POLYAMINE LEVELS IN STEM RUST INFECTED WHEAT LEAVES AND EFFECTS OF ALPHA-DIFLUOROMETHYLORNITHINE ON FUNGAL INFECTION

The concentrations of the free polyamines putrescine/agmatine (Put/Agm), spermidine (Spd), and spermine (Spm)were determined in three near-isogenic lines of the wheat cultivar Prelude differing in their resistance to the wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt) race 32, over entire infection cycles. In highly resistant wheat plants, no changes in polyamine contents were detected. In moderately resistant and fully susceptible plants, Spm concentrations remained unchanged, while Put/Agm contents were increased over control plants between 3 and 7 days after inoculation. Spd concentrations in both interactions started to rise 3 days after inoculation, reaching a maximum at day 6 then declining in susceptible plants. Injection of alpha-difluoromethylornithine (DFMO), a specific inhibitor of polyamine biosynthesis, into the leaves of susceptible infected plants reduced the production of uredospores at concentrations as low as 0·0625 mM. DFMO had no effect on the germination of Pgt uredospores or growth and polyamine content of healthy wheat plants. © 1990.