ISOLATION AND CHARACTERIZATION OF METABOLITES FROM PSEUDOMONAS-SYRINGAE STRAIN-3366 AND THEIR PHYTOTOXICITY AGAINST CERTAIN WEED AND CROP SPECIES

Phytotoxic effects of metabolites from a naturally occurring rhizobact erial isolate, Pseudomonas syringae strain 3366, were determined on do wny brome and 'Hill 81' winter wheat, along with 10 other weed and cro p species, Centrifuged supernatant and concentrated ethyl acetate extr acts from aerobic shake cultures of strain 3366 suppressed germination of seeds and reduced root and shoot growth in agar diffusion assays, soil assays, and under field conditions, Generally, root growth was in hibited more than shoot growth, Strain 3366 metabolites applied in soi l inhibited all species tested, Crude ethyl acetate extracts in soil i nhibited downy brome at concentrations that had little effect on winte r wheat, Inhibitory activity was greater in Palouse silt loam (pH 5.8, 3.6% organic matter) than in Shano silt loam (pH 9.0, 0.8% organic ma tter), Activity of extracted metabolites decreased rapidly in wet soil but remained high in dry soil, Active metabolites were isolated and p urified from the ethyl acetate extract using column chromatography, th in-layer chromatography, and crystallization. Chemical analysis reveal ed the presence of phenazine-l-carboxylic acid, 2-amino phenoxazone, a nd 2-amino phenol, Activity of these metabolites against downy brome w as confirmed in agar assays, Phenazine-l-carboxylic acid, the major id entifiable metabolite present in ethyl acetate extracts (20% by weight ), inhibited downy brome root growth by 99% at concentrations of 5.7 m g L(-1), Production of these metabolites in field soil by live bacteri a of strain 3366 was confirmed with thin-layer chromatography.