The biocontrol agent
Lactiplantibacillus plantarum
AMBP214 is dispersible to plants via bumblebees
Authors: Temmermans Jari , Legein Marie , Zhao Yijie , Kiekens Filip , Smagghe Guy , de Coninck Barbara , Lebeer Sarah 
Published: October 2023

Microbial biocontrol agents have emerged as a promising alternative for the management of plant diseases and the reduction of chemical pesticide dependence. However, a significant challenge in using these agents is their inconsistent performance under field conditions, often caused by the poor establishment and limited spread of microorganisms. Entomovectoring, a system where microbial biocontrol agents are dispersed to crops via pollinators, provides a potential solution to these challenges. Still, there are limited examples of successful systems, and no studies have tested this technology with versatile and generally beneficial lactobacilli. Here, we demonstrate that
Lactiplantibacillus plantarum
AMBP214 shows potential as a biocontrol agent displaying antimicrobial activity in an
in vitro
and a gnotobiotic seedling experiment, and the ability to establish itself in strawberry flowers. An innovative formulation and dispersal strategy were proven successful with this strain, as it could be formulated into a spray-dried powder that could be loaded onto bumblebees via a dispenser. When loaded bumblebees were released into a greenhouse with strawberry plants,
L. plantarum
AMBP214 was effectively dispersed to flowers, resulting in high bacterial abundances (on average 1 × 10
5
CFUs per flower) and consistent coverage across all sampled flowers. We could not show a protective effect of AMBP214 against
Botrytis cinerea
in a greenhouse trial with strawberry flowers under the tested conditions, so that further screening of other strains against this major pathogen will be necessary. However, our study provides the necessary proof of concept data that spray-dried lactobacilli can be used with entomovectoring, providing a novel and promising approach to biocontrol. These results pave the way for further research and development of spray-dried non-spore-forming bacteria in entomovectoring strategies, which hold great promise for enhancing plant health and mitigating the negative impacts of plant diseases.

IMPORTANCE

Plant protection products are essential for ensuring food production, but their use poses a threat to human and environmental health, and their efficacy is decreasing due to the acquisition of resistance by pathogens. Stricter regulations and consumer demand for cleaner produce are driving the search for safer and more sustainable alternatives. Microbial biocontrol agents, such as microorganisms with antifungal activity, have emerged as a promising alternative management strategy, but their commercial use has been limited by poor establishment and spread on crops. This study presents a novel system to overcome these challenges. The biocontrol agent
Lactiplantibacillus plantarum
AMBP214 was spray-dried and successfully dispersed to strawberry flowers via bumblebees. This is the first report of combining spray-dried, non-spore-forming bacteria with pollinator-dispersal, which scored better than the state-of-the-art in terms of dispersal to the plant (CFU/flower), and resuscitation of the biocontrol agent. Therefore, this new entomovectoring system holds great promise for the use of biocontrol agents for disease management in agriculture.