Growth Promotion of Lettuce (Lactuca sativa L.) by a Rhizobacterium Pseudomonas fluorescens Strain LRB3W1 under Iron-Limiting Condition

Abstract

Pseudomonas fluorescens strain LRB3W1, a rhizobacterium isolated from lettuce, showed both an iron-chelating, siderophore activity and phytohormone indole-3-acetic acid production. Strain LRB3W1 was inoculated into the rhizosphere soils of 11 lettuce cultivars seedlings, resulting in increased growth of both shoot and root in most lettuce cultivars. A marked increase in growth was observed under iron-limiting conditions. Under high-iron conditions, growth of plants inoculated with the bacterium was not significantly increased. These data show that an iron chelator, siderophore, produced by the bacterium plays an important role in the growth enhancement of lettuce by the bacterium under iron-limiting conditions. Population dynamics of the bacterium in the rhizosphere was not influenced by the iron concentration.