The rhizobacterium NJ134, showing strong in vitro antifungal activity against Fusarium oxysporum, was isolated from field grown tomato plants and identified as Pseudomonas sp. based on 16S ribosomal DNA sequence and biochemical analyses. The antifungal compound purified by gas chromatography-mass spectrometry, infrared, and nuclear magnetic resonance analyses from NJ134 cultures was polyketide 2,4-diacetylphloroglucinol (DAPG). Analysis of the sequence of part of one of the genes associated with DAPG synthesis, phlD, indicated that the DAPG producer NJ134 was a novel genotype or variant of existing genotype termed O that have been categorized based on isolates from Europe and North America. A greenhouse study indicated that about 10(8) CFU/g of soil NJ134 culture application was required for effective biocontrol of Fusarium wilt in tomato. These results suggest that a new variant genotype of a DAPG-producing strain of Pseudomonas has the potential to control Fusarium wilt under the low disease pressure conditions.