Enrichment for enhanced competitive plant root tip colonizers selects for a new class of biocontrol bacteria

Abstract

SummaryOur group studies tomato foot and root rot, a plant disease caused by the fungus Forl ( Fusarium oxysporum f.sp. radicis-lycopersici ). Several bacteria have been described to be able to control the disease, using different mechanisms. Here we describe a method that enables us to select, after application of a crude rhizobacterial mixture on a sterile seedling, those strains that reach the root tip faster than our best tomato root colonizer tested so far, the Pseudomonas fluorescens biocontrol strain WCS365. Of the five tested new isolates, four appeared to be able to reduce the number of diseased plants. Analysis of one of these strains, P. fluorescens PCL1751, suggests that it controls the disease through the mechanism 'competition for nutrients and niches', a mechanism novel for biocontrol bacteria. Moreover, this is the first report describing a method to enrich for biocontrol strains from a crude mixture of rhizobacteria. Another advantage of the method is that four out of five strains do not produce antifungal metabolites, which is preferential for registration as a commercial product.

Response of barley to root colonization byPseudomonassp. DSMZ 13134 under laboratory, greenhouse, and field conditions

“…Soil-borne pathogens can be suppressed by PGPB directly or indirectly. While effective colonization of the plant root alone is not sufficient for biocontrol of pathogens (Kamilova et al 2005), pathogen growth is inhibited or slowed by the production of antibacterial and antifungal secondary metabolites (antibiosis), competition for nutrients and niches or signal interference (Lugtenberg and Kamilova 2009). Pseudomonas sp.…”

Survival of Pseudomonas extremorientalis TSAU20 and P. chlororaphis TSAU13 in the rhizosphere of common bean (Phaseolus vulgaris) under saline conditions

“…Strains P. extremorientalis TSAU20 and P. chlororaphis TSAU13 are from the culture collection of the Department of Microbiology and Biotechnology, National University of Uzbekistan, Tashkent (Egamberdieva and Kucharova 2009). The strains were isolated from the rhizosphere of wheat grown in salinated Uzbek soil after using the enrichment procedure for the isolation of enhanced root tip colonisers described by Kamilova et al (2005).…”

Innovative Biological Solutions to Challenges in Sustainable Biofuels Production

“…On the microbial side, several compounds secreted by the soil bacteria such as salicylic acid, Acyl homoserine lactones, acetoin, and 2,3-butanediol have been shown to induce ISR (Ryu et al, 2003;Shuhegge et al, 2006;van Loon, 2007). Interestingly, unlike other biocontrol associations ISR does not require an extensive colonization of the host plant (Kamilova et al, 2005). However, due to the complexity of the bacterial communities in the soil, a more comprehensive understanding of their genomes and secretomes is necessary before we further explore the use of soil bacteria as biocontrol agents.…”