and MGE subtypes in the networks of fumigation treatments. Moreover, bipartite associations between ARGs/MGEs and microbial communities (bacteria and fungi) revealed a higher percentage of linkage between MGEs and microbial taxa in the fumigated soils. Structural equation model analysis further suggested that the increases in antibiotic resistance after fumigation and organic fertilizer application were mainly driven by MGEs and fungal community. Together, our results provide vital evidence that dazomet fumigation process combined with organic fertilizer in plastic shelters has the great potential to promote ARGs' dissemination in the rhizosphere, and raise cautions of the acquired resistance by soil-borne fungal pathogen and the potential spreading of ARGs along soil-plant continuum.