Since global food insecurity is one of the major problems faced by humanity, there is a necessity to increase plant productivity. For this, biofungicides and biofertilizers present an ecologically... Show moreSince global food insecurity is one of the major problems faced by humanity, there is a necessity to increase plant productivity. For this, biofungicides and biofertilizers present an ecologically friendly alternative to their chemical counterparts. Among these bioinoculants, endophytic bacteria with plant growth promotion and biocontrol abilities are the most promising candidates due to their ability to colonize the plant__s interior and establish a stable, long-lasting relationship with a plant. In this thesis, I succeeded in the isolation of many beneficial endophytic strains. Among them, Bacillus subtilis HC8 isolated from giant hogweed proved to be the most versatile promising bioinoculant since it expressed its beneficial effect on diverse plants under different growth conditions. It was also shown that this strain, so far, is the only endophytic Bacillus __ and one out of a few Bacillus strains __ which is capable of producing excessively high levels of a large variety of lipopeptide antibiotics. Attempts were also made to shed light on the endophytic lifestyle of several strains. This resulted in finding L-arabinose, a carbon source which might be important for endophytic pseudomonads in cucumber plants. This and other (yet-) unidentified traits could contribute to the complex interaction of endophytic bacteria and plants Show less
The research described in this thesis shows that the enrichment technique based on competitive root tip colonization allows the isolation of bacteria which can protect plants from TFRR through... Show moreThe research described in this thesis shows that the enrichment technique based on competitive root tip colonization allows the isolation of bacteria which can protect plants from TFRR through the mechanism competition for nutrients (and niches). The efficacy of biocontrol of one of these strains, P. putida PCL1760, was estimated under industrial conditions using both conventional and molecular techniques. Quantitative PCR was used also to distinguish between different forms of Fusarum oxysporum (Fox), which cannot be distinguished using otherwise so far. It was shown that nonpathogenic Fox strains in plant material cannot reach a concentration higher than 50 fg of fungal DNA per ng of total DNA. The obtained results are an illustration of an efficient strategy, which can be exploited for the isolation of biocontrol agents for greenhouses and of the application of fast molecular methods for the estimation of their efficacy in plant protection. Moreover, this molecular method a quantitative PCR can be used to monitor pathogenic strains in tomato. Show less
The biocontrol strain studied in this thesis is Pseudomonas chlororaphis strain PCL1391, which controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-licopersici (Chin-A... Show moreThe biocontrol strain studied in this thesis is Pseudomonas chlororaphis strain PCL1391, which controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-licopersici (Chin-A-Woeng et al., 1998). Production of the anti-fungal metabolite phenazine-1-carboxamide (PCN) and an efficient root colonizing ability (Chin-A-Woeng et al., 2000) are crucial for efficient biocontrol by P. chlororaphis strain PCL1391. This thesis aims at the identification and analysis of environmental conditions affecting the production of PCN and the identification of novel genes involved in the regulation of PCN production. Show less
