Antibiotic-producing Pseudomonas fluorescens mediates rhizome rot disease resistance and promotes plant growth in turmeric plants.

Rhizome rot of turmeric caused by Pythium aphanidermatum is a major threat to turmeric-cultivating areas of India. This study intends to evaluate the performance of fluorescent pseudomonads against Rhizome rot disease and understand the resistance mechanism in Turmeric plants. Fluorescent pseudomonads were screened against Pythium aphanidermatum using dual culture. Selected strains were evaluated for the performance of growth promoting attributes and the presence of antibiotic genes through PCR analysis. Strain FP7 recorded the maximum percent inhibition of P. aphanidermatum under in vitro conditions. Strains FP7 and TPF54 both increased plant growth in turmeric plants in vitro. Strain FP7 alone contained all the evaluated antibiotic biosynthetic genes. Talc and liquid-based formulations were prepared with effective strain and tested for its biocontrol activities under both glasshouse and field conditions. Enzymatic activities of the induced defense enzymes such as PO, PPO, PAL, CAT and SOD were estimated and subjected to spectrophotometric analysis. A combination of rhizome dip and soil drench of FP7 liquid formulation treatment remarkably recorded the minimum disease incidence, higher defense enzymes, maximum plant growth and yield under glasshouse and field conditions. Application of strain FP7 increased the defense molecules, plant growth and yield in turmeric plants thereby reducing the incidence of rhizome rot disease. Moreover, this study has a potential to be adopted for sustainable and eco-friendly turmeric production.