Burkholderia vietnamiensis, a new nitrogen-fixing species associated with rice roots, isolated from an acid sulphate soil in Vietnam: plant-growth-promoting effects on rice

Inoculation of rice with TVV75, a N-2-fixing strain of Burkholderia vietnamiensis, was performed in a Vietnamese acid sulphate soil in pot trials. The effect of this bacterial strain was tested at three nitrogen fertilizer rates: 0, 45 and 90 kg N/ha under outdoor conditions. The inoculated strain had been isolated as a member of the dominant N-2-fixing microflora in the rhizosphere of rice growing in the above mentioned soil: it exhibited the highest acetylene reduction rate and the highest growth promotion effect on rice plantlets. In the present experiment, nitrogen availability was the limiting factor for rice growth, as clearly shown by the plant response to nitrogen fertilizer application in the control treatment. Under these conditions, bacterial inoculation resulted in significant increases in tiller numbers (12%) and plant height (8%) in nursery beds, and significant increases were also observed in both shoot and root dry weight, throughout the growth cycle, leading to a higher final yield (20%).