Quote:
Originally Posted by BlackBear
The link is good ...and the awareness of seed bourne pathogen internal that heat treatment fixes is interesting ...........does anybody know of some dreaded pathogen that for some reason will not be fixed with the standard heat treatment of 50C/ 122F @25 minutes ???
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Interesting subject. A scientific answer would require a survey of the literature
to answer that question for each individual pathogen to characterize its
individual behavior and a variety of circumstances, for example a spore might
withstand a much greater temperature than the corresponding organism:
Most sources quote that heat treatment is especially useful for bacterial
diseases present in the seed endosperm. It is also used to control viral and
fungal disease, but typically in industry seeds are treated with fungicides and
other biocidal chemicals, even in addition to different heat treatments.
Since we are dealing with living organisms, I think looking for a yes/no answer
is an oversimplification. My impression is that heat treatment reduces all these
pathogens to minimal levels if it doesn't eliminate them, but there are no
guarantees in nature. Some pathogens are more stubborn than others, and
each seed presents a different microscopical situation. I would liken it to
chemotherapy in which you get a great success rate and appear cancer-free,
but somewhere, there could be lurking something that for some random
reason persisted. Life, (including viruses) is tenacious.*
Perhaps a virus could have a greater chance of persisting.
I heat treat all of my seeds by the standard 25 min @ 122 F, and have
never had a wholesale problem of seed mortality. It is true that older
seed seems to have lower germination rates after applying a heat treatment,
but to say anything more, a controlled experiment under the specific
conditions is the way to go. After all, it is older seed, and I don't know the
conditions it was stored under. If only 6/10 germinate instead of 9/10, how
would I know why since I don't run a replicated, controlled statistically
meaningful experiment comparing heat treated to non-heat treated of
uniformly produced and stored control seeds. The literature claims that seed
over 2 years old really can suffer greater mortality. I take the researchers'
word for it so far
as sounding plausible. If someone stuck me in a bath of
122 F for 25 minutes, I'm pretty sure I wouldn't even live 5 minutes. But I
would be sure to binge on unsaturated fatty acids if I had advanced notice,
and do whatever I could to increase my odds of survival. Who knows, life
usually finds a way to surprise!
* "Life is tenacious." Apparently I'm getting old, since "tenacious" is not the
word I want here. There is a quote that is more of a one line zinger with a
synonym to tenacious that I was looking for, but my memory is on holiday :-(