Plant growth promoting rhizobacteria from Juan Fernández archipelago improve germination rate of endangered plant Solanum fernandezianum Phil.

Abstract

Robinson Crusoe Island, Chile, has one of the highest densities of endemic plants in the world, however many of its native and endemic species, such as Solanum fernandezianum Phil., are currently declared endangered. Coating the seeds of native plants with locally sourced plant-growth-promoting bacteria can be used as a tool for conservation programs of endangered plant species. Isolation and screening of rhizosphere bacteria from Robinson Crusoe Island resulted in the selection of three bacteria: Serratia sp. RGM 2525, Raoultella sp. RGM 2526, and Pseudomonas sp. RGM 2607, due to their capacity of producing indole compounds (30-45 μL mL-1) and indoleacetic acid (IAA) (5-10 μg mL-1). The effect of these strains on the seed germination rate of S. fernandezianum was evaluated under five treatments: individual inoculation of each bacteria, inoculation of a mixture of the three bacteria and a treatment without bacteria (control). Inoculation of bacteria improved the seed germination rate of S. fernandezianum compared to the control treatment, with the bacterial mix as the best treatment with 26.9% germination (p < 0.05), 10.2% higher than control. Bioinoculants formulated with bacteria isolated from rhizosphere soils could improve the seed germination rate of the endangered plant S. fernandezianum.