Elad, Y., Dept. of Plant Pathology, ARO The Volcani Center, Bet Dagan, 50250, Israel

Difluoromethylornithine (DFMO) - an inhibitor of polyamine biosynthesis, and the polyamine spermidine (Spd) reduced gray mold of tomato, pepper, eggplant, bean and Senecio sp. leaves, and of rose petals by 37-88% when applied at 0.1-1.0 mM each. Higher doses did not result in better control. The disease was also reduced significantly on tomato fruits by 1.0 inM DFMO and by 0.1-1.0 mM Spd, and on cucumber fruits by 0.1-1.0 mM of both compounds, but not on grape berries. The combination of 0.2 mM DFMO with 1.0 mM Spd controlled gray mold of Senecio sp. and tomato leaves additively better than either treatment alone, whereas this effect was not observed in leaves of lettuce and pepper. Ethylene production was reduced significantly by Spd applied to leaves of tomato and pepper, but not by DFMO. Linear growth and germination of the fungus were affected by lower concentrations of DFMO (ED50 0.12-0.97 and 1.4, respectively) as compared with Spd. Spermidine and DFMO controlled white mold (Sclerotinia sclerotiorum) as effectively as did the fungicide benomyl. © 1991 Springer Science + Business Media B.V.