Biocontrol of the Potato Blackleg and Soft Rot Diseases Caused by Dickeya dianthicola

Abstract

Development of protection tools targetingDickeya species is an important issue in the potato production. Here, we present the identification and the characterization of novel biocontrol agents. Successive screenings of 10,000 bacterial isolates led us to retain 58 strains that exhibited growth inhibition properties against several Dickeya sp. and/or Pectobacterium sp. pathogens. Most of them belonged to the Pseudomonas and Bacillus genera. In vitro assays revealed a fitness decrease of the tested Dickeya sp. and Pectobacterium sp. pathogens in the presence of the biocontrol agents. In addition, four independent greenhouse assays performed to evaluate the biocontrol bacteria effect on potato plants artificially contaminated with Dickeya dianthicola revealed that a mix of three biocontrol agents, namely, Pseudomonas putida PA14H7 and Pseudomonas fluorescens PA3G8 and PA4C2, repeatedly decreased the severity of blackleg symptoms as well as the transmission of D. dianthicola to the tuber progeny. This work highlights the use of a combination of biocontrol strains as a potential strategy to limit the soft rot and blackleg diseases caused by D. dianthicola on potato plants and tubers. The Pectobacterium and Dickeya pectinolytic bacteria are phytopathogens responsible for several macerating diseases on a wide range of crop and ornamental plants (1-3). The damage caused by these pathogens remains an important issue in many countries worldwide. In Europe, the pectinolytic pathogens on potato crops include Pectobacterium atrosepticum, Pectobacterium carotovorum subsp. carotovorum, Dickeya dianthicola, and Dickeya solani (4-8). Recently, new Pectobacterium taxa, i.e., P. wasabiae and P. carotovorum subsp. brasiliense, have been characterized (2, 9, 10). Pectobacterium sp. populations are qualified as endemic, as their presence has been observed for almost a century in Europe, while the presence of Dickeya spp. as a cause of the symptoms in potato fields was sporadic until the 2000s and the Dickeya sp. damages were probably exclusively due to the species D. dianthicola. In contrast, D. solani seems to have emerged in the 2000s (3).Pectobacterium and Dickeya potato pathogens induce blackleg on stems and soft rot on tubers (11,12). A polyphyletic pathogen population may be isolated from a single sample of symptomatic plant tissues (13). The pathogens penetrate in host plants through natural pores or wounds (i.e., the lenticels, the elongation zones of roots, or insect wounds) as well as mechanical wounds. Insects can act as vectors; surface water and aerosols may also contribute to the dissemination of the pathogens (12, 14-21). Once the pathogens have infected the plant, they may propagate throughout the whole plant and son tubers by the vascular vessels. Losses due to Pectobacterium and Dickeya, related to stem and tuber rot, are major causes for downgrading and rejection of potatoes during seed potato certification. The certification is based on visual inspections in fields or on lots, ranging in Europe from 0 to 4% blackl...

A Complex Mechanism Involving LysR and TetR/AcrR That Regulates Iron Scavenger Biosynthesis in Pseudomonas donghuensis HYS

“…We found by using a bioinformatics analysis that four additional new strains, as well as P. donghuensis P482 and P. donghuensis HYS, have the same arrangement of cluster 1 and share a high identity (over 77%) with P. donghuensis HYS (data not shown). These strains are Pseudomonas putida strain PA14H7 (31,32), Pseudomonas putida strain ABAC8 (33), Pseudomonas sp. strain NBRC111117, and Pseudomonas putida strain UASWS0946 (34).…”

Comparative genomics reveals signature regions used to develop a robust and sensitive multiplex TaqMan real‐time qPCR assay to detect the genus Dickeya and Dickeya dianthicola

“…Soft rot Enterobacteria are also associated with the most serious problems facing potato production worldwide. The impact of soft rot disease varies from country to country; in the Netherlands, the annual estimated losses are around €30 million per year, while in Israel, potato yield losses of 20–25% have been observed (Tsror (Lahkim) et al ; Raoul des Essarts et al ; Buttimer et al ).…”

“…Infected plants show stunting, chlorosis, wilting, black discoloration and soft rot, which begins at the stem base and progresses upward. Once infection has occurred, the pathogen colonizes the vascular tissues and moves throughout the plant (Raoul des Essarts et al ); severe infections lead to whole plant collapse. Latent infections can result in severe losses during storage, especially in warehouses that lack refrigeration facilities (Laurila et al ).In recent years, D. dianthicola has emerged as one of the most important pathogens infecting potatoes worldwide, and symptoms resemble those of blackleg caused by Pectobacterium species (Boluk and Arif ).…”

When Genome-Based Approach Meets the “Old but Good”: Revealing Genes Involved in the Antibacterial Activity of Pseudomonas sp. P482 against Soft Rot Pathogens

“…atroseptica (currently Pectobacterium atrosepticum ; Cronin et al, 1997 ). Despite other reports on Pseudomonas strains inhibiting the growth of soft rot bacteria, they all lack information on the mechanism of these antagonistic interactions (Krzyzanowska et al, 2012 ; Cigna et al, 2015 ; Raoul des Essarts et al, 2016 ).…”