Grain to Grain transfers for growing mushrooms

Grain to grain transfers are a method widely used in hobby mycology and in larger scale professional operations to greatly increase the yield you can achieve from the original spore source (syringe or agar).

The grain to grain transfer first requires that a grain spawn jar is fully colonised using normal procedure. The type of grain spawn does not matter, as the process can work for any grain spawn, and can even be used to move mycelium to a different grain spawn than the original colonised jar. 

Once colonised the contents of the jar can be carefully transferred to a number of jars. This allows you to turn one jar of fully colonised grain into 10 or 20 jars of mycelium ready to add to your bulk substrate.

Grain jars for growing mushrooms at home
Fully colonised grain jar wtih grain jars ready for grain to grain transfer.
Source: https://www.youtube.com/watch?v=qeTfIH1IzXg&t=40s.

Usually a ratio of 1:10 – 1:20 can be utilised for a grain to grain transfer, meaning that you can divide your original colonised jar into 10-20 new jars and still expect a successful harvest without a significant increase in contamination risk or stalling. Spreading the grain too far will eventually lead to stalling of jars and subsequent contamination so it is best to keep the transfer ratio below 1:20. This will depend on the type of grain used and the genetics of your mycelium. The fresh jars that you are transferring the colonised grain into are prepared the exact same way that a normal spawn jar is prepared ( grain is hydrated, dried, then sterilized in your jars).

The best way to perform a grain to grain transfer is using a flow hood. Failing this, a still air box is able to provide great results. This is as the jars of the colonised grain and the jars of the uncolonised grain will need to be opened to perform the transfers. Follow this guide on how to set up your SAB. 

A key point for performing your transfer is to ensure you shake up the colonised jars prior to starting, to ensure that you do not need to perform excessive movements in the SAB or even in the room you are working in.

Additionally, prepare a metal spoon that will fit easily into your jars to scoop the grain out for the transfers. You want to sterilise this prior to starting by wrapping it in foil and placing it in your pressure cooker during one of your grain preparations. It’s worthwhile to have a couple ready at any one time, in case you drop one during a transfer etc. Simply sterilize the spoon wrapped in alfoil with your spawn jars, then keep in a snap lock bag once cooled (Keep in alfoil until ready for use).

Grain jars days after a grain to grain transfer
source: https://www.youtube.com/watch?v=qeTfIH1IzXg&t=40s

As the grain that you are adding to the new jars during the transfer is already colonised, the growth of mycelium in the new jar is rapid in comparison to using a spore syringe. Usually allowing for colonisation within two weeks. Additionally, the colonised jar will be shaken prior to the transfer, meaning that you will be transferring multiple individual pieces of colonised grain to your fresh jar. The grain can be shaken around your new jars to disperse them throughout the grain. Each grain acts as an inoculation point, meaning that you will have multiple inoculation points throughout your jar, allowing for rapid inoculation.

Crack each of the jar’s lids prior to starting. This involves twisting the jar lid until you feel it give way. You don’t want to open the jar, and you want to turn it as little as possible. This is to ensure that none of the jars are stuck. If you need to open a difficult jar, it is very difficult to do so in an SAB without causing a lot of movement. 

Work with one uncolonised jar at a time. Once you have opened your colonised jar, keep the lid off and out of the way. Gently lift the lid of the colonised jar enough so that you can tip in the grain spawn without touching the sides of the jar or the lid with your spoon, then lower the lid and give a half turn, tighten fully once finished all jars.

Usually only first generation grain spawn is used for a grain to grain transfer. This is the grain that is directly inoculated with your spore syringe or agar. The jars that you then inoculate during the grain to grain transfer are the second generation and so on. The higher the generation number becomes, the higher the risk of contamination, stalling and lower yields becomes. So unfortunately grain to grain transfers cannot create an infinite supply of colonised grain spawn!

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