Characterization of plant growth promoting bacteria isolated from chickpea and lentil nodules

Zbog kontinuiranog porasta svjetskog stanovništva, glavni cilj poljoprivredne proizvodnje je osigurati dovoljne količine hrane, a pritom očuvati okoliš. Neselektivna uporaba mineralnih gnojiva i pesticida neki su od uzroka onečišćenja tla, vode i zraka. Stoga se smatra da je primjena inokulacije sa selekcioniranim sojevima korisnih mikroorganizama alternativa pri uzgoju različitih poljoprivrednih kultura. Postupak podrazumijeva primjenu mikrobioloških preparata koji sadrže kulture korisnih mikroorganizama, direktno na sjeme ili u tlo. Radi se o heterogenoj grupi korisnih mikroorganizama, zajedničkog naziva bakterije promotori biljnog rasta (PGPB, engl. Plant growth promoting bacteria) koja uključuje bakterije koje fiksiraju dušik kao i one koje stimuliraju biljni rast kroz procese solubilizacije fosfata, sintezu fitohormona, produkciju antibiotika te sintezu litičkih enzima i egzopolisaharida. S glavnim ciljem izolacije i selekcije autohtonih sojeva rizobija koji noduliraju slanutak i leću, prikupljeni su uzorci tla s različitih područja uzgoja ovih mahunarki u Hrvatskoj i Hercegovini. Početna identifikacija bakterijskih sojeva izoliranih iz kvržica slanutka i leće, provedena je sekvenciranjem rrs gena. U ovo istraživanje uključeno je ukupno 44 izolata od kojih je 40 izolirano iz kvržica slanutka, a 4 iz kvržica sa korijena leće. Provedeno je ispitivanje izolata na pet PGP mehanizama: sposobnost otapanja fosfata, produkciju indol–3–octene kiseline, produkciju litičkih enzima te produkciju egzopolisaharida. Tri izolata su pokazala pozitivan rezultat na četiri od ukupno pet svojstava, a pripadaju rodovima Rhizobium (47e i 17a) i Paenibacillus (40d), čime pokazuju najizraženija PGP svojstva. Navedeni izolati predstavljaju potencijalne sojeve korisnih bakterija koje bi se mogle primjenjivati za inokulaciju raznih usjeva u cilju promocije biljnog rasta i povećanja poljoprivredne održivosti.Due to the continuous growth of the world's population, the main goal of agricultural production is to provide sufficient amounts of food, while preserving the environment. The non-selective use of mineral fertilizers and pesticides are some of the causes of soil, water and air pollution. Therefore, it is considered that the application of inoculation with selected strains of beneficial microorganisms is an alternative when growing different agricultural crops. The procedure involves the application of microbiological preparations containing cultures of beneficial microorganisms, directly on the seeds or in the soil. It is a heterogeneous group of beneficial microorganisms, collectively known as plant growth promoting bacteria (PGPB), which includes nitrogen-fixing bacteria, as well as those that stimulate plant growth through phosphate solubilization, phytohormone synthesis, antibiotic production, and lytic enzymes and exopolysaccharide synthesis. With the main aim of isolation and selection of the indigenous chickpea and lentil rhizobia, soil samples were collected from different growing area of these legumes in Croatia and Herzegovina. The initial identification of the bacterial strains isolated from chickpea and lentil nodules was carried out by sequencing the rrs gene. A total of 44 isolates were included in this research, of which 40 were isolated from chickpea nodules, and 4 from lentil root nodules. The isolates were tested for five PGP mechanisms: phosphorus solubilization, production of lytic enzymes, production of exopolysaccharides, indole-3-acetic acid production. Three isolates showed a positive result on four out of a total of five features, and they belong to the genera Rhizobium (47e and 17a) and Paenibacillus (40d), which show the most pronounced PGP properties. Therefore, these isolates represent potential strains of beneficial bacteria that could be used for the inoculation of variuos crops in order to promote plant growth and increase agricultural sustainability