Dor, E., Newe Ya'ar Research Center, Institute of Plant Protection, Agricultural Research Organization (ARO), P.O. Box 1021, 30095 Ramat Yishay, Israel
Joel, D.M., Newe Ya'ar Research Center, Institute of Plant Protection, Agricultural Research Organization (ARO), P.O. Box 1021, 30095 Ramat Yishay, Israel
Kapulnik, Y., The Volcani Center, Institute of Plant Sciences, Agricultural Research Organization (ARO), P.O. Box 6, 50250 Bet Dagan, Israel
Koltai, H., The Volcani Center, Institute of Plant Sciences, Agricultural Research Organization (ARO), P.O. Box 6, 50250 Bet Dagan, Israel
Hershenhorn, J., Newe Ya'ar Research Center, Institute of Plant Protection, Agricultural Research Organization (ARO), P.O. Box 1021, 30095 Ramat Yishay, Israel

Strigolactones that are released by plant roots to the rhizosphere are involved in both plant symbiosis with arbuscular mycorrhizal fungi and in plant infection by root parasitic plants. In this paper, we describe the response of various phytopathogenic fungi to the synthetic strigolactone GR24. When GR24 was embedded in the growth medium, it inhibited the growth of the root pathogens Fusarium oxysporum f. sp. melonis, Fusarium solani f. sp. mango, Sclerotinia sclerotiorum and Macrophomina phaseolina, and of the foliar pathogens Alternaria alternata, Colletotrichum acutatum and Botrytis cinerea. In the presence of this synthetic strigolactone, intense branching activity was exhibited by S. sclerotiorum, C. acutatum and F. oxysporum f. sp. melonis. Slightly increased hyphal branching was observed for A. alternata, F. solani f. sp. mango and B. cinerea, whereas suppression of hyphal branching by GR24 was observed in M. phaseolina. These results suggest that strigolactones not only affect mycorrhizal fungi and parasitic plants, but they also have a more general effect on phytopathogenic fungi. © 2011 Springer-Verlag.