Rhizobacteria

The rhizobacteriaPlant Growth Promoting Rhizobacteria (PGPR) are bacteria that rapidly colonise the rhizosphere, i.e. the root zone in their environment.

In addition, they perform several beneficial actions in turf such as: synthesising phytohormones that facilitate rooting, secreting compounds that improve soil structure, facilitating nutrient uptake and protecting the plant against pathogens, Elliot et al, 2004.

Initially only the genus Pseudomonasbut now includes bacteria of the genera Azotobacter, Arthrobacter, Bacillus, Clostridium, Hydrogenophaga, Enterobacter, Serratia, Azospirillum, Paenibacillus and Rhizobium. Benizri et al., 2001.

The microbiological community is very abundant in the rhizosphere and therefore there is competition between them for nutrients and space colonised by the roots. So to have a positive impact on the turf, inoculations must be highly competitive.

An antibiotic secretion mechanism occurs along the root for pathogen suppression. Lutenberg & Kamilova, 2009.

Rhizobacteria perform various positive actions on turf:

- Promotion of growth. Biofertilisation.

- Damage reduction by insects and parasites through induction of systemic resistance, Van loon 1998, Kloepper et al., 2004.

- Pathogen suppression foliar and soil antagonisms, Backman et al., 1997. Examples of positive antagonisms are those against "Take all patch" and "Pythium" diseases. There are also toxin secretion mechanisms, Howe et al., 2004.

- Increased assimilation of nutrients, Benizri et al., 2001, Dimkpa et al., 2009.

However, studies show that inconsistencies in results can occur from year to year, or between different areas.

This is largely due to environmental conditions.

Temperature and humidity ranges have to be optimal for each particular genus. In addition, all new products are tested at different locations and for several years.

Increasingly, studies are demonstrating the benefits of rhizobacteria to cold climate turfgrasses, Bigelow et al., 2003 and Elliot et al., 2004.