Role of hydrogen peroxide and apoplastic peroxidase in tomato - Botrytis cinerea interaction

The aim of the research was to estimate the sensitivity of tomato tissue and spore from necrotrophic isolate of B. cinerea on H2O2. The influence of exogenic H2O2 and B. cinerea on plant tissue and on the activity of peroxidases (PO), catalase (CAT) and superoxide dismutase (SOD) in apoplastic tomato leaves fraction were investigated. It was proved that 40 mM H2O2 damaged the cells of a host, and inhibited in vitro germination of B.cinerea spores. Complete inhibition of germination was observed after the use 100 mM H2O2. In the presence of spores H2O2 was decomposed to H2O and O-2. Trace activity of catalase was observed in a solution of spores used for inoculation. Necrosis which appeared on the leaves after 40 mM H2O2 treatment resembled hypersensitive response. On the leaves pretreated at this concentration the development of infection was observed. The H2O2 concentration harmful for the tissues, stimulated the PO activity measured with NADH - responsible for generation of O-center dot(2)-, as well as with syringaldazine (S) and ferulic acid (FA), substrates characteristic of forms lignifying and strengthening the cell wall. Clear increase in CAT activity, resulting from infection and early pretreatment with H2O2 was observed in apoplast. No effect on SOD activity was observed. A hypothesis may be put forward, that germinating spores produce enzymes which allow them to decompose H2O2 generated in apoplast,so there is little likelihood that B. cinerea can be directly inhibited by reactive Oxygen forms (ROS) during initial stages of infection. Necrotic lesions resembling HR generated by exogenous H2O2 as well as induction of activity of apoplastic plant enzymes, particularly PO connected with strengthening and lignification of cell wall, were not sufficient factors to inhibit fungal expansion.