SELECTION OF RHIZOBIUM-LEGUMINOSARUM BV VICEAE STRAINS FOR INOCULATION OF PISUM-SATIVUM L CULTIVARS - ANALYSIS OF SYMBIOTIC EFFICIENCY AND NODULATION COMPETITIVENESS

From an analysis of 481 Rhizobium leguminosarum bv. viceae strains wit h 7 pea cultivars in pot and field experiments, we demonstrated that e ffective strains could be isolated from a rich medium-acid grey forest soil of the Orol area (Central region of the European part of Russia) but not from a poor acid podzolic soil of the St. Petersburg area (No rth-West Russia), The proportion of the isolates significantly increas ing N accumulation in pea plants (10.2%) is higher than that of strain s increasing the shoot dry mass (4.6%) in the pot experiments. The mea n values of the increase for N accumulation (33.8%) upon inoculation a re also higher than for shoot mass (27.0%) in these experiments. N acc umulation in the inoculated pea plants in the pot experiments was sign ificantly correlated with seed yield and seed N accumulation in field experiments, while for shoot dry mass these correlations were either w eak or not significant. Two-factor analysis of variance demonstrated t hat the contribution of plant cultivars to the variation of the major symbiotic efficiency parameters is higher (30.8-31.6%) and contributio ns of cultivar-strain specificity is lower (5.4-8.8%) than the contrib utions of strain genotypes (13.4-14.9%). We identified an ineffective R. leguminosarum bv. viceae strain 50 which can be used as a tester fo r assessing the nodulation competitiveness of the effective strains by an indirect method (analysis of dry mass and N accumulation in pea pl ants inoculated with the mixture of the tested effective strains and t he tester strain). The relative competitive ability (RCA) determined b y this method was 75.7-82.8% for strain 52 but only 10.5-13.8% for str ain 250a; this difference was confirmed by a direct method (use of the streptomycin-resistant mutants). Results of screening of the diverse collection of 53 effective R. leguminosarum bv. viceae strains by the indirect method permits us to divide them into 3 groups (32 high-compe titive, 10 medium-competitive and 11 low-competitive strains) but reve als no correlation between the competitiveness and symbiotic efficienc y. N accumulation in the pea shoots is demonstrated to be a much more suitable criterion than the shoot mass for selection either of the hig hly-effective or of highly-competitive (by the indirect estimation) R. leguminosarum bv. viceae strains in the pot experiments.