Biocontrol of Tomato Fusarium Wilt by a Novel Genotype of 2,4-Diacetylphloroglucinol-producing Pseudomonas sp. NJ134

Abstract

The rhizobacterium NJ134, showing strong <TEX>$in$</TEX> <TEX>$vitro$</TEX> antifungal activity against <TEX>$Fusarium$</TEX> <TEX>$oxysporum$</TEX>, was isolated from field grown tomato plants and identified as <TEX>$Pseudomonas$</TEX> 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, <TEX>$phlD$</TEX>, 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 <TEX>$10^8$</TEX> 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 <TEX>$Pseudomonas$</TEX> has the potential to control Fusarium wilt under the low disease pressure conditions.