Co-Authors:
Guenoune, D., Agronomy and Natural Resources Department, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Galili, S., Agronomy and Natural Resources Department, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Phillips, D.A., Agronomy and Range Science Department, University of California, Davis, CA 95616, United States
Volpin, H., Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
Chet, I., Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
Okon, Y., Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
Kapulnik, Y., Agronomy and Natural Resources Department, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Abstract:
Defense responses of alfalfa roots to the pathogenic fungus Rhizoctonia solani were reduced significantly in roots simultaneously infected with the vesicular arbuscular mycorrhizal (AM) fungus Glomus intraradices. R. solani induced five- to tenfold increases in the steady-state levels of chalcone isomerase and isoflavone reductase mRNAs a doubling of root peroxidase activity and a marked autofluorescence in the infected tissue. These changes were inhibited by the presence of G. intraradices. Interestingly, germination of G. intraradices spores and hyphal elongation were sensitive to low concentrations (2 μM) of medicarpin-3-O-glucoside, an isoflavonoid phytoalexin that accumulated both in roots colonized by the pathogenic fungus as well as in AM-treated roots receiving high P, where no colonization by the beneficial fungus occurred. These data support the hypothesis that during early stages of colonization by G. intraradices, suppression of defense-related properties is associated with the successful establishment of AM symbiosis. © 2001 Elsevier Science Ireland Ltd.