Induction and accumulation of phytoalexins in cowpea roots infected with a mycorrhizal fungusGlomus fasciculatum and their resistance toFusarium wilt disease |
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Authors: | P Sundaresan N Ubalthoose Raja P Gunasekaran |
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Institution: | (1) Department of Microbiology, School of Biological Sciences, Madurai Kamaraj University, 625 021 Madurai, India |
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Abstract: | The interaction of a vesicular-arbuscular mycorrhizal fungusGlomus fasciculatum with a wilt-causing soil borne pathogen,Fusarium oxysporum, was studied in cowpea (Vigna unguiculata). It was found that pre-establishment by vesicular-arbuscular mycorrhizal fungus reduced the colonization of the pathogen and
the severity of the disease, as determined by reduction in vascular discolouration index. In mycorrhizal plants, the production
of phytoalexin compounds was always higher than in the nonmycorrhizal plants. There appeared to be a direct correlation between
the concentration of the phytoalexins and the degree of mycorrhizal association. Three different compounds withR
f values of 0.23 (I), 0.17 (II) and 0.11 (III) were obtained from mycorrhizal plants. Similar compounds were also found to
be induced by an abiotic elicitor CuSO4. The first compound was identified as an isoflavonoid, daidzein and the other two remain to be identified. These compounds
were checked for their antifungal activityin vitro. The germination of conidial spores ofFusarium oxysporum was strongly inhibited by the compound III than the other two. It is argued that the production of phytoalexin compounds
in mycorrhizal plant could be one of the mechanisms imparting tolerance of the plants to wilt disease. |
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Keywords: | Phytoalexins mycorrhizae cowpea Glomus fasciculatum disease control |
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