Osmotic stress tolerance, PGP traits and RAPD analysis of Bradyrhizobium japonicum strains

Abstract

The osmotic stress tolerance of B. japonicum strains assessed according to their persistence in PEG solution. The lowest tolerance to osmotic stress was observed in strain 511 (43.3%), and the highest tolerance was observed for strain D216 (3.3% growth reduction in presence of PEG). PGP traits of B. japonicum strains were tested. None of five B. japonicum strains produced siderophore, strains 511 and 518 had the urease ability, and only B. japonicum 518 strain showed the ability to solubilize insoluble tricalcium phosphate. RAPD analysis, using AP10, BC318, AF14 and SPH1 primers, indicated genetic differences between Bradyrhizobium strains. The first group (strains 3, 6 and 518) showed more than 80% similarity. Strains 511 and D216 formed separate clusters. Difference between strains D216 and the other strains were more than 60%, with maximum value of 72% in comparison with strain 511. Plant-growth promoting (PGP) traits, osmotic stress tolerance and RAPD analysis highlighted strain D216 as useful for further investigation of B. japonicum impact on drought reduction in symbiosis with soybean.

Tolerantnost sojeva B. japonicum prema osmotskom stresu ispitana je na osnovu preživljavanja sojeva u rastvoru PEG-a. Najmanju tolerantnost prema osmotskom stresu pokazao je soj 511 (43.3%), dok je najtolerantniji bio soj D216 (sa 3.3% smanjenja rasta u prisustvu PEG-a). Ispitane su PGP osobine sojeva B. japonicum. Nijedan od pet sojeva B. japonicum nije produkovao siderofore, ureaznu aktivnost pokazali su sojevi 511 i 518, a sposobnost solubilizacije neorganskog tri-kalcijum fosfata imao je samo soj B. japonicum 518. RAPD analiza, prajmerima AP10, BC318, AF14 i SPH1, ukazala je na genetske razlike između sojeva Bradyrhizobium. Prva grupa (sojevi 3, 6 i 518) pokazala je više od 80% sličnosti. Sojevi 511 i D216 formiraju zasebne klastere. Razlika između soja D216 i ostalih sojeva bila je veća od 60%, a maksimalna divergentnost od 72% zabeležena je u poređenju sa sojem 511. PGP osobine, tolerantnost prema osmotskom stresu i RAPD analiza izdvojili su soj D216 kao veoma značajan za dalja istraživanja B. japonicum u smanjenju negativnih posledica suše na simbioznu zajednicu sa sojom.