Compatibility of Rhizobial Genotypes within Natural Populations of Rhizobium leguminosarum Biovar viciae for Nodulation of Host Legumes

Abstract

Populations of Rhizobium leguminosarum biovar viciae were sampled from two bulk soils, rhizosphere, and nodules of host legumes, fava bean (Vicia faba) and pea (Pisum sativum) grown in the same soils. Additional populations nodulating peas, fava beans, and vetches (Vicia sativa) grown in other soils and fava beannodulating strains from various geographic sites were also analyzed. The rhizobia were characterized by repetitive extragenomic palindromic-PCR fingerprinting and/or PCR-restriction fragment length polymorphism (RFLP) of 16S-23S ribosomal DNA intergenic spacers as markers of the genomic background and PCR-RFLP of a nodulation gene region, nodD, as a marker of the symbiotic component of the genome. Pairwise comparisons showed differences among the genetic structures of the bulk soil, rhizosphere, and nodule populations and in the degree of host specificity within the Vicieae cross-inoculation group. With fava bean, the symbiotic genotype appeared to be the preponderant determinant of the success in nodule occupancy of rhizobial genotypes independently of the associated genomic background, the plant genotype, and the soil sampled. The interaction between one particular rhizobial symbiotic genotype and fava bean seems to be highly specific for nodulation and linked to the efficiency of nitrogen fixation. By contrast with bulk soil and fava bean-nodulating populations, the analysis of pea-nodulating populations showed preferential associations between genomic backgrounds and symbiotic genotypes. Both components of the rhizobial genome may influence competitiveness for nodulation of pea, and rhizosphere colonization may be a decisive step in competition for nodule occupancy.

The effect of inter cross-inoculation host group rhizobia on the growth and nitrogen fixation of Faba Bean (Vicia faba L.) varieties in North Showa, Amhara Regional State, Ethiopia

“…The finding showed that strains isolated from vicieae tribe's cross-inoculation group were able to form nodules with faba bean plant but, the number, color, and shape of nodule varied according to the strain inoculated (Laguerre et al, 2003). Nodules produced by strain on one legumes host may have no resemblance to nodules produced by the same strain on another host in the same cross-inoculation group (Mahajan and Gupta, 2009) (Table 6).…”

“…The finding showed that Rhizobia strain that is effective in nitrogen fixation in association with one plant species may also be effective with certain other legumes (Amara, 1990). This is demonstrated by isolates of pea and faba bean able to form nodules and fix nitrogen with faba bean host (Laguerre et al, 2003). However, due to the influence of host plant on diversity and the genetic structure, R. lguminosarum bv.viciae reflect differences in the degree of host specificity and effectiveness of nitrogen fixation within the viceae tribe cross-inoculation group (Handley et al, 1998).…”

“…The result is similar with that of Shimeket et al (2008) who reported variation in symbiotic effectiveness from a population of R. leguminosarum bv.viciae on vetch from different soils. Laguerre et al (2003) reported that specific symbiotic plasmid-encoded genes showed variation in competition for modulating of faba beans and nitrogen-fixing effectiveness. Generally, isolates of AUFBR2 (faba bean) and AUGPR14 (grass pea) were highly effective in both hachallu and wolki varieties, and showed tolerance wide range of salt, pH, and temperature than their crossinoculation group of R. leguminosarum var viciae (Table 8).…”

Potential of indigenous bradyrhizobia versus commercial inoculants to improve cowpea (Vigna unguiculataL. walp.) and green gram (Vigna radiataL. wilczek.) yields in Kenya

“…IGS III was predominant in both legumes and was distributed in all the treatments applied to cowpea and green gram. The dominance of indigenous strains can be attributed to a number of factors; the adaptability of indigenous rhizobia to their environment results in high levels of saprophytic competence (Zengeni et al 2006); build up of background strains in the presence of the host rhizosphere (Dowling and Broughton 1986;Bushby 1993;Mendes and Bottomley 1998) and the competitive ability of background strains for sites of infection on the host plant roots and nodulation (Laguerre et al 2003;Leite et al 2009). It is therefore imperative to consider how rhizobial populations in the soil can be manipulated to influence, with or without effectual inoculation, legume nodulation, N 2 fixation and plant productivity (Brockwell et al 1995;McInnes and Haq 2003).…”

Molecular diversity, effectiveness and competitiveness of indigenous rhizobial population infecting mungbean Vigna radiata (L. Wilczek) under semi-arid conditions

“…Negligible reports on the molecular diversity of rhizobia infecting legumes of Indian origin and particularly mungbean (Vigna radiata (L. Wilczek) are available [5]. Studies on the molecular diversity of root nodule bacteria in rhizosphere, soil or nodules have been conducted to properly classify these rhizobia and also to correlate with promiscuity, symbiotic properties, effectiveness and competitiveness of these bacteria in different legumes but no conclusion has been drawn fi nally [6][7][8][9][10]. There may be differences between the population densities of different strains in soil and these differences may infl uence the outcome of nodulation.…”