Is Arachis pintoi associated with effective native rhizobial strains in the Central Highlands of Vietnam?

Aims

Intensive agricultural practices have led to severe soil degradation in the Central Highlands of Vietnam. Integrating legumes as cover crops is a promising strategy to restore soil fertility via biological nitrogen fixation (BNF). Arachis pintoi has been increasingly promoted in Vietnam for adoption as a cover crop but the diversity and efficiency of its native rhizobial partners remain poorly documented. This study assessed the diversity of indigenous rhizobial strains nodulating A. pintoi in the Central Highlands of Vietnam and evaluated their symbiotic efficiency and ability to support plant growth under greenhouse conditions.

Methods

AND

Results

Nodule occupancy was analyzed by Restriction Fragment Length Polymorphism and 16rDNA sequencing was performed for representative strains of each group. Seven distinct profiles were found, all identified as Bradyrhizobium spp. While the diversity of rhizobia was relatively similar across both provinces, nodule occupancy varied markedly between locations. Strains from IGS 04 group dominated in Dak Lak (66.3%), whereas IGS 01 was the most prevalent group in Gia Lai (78.3%). A greenhouse trial was conducted to assess the performance of the different rhizobial groups. Inoculation significantly improved plant growth and nitrogen levels compared to uninoculated treatment. Plants inoculated with IGS 03 and IGS 06 groups exhibited the highest performance, exceeding that of the positive control. Conversely, IGS 01 and IGS 07 strains demonstrated the poorest symbiotic efficiency.

Conclusions

These results highlight the critical need to select high-efficiency native strains for bioinoculants to maximize BNF potential and support the long-term sustainability of perennial agroecosystems in Vietnam.