title: Assessment of DAPG-producing Pseudomonas fluorescens for Management of Meloidogyne incognita and Fusarium oxysporum on Watermelon.
abstract: Pseudomonas fluorescens isolates Clinto 1R, Wayne 1R, and Wood 1R, which produce the antibiotic 2,4-diacetylphloroglucinol (DAPG), can suppress soilborne diseases and promote plant growth. Consequently, these beneficial bacterial isolates were tested on watermelon plants for suppression of Meloidogyne incognita (root-knot nematode: RKN) and Fusarium oxysporum f. sp. niveum (Fon). In a greenhouse trial, Wayne 1R root dip suppressed numbers of RKN eggs per gram root on 'Charleston Gray' watermelon by 28.9%. However, in studies focused on 'Sugar Baby' watermelon, which is commercially grown in Maryland, a Wayne 1R root dip did not inhibit RKN reproduction or plant death caused by Fon. When all three isolates were applied as seed coats, plant stand in the greenhouse was reduced up to 60% in treatments that included Fon ± P. fluorescens, and eggs per gram root did not differ among treatments. In a microplot trial with Clinto 1R and Wayne 1R root dips, inoculation with P. fluorescens and/or Fon resulted in shorter vine lengths than treatment with either P. fluorescens isolate plus RKN. Root weights, galling indices, eggs per gram root, and second-stage juvenile (J2) numbers in soil were similar among all RKN-inoculated treatments, and fruit production was not affected by treatment. Plant death was high in all treatments. These studies demonstrated that the tested P. fluorescens isolates resulted in some inhibition of vine growth in the field, and were not effective for enhancing plant vigor or suppressing RKN or Fon on watermelon.
authors.affiliation: USDA, ARS, Nematology Laboratory, Northeast Area, Henry A. Wallace Beltsville Agricultural Research Center (BARC)-West, Beltsville, MD 20705.
authors.forename: Susan L F
authors.initials: SL
authors.lastname: Meyer
authors.affiliation: University of Maryland College Park/University of Delaware, The Lower Eastern Shore Research and Education Center, Salisbury, MD 21801.
authors.forename: Kathryne L
authors.initials: KL
authors.lastname: Everts
authors.affiliation: Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691.
authors.forename: Brian McSpadden
authors.initials: BM
authors.lastname: Gardener
authors.affiliation: USDA, ARS, Nematology Laboratory, Northeast Area, Henry A. Wallace Beltsville Agricultural Research Center (BARC)-West, Beltsville, MD 20705.
authors.forename: Edward P
authors.initials: EP
authors.lastname: Masler
authors.affiliation: Department of Plant Protection, Faculty of Agriculture, Benha University, Qaliubia, Egypt.
authors.forename: Hazem M E
authors.initials: HM
authors.lastname: Abdelnabby
authors.affiliation: USDA, ARS, Nematology Laboratory, Northeast Area, Henry A. Wallace Beltsville Agricultural Research Center (BARC)-West, Beltsville, MD 20705.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Skantar
keywords: Citrullus lanatus var. lanatus; DAPG; Fusarium oxysporum; Fusarium wilt; Meloidogyne incognita; Pseudomonas fluorescens; beneficial bacteria; biological control; management; root-knot nematode; watermelon