New Rhizobium leguminosarum bv. trifolii isolates: collection, identification and screening of efficiency in symbiosis with clover

Abstract

Suitable clover stands (field and meadow) were chosen to isolate new R. leguminosarum bv. trifolii strains. Together 49 strains were isolated, labelled and maintained. Ten primers were used for identification and amplification products were detected by agarose electrophoresis. Amplification products of individual primers did not make possible to distinguish all isolates; a combination of at least two primers was necessary. No differences in genetic variability level between field and meadow isolates were found. Hydroponic perlite experiments were used for the screening of rhizobial isolates and the tetraploid red clover variety Amos was used as a host plant. Shoots were weighed and the root volume was determined at the onset of anthesis. Total nitrogenase activity (TNA) of the symbiotic system was measured and the root dry weight was determined. High differences among individual isolates were found in all the characteristics. Statistically significant were differences among individual isolates for TNA, growth characteristics did not differ significantly. Strong positive relationships between fresh forage, dry forage, root volume and root dry weight were determined (r = 0.69–0.98; p > 0.05). Nine isolates were selected as effective, based on the mean values of all isolates screened. Selected isolates achieved the above average values in most measured characteristics. Out of the nine isolates, two were isolated from root nodules of clover cultivated in field stands, seven strains were isolated from clover grown in natural meadows. Additional study of isolates in soil condition will follow.