Identification and molecular phylogeny of Epulorhiza isolates from tropical orchids

Abstract

24 isolates of Epulorhiza were obtained from the roots and protocorms of orchids in Singapore. Two groups were distinguished based on morphological and cultural characteristics. Group 1 comprised 20 isolates which were identified as E. repens, while those in group 2 were identified as E. calendulina-like; Rhizoctonia. The ITS-5.8S rDNA sequence identity ranged from 88-100% among isolates of E. repens and six sub-groups were further delineated. The sequence identity was 98-100% among E. calendulina-like, Rhizoctonia isolates. The sequence identity between E. repens isolates and E. calendulina-like Rhizoctonia isolates ranged from 18-44%. Apparently, isolates from both groups 1 and 2 were genetically distinct. Phylogenetic analysis showed that the distribution of the isolates correlated with the sites and the hosts from which the fungi were isolated. No matching sequences have been found in the GenBank database for the ITS region of E. repens and E. calendulina-like Rhizoctonia.