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Influence of Low Oxygen Levels in Aeroponics Chambers on Eucalypt Roots Infected with Phytophthora cinnamomi

April 1998 , Volume 82 , Number  4
Pages  368 - 373

Treena Burgess , Jen McComb , and Giles Hardy , Biological Sciences, Murdoch University, Perth, Western Australia, 6150 , and Ian Colquhoun , Alcoa of Australia Limited, Perth, Western Australia, 6153

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Accepted for publication 13 November 1997.

Aeroponics root chambers were designed to evaluate the influence of low oxygen on disease development in clones of Eucalyptus marginata susceptible or resistant to infection by Phytophthora cinnamomi. Actively growing 7-month-old clones of E. marginata were transferred into the aeroponics chambers, into which a nutrient solution was delivered in a fine spray, providing optimal conditions for root growth. Prior to inoculation by zoospores of P. cinnamomi under normal oxygen, the roots were exposed to four treatments: (i) normal oxygen, approximately 8 mg of O2 liter-1; (ii) 6 days of hypoxia, 2 mg of O2 liter-1; (iii) anoxic acclimatization 2 days at 2 mg of O2 liter-1, 2 days at 1 mg of O2 liter-1, 2 days at 0.5 mg of O2 liter-1, 2 days at 2 mg of O2 liter-1, and 6 h at <0.05 mg of O2 liter-1; and (iv) 6 h of anoxia, <0.05 mg of O2 liter-1. Root extension during hypoxia was greatly reduced. Lesion development was least for roots exposed to hypoxia and greatest for roots exposed to anoxia for 6 h, suggesting increased resistance of E. marginata to P. cinnamomi following hypoxia.

© 1998 The American Phytopathological Society