Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 9/1/2008
Publication Date: 9/1/2008
Citation: Shapiro Ilan, D.I., Reilly, C.C., Hotchkiss, M.W. 2008. Suppressive effects of metabolites from Photorhabdus spp. and Xenorhabdus spp. on phytopathogens of peach and pecan [abstract]. 41st Annual Meeting of Society for Invertebrate Pathology, August 3-7, 2008, Warwick, UK. p. 35. Available: http://www.sipweb.org/Meeting_Abstracts/2008abstracts.pdf. Interpretive Summary: Pecan and peach trees are plagued by fungal diseases that can severely limit orchard productivity. Research aimed at developing environmentally friendly methods to control these fungal diseases is warranted. Our objective was to determine the suppressive abilities of certain metabolites (by-products) derived from naturally occurring bacteria (called Photorhabdus and Xenorhabdus spp.). In laboratory studies, we found that these metabolites caused high levels of suppression in pecan and peach diseases including scab, Phytophthora, and shuck decline in pecan, and brown rot in peaches. These results were indicated on Petri dish tests as well as on live tissue experiments conducted in the laboratory on detached pecan twigs or leaves. In future studies we will determine the efficacy of these metabolites under field conditions.
Technical Abstract: Our objective was to determine the suppressive abilities of bacterial metabolites derived from Photorhabdus and Xenorhabdus spp. on Glomerella cingulata, Phomopsis sp., Phytophthora cactorum, and Fusicladosporium effusum, which are fungal or oomycete pathogens of pecan, and Monilinia fructicola, a fungal pathogen of peach. In in vivo tests, 6 or 12% dilutions of P. luminescens (Hb) or X. bovienii (SN) metabolites caused 90 to 100% suppression of P. cactorum lesions on pecan leaves with only slight phytotoxicity. No phytotoxic effects were observed in detached peach leaves at dilutions up to 25%. Metabolite treatments, derived from P. luminescens (Hb) and X. bovienii (SN) were also tested for suppression of F. effusum sporulation in detached pecan shoots. Reductions in sporulation caused by bacterial metabolites were similar to those following treatment with two chemical fungicides, dodine and fenbuconazole; a third chemical, triphenyltin hydroxide had no effect. Further research is warranted to determine if fungal or oopmycete incited diseases in pecan and peach can be controlled with metabolites of Xenorhabdus spp. and Photorhabdus spp.