Molecular characterization of &lt;i&gt;Colletotrichum&lt;/i&gt; species causing &lt;i&gt;Begonia&lt;/i&gt; anthracnose in Sri Lanka

P Wickramasinghe,D Yakandawala,N Adikaram

doi:10.4038/cjs.v49i5.7803

Abstract

Anthracnose disease is known to affect many tropical and subtropical fruits, vegetables and also certain cut-flowers and foliage plants. The disease was known to be caused by Colletotrichum gloeosporioides or C. acutatum which are presently accepted as species complexes. The present study was conducted with the main objective of identifying Colletotrichum species causing begonia anthracnose using morphological and molecular data. Begonia is an ornamental foliage plant grown worldwide. Anthracnose symptoms appear in begonia leaves as brownish, irregular, necrotic lesions. Colletotrichum was isolated from three Begonia species showing anthracnose symptoms, collected from three Provinces of Sri Lanka. Thirty isolates were obtained in the study of which 29 formed oblong conidia and the remainder produced falcate conidia. Six randomly selected isolates forming oblong conidia and the isolate with falcate conidia were sequenced for Internal Transcribed Spacer (ITS) and β-tubulin 2 (TUB2) regions. Considering >98% similarity with NCBI GenBank database for both sequences, the isolates with oblong conidia were identified as C. siamense and the isolate with falcate conidia as C. truncatum. Newly generated sequences were subjected to phylogenetic analysis with the closely related ex-type and authenticated isolates sequences. Phylogenetic analysis confirmed the species as C. siamense and C. truncatum. Koch’s postulates were performed to establish whether the fungi isolated from anthracnose lesions were actually causing anthracnose disease in Begonia leaves. This is the first report of C. siamense causing Begonia anthracnose.

Highlights

Begonia, belonging to the Family Begoniaceae, is one of the largest angiosperm genera comprising over 1500 species (Hughes and Hollingsworth, 2008)
The disease was known to be caused by Colletotrichum gloeosporioides or C. acutatum which are presently accepted as species complexes
Anthracnose disease was observed in the four Begonia varieties belonging to three species, Begonia rex var

Summary

Introduction

Begonia, belonging to the Family Begoniaceae, is one of the largest angiosperm genera comprising over 1500 species (Hughes and Hollingsworth, 2008). They are native to moist tropical and subtropical climates and cultivated as indoor or outdoor houseplants and as edgings in gardens for their elegant, succulent, often varicolored leaves and waxy flowers. A leaf rust caused by Coleosporium solidaginis has been reported which produces orange-red pustules on the under surface of leaves resulting in shedding them prematurely. One of the most common and wide-spread diseases in Begonia is bacterial leaf spot or blight with small blisterlike spots on leaves caused by Xanthomonas campestris pv.

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