Legume-nodulating rhizobia are widespread in soils and plants across the island of O‘ahu, Hawai‘i

Abstract

AbstractLegumes and their interaction with rhizobia represent one of the most well-characterized symbioses that are widespread across both natural and agricultural environments. However, larger distribution patterns and host associations on isolated Pacific islands with many native and introduced hosts have not been well-documented. Here, we used molecular and culturing techniques to characterize rhizobia from soils and 24 native and introduced legume species on the island of O’ahu, Hawai’i. We chose two of these isolates to inoculated an endemic legume tree,Erythina sandwicensisto measure nodulation potentials and host benefits. We found that all rhizobia genera can be found in the soil, where onlyCupriaviduswas found at all sites, although at lower abundance relative to other more common genera such as Rhizobium (and close relatives),Bradyzhizobium, andDevosia. Bradyrhizobiumwas the most common nodulator of plants, where the strainBradyrhizobiumsp. strain JA1 is a generalist capable of forming nodules on nine different host species, including two native species. In greenhouse nursery inoculations, the two differentBradyrhizobiumstrains successfully nodulate the endemicE. sandwicensis;both strains equally and significantly increased seedling biomass in nursery inoculations. Overall, this work provides a molecular-based framework in which to study potential native and introduced rhizobia on one of the most isolated archipelagos on the planet.