Growth promotion of winter wheat by fluorescent pseudomonads under growth chamber conditions

Abstract

The efficacy of Pseudomonas cepacia R85, P. putida R104 and R105, and P. fluorescens R111 and their rifampicin-nalidixic acid resistant (Rif r Nal r) counterparts to enhance the growth of winter wheat ( Triticum aestivum L. var Norstar) was assessed in two soils under simulated fall conditions (at 5°C) in a growth chamber. Bacterial colonization and survival on wheat roots, and the effects of inoculation on plant yield, total-P, total-Fe and 15N-uptake from fertilizer were determined. Introduced Rif r Nal r pseudomonads colonized and survived on the plant roots throughout the 150-day study. Some wild-type and their Rif r Nal r mutants enhanced early plant biomass of winter wheat in a low-fertility Dark Brown Chernozemic soil, whereas grain yield was enhanced by 46–75% in a more fertile Ortho Black Chemozemic soil. Inoculation also affected the uptake of fertilizer N and soil Fe by winter wheat in both soils. Our results show that some fluorescent pseudomonads and their Rif r Nal r mutants stimulated growth and nutrient uptake of vernalized winter wheat, although the response to inoculation was dependent on soil characteristics. The use of Rif r Nal r marked bacteria allowed root colonization and population dynamics of inoculants in the rhizosphere of winter wheat to be studied, and may facilitate plant-inoculant studies under field conditions.