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Ecology and Epidemiology

Temperature-Growth Relationships of Phytophthora cinnamomi in the Secondary Phloem of Roots of Banksia grandis and Eucalyptus marginata. B. L. Shearer, Research Station, Department of Conservation and Land Management, Dwellingup, West Australia 6213; S. R. Shea, and P. M. Deegan. Research Station, Department of Conservation and Land Management, Dwellingup, West Australia 6213. Phytopathology 77:661-665. Accepted for publication 28 August 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987.. DOI: 10.1094/Phyto-77-661.

The form of the temperature-growth rate relationships of Phytophthora cinnamomi in excised roots of Banksia grandis and Eucalyptus marginata was skewed toward optimal temperatures (2530 C) and could be divided into two linear components. There was a linear increase in growth rate as temperatures increased from 10 to 30 C and a decrease for temperatures greater than 30 C. Most of the variation in fungal growth in field-inoculated intact roots of E. marginata was explained by variation in maximum daily temperature. Introduction of nonlinear components into the regression model did not improve the variation explained over that obtained for simple linear relationships. For the susceptible host B. grandis, there was close correlation between lesion lengths predicted from temperature-growth relationships in excised roots and observed lesion lengths in the field. Closest agreement between observed and predicted lesion lengths in E. marginata occurred for winter-inoculated roots. For roots of E. marginata inoculated in summer there was divergence between observed and predicted lesion lengths. Observed lesion lengths did not increase as optimal temperatures for fungal development increased. Host resistance or the physiological status of tissue could have inhibited fungal growth.

Additional keywords: epidemiology, forest site type.