Enhanced production of indole-3-acetic acid by a genetically modified strain of Pseudomonas fluorescens CHA0 affects root growth of cucumber, but does not improve protection of the plant against Pythium root rot

Abstract

The biocontrol strain CHA0 of Pseudomonas fluorescens produces small amounts of indole‐3‐acetic acid via the tryptophan side chain oxidase and the tryptophan transaminase pathways. A recombinant plasmid (pME3468) expressing the tryptophan monooxygenase pathway was introduced into strain CHA0; this resulted in elevated synthesis of indole‐3‐acetic acid in vitro, especially after addition of l‐tryptophan. In natural soil, strain CHA0/pME3468 increased fresh root weight of cucumber by 17–36%, compared to the effect of strain CHA0; root colonization was about 106 cells per g of root. However, both strains gave similar protection of cucumber against Pythium ultimum. In autoclaved soil, at 6×107 cells per g of root, strain CHA0 stimulated growth of roots and shoots, whereas strain CHA0/pME3468 caused root stunting and strong reduction of plant weight. These results are in agreement with the known effects of exogenous indole‐3‐acetic acid on plant roots and suggest that in the system examined, indole‐3‐acetic acid does not contribute to the biocontrol properties of strain CHA0.

Isolation and Characterization of Amycolatopsis sp. strain CRJ2-11 with Biocontrol and Plant Growth Promoting Potential from Upland Rice Rhizosphere in Manipur, India

“…This is comparable to that of Pseudomonas fluorescens CHAO, an IAA hyperproducing strain (195 mg/L) [31]. The strain produced much higher levels of IAA than those reported for bacterial strains reported by various authors such as Hata, et al [7], Khamna, et al [32], Shrivastava, et al [33], Harikrishna, et al [34] and Jog, et al [35].…”

Production of Indole-3-Acetic Acid via the Indole-3-Acetamide Pathway in the Plant-Beneficial Bacterium Pseudomonas chlororaphis O6 Is Inhibited by ZnO Nanoparticles but Enhanced by CuO Nanoparticles

“…The IAA levels produced by P. chlororaphis O6 with the various treatments (5 to 37 g/ml) were in the region that would boost rather than inhibit growth (3,4,24,32). The levels of Cu and Zn from the NPs used in testing the soil bacterium were relevant to levels reported for contaminated soils, ranging from 100 mg/kg to 1,000 mg/kg of Cu and 2,000 mg/kg of Zn; normal soils contain between 22 and 68 mg/kg Cu and 92 and 180 mg/kg Zn (14,33,38,39,41).…”

“…One biofertilizer, the phytohormone indole-3-acetic acid (IAA), is important in microbe-microbe and microbe-plant signaling and promotes growth in a variety of plant species (1,3,4,9,14,16,17,19,24,26,32,36,40). However, the plant growth effects of bacterial IAA are concentration dependent: improved cucumber growth in sterile soil correlates with IAA production from Pseudomonas fluorescens CHA0 at Ͻ0.7 g/ml, whereas an overproducing mutant generating IAA at ϳ153 g/ml stunts cucumber growth (4). Canola root growth was increased 35% by a wildtype P. putida strain producing IAA at about 26 g/ml (32).…”

Efeito de glyphosate e imazaquin na comunidade bacteriana do rizoplano de soja (Glycine max (L.) Merrill) e em características microbiológicas do solo

“…Essa exsudação mantém o equilíbrio ecológico entre os microrganismos na rizosfera, o que pode restringir o desenvolvimento de fitopatógenos e contribuir para a atividade de microrganismos benéficos, como os promotores de crescimento vegetal, solubilizadores de fosfato e fixadores de N 2 (Beyeler et al, 1999;O'Donnell et al, 2001;Salles et al, 2002;Botelho & Hagler, 2006).…”