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United States Department of Agriculture

Agricultural Research Service

Research Project: SOYBEAN DISEASE AND PEST MANAGEMENT Title: Response of soybean pathogens to glyceollin

Authors
item Lygin, Anatoly -
item Hill, Curtis -
item Zernova, Olga -
item Crull, Lalura -
item Widholm, Jack -
item Hartman, Glen
item Lozovaya, Vera -

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2010
Publication Date: November 1, 2010
Repository URL: http://hdl.handle.net/10113/45399
Citation: Lygin, A.V., Hill, C.B., Zernova, O.V., Crull, L., Widholm, J.M., Hartman, G.L., Lozovaya, V.V. 2010. Response of soybean pathogens to glyceollin. Phytopathology. 100:897-903.

Interpretive Summary: The ability to recognize pathogens and respond biochemically to prevent or inhibit pathogen invasion and colonization in plant cells is an active disease resistance response in plants. An incompatible interaction between plants and pathogenic fungi induces a resistance response that results in an increase in the activity of multiple local and systemic biochemical responses in the host plants. Plant antimicrobial compounds such as phytoalexins, synthesized in response to pathogen invasion, are capable of arresting or inhibiting colonization of pathogenic invaders. The involvement of soybean phytoalexin glyceollin in defense responses to the soybean pathogens Diaporthe phaseolorum var. meridionales, Macrophomina phaseolina, Sclerotinia sclerotiorum, and Phytophthora sojae was assessed in soybean hairy roots of two soybean genotypes, Spencer and PI567374, transformed with either soybean isoflavone synthase or chalcone synthase genes in order to determine the effect of glyceollin on fungal infection. The hairy-root-transformed lines had several-fold decreased levels of isoflavone daidzein, the precursor of glyceollin, and considerably lower concentrations of glyceollin induced by pathogens measured 5 days after fungal inoculation compared to the non-transformed controls without phenolic transgenes. Glyceollin was found to inhibit the growth of a range of soybean pathogens in this study. Rapid glyceollin synthesis during infection may be an important component of innate resistance to fungal pathogens in soybean. Thus breeding and genetic engineering targeted to enhance the capacity of glyceollin production in response to pathogen invasion could increase overall plant resistance to multiple diseases in soybean. It is conceivable that new soybean cultivars with stronger innate resistance would have a superior ability to accumulate the antibiotic glyceollin in response to general pathogen invasion, and not just to specific pathogens only. Cultivars with such enhanced innate resistance could help stabilize soybean production in the presence of diseases. This information is useful for scientist interested in the biochemical pathways related to resistance in plants.

Technical Abstract: The ability to recognize pathogens and respond biochemically to prevent or inhibit pathogen invasion and colonization in plant cells is an active disease resistance response in plants. The involvement of soybean phytoalexin glyceollin in defense responses to the soybean pathogens Diaporthe phaseolorum var. meridionales (Dpm), Macrophomina phaseolina (Mp), Sclerotinia sclerotiorum (Ss), and Phytophthora sojae (Ps) was assessed in soybean hairy roots of two soybean genotypes, Spencer and PI567374, transformed with either soybean isoflavone synthase (IFS2) or chalcone synthase (CHS6) genes in order to determine the effect of glyceollin on fungal infection. The hairy-root-transformed lines had several-fold decreased levels of isoflavone daidzein, the precursor of glyceollin, and considerably lower concentrations of glyceollin induced by pathogens measured 5 days after fungal inoculation compared to the non-transformed controls without phenolic transgenes. Mp, Ps and Ss grew much more aggressively on IFS2 and CHS6-transformed roots than on control roots, although, there was no significant difference in growth of Dpm on the hairy-root-transformed lines. Apparently, Dpm does not induce the normal pathogen response since very low glyceollin concentration was detected in Dpm inoculated roots even in the control. Glyceollin also inhibited the growth of these and three additional soybean pathogens, Cercospora sojina (Cs), Phialophora gregata (Pg), and Rhizoctonia solani (Rs) on glyceollin-amended agar medium. 7-hydroxyglyceollin was the main and most common product of glyceollin conversion/degradation by the pathogens with the exception of Ps, whereas no glyceollin degradation products in the culture medium were detected.

Last Modified: 10/26/2014
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