Efficacy of Soft-Rot Disease Biocontrol Agents in the Inhibition of Production Field Pathogen Isolates

Abstract

The Dickeya and Pectobacterium bacterial species cause blackleg and soft-rot diseases on potato plants and tubers. Prophylactic actions are essential to conserve a high quality of seed potato tubers. Biocontrol approaches are emerging, but we need to know how efficient biocontrol agents are when facing the natural diversity of pathogens. In this work, we sampled 16 production fields, which were excluded from the seed tuber certification scheme, as well as seven experimental parcels, which were planted with seed tubers from those production fields. We collected and characterized 669 Dickeya and Pectobacterium isolates, all characterized using nucleotide sequence of the gapA gene. This deep sampling effort highlighted eleven Dickeya and Pectobacterium species, including four dominant species namely D. solani, D. dianthicola, P. atrosepticum and P. parmentieri. Variations in the relative abundance of pathogens revealed different diversity patterns at a field or parcel level. The Dickeya-enriched patterns were maintained in parcels planted with rejected seed tubers, suggesting a vertical transmission of the pathogen consortium. Then, we retained 41 isolates representing the observed species diversity of pathogens and we tested each of them against six biocontrol agents. From this work, we confirmed the importance of prophylactic actions to discard contaminated seed tubers. We also identified a couple of biocontrol agents of the Pseudomonas genus that were efficient against a wide range of pathogen species.

Pseudomonas PA14H7: Identification and Quantification of the 7-Hydroxytropolone Iron Complex as an Active Metabolite against Dickeya, the Causal Agent of Blackleg on the Potato Plant

“…The CFSs of PA14H7, PA1G7, and PP1-210 showed a bactericidal effect against P. atrosepticum P8-Me25a (Table 1). These three bacteria had already presented a largescale inhibitory effect against SRP during direct confrontation in vitro tests [19]. However, the CFS of PA14H7 was the only one that displayed a bacteriostatic effect against the whole tested panel of SRP (Table 1).…”

“…Their antagonistic activities were first evaluated against Pectobacterium atrosepticum and Dickeya dianthicola [17,18]. As a second step, this evaluation was extended to a representative panel of Pectobacterium and Dickeya diversity in France, which showed that PA14H7, as well as PA1G7 and PP1-210F, had the greatest activity against SRP [19].…”

Looking for Resistance to Soft Rot Disease of Potatoes Facing Environmental Hypoxia

“…The natural interactions between soil microorganisms, which may impact both pathogens and their hosts, can be considered to protect plants from soft rot [175]. There is an increasing emphasis on research dedicated to the discovery of new strains of bacteria active against soft rot disease, including, but not limited to, the genera Agrobacterium [176], Bacillus [160,[176][177][178][179][180][181][182][183][184][185][186][187], Bdellovibrio [188], Brevibacillus [185], Lactobacillus [177], Lellilottia [189], Ochrobactrum [190,191], Paenibacillus [192], Pseudomonas [178,179,183,184,186,[193][194][195][196], Rahnella [189], Rhodococcus [197][198][199], Serratia [110,189,200], Streptomyces [178,201,202], and Variovorax [176]. There are several reports of biocontrol strains against SRP of fungi: Aspergillus [203], Penicillium…”

Assessment of Resistance to the Pathogen of Soft Rotand Blackleg Common in Ukraine Potato Varieties

“…Чорна ніжка та м'яка гниль -поширені бактеріальні хвороби картоплі (De Boer et al, 2012). До етіологічних збудників м'якої гнилі бульб і чорної ніжки картоплі в полі відносять представників родини Enterobacteriaceae, родів Dickeya та Pectobacterium (Cigna et al, 2023). У світі лідируюче місце в ураженні картоплі чорною ніжкою та м'якою гниллю посідає Pectobacterium atrosepticum, який, на відміну від деяких інших представників, таких як Pectobacterium carotovorum, Pectobacterium brasiliense або Dickeyadadantii, обмежений вузьким колом господарів (Sledz et al, 2023).…”