African Journal of Microbiology Research Vol. 5(25), pp. 4368-4372, 9 November, 2011 Available online at http://www.academicjournals.org/AJMR ISSN 1996-0808 ©2011 Academic Journals DOI: 10.5897/AJMR11.476 Full Length Research Paper Morphological, pathological and molecular variability of Colletotrichum capsici causing anthracnose of chilli in the North-east of Thailand Aphidech Sangdee*, Sarawut Sachan and Surasak Khankhum Department of Biology, Faculty of Science, Mahasarakham University, Thailand 44150, Thailand. Accepted 23 August, 2011 Anthracnose disease is one of the major economic constraints to chilli production in tropical and subtropical regions. Ten isolates of Colletotrichum capsici causing chilli anthracnose were collected from 10 provinces in the northeast of Thailand. The isolates were evaluated for their morphological and cultural characteristics, pathogenic variability on chilli fruits and genetic characterization using random amplified polymorphic DNA (RAPD-PCR). Based on the morphological traits and cultural characteristics of the C. capsici populations, 10 isolates were categorized into six groups. These were designated, respectively, as CC-I, CC-II, CC-III, CC-IV, CC-V and CC-VI. In Potato Dextrose Agar culture, most of the isolates produced cottony colonies. However, differences were obtained in colony color, shape and size of conidia. Based on the effect of carbendazim, 10 isolates were classified into two groups designated as highly resistant group (<40% inhibition) and highly sensitive group (>90% inhibition). Three virulence degrees of 10 isolates on chilli fruits were evaluated. Molecular polymorphism generated by RAPD confirmed the variation of the different isolates and they were grouped into two clusters. However, morphological, pathological and RAPD grouping of isolates suggested no correlation among the test isolates. Key words: Colletotrichum capsici, morphological and cultural characteristics, pathogenic variability, random amplified polymorphic DNA (RAPD). INTRODUCTION Chilli (Capsicum annuum L.) is one of the most popular and widely grown vegetables in the world and the most popular in Asia (Makari et al., 2009). However, a major problem for chilli production in tropical and subtropical areas is anthracnose disease (Sharma et al., 2005). Anthracnose, caused by Colletotrichum capsici is one of the most serious fungal pathogens of chilli in Asia. In Thailand, C. capsici is reported to be an important pathogen in chilli crop production areas (Than et al., 2008; Montri et al., 2009). This disease produces symptoms on leaves, stem and fruits and causes severe *Corresponding author. E-mail: aphidech_sangdee@yahoo.com. damage to mature fruits in the field. Moreover, during transit and storage, this disease also causes severe damage to chilli fruit (Mehrotra and Aggarwal, 2003). The virulence degree of disease symptoms on host plants depends on the fungal pathotype. Sharma et al. (2005) reported the existence of 15 pathotypes of C. capsici based on disease symptom development on inoculated fruit of C. annuum genotypes. Montri et al. (2009) showed virulent pathotype differences within C. capsici isolates based on percent lesion size, appearance of necrotic or water-soaked tissue and presence of acervuli on Capsicum species. Therefore, information on the distri- bution of race or pathotype in chilli growing areas and an accurate method for identification and characterization of C. capsici is necessary for effective disease management and development of host resistance in breeding programs