Occurrence of Eutypella species on cotton (Gossypium hirsutum L.) in New South Wales, Australia

Abstract

We report for the first time the occurrence of an Eutypella species on cotton in New South Wales (NSW), Australia. The putative Eutypella was isolated from dead cotton plants that exhibited atypical symptoms of either Fusarium or Verticillium wilt. Dead plants had symptoms resembling lightning strike damage with blackened outer bark around the fifth node zone. Internal vascular discoloration was reddish grey and often occurred in V-shaped sections. Sequences of the internal transcribed spacer (ITS) revealed a 93.7–94.1% similarity to Eutypella scoparia, indicating that the NSW cotton isolates represented a putatively novel species within the Eutypella genus. Pathogenicity of the isolated Eutypella was assessed on cotton stem cuts and living plants inoculated with culture agar plugs. Typical black necroses on outer bark and reddish vascular discoloration were reinduced in both Eutypella-inoculated stem cuts and living plants. Subsequently, the same Eutypella pathogen was successfully recovered, thus fulfilling Koch’s postulates. The detection of Eutypella on NSW cotton is believed to be an independent event from a recently reported occurrence of Eutypella on Queensland cotton. The Queensland detection occurred in the same 2017/18 cropping season at approximately 730 km apart and was associated with distinct Eutypella isolates.