Evaluation of Rhizobium strains collected in Tungurahua and Cotopaxi on the growth of Lupinus mutabilis, under semi-controlled conditions

Abstract

Two Rhizobium strains collected from chocho (Lupinus mutabilis, Sweet) plantations in the provinces of Tungurahua and Cotopaxi, Ecuador, were isolated and characterized in order to determine the effect of their inoculation on the vegetative development of Andean chocho, under semicontrolled conditions, under agricultural plastic cover. Molecular identification was performed by partial sequencing of the 16S rRNA gene, and the contrast with the GenBank database for Rhizobium was positive (99.7% certainty). The strains obtained were suspended in a sodium alginate matrix, both polymerized in alginate beads in a 0.1 M CaCl2 solution and in suspension, to be inoculated on selected chochocho seeds. The effect of strain origin, inoculation method and substrates on plant vegetative development was evaluated. Vegetative development was influenced by the substrate used for germination. The black Andean soil allowed the migration of the bacteroids towards the roots, taking advantage of the retained capillary water. The clay loam soil determined the lower vegetative development of the plant, as it was more susceptible to dehydration under canopy conditions. Strain origin also influenced vegetative development, although it was not evident in nodulation. The strain originating in Tungurahua produced more vigorous plants, especially in interaction with the Andean black soil substrate. Nodulation was significantly influenced by the substrates sand and Andean black soil, resulting in a higher number of nodules.