Submitted to: Archives of Phytopathology and Plant Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/28/2007
Publication Date: 8/1/2009
Citation: Shapiro Ilan, D.I., Reilly, C.C., Hotchkiss, M.W. 2009. Suppressive effects of metabolites from Photorhabdus and Xenorhabdus spp. on phytopathogens of peach and pecan. Archives of Phytopathology and Plant Protection. 42:715-728. Interpretive Summary: Several fungal diseases such as brown rot on peach, and shuck decline, Phytophthora shuck and kernel rot, and scab on pecan can cause serious yield reductions in pecan and peach crops. Our objective was to investigate the potential of some new environmentally friendly pesticide agents to control these diseases. The pesticide agents are derived from by-products of naturally occurring bacteria (which are called Xenorhabdus and Photorhabdus). In laboratory experiments, we found that these by-products can suppress the fungal diseases of pecan and peach on a Petri dish as well as on pecan leaves and stems. Thus, these bacteria by-products might be used as alternatives to chemical fungicides. The next step in the research program will be to test the efficacy of these bacteria products under field conditions.
Technical Abstract: Our objective was to determine the suppressive abilities of bacterial metabolites derived from Xenorhabdus and Photorhabdus spp. on Glomerella cingulata, Phomopsis spp., Phytophthora cactorum, and Fusicladosporium effusum, which are fungal pathogens of pecan, and Monilinia fructicola, a fungal pathogen of peach. In vitro assays indicated that P. luminescens (VS) exhibited greater suppression than P. luminescens (Hb), Photorhabdus sp. (MX4), X. bovienii (SN), and Xenorhabdus sp. (3-8b). In in vivo tests, X. bovienii (SN) or P. luminescens (Hb) metabolites caused 90 to 100% suppression of P. cactorum on detached pecan leaves with only slight phytotoxicity. Metabolites derived from X. bovienii (SN) and P. luminescens (Hb), were also tested for suppression of F. effusum sporulation in detached pecan twigs and caused reduction (84%) that was equivalent to effects produced by chemical fungicides, dodine and fenbuconazole; a third chemical, triphenyltin hydroxide had no effect. Our results indicate that further research is warranted to determine if fungal diseases in pecan and peach can be controlled with these metabolites.