Azospirillum effects on susceptibility to Rhizobium nodulation and on nitrogen fixation of several forage legumes

Abstract

Azospirillum brasilense Cd cell concentration of 105–107 colony-forming units (cfu)/mL applied 24 h before Rhizobium (106 cfu/mL), increased nodule formation in the non root hair zone, more than twofold, in pouch-grown Medicagopolymorpha and Macroptilium atropurpureum seedlings, compared with Rhizobium alone. The increase in nodule formation in pouch-grown Trifolium alexandrinum following preinoculation with Azospirillum was 20%. The percentage of nodulated seedlings rose from 0 to 25% when Medicago polymorpha was preinoculated with Azospirillum followed by the application of 10 cfu/mL Rhizobium meliloti, a level which by itself was not sufficient to initiate nodule formation. Acetylene reduction activity in Medicago polymorpha and Macroptilium atropurpureum seedlings after inoculation with Azospirillum–Rhizobium was markedly increased. A possible reason for the increased susceptibility to Rhizobium infection may be that Azospirillum stimulates the formation of a larger number of epidermal cells that differentiate into infectable root hairs.

Response of Faba bean (Vicia faba L.) to combined inoculation with Azotobacter and Rhizobium leguminosarum bv. viceae

“…The cell density of the bacteria applied as inocula has been also described as a factor involved in the nature of the effects observed in coinoculated legumes (Plazinsky and Rolfe, 1985;Yahalom et al, 1987). We have previously reported enhancement of R. leguminosarum bv.…”

“…Many papers have reported enhancement of nodulation and growth of a wide variety of forage and grain legumes, due to a positive interaction between Rhizobium species and diazotrophic soil bacteria of the genus Azospirillum (Iruthayathas et al, 1983;Plazinsky and Rolfe, 1985;Sarig et al, 1986;Yahalom et al, 1987;del Gallo and Fabbri, 1991). Azotobacter (particularly A. chroococcum) occurs widely in agricultural soils of temperate regions with almost neutral pH, and can be easily found in association with cereal and legume rhizospheres (Kole et al, 1988;Martõ Ânez-Toledo et al, 1991).…”

Effects of Plant Growth Promoting Rhizobacteria (PGPRs) on the Biological Nitrogen Fixation, Nodulation, and Growth of Lupinus albus l. cv. Multolupa

“…However, little is known about the effects of these bacteria on the nodulation process and biological nitrogen fixation. Some studies indicated that co-inoculation of Bradyrhizobium and certain PGPRs can positively affect symbiotic nitrogen fixation by enhancing both root nodule number or mass [25,26] and increasing the nitrogenase activity [27]. The co-inoculation of PGPRs with Bradyrhizobium increased the nodulation and nitrogen fixation in Glycine max at a low root zone temperature [2,3].…”

Legume Crops, Importance and Use of Bacterial Inoculation to Increase Production

“…Azospirilla species are being used as seed inoculants under field conditions for more than a decade (Dobbelaere et al, 2001;Puente et al, 2009). The positive effect of Azospirillum in the nodulation and nitrogen fixation by rhizobia on several forage legumes was early reported (Yahalom et al, 1987). Since then, many works have been done and mostly are summarized in Bashan et al (2004).…”