Growth response of Pterocarpus santalinus seedlings to native microbial symbionts (arbuscular mycorrhizal fungi and Rhizobium aegyptiacum) under nursery conditions

Abstract

The objective of this research was to improve the growth and biomass of Pterocarpus santalinus L.f. (an endangered leguminous tree) using native microbial symbionts such as arbuscular mycorrhizal fungi and Rhizobium associated with native populations of P. santalinus. The native arbuscular mycorrhizal fungi isolated from P. santalinus soils were identified as (1) Glomus fasciculatum; (2) Glomus geosporum; and Glomus aggregatum. A nitrogen-fixing microbial symbiont was isolated from the root nodules of P. santalinus and identified as Rhizobium aegyptiacum by 16s rRNA gene sequencing. These microbial symbionts were inoculated individually and in combination into P. santalinus seedling roots. After 90 days, growth and biomass had improved compared with uninoculated controls. Shoot and root lengths, number of leaves, stem circumference, number of root nodules, biomass, nutrient uptake and seedling quality index were significantly increased by a combined inoculation of arbuscular mycorrhizal fungi + Rhizobium aegyptiacum. It was concluded that native microbial symbionts positively influenced P. santalinus seedling growth which will be helpful for successful field establishment.