A scalable screening approach reveals phylogenetic patterns of bacterial antagonism against potato pathogens
Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Microbial biological control agents (mBCAs) offer a promising alternative to conventional disease management, but identifying effective strains requires screening large microbial collections against many pathogens. Here, we developed a scalable screening approach to characterize the antagonistic activity of potato-associated bacteria against multiple pathogens and investigated how bacterial origin and phylogeny relate to antagonistic phenotypes. A collection of 600 bacterial strains isolated from two potato cultivars, three plant compartments using four cultivation media was screened against six major potato pathogens: the bacteria Dickeya solani and Pectobacterium carotovorum , the fungi Alternaria solani and Rhizoctonia solani , and the oomycetes Phytophthora infestans and Pythium ultimum . A scalable confrontation method was developed for non-filamentous bacteria, while complementary lower-throughput assays were used for filamentous strains. This approach enabled successful assessment of 92% of non-filamentous and 97% of filamentous strain-pathogen combinations. Isolation cultivar, plant compartment and cultivation medium had only limited effects on the proportion of antagonistic strains. In contrast, pathogen sensitivity varied markedly: P. infestans was the most susceptible pathogen, whereas D. solani and P. carotovorum were generally resistant to bacterial antagonism. Antagonistic activity clustered phylogenetically, with Bacillus and Streptomyces containing many broad-spectrum inhibitors. In addition, several taxa showed preferential activity against the oomycetes, including P. infestans -specific antagonists from the Pseudomonas genus and P. ultimum -specific antagonists from the Frigoribacterium , Curtobacterium , Pedobacter and Phyllobacterium genera. Overall, multi-pathogen screening revealed distinct generalist and specialist antagonistic profiles and identified candidate strains and taxa for further evaluation as mBCAs.
Highlights
-
A scalable confrontation method enabled the screening of 400 non-filamentous bacterial strains against six potato pathogens. Two hundred filamentous strains from the Actinomycetes class required separate lower-throughput methods because growth conditions were incompatible with the scalable assay.
-
The screening of these 600 potato-associated bacterial strains revealed distinct phylogenetic patterns of broad-spectrum and pathogen-specific antagonism across six major potato pathogens.
-
Pathogen sensitivity differed strongly among taxonomic groups: the bacterial pathogens Dickeya solani and Pectobacterium carotovorum were the most resistant, the oomycetes Phytophthora infestans and Pythium ultimum were the most sensitive, and the fungi Alternaria solani and Rhizoctonia solani showed intermediate sensitivity.
-
Specialist antagonists were identified in several bacterial taxa, including Micrococcales, Sphingobacteriales and Rhizobiales against P. ultimum , and Streptomycetales and Pseudomonadales against Phytophthora infestans .
-
The bacterial and fungal pathogens were almost exclusively inhibited by broad-spectrum bacterial strains from the Streptomyces and Bacillus genera.
