Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2001
Publication Date: 2/1/2002
Citation: KLUEPFEL, D.A., NYCZEPIR, A.P., LAWRENCE, J.E., WECHTER, P.W., LEVERENTZ, B. BIOLOGICAL CONTROL OF THE PHYTOPARASITIC NEMATODE MESOCRICONEMA XENOPLAX ON PEACH TREES. JOURNAL OF NEMATOLOGY. 2002. v.34. p.120-123. Interpretive Summary: Probably the most studied ring nematode species on Prunus is Mesocriconema xenoplax. This nematode is the only plant parasitic nematode that has been associated with the peach tree short life (PTSL) disease complex in the southeastern United States. Tree loss due to PTSL in South Carolina alone was estimated at over $5 million per year. New alternatives to chemical control (i.e., biological control) that are less hazardous to man and also more environmentally safe must be found to protect peach trees from this ring nematode. In the early 1990's, a bacterium [Pseudomonas sp (BG33R)], was isolated from a ring nematode suppressive soil in South Carolina that was later shown to inhibit ring nematode reproduction under laboratory and greenhouse conditions. The efficacy of BG33R on suppression of the ring nematode population was then investigated in conjunction with soil solarization under peach orchard conditions from 1996-00. Results indicate that the nematode populations remained at or below detection limits for about 18 months in soil solarized as compared to unsolarized plots. Additionally, five Tn5 egg killed mutants have been generated and the insertion site in each mutant cloned and sequenced. These data provide useful insights into the potential use of BG33R and soil solarization as a pre- and postplant alternative to chemical control of the ring nematode on PTSL sites in the Southeast.
Technical Abstract: Seven fluorescent Pseudomonad spp. capable of inhibiting reproduction of Mesocriconema xenoplax have been isolated from soil sites that suppress both nematode multiplication and peach tree short life. One of these seven isolates, BG33R, inhibits M. xenoplax multiplication in vivo and egg hatch in vitro. Mesocriconema xenoplax populations on peach seedlings inoculated with BG33R and planted into soil solarized field plots remained at or below the economic nematicide treatment threshold limit for South Carolina for nearly 18 months post inoculation and soil solarization. Soil solarization alone created a microbial community suppressive to nematode development. Additionally, five Tn5 egg-kill negative mutants of BG33R have been generated. The Tn5 insertion site in each mutant has been cloned and sequenced. DNA sequence analysis has revealed a high degree of homology to several genes of interest because of their potential involvement in the production of the egg-kill factor. The mutants are also protease and salicylic acid negative, which is twice the concentration detected in the fluorescent wild type parent.