Use of optical density as a measure of Claviceps africana conidial suspension concentration

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Contents Vol 35(1)

doi:10.1071/AP05093

Use of optical density as a measure of Claviceps africana conidial suspension concentration

D. J. Herde ^A ^B ^F, M. J. Ryley ^C, S. D. Foster ^D, V. J. Galea ^A, R. G. Henzell ^E, D. R. Jordan ^E

^A School of Agronomy and Horticulture, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia.
^B Department of Primary Industries and Fisheries, Leslie Research Centre, PO Box 2282, Toowoomba, Qld 4350, Australia.
^C Department of Primary Industries and Fisheries, PO Box 102, Toowoomba, Qld 4350, Australia.
^D Biometrics SA, The University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia.
^E Department of Primary Industries and Fisheries, Hermitage Research Station, Warwick, Qld 4370, Australia.
^F Corresponding author. Email: damian.herde@dpi.qld.gov.au





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Australasian Plant Pathology 35(1) 77–80 http://dx.doi.org/10.1071/AP05093
Submitted: 10 June 2005 Accepted: 29 August 2005 Published online: 23 January 2006

Abstract

Sorghum ergot, caused by Claviceps africana, has remained a major disease problem in Australia since it was first recorded in 1996, and is the focus of a range of biological and integrated management research. Artificial inoculation using conidial suspensions is an important tool in this research. Ergot infection is greatly influenced by environmental factors, so it is important to reduce controllable sources of variation such as inoculum concentration. The use of optical density was tested as a method of quantifying conidial suspensions of C. africana, as an alternative to haemocytometer counts. This method was found to be accurate and time efficient, with possible applications in other disease systems.

Keywords: colorimeter, inoculum concentration, light transmittance, Sorghum bicolor.