Pseudomonads isolated from within fruit bodies of Tuber borchii are capable of producing biological control or phytostimulatory compounds in pure culture

From the core of surface-sterilized sporocarps of Tuber borchii collected i n Spring 1997, 600 bacterial strains were isolated, among which were about 300 pseudomonads. Counts revealed a consistent presence of Pseudomonas spp. , at 10(5)-10(8) cfu per gram of dry weight. Identification showed the isol ates mainly representing species of Pseudomonas fluorescens, P, corrugata a nd P. tolaasii. Using a monoclonal antibody against indole-3-acetic acid (I AA) all isolates studied were found to be phytohormone-producing ex-planta. Some isolates were examined and found to be producers of biocontrol substa nces (2,4 diacetylphloroglucinol, HCN, proteases and fluorescent siderophor es) and active in carboxy-methyl cellulase and collagenase activities. Biol ogical assays revealed weak biocontrol activity explanta against Botrytis c inerea, Cryphonectria parasitica, Diplodia mutila, Phytophthora cactorum an d Phytophthora cinnamomi, whereas Fusarium oxysporum f.sp. dianthii was una ffected by the strains tested.