Post-infection antagonism in Eucalyptus sieberi seedlings growing in Phytophthora cinnamomi - infected soils that suppress root disease.  G. C. Marks and I. W. Smith.  November 1984.  8 pp. (unpubl.)

SUMMARY

Post-infection antagonism in Eucalyptus sieberi L.A.S. Johnson (silvertop) roots infected by Phytophthora cinnamomi Rands (phytophthora root rot) was tested by growing large seedlings in a core of suppressive soil and surrounding them with a jacket of similar inoculated soil.

The core and jacket soils were steam-treated, when required, to reduce disease suppression, and optimum conditions for infection were maintained in a controlled environment.

When the microflora of the core soil were not steamed, total mortality and mortality rates were reduced significantly. Yet, inoculum densities of P. cinnamomi were not reduced in these unsteamed suppressive soils, and zoospore production may have been stimulated. The results provide indirect evidence that penetration and establishment of P. cinnamomi within a root was slowed by the soil microflora, indicating that post-infection antagonism had occurred.