Enzyme activity and effect of heat treatment on some fungal diseases of postharvest tomato fruits.
The activity of heat treatments for controlling tomato black mould caused by Alternaria alternata (Fr.) Keissler and grey mould caused by Botrytis cinerea Pers. Ex. Pers. wWas tested. Spore suspension of the grey mold pathogen which was exposed to hot water treatment at 58 degrees C for 6 min., failed to germinate, whereas A. alternata failed to germinate when exposed to hot water at 58 degrees C, for 8 min. Exposing discs bearing growth of any both tested fungi to hot air at 48 degrees C for 72 h caused growth suppression for the both tested pathogens. Dipping tomato fruits in hot water at 58 degrees C for 8 min or keeping in hot air for 72 h at 40 degrees C prevented decay development in non inoculated or artificially inoculated fruits with A. alternata and B. cinerea up to 12 days when stored at 24 degrees C. The high amount of polygalacturonase (PG) and pectinmethylestrase (BME) enzymes were investigated in infected fruits by the two tested pathogens as compared by healthy ones. The culture filtrate of A. alternata had the highest protease activity, white B. cinerea was the lowest. Protease activity was higher when CD liquid medium contain casein was used.