Athelia rolfsii causes sett rots and germination failure in sugarcane (Saccharum hybrid): pathogenicity and symptomatology

Abstract

An unknown sclerotium-forming fungus was observed and isolated in 2016 from sugarcane grown at Sugar Research Australia, Woodford Pathology farm, Woodford, Queensland. The fungus appeared to be causing germination failure of sugarcane setts. The fungus was isolated from infected tissues and mycelia from internal pithy sett tissues. White mycelia and abundant sclerotia were grown on PDA. Morphological observation and molecular analysis confirmed the identification of the fungus as Athelia rolfsii. Significant reductions in sett germination (>70%) were observed in the field when inoculated setts were planted. Reddish and patchy lesions were observed on the external surface of the setts and pale-red to red discolouration in internal tissues (associated with white mycelial growth in the pithy tissues and on the cut end of setts). Symptoms on young plants included water-soaked to light-brown lesions at their base, production of sclerotia / white mycelium in and around the lesions, and death of the young plants. This is the first report demonstrating that A. rolfsii can cause germination failure and young plant death in sugarcane.