Chitinolytic Pseudomonas maltophila antagonistic to root-rot pathogens of sunflower (Helianthus annuus)

Forty bacterial isolates from rhizosphere of sunflower were screened for their antagonistic activity against two root-rot pathogens Rhizoctonia solani and Sclerotinia sclerotiorum. On the basis of inhibition zone on solid medium a Gram-negative antagonistic bacterium identified as Pseudomonas maltophila that could be used as a biocontrol agent against Rhizoctonia solani and Sclerotinia sclerotiorum causing root-rot of sunflower, was identified. Reduction in biomass of fungal pathogens was observed on addition of various levels of Pseudomonas maltophila cells (10⁴-10⁸ cells). Pseudomonas maltophila was found to produce chitinase, which was responsible for the lysis of mycelial biomass. Pseudomonas maltophila showed good growth on chitin and cell wall preparations of both the fungi when supplied as a sole source of carbon.