Phytohormone production and colonization of canola (Brassica napus L.) roots by Pseudomonas fluorescens 6-8 under gnotobiotic conditions

• Published in: Canadian journal of microbiology Vol. 58; no. 2; pp. 170 - 178
• Main Authors: Pallai, Rajash, Hynes, Russell K, Verma, Brij, Nelson, Louise M
• Format: Journal Article
• Language: English
• Published: Ottawa, ON NRC Research Press 01.02.2012; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Acetic acid; adenosine; Animals; aseptic conditions; Bacteriology; Bioassays; Biochemistry; Biological and medical sciences; Brassica napus; Brassica napus - growth & development; Brassica napus - microbiology; Brassica napus - physiology; canola; cytokinins; Cytokinins - metabolism; Fundamental and applied biological sciences. Psychology; Germ-Free Life; Gram-negative bacteria; green fluorescent protein; indole acetic acid; Indoleacetic Acids - metabolism; Isopentenyladenosine - analogs & derivatives; Isopentenyladenosine - metabolism; Microbiology; Miscellaneous; mutants; Plant growth; Plant Growth Regulators - metabolism; Plant Roots - growth & development; Plant Roots - microbiology; Plant Roots - physiology; Pseudomonas fluorescens; Pseudomonas fluorescens - physiology; Rape plants; Rhizosphere; root growth; Roots; seed inoculation; seedling growth; Seedlings; Seedlings - microbiology; Seeds - microbiology; Symbiosis; zeatin; Pseudomonadales; Gnotobiotic animal; Root; Pseudomonas fluorescens; Cruciferae; Dicotyledones; Angiospermae; Brassica napus; Bacteria; Pseudomonadaceae; Spermatophyta; Phytohormone; Oil plant (vegetal)
• ISSN: 1480-3275; 0008-4166; 1480-3275
• DOI: 10.1139/W11-120

Pseudomonas fluorescens 6-8, a rhizosphere isolate previously shown to enhance root elongation of canola (Brassica napus L.), was characterized for its ability to produce indole-3-acetic acid and cytokinins in pure culture and in the rhizosphere of canola under gnotobiotic conditions in comparison with the cytokinin-producing strain P. fluorescens G20-18 and its mutant CNT2. Strain 6-8 produced isopentenyl adenosine, zeatin riboside, and dihydroxyzeatin riboside at levels similar to those of G20-18, but only very low concentrations of indole-3-acetic acid. In a gnotobiotic assay canola inoculated with 6-8 and G20-18 had higher concentrations of isopentenyl adenosine and zeatin riboside in the rhizosphere and greater root length than the noninoculated control. The ability of strain 6-8 to colonize canola roots was assessed following transformation with the green fluorescent protein and inoculation onto canola seed in a gnotobiotic assay. Higher populations of strain 6-8 were observed on the proximal region of the root closest to the seed than on the mid and distal portions 9 days after seed inoculation. The ability of P. fluorescens 6-8 to produce cytokinins, colonize the roots of canola seedlings, and enhance root elongation may contribute to its ability to survive in the rhizosphere and may benefit seedling growth.