Interaction Of Rhizobia Research Articles

Interaction ofrhizobiumandmeloidogyne incognitaon symbiotic nitrogen fixation in mungbean under different concentrations of iron

Abstract Effects of the interaction of Rhizobium and the nematode Meloidogyne incognita were studied on N2 fixation and translocation of Fe in the shoots of mungbean (Vigna radiata L.) cv. ML‐267 grown in pots containing steam‐sterilized river sand supplied with different concentrations of Fe. Rhizobium. along with 20 ppm concentration of Fe enhanced the number and dry weight of nodules, nitrogenase activity of nodules and total N‐uptake, whereas 30 ppm concentration of Fe had an adverse effect on all these characters. M. incognita infection reduced all the growth characteristics, as well as translocation of Fe in the shoots of nodulated and non‐nodulated plants.

Nutrient and growth interactions in soybeans colonized withGlomus fasciculatum andRhizobium japonicum

Glycine max (L. Merr. cv. Amsoy 71) plants were grown in a greenhouse in a sand/perlite medium low in plant-available N and P. Plants were either inoculated with a vesicular-arbuscular mycorrhizal (VAM) fungus alone, a strain ofRhizobium japonicum alone, both endophytes together or were left non-inoculated to serve as a control. All combinations received a N-and P-free nutrient solution. Nodulated plants contained 4 to 5 times the phytomass of non-inoculated controls, and plants colonized with both the VAM fungus and Rhizobium were 18% greater in dry weight than nodulated, non-VAM plants due to a positive VAM times Rhizobium interaction. Nitrogen fixation, calculated from C2H4 and H2 data, was significantly higher in the tripartite symbiosis, with 80% of the increase attributable to increased nodule mass and 20% due to increases in specific nodule activity. Colonization by the VAM fungus and the development of vesicles increased significantly following nodulation. The synergistic interactions between the microsymbionts suggests that the response of the host to dual colonization is complex and depends on a balance between the three members of the symbiosis.

Interaction ofRhizobium loti strain and host on the biosynthesis of unusual amino acids in leguminous plants

The effect of differentRhizobium loti strains on the biosynthesis of 2,3-diamino-butanoic acid and 2,4-diamino-3-methyl-butanoic acid in root nodules ofLotus tenuis, Anthyllis vulneraria andLupinus densiflorus has been investigated. Results suggest that biosynthesis isRhizobium strain dependent, that the bacteroid is the site of synthesis of the compounds and that their biosynthesis is confined to the symbiosis.

Natural variation in symbiotic nitrogen-fixing Rhizobium and Frankia spp.

A description is given of the natural variation in nitrogen-fixing Rhizobium and Frankia spp. strains and the ability to form root nodules on compatible host plants. Arguments are given for the hypothesis that co-evolution has taken place through mutual interaction of host plants and indigenous Rhizobium and Frankia populations in the soil leading to most efficient symbiotic associations. The significance of root nodules as selective enrichment cultures of particular strains in natural and cultivated soils is exemplified by Rhizobium leguminosarum on various ecotypes of Pisum sativum and with Frankia sp. on various actinorhizal plants, in particular Alnus spp., in different geographic regions. The importance of a host-dependent distribution of Rhizobium and Frankia spp. for agriculture and forestry is discussed.

Rhizobial Interaction in the Rhizosphere of Soybean for Nodule Sites

Summary Irrespective of different host varieties, the ability of competition of a completely ineffective strain was very poor in presence of a less virulant but effective strain of Rhizobium . This weak competition could not be improved by increasing the proportion (population) of the ineffective strain in the inoculum. The nodulating ability of the effective strain was improved in presence of the ineffective one. Different effective strains, when applied in a mixture of two at a time, the nodulation was modified in either of the following ways, viz., (1) increased nodulation, (2) decreased nodulation, and (3) normal nodulation. Interactions of different strain mixtures of rhizobia in the rhizospheres of different soybean cultivars were discussed.

