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Paul Stamets P value system

Posts: 125
Location: Westport, CA Zone 8-9; Off grid on 20 acres of redwood forest and floodplain with a seasonal creek.
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Link to explanation for those who are not aware of it: http://www.hostdefense.com/pvalue/
So I understand the P value system as it applies to growing out a strain in a petri dish. My question is should one follow this system if producing from existing mushrooms? Let me better explain: So assume I order a strain of mushrooms from Paul designated as P2. I directly use this strain to produce spawn and grow mushrooms. Next I use stem butts from the crop just produced to start a new batch of mushrooms. Would this then by his system be considered P3? If I did this again would that be considered P4?

I am interested in outdoor growing so I will not most likely be constantly returning to an original strain as you would in indoor culture and I am having a hard time understanding where if ever I should consider cutting my losses so to speak and returning to an original young strain. Obviously if I get a mushroom bed growing and can successfully keep it producing I would not be interested in tilling it all up to start again with a younger strain.... so I guess I am thinking how this applies more towards log cultures etc. Sepp mentions he will inoculate logs originally, but then will allow the inoculated logs to inoculate more logs in an endless cycle. Would the P value system apply here? Might you still want to periodically go back to an original strain every so many years?

Thanks for any insight.
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The P value system is in regards to cloning. It is based upon the idea that a clone is like a photocopy. If you copy a photocopy, and then copy that copy, etc. eventually the copy becomes an unreadable blur. The P system is simply a method of roughly keeping track how many times a cell line has been "photocopied".

Some species of mushrooms undergo quick degradation in viability when grown on agar mediums, possibly due to inadequate nutrients present in the growth medium. (Other species can seemingly be cloned forever.) In nature, the "photocopy effect" seems less pronounced. Some research seems to indicate that spores dropping from the mushrooms provide fresh genetic material to the parent colonies, allowing them to stay "young".

Indoor industrial growers like to use clones because it allows them to custom tailor their artificial growing environments to the precise requirements of the fungi in a repeatable way.

It is always best to keep the original strains in storage with as low a P value as possible, as "insurance", or as a deposit in your "gene bank". Adding fresh clones of wild specimens to the "gene bank" storage on a yearly basis would be a good idea too.

If you get a natural system up and running on its own, there is no need to artificially wipe it out and start fresh. But it is always nice to have a backup stored away for unforeseen emergencies.
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Location: Jackson County, OR (Zone 7)
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I think Frankenstoen probably already answered your basic question, but i can add in my thoughts from having worked with tissue culture in molecular biology labs.

In tissue culture, you are working with either clones, as Frankenstoen mentions, or strains. Where ever and how ever your clone/strain originates (genetic recombination, isolation, etc..) you want to maintain the characteristics that you were working towards. If you initially develop ten clonal cell lines, they can be named c#1 through c#10, and all would be P#1, or passage #1. As you expand out the cell lines by letting them divide and grow up to fill the tissue culture vessel (petri dish, flask, culture slant, etc...), you pass them again by taking a small amount of the cells and inoculating the next growth vessel and adding fresh growth media or substrate. This is now passage #2 or P#2. It is best to freeze down or somehow maintain samples of early passage numbers so that they still have the characteristics that you initially selected for and characterized.

I've seen some interesting results of genetic drift on some human astrocytoma cell lines that were passaged well in to the P#100+. In looking at a karotype to assess the chromosomal complement, they were no longer anywhere near that what they started out with!

With regard to your questions on growing mushrooms outside... anytime you are culturing the same strain through pieces of the mycelium or fruiting body (stem butts), I would consider it a passage increase. If you are growing a new strain from spores released by a mushroom, it is no longer a passage, in my opinion. You've now got your own wild-type strain to characterize.
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