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Title: Isolation and identification of nematode-antagonistic compounds from the fungus Aspergillus candidus

item SHEMSHURA, OLGA - Institute Of Microbiology And Virology
item BECKMAKHANOVA, NADIYA - Institute Of Microbiology And Virology
item MAZUNINA, MARIYA - Institute Of Microbiology And Virology
item Meyer, Susan
item Rice, Clifford
item Masler, Edward

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2016
Publication Date: 2/5/2016
Citation: Shemshura, O.N., Beckmakhanova, N.E., Mazunina, M.N., Meyer, S.L., Rice, C., Masler, E.P. 2016. Isolation and identification of nematode-antagonistic compounds from the fungus Aspergillus candidus. FEMS Microbiology Letters. 363(5):1-9.

Interpretive Summary: Plant-parasitic nematodes attack all crops of agricultural importance, causing over $100 billion in losses annually worldwide. Current chemical pesticides used to control nematodes can harm the environment, and growers possess a critical need for the discovery of environmentally and economically sound nematode control agents. One approach to discovering new ways to control nematodes is to identify natural compounds that can inhibit their ability to survive. We discovered that a fungus produced compounds that can kill plant-parasitic nematodes. Using chemical and biological analyses we identified two of the fungal compounds, each related to citric acid. The results are significant because they show how the fungus might act against nematodes in the soil and that natural compounds are effective at killing nematodes. These results will be used by scientists studying management of plant-parasitic nematodes.

Technical Abstract: An isolate of the fungus Aspergillus candidus was tested for production of nematicidal compounds. Adults of the nematode Ditylenchus destructor were completely inactive after 24 hr exposure to soy medium in which A. candidus was cultured. Column, thin layer and preparative chromatographies, and spectral and elemental analyses, were used to isolate and identify two major constituents of the culture medium: citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid) and an isomer of dimethyl citrate (1’,2’-dimethyl citrate (3-hydroxy-5-methoxy-3-(methoxycarbonyl)-5-oxopentanoic acid). Citric acid and the dimethyl citrate isomer each caused D. destructor inactivation (67.5% and 73.0%, respectively) at 50mg/ml water. A citric acid standard and the natural citric acid isolated from the fungal culture medium were also toxic to the plant-parasitic nematode Meloidogyne incognita. Exposure of M. incognita to either compound (50 mg/ml water) caused a 94-98% decrease in egg viability and 100% inhibition in the activity of second-stage juveniles.