V.M. Lanoiselet1*, E.J. Cother2, G.J. Ash1 and J.D.I Harper1
1 Farrer Centre, School of Agriculture, Charles Sturt University, Wagga Wagga NSW 2678, Australia
2 NSW Agriculture, Agricultural Institute Orange NSW 2800, Australia
Accepted: 31 Jul 2002
Aggregate sheath spot caused by Rhizoctonia oryzae-sativae (Sawada) Mordue, and sheath spot, caused by Waitea circinata Warcup and Talbot have recently been reported on rice in Australia (Lanoiselet et al., 2001). Several disease surveys were conducted to investigate the presence of other sclerotial diseases of rice.
In 2001 and 2002 infected leaf sheaths were observed on several rice plants. Pieces of infected leaf sheaths were surfaced sterilised (2% sodium hypochlorite solution for 2 min), rinsed with sterile distilled water, placed on Potato Dextrose Agar (PDA) and incubated at 25°C. Eighteen isolates of R. oryzae-sativae, 10 isolates of W. circinata and 2 isolates of an unknown fungus were isolated. The unknown fungus was identified by The Centraalbureau voor Schimmelcultures (Utrecht, The Netherlands) as Sclerotium hydrophilum Saccardo (NSW Agriculture accession number DAR 75575).
In 2002, soil and floating plant material were collected from rice fields and screened for the presence of sclerotia. Tiny globose black sclerotia were recovered from 5 samples out of 6. These sclerotia germinated on PDA and the sclerotia which subsequently formed were identified as those of S. hydrophilum.
Koch's postulates was completed by inoculating rice plants with plugs of PDA bearing both mycelium and sclerotia of S. hydrophilum. After ten days at 30°C, sheath leaf necrosis was observed around the inoculation plugs. S. hydrophilum was re-isolated from the lesions.
Several authors have previously reported S. hydrophilum as a pathogen of cultivated rice (Cedeno et al., 1997). Kernkamp et al. (1977) reported S. hydrophilum on wild rice (Zizania aquatica) and Johnson et al. (1976) on water lilies (Nymphaea odorata).
This is the first report of S. hydrophilum occurring on cultivated rice in Australia.
This work was funded by the Cooperative Research Centre for Sustainable Rice Production.
Cedeno L, Nass H, Carrero C, Cardona R, Rodriguez H, Aleman L, 1997. Sclerotium hydrophilum en arroz en Venezuela. Fitopatologia Venezolana 10, 9-12.
Johnson DA, Stewart EL, King TH 1976. A Sclerotium species associated with water lilies in Minnesota. Plant Disease Reporter 60, 807-808.
Kernkamp MF, Kroll R, Woodruff WC 1977. Wild rice infected by Sclerotium sp. isolated from water lily. Plant Disease Reporter 61, 187-188.
Lanoiselet VM, Ash GJ, Cother EJ, Priest MJ, Watson A, 2001. First report of Waitea circinata causing sheath spot and Rhizoctonia oryzae-sativae causing aggregate sheath spot on rice in south-eastern Australia. Australasian Plant Pathology 30, 369-370.
©2002 The Authors