Seed Hygiene Issues

[travis]

Originally Posted by Gerardo

The Sterilization protocol seems pretty easy
Soak seeds in 70% EtOH for 10 min
Rinse with sterile water (1x)
Soak seeds in 50% bleach for 20 min
Rinse with sterile water (3x)

What are the germ rates after a thorough cleaning such as this? >50%?

Thank you.

I think this is excessive, and may result in lowering germination rates.

I think a minute or two in 1 part household bleach to 4 parts water is sufficient

http://ohioline.osu.edu/hyg-fact/3000/3085.html

Hot Water and Chlorine Treatment of Vegetable Seeds to Eradicate Bacterial Plant Pathogens; Facts Sheet from Ohio State University

[dustdevil]

Originally Posted by travis

I think this is excessive, and may result in lowering germination rates.

I think a minute or two in 1 part household bleach to 4 parts water is sufficient

http://ohioline.osu.edu/hyg-fact/3000/3085.html

Hot Water and Chlorine Treatment of Vegetable Seeds to Eradicate Bacterial Plant Pathogens; Facts Sheet from Ohio State University

Please take note that this paper has to do with BACTERIAL pathogens...no mention of viral pathogens

[ginger2778]

I am hoping one of our scientist experts can help me out with this question. I learned that viruses are obligate intracellular parasites, and are very perishable when outside of their living cell host. So my question is if a seed is thoroughly dried out for months or longer, can a virus live in the germplasm?
Asking here specifically about viruses, not bacteria or fungi.
Hoping for a response from Chris or Morayeelbite.

[Fred Hempel]

Yes. Viruses can live in dried seeds.

In fact, some viruses (TMV in particular) can survive over 100 years in the soil waiting to re-infect a plant.

This is why TMV is so problematic. Once you have it, it is very hard to get rid of.

Any virus that gets into the embryo in the seed (not all can easily get into the embryo) can not be removed with surface sterilization. This is where the heat treatments come in. A dried seed is a living organism, and both viruses can easily exist within a dried seed (if they can get in).

Originally Posted by ginger2778

I am hoping one of our scientist experts can help me out with this question. I learned that viruses are obligate intracellular parasites, and are very perishable when outside of their living cell host. So my question is if a seed is thoroughly dried out for months or longer, can a virus live in the germplasm?
Asking here specifically about viruses, not bacteria or fungi.
Hoping for a response from Chris or Morayeelbite.

[Gerardo]

Originally Posted by Fred Hempel

There should be very little, if any, reduction in germination percentage with ethanol and bleach treatments.

You have to walk away and forget about the seed to damage it significantly, and you could probably double the treatment times without much effect.

At least that is my personal experience.

Awesome Fred, I'll start treating my incoming/outgoing seeds to reduce inoculums. I've been battling whiteflies and they are a virus-laden zombie horde.

[Fred Hempel]

Gerardo,

I think Travis is right. The times on the protocol I posted are probably overkill. I would cut them in half, and I think you will still get a complete surface sterilization.

Sometimes adding a small amount of detergent helps too, particularly if you are sterilizing dry seed. The detergent helps remove surface bubbles on the seed that can harbor pathogens.

[Gerardo]

Originally Posted by travis

I think this is excessive, and may result in lowering germination rates.

I think a minute or two in 1 part household bleach to 4 parts water is sufficient

http://ohioline.osu.edu/hyg-fact/3000/3085.html

Hot Water and Chlorine Treatment of Vegetable Seeds to Eradicate Bacterial Plant Pathogens; Facts Sheet from Ohio State University

Originally Posted by Fred Hempel

Gerardo,

I think Travis is right. The times on the protocol I posted are probably overkill. I would cut them in half, and I think you will still get a complete surface sterilization.

Sometimes adding a small amount of detergent helps too, particularly if you are sterilizing dry seed. The detergent helps remove surface bubbles on the seed that can harbor pathogens.

So aprox. 20% solution of regular strength Clorox for a few mins is plenty.

Skip the EtOh then?

Can Alconox, or maybe Citranox, be brought into the picture too?

[Fred Hempel]

I use approximately 25-35% for 1-2 minutes, because I don't want to wait around long. And I typically am treating seed that has already been fermented, and rinsed.

After adding the bleach, I wait a minute or so and swirl the seeds. Then I start rinsing (3X minimum).

I typically do not use Ethanol.

I don't know about Alconox or Citranox -- I just use a drop of dish soap when I make up a half gallon of bleach solution.

[Worth1]

I'm not the expert you are asking for but the answer is yes.
This is called vertical infection by way of pollen or seed.

Plant virus transmission from generation to generation occurs in about 20% of plant viruses. When viruses are transmitted by seeds, the seed is infected in the generative cells and the virus is maintained in the germ cells and sometimes, but less often, in the seed coat. When the growth and development of plants is delayed because of situations like unfavourable weather, there is an increase in the amount of virus infections in seeds. There does not seem to be a correlation between the location of the seed on the plant and its chances of being infected. [5] Little is known about the mechanisms involved in the transmission of plant viruses via seeds, although it is known that it is environmentally influenced and that seed transmission occurs because of a direct invasion of the embryo via the ovule or by an indirect route with an attack on the embryo mediated by infected gametes. [5] [6] These processes can occur concurrently or separately depending on the host plant. It is unknown how the virus is able to directly invade and cross the embryo and boundary between the parental and progeny generations in the ovule. [6] Many plants species can be infected through seeds including but not limited to the families Leguminosae, Solanaceae, Compositae, Rosaceae, Cucurbitaceae, Gramineae. [5] Bean common mosaic virus is transmitted through seeds.

https://www.google.com/url?sa=t&rct=...H8p1KkKmP1RXtQ

[Gerardo]

Originally Posted by Fred Hempel

I use approximately 25-35% for 1-2 minutes, because I don't want to wait around long. And I typically am treating seed that has already been fermented, and rinsed.

After adding the bleach, I wait a minute or so and swirl the seeds. Then I start rinsing (3X minimum).

I typically do not use Ethanol.

I don't know about Alconox or Citranox -- I just use a drop of dish soap when I make up a half gallon of bleach solution.

Sounds perfectly simple. I'll give it a whirl. Thanks!

[Fusion_power]

There is more to this than meets the eye. I contacted a guy in Costa Rica about producing some hybrid seed about 3 years ago. He does commercial seed production. The first question he asked was who would be certifying the seed I provided was disease free. Fred has quite a bit more on the line with this question given his recent decision to develop some hybrids for commercial sale.

[bower]

Well, when hybrid seed production goes offshore, it stands to reason there's going to be a phytosanitary certificate required every time the seed crosses borders. It's not cheap to get one!

Afaik a phytosan cert is required now even for seed orders from Johnny's to Canada.

[Fiishergurl]

Originally Posted by Fred Hempel

Yes. Viruses can live in dried seeds.

In fact, some viruses (TMV in particular) can survive over 100 years in the soil waiting to re-infect a plant.

This is why TMV is so problematic. Once you have it, it is very hard to get rid of.

Any virus that gets into the embryo in the seed (not all can easily get into the embryo) can not be removed with surface sterilization. This is where the heat treatments come in. A dried seed is a living organism, and both viruses can easily exist within a dried seed (if they can get in).

Fred,

What about TYLCV? Can it be transmitted via seed from infected plants?

Thanks
Ginny

[Fred Hempel]

From what I understand it is not transmitted into the seeds of infected plants, and the sole vector is the whitefly. Of course it is difficult to prove a negative (that it is never transmitted through the seeds of infected plants).

[Barbee]

I wonder if you could heat treat seeds using an incubator?