Chromium Toxicity to Tomato ( Lycopersicum esculentum Mill) Susceptible to Fusarium Wilt Pathogen

Fusarium wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL), and toxicity of Cr(III) and Cr(VI) in agricultural soils adversely affect growth and physiology of tomato (Lycopersicum esculentum Mill). The present study was conducted in vitro to assess growth and physiology of tomato under single and combined stress of conidial suspension of FOL, and Cr(III) or Cr(VI). Polygonal interactions of metal- pathogen-plant were investigated in Petri plates lined with sterilized filter papers provided with conidial suspension of FOL (1 × 10⁶) and six different concentrations (50-300 ppm) of Cr(III) and Cr(VI) under controlled laboratory conditions in completely randomized design. Maximum inhibition in growth, biomass and chlorophyll contents of tomato seedlings was due to conidial suspension of FOL. Peroxidase activity increases while catalase activity decreases significantly due to conidial suspension of FOL. The toxicity of Cr ions was influenced by their concentration in the solution and speciation. Therefore, growth, biomass and physiology of tomato seedlings were more significantly affected by ions of Cr(VI) than those of Cr(III). The drastic influence of both oxidation states of metal ions increases with increase in concentration of the metal ions. When FOL was given in combination with Cr(III) or Cr(VI), negative effect on the studied parameters of tomato seedlings was less pronounced compared to solitary influence of either FOL or Cr ions.