Selection of promising rhizobia to inoculate herbaceous legumes in saline soils

I. Hernández, Susana L. Estévez, Maida Peña, María Nápoles

Abstract


Salinity of soils constitutes a limiting factor for growth and development of legumes of agricultural and livestock interest. The objective of this study was to select rhizobia isolates with potentialities to improve the establishment of herbaceous legumes in saline soils. Nodulation pattern of the herbaceous legumes Desmodium triflorum (L.) DC., Alysicarpus vaginalis (L.) DC. and Crotalaria retusa L., established in a strongly saline soil and under water deficit conditions, was studied. Possible rhizobia
were isolated from the rhizosphere and from nodules of these plants, and were culturally, morphologically and physiologically characterized. In addition, nodulation tests of rhizobia isolates were carried out in siratro plants under controlled conditions. The three legumes presented small nodules and scarce nodulation. Twelve possible isolates of rhizobia were obtained. Of these, 66.7% showed cultural and physiological characteristics
similar to strains of Rhizobiaceae family and 33.3 % similar to Bradyrhizobium strains. Out of these isolates, 100 % produced effective nodules for biological nitrogen fixation in siratro plants. Plants inoculated with Riz 5-1, Riz 8-11 and Riz 8-12 isolates presented higher number and dry mass of nodules, aerial dry mass and radical dry mass. These isolates survive saprophytically in soils affected by water deficit and salinity, which makes them attractive for the preparation of bio-preparations that allow
the rehabilitation of pastures and forages under the previously mentioned conditions.
Key words: Rhizobium, salinity, forage, characterization, growth

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