Invasive Species Compendium

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Abstract

Distribution of clones of Phellinus noxius in a windbreak on Ishigaki Island.

Abstract

The distribution of clones of Phellinus noxius, the causal agent of brown root rot, was studied in a windbreak on Ishigaki Island, Ryukyu Archipelago, Japan. In total, 99 isolates obtained from infected trees of Calophyllum inophyllum, Casuarina equisetifolia and Bauhinia racemosa were analysed by means of a somatic compatibility test on a sawdust-rice-bran medium, an antagonism test on PDA with guaiacol solution, and by esterase analysis with isoelectric focusing. Results obtained from the three methods were almost identical, although the somatic compatibility test was less precise than the other methods. Isolates from neighbouring infected trees belonged to the same clone in many cases. On plots of 150-400 m2, 1-5 clones were found. Single clones covered an area of up to 20Ă—20 m. A total of 25 different clones were recognized within the sample sites. This suggested that multiple basidiospore infection existed in the site, although infection centres spread by vegetative growth across root contacts of neighbouring trees. Results indicated that Casuarina equisetifolia was the most susceptible tree species on the site. Hibiscus rosa-sinensis planted in the windbreaks was not killed, although P. noxius damage has been reported elsewhere. In windbreak plantations of Pinus luchuensis, dead or declining trees were not observed, indicating that this species may be less susceptible.