Bio‐organic soil amendment promotes the suppression of Ralstonia solanacearum by inducing changes in the functionality and composition of rhizosphere bacterial communities

Abstract

Stimulating the development of soil suppressiveness against certain pathogens represents a sustainable solution toward reducing pesticide use in agriculture. However, understanding the dynamics of suppressiveness and the mechanisms leading to pathogen control remain largely elusive.Here, we investigated the mechanisms used by the rhizosphere microbiome induces bacterial wilt disease suppression in a long-term field experiment where continuous application of bio-organic fertilizers (BFs) triggered disease suppressiveness when compared to chemical fertilizer application. We further demonstrated in a glasshouse experiment that the suppressiveness of the rhizosphere bacterial communities was triggered mainly by changes in community composition rather than only by the abundance of the introduced biocontrol strain.Metagenomics approaches revealed that members of the families Sphingomonadaceae and Xanthomonadaceae with the ability to produce secondary metabolites were enriched in the BF plant rhizosphere but only upon pathogen invasion. We experimentally validated this observation by inoculating bacterial isolates belonging to the families Sphingomonadaceae and Xanthomonadaceae into conducive soil, which led to a significant reduction in pathogen abundance and increase in nonribosomal peptide synthetase gene abundance.We conclude that priming of the soil microbiome with BF amendment fostered reactive bacterial communities in the rhizosphere of tomato plants in response to biotic disturbance.

Characterization of the Soil Bacterial Community from Selected Boxwood Gardens across the United States

“…Boxwood is also considered a low maintenance woody shrub plant once it is established [ 96 ]. This relatively low maintenance may have further contributed to the stability of the bacterial composition in these gardens and, consequently, to the improved soil suppressiveness, in contrast to intensively managed agricultural soils [ 97 , 98 , 99 , 100 ]. Yet, two questions of practical importance remain: (1) how applicable are the results of the present study to other private gardens; and (2) whether these results also are applicable to public gardens, which likely utilize rather different cultural practices than private gardens.…”

Partitioning the Effects of Soil Legacy and Pathogen Exposure Determining Soil Suppressiveness via Induced Systemic Resistance

“…For example, the enrichment of the seed-endophytic bacterium Sphingomonas was shown to produce anthranilic acid and induce resistance in disease-susceptible rice genotypes [ 52 ]. In our previous study, three Sphingomonas strains isolated from the tomato rhizosphere also showed to be effective in the control of bacterial wilt disease [ 24 ]. Furthermore, members of the genus Niastella were reported to be important biocontrol agents against stripe rust in wheat [ 53 ].…”

“…Soils with different histories (i.e., suppressive and conducive soils, respectively) were collected from a long-term experimental field site located at the Nanjing Institute of Vegetable Science, Nanjing, China (32°02′ N, 118°50′ E). The disease suppressiveness of the suppressive soil was determined in our previous study [ 24 ]. In brief, conducive soils were mixed with 10% of suppressive soils heat-treated at different temperatures.…”

Application and Development of Biocontrol Agents in China

“…Plant disease suppression by a bio-organic fertilizer not only relies on its own beneficial microorganism but also involves mobilizing beneficial indigenous soil bacteria [ 29 , 30 ]. In an elegant study, Deng et al reported that bio-organic fertilizer could promote the suppression of R. solanacearum by inducing changes in the functionality and composition of rhizosphere bacterial communities [ 31 ].…”