Nursery growth and rhizobia symbiosis of scandent Leguminosae species native to the Amazon region

Abstract

A great number of species and individuals of scandent legumes establishing symbiosis with nitrogen fixing bacteria occurs in the Amazon Forest. These symbiosis probably play an important role in contributing to nitrogen incorporation in this ecossystem. The objectives of this study were to evaluate the growth of eight species of scandent legumes in five nursery substrates; to compare nodulation with rhizobia strains introduced or native to these substrates; and to characterize phenotypically and genetically these rhizobia. The experiment was carried out in a completely randomized design with five replications. Five to seven months after seedling emergency, according to the legume species, growth and nodulation parameters were determined. Rhizobia identification of strains was carried out by 16S rRNA gene partial sequencing. The survival of seedlings after the transplanting varied from 93 to 98%, in Ultisol (Argissolo in Brazilian classification), collected in primary forest, and fertilized with all nutrients, except nitrogen (ULTfert); and in a clay and sand mixture, in a ratio 3:2 (CONV), respectively. Species with height superior to 30 cm, in general, grew better in substrates with higher fertility: ULTfert and Humic Gley soil (HG). Seven out of the eight species were able to nodulate. The percentage of nodulation per substrate was: SAND, washed sand with mixed inoculum of 100 rhizobia strains plus fertilization (100), HG (80), CONV (100), ULT, A-horizon of red-yellow Ultisol collected in the Ducke Forest Reserve (Manaus) (44), and ULTfert (55%). Bradyrhizobium spp. were isolated from nodules of all species and substrates. Burkolderia fungorum was isolated from Dalbergia inundata. For Dalbergia riedelli and Dalbergia inundata, this is the first report on the identification of symbiotic strains. Scandent legumes present high survival of seedlings in nursery, and develop better in substrates with higher fertility, and generally present symbiosis with Bradyrhizobium.