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The effect of phosphonate concentration on phytotoxicity symptoms in three understorey species of Eucalyptus marginata Donn ex Sm. forest and their colonisation by Phytophthora cinnamomi Rands

Bennalick, Rosalynn (1995) The effect of phosphonate concentration on phytotoxicity symptoms in three understorey species of Eucalyptus marginata Donn ex Sm. forest and their colonisation by Phytophthora cinnamomi Rands. Honours thesis, Murdoch University.

Abstract

The application of varying concentrations of phosphonate, its phytotoxicity and its ability to contain Phytophthora clnnamomi in Adenanthos barbiger, Davies/a decurrens and Xanthonl7oea prelsstl were examined. Pre-treatment of plants with foliar sprays of 0.2, 0.5 and 2% phosphonate restricted colonisation by P. cinnamoml in inoculated stems of A. barbiger and 0. decurrens, and led to a reduction. in the isolation of P. cinnamomi from Inoculated stems in' comparison with the plants not sprayed with phosphonate. P. cinnamoml was not isolated from stems of 0. decurrens plants treated with 2% phosphonate, but was isolated from 22% of the stems of A. barbiger. In X preissll, colonisation by, and isolation of, P. cinnamomi from inoculated roots was not significantly affected by pre-treatment of the foliage with 0.2, 0.5 and 2% phosphonate. Very low concentrations of phosphonate were detected in the roots of X preissii in comparison with the phosphonate concentration measured in the foliage of A. barbiger and 0. decurrens plants treated with phosphonate.

The effect of phosphonate concentration on phytotoxicity symptoms was also examined in A. barbiger, 0. decurrens and X preisstl. Phytotoxicity was expressed as leaf necrosis. Treatment with 0.2% phosphonate resulted in minimal phytotoxicity in each of the three species, while treatment with 1 , 2, 5 and 1 0% phosphonate led to the development of severe phytotoxicity symptoms. Histological examination of A. barbiger leaves indicated that photosynthetic processes were disrupted within two days after treatment with 10% phosphonate, before macroscopic changes were visible.

This study indicates that phosphonate has considerable potential for the management of P. cinnamomi in native plant communities. However, additional work is required on a wide range of plant species from all the major families to ascertain the effects of phytotoxicity, timing of application and phosphonate concentration on the effectiveness of phosphonate in containing P. cinnamomi .

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Biological and Environmental Sciences
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor: Hardy, Giles and Shearer, Bryan
URI: http://researchrepository.murdoch.edu.au/id/eprint/32815
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