Pseudomonas fluorescens LBUM223 Increases Potato Yield and Reduces Common Scab Symptoms in the Field

Abstract

Common scab of potato, caused by pathogenic Streptomyces spp., is an important disease not efficiently controlled by current methods. We previously demonstrated that Pseudomonas fluorescens LBUM223 reduces common scab development under controlled conditions through phenazine-1-carboxylic (PCA) production, leading to reduced thaxtomin A production by the pathogen, a key pathogenicity and virulence factor. Here, we aimed at determining if LBUM223 is able to increase potato yield and control common scab under field conditions, while characterizing the biocontrol mechanisms involved. We investigated if a reduction in pathogen soil populations, activation of induced systemic resistance in potato, and/or changes in txtA gene expression, involved in thaxtomin A biosynthesis in pathogenic Streptomyces spp. were involved in common scab control by LBUM223. Common scab symptoms were significantly reduced and total tuber weight increased by 46% using biweekly applications of LBUM223. LBUM223 did not reduce pathogen soil populations, nor was potato systemic defense-related gene expression significantly altered between treatments. However, a significant down-regulation of txtA expression occurred in the geocaulosphere. This is the first demonstration that a Pseudomonas strain can directly alter the transcriptional activity of a key pathogenesis gene in a plant pathogen under field conditions, contributing to disease control.

Efficiency of two inoculation methods of Pseudomonas putida on growth and yield of tomato plants

“…Inoculating microcapsules of rhizobacteria on plants increased growth and yield of tomato because this type of inoculation improves the effect of PGPR, acting as mini-reactors that confer stability, protection, population increase, and a gradual liberation of bacterial cells in the plant rhizosphere environment (Sivakumar et al, 2014;Schoebitz and Belchí, 2016). Different authors have mentioned a greater effect in applying rhizobacteria based on microcapsules compared with its liquid application, increasing diverse morphological parameters and productivity in tomato (Pastor et al, 2016), corn (Hungria et al, 2010) and potato (Arseneault et al, 2015), among others. The stimulating activity of plant growth by rhizobacteria as P. putida is due to its capacity of synthesizing growth regulators, such as auxins, gibberellins, cytokinins, and vitamins; antagonistic metabolites as siderophores and hydrocyanic acid (HCN), as well as for their ability to facilitate nutrients through phosphorus solubilization, biological fixation of atmospheric nitrogen, and ion chelation (Vacheron et al, 2013;Bashan et al, 2014;Ul Hassan and Bano, 2015).…”

Phenazines in plant‐beneficial Pseudomonas spp.: biosynthesis, regulation, function and genomics

“…Phenazines have also been shown to reduce the expression of key pathogenicity‐related genes in Streptomyces scabies (St‐Onge et al ., ). Inoculation of potato plants with Pseudomonas synxantha LBUM223 (formerly P. fluorescens ) significantly reduced common scab symptoms under controlled (Arseneault et al ., ) and field conditions (Arseneault et al ., ). Symptom reduction was associated with a significant decrease in txtA transcript abundance.…”

“…tritici (Thomashow and Weller, 1988), Rhizoctonia solani (Gurusiddaiah et al, 1986;Jaaffar et al, 2017), Fusarium oxysporum f. sp. radicis-lycopersici (Chin-A- Woeng et al, 1998), Streptomyces scabies (St-Onge et al, 2011;Arseneault et al, 2015), Pythium spp. (Gurusiddaiah et al, 1986;Anjaiah et al, 1998), and Phytophthora infestans (Morrison et al, 2016a).…”

Efecto de microcápsulas de Pseudomonas putida sobre crecimiento y rendimiento de pimiento morrón

“…El aprovechamiento de cepas rizobacterianas de diversos géneros como Pseudomonas, Bacillus, Azospirillum, Serratia, entre otros, han sido ampliamente estudiadas, particularmente por su cualidad para promover el crecimiento vegetativo y productividad en los cultivos de chile (Gupta et al, 2015), tomate (Agrawal y Agrawal, 2013), arroz (García et al 2010), soya (Husen et al, 2011), maíz (Hungria et al, 2010) y papa (Arseneault et al, 2015).…”