Pseudomonas fluorescens (Pf1) mediated chitinolytic activity in tomato plants against Fusarium oxysporum f. sp. lycopersici

Liquid formulation of Pseudomonas fluorescens strain Pf1 was found to protect tomato plants from wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL). The lytic enzyme and chitinase activity were assayed in the tomato plants treated with liquid as well as talc based formulations of Pf1 and challenged with the FOL. The chitinase activity was significantly increased in tomato plants treated with sequential application of seedling dip + soil drench + foliar spray of liquid formulation followed by the treatment with talc product application. The increased activity was observed up to 5 days after bioformulation treatment and thereafter declined. The enzyme activity of bioformulation treatment was significantly higher than the control treatments. Isoform analysis showed that sequential application of the treatment expressed three chitinase isoforms, whereas in the control plants no isoform was observed. Western blot analysis revealed that two isoforms of chitinase with a molecular weight of 28 and 23 kDa were newly induced by liquid formulation of Pf1 treatment challenged with the pathogen. These results suggest that induction of chitinase enzymes and accumulation of these PR-proteins might have contributed to restriction of FOL invasion in tomato roots.