Improvement of Fitness and Efficacy of a Fire Blight Biocontrol Agent via Nutritional Enhancement Combined with Osmoadaptation

Abstract

The efficacy of Pseudomonas fluorescens EPS62e in the biocontrol of Erwinia amylovora was improved by a procedure of physiological adaptation to increase colonization and survival in the phytosphere of rosaceous plants. The procedure consisted of osmoadaptation (OA) and nutritional enhancement (NE). OA was based on saline stress and osmolyte amendment of the growth medium during inoculum preparation. NE consisted of addition of glycine and Tween 80 to the formulation. NE and OA increased the growth rate and carrying capacity of EPS62e under high-relative-humidity (RH) conditions and improved survival at low RH on flowers under controlled environmental conditions. NE did not promote growth or affect infection capacity of E. amylovora. The effect of both methods was tested in the field by following the population of EPS62e using quantitative PCR (Q-PCR) (total population) and CFU counting (culturable population) methods. Following field application, EPS62e colonized blossoms, but it was stressed, as indicated by a sharp decrease in culturable compared to total population levels. However, once established in flowers and at the end of bloom, almost all the total population was culturable. The physiological adaptation treatments increased population levels of EPS62e over those of nonadapted cells during the late stage of the flowering period. Control of fire blight infections in flowers and immature fruits was tested by field application of EPS62e and subsequent inoculation with E. amylovora under controlled-environment conditions. The efficacy of fire blight control increased significantly with the combination of nutritional enhancement and osmoadaptation, in comparison with the absence of physiological adaptation.

Biological control of bacterial plant diseases with Lactobacillus plantarum strains selected for their broad‐spectrum activity

“…Because of the European Union (EU) regulatory quarantine restrictions for pathogens, the assessment of disease management strategies in orchards affected with these pathogens is practically unworkable in designated protected zones such as Spain. Therefore, semi‐field experiments have been performed in this study as they have been previously reported as being comparable to field experiments for biocontrol testing (Cabrefiga, Francés, Montesinos, & Bonaterra, ).…”

Physiological and Transcriptional Responses to Osmotic Stress of Two Pseudomonas syringae Strains That Differ in Epiphytic Fitness and Osmotolerance

“…Similarly, small differences in osmotolerance may reflect subtle differences in osmoadaptation mechanisms, with these differences influencing the relative fitness of individual species and strains. In most terrestrial environments, water stress tolerance is an important component of bacterial fitness and is therefore relevant to understanding, predicting, and manipulating the ecological success of target organisms, such as for biocontrol (1,2). Pseudomonas syringae is a foliar pathogen, as well as a common resident on leaves.…”

Adaptation strategies of Pseudomonas protegens SN15‐2 to hyperosmotic growth environment

“…Notably, stress tolerance in micro‐organisms can be induced by cultivation under suboptimal conditions to meet certain specific requirements for micro‐organisms (den Besten et al ; Caspeta et al ; Tronchoni et al ). Numerous studies have investigated the addition of short‐ or long‐term stress conditions in the microbial culture process to effectively solve problems in practical production applications (Bonaterra et al ; Cabrefiga et al , ). For probiotics, such as Lactobacillus and Propionibacterium , some studies have used a variety of stress methods to improve cell resistance and reduce the loss of living cells during processing and after entering the digestive tract (Leverrier et al ; Barbosa et al ).…”