INHIBITION OF GROWTH OF FUSARIUM-OXYSPORUM SCHL BY PATHOGENESIS-RELATED (PR) PROTEINS OF TOBACCO NECROSIS VIRUS (TNV)-INFECTED CUCUMBER

Pathogenesis-related (PR) proteins of cucumber after TNV infection wer e isolated and their activity tested in bioassays with Fusarium oxyspo rum Schl. f.sp. cucmerinum Owen. Crude plant-protein extracts with hig h concentration of chitinase and beta-1,3-glucanase caused an inhibiti on of growth. The inhibitory effect was visible for 3 days, then the g rowth of mycelium continued, bur in different consistency. Purified PR 1, PR2, PR3, PR4 (corresponding to peroxidase, beta-1,3-glucanase, chi tinase), had little inhibitory effects. The growth inhibition appears to be due to rip lysis of the growing hyphae. Apparently F. oxysporum has the capacity to adapt to the presence of the inhibitory proteins. Under field conditions, it may be an example of acquired resistance.