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Universiteit Hasselt / Maastricht University (2017)

Can drought-resistant plant-growth promoting bacteria help plants to survive in arid environments ?

Paredis, Elke

Titre : Can drought-resistant plant-growth promoting bacteria help plants to survive in arid environments ?

Auteur : Paredis, Elke

Université de soutenance : Universiteit Hasselt / Maastricht University

Grade : Master in de biomedische wetenschappen-milieu en gezondheid 2017

INTRODUCTION Drought is an insidious hazard of nature expected to cause serious plant growth problems for more than 50% of the arable lands by 2050. It is a worldwide, natural occurring phenomenon defined as sustained large-scale occurrence of a below average water availability. Together with the continuous rise in population, major challenges for the agricultural sector are implied to sustain food availability. Therefore, investigation towards an alternative method is necessary. Plant growth promoting bacteria (PGPB) may be beneficial to plants by providing nutrients, modulate hormone levels to protect plants from abiotic stresses. The aim of this research is to investigate if PGPB isolated from the drought resistant Pistacia terebinthus (in spring and autumn), a tree existing in the arid Bulgarian Rhodope Mountains, and PGPB isolated from the grass around the Pistacia (autumn) can transfer their drought resistance to wheat (Triticum turgidum var. durum cv. Vitron).
MATERIALS AND METHODS In vitro bioassays for plant growth promotion (PGP) and drought tolerance (DT) tests were performed for strains isolated from pistacia and grass, followed by in planta drought exposure experiments where wheat was inoculated with the most promising strains. Plant parameters such as biometric measurements, anti-oxidative capacity and photosynthetic parameters were measured. A genotypic characterization was performed for a subset of the community obtained from Pistacia. Automated rDNA intergenic spacer analysis (ARISA) fingerprinting was performed for DNA extracted from rhizosphere and bulk soil originating from Pistacia to compare total bacterial communities between the seasons. Furthermore, quantification of vesicular arbuscular mycorrhizal (VAM) fungi colonization was performed for Pistacia roots obtained from the different seasons of sampling (spring and autumn).
RESULTS When plants were not exposed to drought, no difference could be observed between the non-inoculated and inoculated conditions. Inoculation with strains derived from Pistacia caused an increase in the biometrical and photosynthetic parameters. With the exception for strain 157a Raoultella sp., where a decrease in antioxidant capacity was observed. Overall, inoculation with strains derived from grass yield negative effects when considering the plant parameters. Genera were diverse between spring and autumn for the cultivable bacteria. A trend towards separation of total bacterial communities in spring and autumn was visible. Pistacia roots showed VAM colonization over the two different seasons.
DISCUSSION AND CONCLUSION Based on this research, our findings suggest that PGP activity is a stress-dependent and not a per se feature of the strains. Moreover, strains isolated from the Pistacia are better in alleviating drought stress in wheat than strains derived from grass. Thereby stating that drought-resistance PGPB obtained from Pistacia are cross compatible with different plant models. The abundance of VAM in the roots of Pistacia can lead towards promising results in further research. The use of selected microorganisms, alone or in a consortium may represent an important approach to decrease the deleterious effects of stress in crops.


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