EFFECTS OF SOME POLYAMINE BIOSYNTHESIS INHIBITORS AND CALCIUM-CHLORIDE ON IN-VITRO GROWTH AND DECAY DEVELOPMENT IN APPLES CAUSED BY BOTRYTIS-CINEREA AND PENICILLIUM-EXPANSUM

Three polyamine biosynthesis inhibitors, alpha-difluoromethylornithine (DFMO), alpha-difluoromethylarginine (DFMA), and alpha-methylornithin e (MeOrn), alone and in combination with CaCl2, mere tested for their ability to reduce in vitro growth and soft rot development in apple (M alus domestica Borkh.) fruit caused by Botrytis cinerea Pers.:Fr. and Penicillium expansum Link. All three inhibitors reduced the in vitro g rowth of the pathogens. Calcium had no effect on fungal growth in vitr o. Pressure infiltration of millimolar concentrations of DFMO or DFMA or 25 g . L-1 CaCl2 solutions into apples reduced subsequent soft rot development by B. cinerea and P. expansum >40%. A combination treatmen t of Ca and DFMO or DFMA reduced decay >67%. Treatment of apples with MeOrn was less effective at inhibiting decay development. None of the inhibitors affected polyamine levels in apple cortical tissues. Some i njury to the fruit surface was observed with Ca treatments. Fruit trea ted with Ca and any of the inhibitors were less firm than those treate d with Ca alone. Specific polyamine biosynthesis inhibitors in combina tion with Ca may prove useful in reducing postharvest decay in apples.