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 in 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 isolates mainly representing species of Pseudomonas fluorescens, P, corrugata and P. tolaasii. Using a monoclonal antibody against indole-3-acetic acid (IAA) all isolates studied were found to be phytohormone-producing ex-planta. Some isolates were examined and found to be producers of biocontrol substances (2,4 diacetylphloroglucinol, HCN, proteases and fluorescent siderophores) and active in carboxy-methyl cellulase and collagenase activities. Biological assays revealed weak biocontrol activity explanta against Botrytis cinerea, Cryphonectria parasitica, Diplodia mutila, Phytophthora cactorum and Phytophthora cinnamomi, whereas Fusarium oxysporum f.sp. dianthii was unaffected by the strains tested.