Biological and molecular characterization of Lasiodiplodia theobromae causing dieback disease of strawberry in Thailand

Abstract

Strawberry (Fragaria × ananassa) is commercially grown in Chiang Mai Province of Northern Thailand. Strawberry dieback, whose symptoms include dieback of runners and roots followed by wilt and necrotic discoloration in crowns, was first observed in diseased strawberry cultivated in the greenhouse. Fungi were isolated from infected parts of diseased strawberry and a pathogenicity assay was conducted for confirmation of fungal pathogenesis. Morphological features of fungal isolates were observed using stereo and compound microscopes. For molecular characterization, internal transcribed spacer (ITS) and large subunit 28S rRNA (LSU) regions were amplified using polymerase chain reaction (PCR) and sequenced. Based on morphological and molecular identification, the fungi were identified as Lasiodiplodia theobromae. Koch's postulates were fulfilled by reisolating the pathogen. To the best of our knowledge, this is the first report of L. theobromae causing dieback of strawberry in Thailand.