Research Unveils Rhizobia Strains Effective Against Soybean Root Rot Fungal Pathogens

A research team has identified three rhizobia strains, Rhizobium sp. TZSR12C, Rhizobium sp. TZSR25B, and Bradyrhizobium sp. TZSR41A, which effectively suppressed root rot fungal pathogens in soybeans under both in vitro and greenhouse conditions. These strains demonstrated significant potential as biocontrol agents, particularly Rhizobium sp. TZSR12C in greenhouse settings.

The study suggests the promising application of these rhizobia strains in managing root-rot diseases in soybeans, paving the way for future on-farm trials and deeper exploration into their biocontrol mechanisms.

Rhizobia is known for nitrogen fixation in legumes, reducing the need for synthetic fertilizers. Additionally, they can suppress soil-borne pathogens like F. solani and R. solani in soybeans, which are highly prone to root-rot diseases. However, their effectiveness varies due to agro-ecological factors, requiring multi-location trials. Current research has limited attention on the combined effects of multiple pathogens.

A research article published in Technology in Agronomy on 20 May 2024, investigates the ability of Rhizobium and Bradyrhizobium species to suppress root rot fungi in soybean seedlings, aiming to enhance biocontrol strategies.

To evaluate the inhibition of root rot fungal pathogens, 25 rhizobia strains were tested under in vitro conditions. Three strains, Rhizobium sp. TZSR12C, TZSR25B, and Bradyrhizobium sp. TZSR41A demonstrated the ability to suppress four fungal pathogens which are F. solani, M. phaseolina, R. solani, and F. oxysporum.

Rhizobium sp. TZSR25B formed the largest inhibition zone (8.3 mm) against F. oxysporum, while Rhizobium sp. TZSR12C was effective against three fungi, forming clear zones. For the pot experiments, the soil had a sandy clay loam texture, a neutral pH, and high levels of organic carbon, nitrogen, and essential nutrients, making it conducive to microbial activities.