A checklist of plant pathogenic fungi and Oomycota in Sri Lanka

Sri Lanka is blessed with a rich ecosystem diversity, however, only a small fraction of the diverse flora and fauna in the country is known. Only around 3,000 species of fungi are currently known out of the estimated number of 25,000 species of native fungal flora of Sri Lanka. This includes the 2,000 species, belonging to 640 genera, recorded prior to 1950. The fungi studied, prior to 1950, have been well documented, as journal publications, checklists or books. In contrast, the information on Sri Lankan fungal flora, available especially after 1950, is scattered. The present `Checklist of Plant Pathogenic Fungi in Sri Lanka’ is intended to bring together all species of plant pathogenic fungi and Oomycota recorded in the country after late nineteen forties. The checklist consists of 404 species of plant pathogenic fungi and Oomycota, belonging to 110 genera and 230 species, associated with diseases of horticultural, agricultural and plantation crops and their harvested produce and forests plants in Sri Lanka.


INTRODUCTION
Sri Lanka is an island in the Indian ocean located at the southern point of the Indian sub-continent, between 5 o 54' and 9° 52' North Latitude and 79 o 39' and 81 o 53' East Longitude with a land area of 6,570,134 ha. Topographically, the island comprises of central mountains with an elevation of up to 2500 m, surrounded by the lowlands. The overall climate of the Island could be considered as tropical, mainly due to the differences in rainfall and elevation. A variation in the weather is observed across the island with a very distinctive dry and wet seasons. The rainfall shows a seasonal variation and country depends on the southwest and northeast monsoons and on convectional and cyclonic effects. The average temperature ranges between 28 -32 ͦ C.
Despite its small size, Sri Lanka is blessed with a rich ecosystem diversity owing to its topographic and climatic heterogeneity as well as its coastal influence. Higher plants, vertebrates and few other selected groups have been studied in detail. Most other groups remain to be explored. The native fungal flora in Sri Lanka has been conservatively estimated to be around 25,000 species (Adikaram, 2004), based on the fungus to higher plant species ratio of 6:1 (Hawksworth, 1991).
The total number of species known to date could be around 3,000, including those that were recorded prior to 1950 by Berkeley and Broome (1871), Petch (1906Petch ( , 1910Petch ( , 1923 and Petch and Bisby (1950) which amount to about 640 genera and 2,000 species. It is quite unlikely that ancient Ceylonese people lacked even an awareness, if not an understanding, of the organisms that the Western world has described as 'fungi'. It is possible that they may have used their own terminology to describe, mushrooms and toadstools for example, that would have been common in their surroundings and visible to the naked eye. However, the earliest records of fungi, by species names and drawings in Ceylon, were Peziza ceylonsche and Peziza lembosa in 1783 by Houttuyn.
The fungi studied, prior to 1950, in Ceylon have been well documented and mostly compiled in to checklists or books. In contrast, the information on Sri Lankan fungal flora, recorded after 1950, is scattered in Scientific Journals, Proceedings of Scientific Meetings and Annual Reports of Research Institutes (Karunarathna et al. 2012). A reasonable number of fungi, though known, do not appear to have been published.
Except for a few major plantation crops such as tea and rubber, understanding of the fungi infecting agricultural, horticultural, ornamental or forest plants etc. is incomplete. 'Diseases of cultivated plants -their Diagnosis and Treatment in Ceylon' by D.V.W. Abeygunawardena in 1969 was a comprehensive guide to Plant Pathology as a subject as well as to the diseases in plants cultivated in Ceylon. The book is useful even in today's context of Plant Pathology, 50 years after the book was first written. 'A handbook to the fungi parasitic on the plants of Sri Lanka ' (1979) that carries morphological illustrations of numerous genera of parasitic fungi, is mainly a guide to identification of fungi causing numerous plant diseases and disease diagnosis.
The present 'Checklist of Plant Pathogenic Fungi' is intended to bring together all species of plant pathogenic fungi and Oomycota recorded in the country after late nineteen forties. Plant pathogenic fungi recorded in Sri Lanka were compiled using literature published in the country. The checklist consists of 404 entries of fungi and Oomycota, belonging to 110 genera and 230 species that have been recorded from agricultural, horticultural, plantation, forest and ornamental plants and freshly harvested produce in the country after late nineteen fifties.
The checklist provides, for every fungal species the common and the species name of the host plant/s, the name of the disease in most cases, and the source of publication or the communication. The name of the fungus given in the checklist is the same name as it appeared in the publication. In a separate column, the current name of each species is also given.
For easy reference the names of fungi are given in alphabetical order. Oomycota, belonging to the Kingdom Chromista, are listed separately from fungi in the checklist. Some of the fungi in the checklist may have also been recorded in publications prior to 1950's.
Among the genera in the Checklist, Colletotrichum, causing anthracnose disease (Figure 1), was the most recorded plant pathogen during the period. Colletotrichum thrives under the warm and humid conditions prevailing in many parts of the country. Colletotrichum infections are most common in edible fruit species where infections usually occur in the field at early stages of fruit development. The fungus remains quiescent until the fruit undergo ripening to develop progressive anthracnose symptoms  (Adikaram et al. 1983). The genus has also undergone intense molecular revision recently increasing its species in great numbers and attention as a pathogen in a wider range of plants ( Baroncellil et al. 2016). Powdery mildews are most common in many parts of the country, again due to prevailing favorable weather conditions. Botrytis cinerea infections were found only in the coldest, hilly area in the Central Province. Penicillium diseases were found under moderate temperatures.
The highest number of fungi have been recorded from vegetable diseases followed by fruit and plantation crops respectively and the total number of fungi from vegetable, fruit and plantation crops added together amounts to 69% of the total number in the checklist.
This data provided in the Checklist will be useful in the compilation of fungal biodiversity of Sri Lanka. The checklist will, not by any means, be a conclusive list and new records will continue to be added regularly in the future.  Fernando and Abeywickrama (1996) 18.