The dynamic of biological inoculants in the rhizosphere and the disease pyramid

Abstract

The use of biological products in agriculture, including biopesticides, biostimulants and biofertilizers, has increased considerably in recent years with a projected global market value expected to reach $20 billion in 2026. However, the efficacy of microbiological inoculants is still limited and their use often yields inconsistent outcomes. Some of the observed limitations in the use of biological inoculants include the variation in efficiency, when used in different locations or seasons, and their transient effect, which requires successive applications throughout the crop cycle to achieve satisfactory results. Thus, considering that the soil microbiome directly affects the establishment and functions of the rhizosphere inoculant, in this proposal, we will evaluate in planta the correlation between the presence of the inoculant and the structure of the bacterial community in the wheat rhizosphere during the evolution of a soilborne disease. For this, the project is split into three stages. [Stage I] Inoculant Selection: identification and characterization of plant growth-promoting bacteria (PGPB) and pathogen antagonists that will be inoculated in the rhizosphere to manipulate the microbiome. [Stage II] Microbiome dynamics: assessment of the inoculant establishment in the rhizosphere after successive introductions throughout the plant cycle and evaluation of its effect on plant development. [Stage III] Pyramid of the disease: assessment of the interaction between the inoculant and the microbiome during rhizosphere invasion by a pathogen. As a model, we will use the system of wheat root rot disease caused by the soilborne pathogen Bipolaris sorokiniana. With the accomplishment of this research project we are aiming i) to obtain potential inoculants for wheat growth promotion, ii) to understand the dynamics of the inoculant throughout the wheat cycle in the rhizosphere microbiome, and iii) to extend the classic concept of the "disease triangle" to the "pyramid of disease " with the inclusion of the microbiome as the fourth vertex. In this context, it is urgent to integrate into the traditional strategy to develop inoculants, the use of advanced molecular biology approaches, including second-generation sequencing, as well as the application of microbial ecology principles, in order to overcome current limitations in the use of biological inoculants to promote a sustainable agriculture. (AU)