Utjecaj suše na autohtone sojeve Rhizobium spp. u in vitro uvjetima

master's thesis

• Title (english): Impact of drought on indigenous Rhisobium spp. strains under in vitro conditions
• Author: Edita Maskalan
• Mentor: Sanja Sikora (mentor)
• Committee member: Sanja Sikora (predsjednik povjerenstva)
• Committee member: Nina Toth (član povjerenstva)
• Committee member: Snježana Kereša (član povjerenstva)
• Committee member: Ivana Rajnović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Agriculture; (Microbiology); Zagreb
• Defense date and country: 2019-09-30, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Agronomy

Abstract

Nedostatak vode je abiotski čimbenik koji utječe na poljoprivrednu proizvodnju ugrožavajući biljni i bakterijski rast te je često glavni uzrok izostanka nodulacije i simbiozne fiksacije dušika. Kako bi se iskorištavanje fiksacije dušika unaprijedilo danas je sve više u upotrebi inokulacija mahunarki pa je uz odabrane genotipove graha potrebno izvršiti i selekciju sojeva kvržičnih bakterija (rizobija). U tlu postoje autohtone populacije rizobija koje su često u kompeticijiskim odnosim sa introduciranim bakterijama zbog svoje bolje prilagođenosti na ekološke uvjete okoline. U ovom radu, 49 autohtonih sojeva koji noduliraju grah podvrgnuto je ispitivanju u uvjetima in vitro suše. Polietilen glikol 6000 korišten je kako bi se odredila tolerantnost odabranih sojeva na induciranu sušu u laboratorijskim uvjetima. U optimalnim uvjetima (0% PEG 6000) najbolji rast uočen je kod soja 1BT (Rhizobium sp.), a soj 1AT (Rhizobium leguminosarum) imao je najslabiji rast. Dodatkom polietilen glikola (PEG 6000) u koncentraciji od 15% u hranjivu otopinu došlo je do znatnog smanjenja rasta svih ispitanih autohtonih sojeva kao i referentnih sojeva. Pri povećanju koncentracije PEG 6000 na 30% inducirajući izrazitu sušu, najbolji rast pokazao je autohtoni soj 8Z (Rhizobium sp.) dok je soj 21Z (R. leguminosarum) bio najosjetljiviji na nedostatak vode. Uočena je veća prosječna vrijednost rasta ispitanih autohtonih sojeva u odnosu na referentne sojeve. Najveća otpornost na sušu utvrđena je kod izolata Rhizobium sp. čiji taksomski status još nije u potpunosti definiran i koji potencijalno predstavljaju nove vrste kvržičnih bakterija. Rezultati ovih istraživanja jasno potvrđuju značaj selekcije autohtonih sojeva rizobija na nepovoljne uvjete u okolišu.

Abstract (english)

Water deficiency is an abiotic factor affecting agricultural production, endangering plant and bacterial growth and is often the main cause of absence of nodulation and symbiotic nitrogen fixation. In order to improve the utilization of nitrogen fixation, inoculation of legumes is increasingly used today, so with selected bean genotypes it is also necessary to select strains of nodule bacteria (rhizobia). Indigenous rhizobial populations can be present in the soil and they are often in competitive relations with introduced bacteria because of their better adaptation to environmental conditions. In this study, 49 indigenous strains nodulating common bean were subjected to in vitro drought testing. Polyethylene glycol 6000 was used to determine the tolerance of selected strains to induced drought under laboratory conditions. Under optimal conditions (0% PEG 6000), the best growth was observed for strain 1BT (Rhizobium sp.), and the lowest growth for the strain 1AT (Rhizobium leguminosarum). The addition of polyethylene glycol (PEG 6000) in concentration of 15% to the nutrient solution, has resulted in a significant decrease in growth of all tested indigenous strains as well as the reference strains. After the concentration of PEG 6000 was increased to 30% inducing severe drought, indigenous strain 8Z (Rhizobium sp.) showed the best growth while the most sensitive to water shortage was the strain 21Z (R. leguminosarum). In comparison to the reference strains, higher average growth values of the indigenous strains was observed. The highest drought resistance was found in Rhizobium sp. whose taxonomic status has not yet been fully defined and which potentially represent new species of nodule bacteria. The results obtained in this study, clearly confirmed the importance of rhizobial strain selection in adverse environmental conditions.

• Keywords: simbiozna fiksacija dušika; kvržične bakterije; autohtoni sojevi; in vitro suša; PEG 6000
• Keywords (english): symbiotic nitrogen fixation; nodule bacteria; indigenous strains; in vitro drough; PEG 6000
• Language: croatian
• URN:NBN: urn:nbn:hr:204:305937
• Study programme: Title: Agroecology; Study programme type: university; Study level: graduate; Academic / professional title: magistar/ magistra inženjer/inženjerka agroekologija (magistar/ magistra inženjer/inženjerka agroekologija)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2019-11-28 08:01:33