The nitrogen-fixing Bradyrhizobium elkanii significantly stimulates root development and pullout resistance of Acacia confusa

Abstract

Reforestation of native Acacia confusa Merr. on landslide areas in Taiwan is important for agroforestry and soil conservation. To ensure high survival and growth vigor, A. confusa seedlings must develop a strong root system. Inoculating of acacia with symbiotic nitrogen-fixing bacteria (NFB) may ameliorate the problems associated with soil nutrient deficiency on landslide sites. In this study, under plastic house condition, a NFB was isolated from the root nodules of native A. confusa and identified as Bradyrhizobium elkanii, and its effects on growth, root system morphology and pullout resistance of acacia seedlings were investigated. Our results revealed that the growth of inoculated seedlings is significantly more vigor than that of the noninoculated controls. The enhancements in height, tap root length, shoot biomass and root biomass were 40, 100, 140 and 130%, respectively. Also, inoculated seedlings had significantly longer total root length (150%), larger external root surface area (130%), larger root volume (70%), and more root tip number (60%) than the controls. Moreover, the inoculated seedlings developed significantly stronger root functional traits, that is, root density (130%), root length density (60%) and specific root length (60%), than the controls. Consistently, the root pullout resistance of inoculated seedlings was significantly higher than that of the noninoculated ones. These results demonstrate that B. elkanii is an effective nitrogen-fixing bacterium capable of enhancing growth, root development and pullout resistance of A. confusa.

Eucalyptus in Malaysia: Review on Environmental Impacts

“…The nitrogen-fixing tree species is vulnerable to numbers of diseases with heart rot, root rot and phyllode rust causing the most debilitating damages to the trees (Jung-Tai et al, 2017). Disease infection interfere the growth and development of the plant which consequently reduces quality and productivity.…”

Insights into the Endophytic Bacterial Community Comparison and their Potential Role in the Dimorphic Seeds of Halophyte Suaeda Glauca

“…Bradyrhizobium, a genus of Gram-positive that initially proposed as a group of slowgrowing, alkaline-producing root nodule nitrogen-xing bacteria [78]. B. elkanii isolated from the root nodules of Acacia confusa, exhibit the nitrogen-xing ability and can enhance the growth and root development of A. confuse [79]. Numerous studies revealed that endophytic bacteria can improve plant tness by enhancing nutrient mobilization, nitrogen xation, phosphate solubilization and conferring resistant against pathogens [27,80].…”

Response of Acacia mangium to inoculation with symbiotic microorganisms in the remediation of metal-contaminated soil at Bonoua, Ivory Coast

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