International Journal of Silviculture and Agroforestry ISSN 1720-349X Vol. 1 (7), pp. 046-056, September, 2017.  © Advanced Scholars Journals

Full Length Research Paper

Isolation of indigenous rhizobium strain from A. confusa for re-inoculating A. confusa seedlings

*Yaobang Dowager, Zhou Pei and Jack Jianlian

Department of Forestry and Natural Resources, National Chiayi University, Chiayi 60004, R.O.C. Taiwan.

*Corresponding Author. Email: [email protected]

Accepted 01 April, 2017

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.

Key words: Fabaceae, inoculation, nodules, pullout resistance, root morphology.