Use of plant growth promoting rhizobacteria on hydroponic systems

Rast-spodbujajoče rizobakterije (PGPR) so tiste bakterije, ki z vidika rastlinske pridelave koristno vplivajo na gostiteljsko rastlino. Da bakterijo v rizosferi prištevamo med bakterije, ki pospešujejo rast rastlin, mora izpolnjevati vsaj dva od treh pogojev: tekmovalno kolonizirajo korenine, stimulirajo rast rastline ali zavirajo fitopatogene mikroorganizme. Kljub temu, da je večina hidroponskih sistemov postavljenih v zavarovanih prostorih, so rastline izpostavljene različnim patogenom. Hranilna raztopina predstavlja idealno življenjsko okolje za številne glive in bakterije, ki se z njo lahko hitro razširijo po celotnem sistemu in okužijo vse rastline. Možnost okužbe lahko zmanjšamo fizično, kemično ali biološko, za kar se uporablja PGPR. PGPR lahko tako ločimo v dve skupini in sicer na biognojila in na biotična fitofarmacevtska sredstva (bFFS). Rizobakterije lahko kot biognojilo delujejo preko fiksacije dušika, povečanja dostopnosti fosfatov, tvorbe rastlinskih hormonov ali sinteze hlapnih pospeševalcev rasti. Za biotične FFS pa so primerne bakterije, ki s patogenimi mikroorganizmi tekmujejo za dostopna hranila, kolonizacijo korenin ali pa zavirajo širjenje patogenov s pomočjo izločanja antibiotikov ter litičnih encimov, tvorbe sekundarnih metabolitov, in sideroforjev ter inducirane sistemične odpornosti. Vse koristne bakterije predstavljajo velik potencial v razvoju kmetijstva v smeri bolj trajnostne in okolju prijazne panoge, ki bi znatno zmanjšala vnos sintetičnih gnojil in fitofarmacevtskih sredstev v okolje.Plant growth promoting rhizobacteria (PGPR) is bacteria that has a positive effect on the primary production of the host plant. To be classified as plant growth promoting rhizobacteria must meet at least two of the following demands: to competitively colonize the root system, to stimulate plant growth or to inhibit phytopathogens. Although most hydroponic systems are set up in greenhouses plants are still exposed to different pathogens. The nutrient solution is an ideal environment for pathogens to develop and growthey can also spread throughout the system with it and infect the majority of the plants quickly. The risk of infection can be reduced physically, chemically or biologically which is what PGPR can be used for. PGPR can be divided in to biopesticides and biofertilizers. Biofertilizers effect plant growth through non-symbiotic fixation of nitrogen, solubilisation of phosphorus production of phytohormones or volatile growth enhancers. Biopesticides are those bacteria that are in direct competition with the pathogenic microorganism for the available nutrients or produce antibiotics, lytic enzymes, secondary metabolites or siderofores. They can also provoke induced systemic resistance in the host plant. All beneficial bacteria represent a potential for agriculture to become a more sustainable and environmentally friendly sector with reduced rates of synthetic fertilizer and phytopharmaceuticals input into the environment