Characterizations of Colletotrichum spp., Pathogens on Mango Fruits (Mangifera indica L. cv. ‘Nam Dok Mai’)

Abstract

Mango anthracnose disease is caused by several species of Colletotrichum including C. gloeosporioides, C. acutatum, C. siamense and C. asianumand. The disease is considered as one of the major constraints of Thai mango export. However, the classification of these pathogens was still unclear. Generally, Colletotrichum spp. are classified based on their morphology. The aims of this study were to characterize and confirm the species of Colletotrichum isolates collected from mango orchards for exporting located in 6 different provinces of Thailand. The characterization was based on pathogenicity test, morphological and molecular characteristics. Forty four isolates were obtained from the symptomatic fruits. Pathogenicity test of all isolates showed typical anthracnose symptoms on the tested mango fruits and Koch’s postulates were fulfilled by re-isolation from the inoculated fruits. The morphological characterization identified all isolates as C. gloeosporioides with 6 morphotypes, as their conidia were hyaline, cylindrical with rounded-end and approximately 14.90x4.02 μm in size. Setae on infected tissue were also observed is some isolates. Species specific primer analysis could confirm 39 isolates of Colletotrichum as C. gloeosporioides. Ribosomal DNA (rDNA) gene sequencing and homology analysis of other five isolates revealed that these isolates were C. gloeosporioides except for the WH9 isolate which was identified as C. acutatum. By combining the results from molecular analysis with morphological characterization and pathogenicity test, we report that C. gloeosporioidesis is the main causal pathogen of mango anthracnose in the mango orchards for exporting in Thailand.