Monday 5 August 2013

A new species of Leaf-spot Fungus from Fish Poison Trees in Thailand.

Leaf-spot infections are among the most common diseases in plants, and are caused by a wide variety of fungi. Though unsightly, few of these pathogens are capable of doing serious, long-lasting damage to their hosts. Pathogenic fungi tend to be well studied in crop-plants, particularly in cool climates, but are on the whole poorly studied in the tropics and in undomesticated plants in general.

In a paper published in the journal Phytotaxa on 30 May 2013, a team of scientists led by Hiran Ariyawansa of The Engineering and Research Center for Southwest Bio-Pharmaceutical Resources of National Education Ministry of China at Guizhou University, and the Institute of Excellence in Fungal Research and the School of Science at Mae Fah Luang University describe a new species of Leaf-spot fungi found growing on Fish Poison Trees (Barringtonia asiatica) in Chiang Rai Province, Thailand.

The Fish Poison Tree is a mangrove dwelling plant found across the Indian and Pacific Oceans from Zanzibar to French Polynesia, its fruit being dispersed on ocean currents in a similar way to Coconuts. All parts of the plant are extremely toxic, and in many places the fruit is ground up and used to make a poison used to kill and capture fish. In Thailand the plant is used by herbalists to treat stomach aches, rheumatism and worm infections. The plant is also widely grown as an ornamental.

The new fungus is given the name Deniquelata barringtoniae, where Deniquelata means 'short and broad' in reference to the shape of the asci (sexual, spore-bearing cells) and barringtoniae refers to the host-plant. DNA analysis suggests that the closest known relative of Deniquelata barringtoniae is Bimuria novae-zelandiae, a soil dwelling fungus from New Zealand.

Infections of Deniquelata barringtoniae start out as small ash-coloured spots, turning darker brown as they age, and reaching 2 mm across after about 10 days. Eventually these enlarge to become sunken areas of decay surrounded by a white fungal colony. The fungus apparently needs the leaf surface to be damaged to gain a foothold. 

Early stage Deniquelata barringtoniae infection on a Fish Poison Tree leaf. Ariyawansa et al. (2013).

Later stage Deniquelata barringtoniae infection on Fish Poison Tree leaves. Ariyawansa et al. (2013).

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