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Research Project: MANAGEMENT STRATEGIES FOR PLANT-PARASITIC NEMATODES: COVER CROPS, AMENDMENTS, AND INTERNAL MOLECULAR TARGETS

Location: Mycology and Nematology Genetic Diversity and Biology Laboratory

Title: Assessment of DAPG-producing Pseudomonas fluorescens for management of Meloidogyne incognita and Fusarium oxysporum on watermelon

Author
item Meyer, Susan
item EVERTS, KATHRYNE - University Of Maryland
item GARDENER, BRIAN - The Ohio State University
item Masler, Edward
item ABDELNABB, H - Benha University
item Skantar, Andrea

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2016
Publication Date: 3/30/2016
Publication URL: http://handle.nal.usda.gov/10113/62646
Citation: Meyer, S.L., Everts, K., Gardener, B.M., Masler, E.P., Abdelnabby, H.M., Skantar, A.M. 2016. Assessment of DAPG-producing Pseudomonas fluorescens for management of Meloidogyne incognita and Fusarium oxysporum on watermelon. Journal of Nematology. 48(1):43–53.

Interpretive Summary: Root-knot nematodes are economically important plant parasites that attack most crop plants. Prohibition of use of many synthetic nematicides has led to a need for novel means of managing these nematodes. Fusarium wilt is also a damaging plant disease, and is the major watermelon disease in Maryland. When both diseases occur together, damage is increased even further on watermelon plants. Therefore, beneficial bacteria were tested for the ability to suppress one or both diseases on watermelon. One of the bacteria reduced numbers of nematode eggs on a cultivar of watermelon not commercially grown in Maryland. With a commercially grown watermelon cultivar, none of the three tested bacteria suppressed nematode numbers on plant roots, and plant death caused by Fusarium wilt was not reduced either. These studies demonstrated that the bacteria resulted in some inhibition of vine growth in the field, and were not effective for enhancing plant vigor or suppressing these pathogens on watermelon. Researchers and growers will be able to use these results for determining useful applications of these beneficial bacteria.

Technical 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/g root on ‘Charleston Gray’ watermelon by 29%. 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/g root did not differ among treatments. In trial with Clinto 1R and Wayne 1R root dips, a microplot inoculation with P. fluorescens and/or Fon resulted in shorter vine lengths than treatment with either isolate plus RKN. Root weights, galling indices, eggs/g root, and second-stage juvenile 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 P. fluorescens isolates resulted in some inhibition of vine growth in the field, and were not effective for enhancing plant vigor or suppressing these pathogens on watermelon.