Eco-friendly Management of Rhizoctonia solani, the Cause of Tomato Root Rot Disease

Controlling soil-borne fungal diseases is challenging due to the fungi’s ability to endure in the soil for extended time frames. Tomato plants are one of the crops that suffer from root rot disease caused by Rhizoctonia solani. Biocontrol agents, such as rhizobacteria are a new trend to control this pathogen as alternative to chemical fungicides.

The morphological and physiological traits of four rhizobacterial isolates of Leclercia adecarboxylata DKS3, Bacillus halotolerans DMC8, Bacillus subtilis NAS1 and Paenibacillus polymyxa TRS4 were examined in vitro and their efficacy in managing tomato root rot disease caused by R. solani was assessed under greenhouse conditions, along with their impact on plant growth metrics and enzyme activities.

The isolate DMC8 significantly enhanced the germination percentage of tomato seedlings, whilst the other isolates showed no difference compared to the positive control treatment. The isolates DMC8, NAS1 and TRS4 demonstrated a substantial reduction in disease incidence, ranging from 50% to 55%, in contrast to the positive control, which recorded 85% incidence. All isolates, however, demonstrated a notable reduction in disease severity, ranging from 30% to 49%, in contrast to the positive control, which exhibited a severity rate of 56%. All bacterial isolates exhibited a notable enhancement in growth metrics in the absence of the pathogen, whereas in the presence of the pathogen, isolates DMC8, NAS1 and TRS4 demonstrated a considerable improvement in growth markers. An elevation in the activities of peroxidase and phenylalanine ammonium lyase enzymes was observed, signifying the development of resistance in the plant by the rhizobacterial isolates.