Albert Kausch akausch at
Tue Mar 23 11:48:36 EST 1999

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.

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