EFFECT OF SALINITY ON RHIZOBIUM-ROOT-HAIR INTERACTION, NODULATION AND GROWTH OF SOYBEAN

The interaction of rhizobia with root-hairs in the rhizosphere of soybean was investigated under saline concentrations of 0–1.8%. At 1.0% NaCl, root-hairs showed little curling and deformation in response to rhizobial inoculation. At 1.5% or above, shrinkage of root-hairs was evident. The growth and multiplication of rhizobia declined rapidly when NaCl concentrations were increased from 0.2 to 0.8%. At higher concentrations, rhizobial growth was minimal. Nodulation was completely eliminated at concentrations of 1.2% NaCl or higher and increasing salinity caused a gradual continuous decline in soybean fresh weight and plant height. The failure of soybean to nodulate at high salinity was attributed to decreased rhizobial colonization and, at higher salinity, to shrinkage of root-hairs. Thus, the reduction in soybean growth under conditions of high salinity could only be partly accounted for by the reduction or failure in nodulation.

Rhizobium screening of Stylosanthes species for effectiveness in nitrogen fixation

The Rhizobium strain specificity and effectiveness in nitrogen fixation of 336 accessions of the genus Stylosanthes were determined in glasshouse screening trials. In preliminary screening, against a wide-spectrum strain CB756, 224 accessions were effective (> 50% dry weight of nitrogen control). Sixty-two of these were evaluated subsequently against a spectrum of 22 strains of Rhizobium selected on the basis of host and geographic origins. Thirty-three were effective with 10 or more strains. Seventy-two accessions that were ineffectively nodulated in preliminary tests were also screened against the 22 strains. Fifty-four of these were effective with one or more strains of Rhizobium. A minimum spanning tree (MST) analysis was used to examine the interrelationships between, and the distribution of, accessions according to their effectiveness response (ER) to the 22 strains of Rhizobium. Accessions were classified into six groups, also according to their effectiveness response, by the program MULTBET. Groups I–IV were nodulated effectively by a large number of strains (mean 9.4) and groups V and VI by a limited number of strains (mean 1.3). Significant and wide-ranging Stylosanthes accession x strain of Rhizobium interactions for effectiveness in nitrogen fixation were observed, particularly in S. guianensis and S. hamata. Various reclassifications were made by MULTBET on a reduced number of strains which were selected on the basis of discriminatory powers between groups (eident values), contribution to the classification (Cramér measures) and intuitively on the basis of level of effectiveness specificity and soil pH adaption. Classifications based on Cramér measures gave least (9%) non-conforming accessions, but intuitively selected strains the widest range of effective associations. The majority of non-conforming accessions were found in effectiveness response groups ER-III and ER-IV and were mostly S. guianensis from M–A groups 2 and 14 andS. hamata M–A 28. For future screening programs strains CB 82, CB 159, CB 530, CB 756, CB 1408 and CB 2126 will be used as diagnostic strains for classification of accessions by effectiveness response, and strains CB 82, CB 1650 and CB 2126 as 'key strains' for provision of inocula for experimental purposes.Classification of strains of Rhizobium into six groups was obtained by a MULTCLAS analysis of the data matrix. A principal coordinates analysis suggested distinct clustering of strains on the basis of host specificity for effective nodulation. These corresponded very closely to the six classificatory groups.

Tobacco Ringspot Virus and Rhizobium Interactions in Soybean: Impairment of Leghemoglobin Accumulation and Nitrogen Fixation

Tobacco Ringspot Virus and Rhizobium Interactions in Soybean: Impairment of Leghemoglobin Accumulation and Nitrogen Fixation

Influence of rhizosphere micro-organisms on the virulence of Rhizobium trifolii.

THE increasing interest which has been shown in the interactions of Rhizobia with other microorganisms of the indigenous population of the soil has been reflected in the growing list of organisms which have been found to be inhibitory or antagonistic to their growth in various media. The reviews by Casas-Campillo1 and Abdel-Ghaffar and Allen2 emphasize the prominent role of Actinomycetes in such antibioses, but indicate that quite a wide range of bacteria may produce significant effects also. It is noteworthy that, though much attention has been paid to antagonistic organisms, relatively little has been reported of micro-organisms stimulating the activity of Rhizobia. Krasilnikov and Korenyako3 found that a number of non-sporing bacteria of the genera Pseudomonas and Achromobacter introduced into the rhizosphere of the leguminous host induced an increase in the numbers of Rhizobia per gram of rhizosphere soil, and that as a consequence the number of nodules per plant showed an increase and the time taken for nodules to appear was shortened. Such bacteria were termed ‘activators’ in contrast to types which were inhibitors, or to others which were without effect. These workers advocate that seed should be inoculated with mixed cultures of Rhizobia plus activators on the basis of their findings of increased herbage yield and seed set of beans, lucerne and lupins.