A NEW RECORD OF BROWN ROT DISEASE IN WATER FERN AZOLLA MICROPHYLLA (AZOLLACEAE): LOSS OF IMPORTANT BIO-RESOURCE.

Severely infected water fern, Azolla microphylla Kaulf., has been observed in natural habitats in different districts in the lower Gangetic plain of West Bengal, India. The infected plants have turned dark brown and been rotted entirely within 5-7 days, causing loss of natural resource as the plant species has immense commercial value. Specific growing colonies with cottony white mycelium, yellow pigmentation on the cultured medium, macro- and micro- conidial features, and absence of chlamydospore indicate the causal pathogen to be Fusarium thapsinum Klittich., Lesile, Nelson, Marases. The identification of the causal pathogen has been authenticated by standard pathogenicity test (Koch's Postulates). Extensive literature survey reveals that this is a new record of brown rot disease in A. microphylla. [ABSTRACT FROM AUTHOR]