Russ Bulluck lrbulluc at
Wed Mar 24 11:55:53 EST 1999

Which Phytophthora?

Albert Kausch wrote:

> Hi group,
> We are developing methods with which to test phytophthora resistance in
> rhododendron and have run into some trouble getting sporangia to release
> zoospores. We are using the standard protocols which call for rapid
> growth of mycelia on V8 medium followed by a series of washes and
> starvation treatment to induce sporangia formation. We get many hundreds
> or even thousands of sporangia. The next step is a cold treatment in
> sterile water. Our sporangia start out circular and in the water some,
> but not all, become elongated. After 1 - 2 hours at room temp, the
> sporangia do not release the zoopspores. We have a number of articles
> and books which show the elongated sporangia with visible zoospores
> inside. Our sporangia generally look dense without distinct zoospores.
> To try to get our sporangia to become more mature we have done a series
> of test leaving them in the starvation solution longer (a salt solution
> with K+, Ca+, Fe+, etc.), to no avail. We are considering doing a time
> course for the cold treatment. We were thinking that maybe our isolate
> (from Connecticut) is more cold tolerant than some of the isolates used
> in the reported literature. Any ideas?
> Thanks for any input.
> jane

Russ Bulluck
Ph.D. Student
Department of Plant Pathology
North Carolina State University
PO Box 7616
Raleigh, NC  27695-7616

The soil population is so complex that it manifestly cannot
be dealt with as a whole with any detail by any one person,
and at the same time it plays so important a part in the soil
economy that it must be studied.
--Sir E. John Russell
The Micro-organisms of the Soil, 1923

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