Md. Groppa et al., Effect of co-inoculation with Bradyrhizobium japonicum and Azospirillum brasilense on soybean plants, EUR J SOIL, 34(2), 1998, pp. 75-80
In order to assess the effects of co-inoculation with both Bradyrhizobium j
aponicum and Azospirillum brasilense on soybean plants, a pot experiment un
der growth controlled conditions was carried out. Four-week-old plants were
harvested and analyzed for shoot, root and nodule dry weight, nitrogen con
tent, nodule number and distribution, nodule protein and leghaemoglobin con
tent, and nitrogenase and glutamine synthetase activities. Nodule number an
d nodule dry weight were not affected by dual inoculation; however, co-inoc
ulated plants showed a significantly higher proportion of nodules attached
to the main root and located in the upper 3 cm of the root system. Although
no significant difference in total dry matter production could be detected
, nitrogen content of dual inoculated plants was significantly increased (2
3 % over B. japonicum-single inoculated plants). Accordingly, a strong stim
ulation of acetylene reduction activity was observed for this treatment. Li
kewise, leghaemoglobin content significantly increased (39 %). These result
s suggest that co-inoculation with B. japonicum and A. brasilense leads to
an increased number of the most active nodules, therefore, to a greater nit
rogen fixation and assimilation. In addition, an enhancement of nodule effe
ctiveness due to A. brasilense presence in the root system is suggested. (C
) Elsevier, Paris.