> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/novaseq-x-x-plus/instrumentation-novaseq-x-x-plus-reference_material-list/000008394.md).
# Custom recipes for Illumina Stranded Total RNA and mRNA libraries on NovaSeq X Series
**Background**
Insert Read 1 and Insert Read 2 of Illumina Stranded mRNA Prep, Ligation and Illumina Stranded Total RNA Prep Ligation with Ribo-Zero Plus libraries begin with a T base because of [how the adapters are added](https://www.illumina.com/content/dam/illumina/gcs/assembled-assets/marketing-literature/illumina-stranded-rna-t-overhang-tech-note-470-2020-010/illumina-stranded-rna-t-overhang-tech-note-470-2020-010.pdf). This T makes the first cycle of each read low diversity, which can cause reduced clusters Passing Filter (PF) and quality.
Illumina provides a dark cycle recipe that skips the imaging step for this cycle for both Read 1 and Read 2. A dark sequencing cycle will perform chemistry only and omit the imaging step of sequencing by synthesis (SBS) chemistry, preventing unwanted impacts on the run metrics.
**Sequencing Illumina Stranded RNA Libraries in all lanes on NovaSeq X Series**When selecting either Illumina Stranded RNA library prep kit in the Run Planning tool on instrument or in BaseSpace, the software automatically selects the correct dark cycle recipe if this is the only library type sequenced on the entire flow cell. However, it will **not** display that it is using the dark cycle recipe. The addition of any other library type to any other lane through additional configurations will result in the default sequencing recipe being applied.
Local runs with analysis started with V2 sample sheets will pull the dark cycle recipe if the "LibraryPrepKits" line contains only the value "ILMNStrandedmRNA" and/or "ILMNStrandedTotalRNA." Note that the "ILMNStrandedmRNA" recipe is used by both Illumina Stranded mRNA and Illumina Stranded Total RNA libraries. If the LibraryPrepKits value is one/both of these *and* another library prep kit, the default sequencing recipe is applied.
**Sequencing Illumina Stranded RNA Libraries with other libraries on the NovaSeq X Series**Because the dark cycle recipe applies to all lanes of the NovaSeq X Series instrument, other library types may be negatively impacted in mixed library runs where this recipe is applied. The following table indicates which libraries are compatible with the dark cycle recipe required for Illumina Stranded RNA libraries.
**Mixed Library Runs Using the Dark Cycle Recipe**
For mixed library runs that are compatible with the Illumina Stranded RNA dark cycle recipe, the dark cycle recipe must be *manually* applied to the run. To manually select the dark cycle recipe to a run set up via any mode, including manual runs, select the file path of the dark cycle recipe during run setup:
On NovaSeq X Series instruments, this dark cycle recipe is **built into the Control Software**, on Software Suite v1.2 and higher.
For 1.5B flow cells, this recipe can be found under the file path:\
/usr/local/illumina/consumables/ILMNStrandedmRNA/1/recipe.xml
For 5B flow cells, this recipe can be found under the file path:\
/usr/local/illumina/consumables/ILMNStrandedmRNA/2/recipe.xml
For 10B flow cells, this recipe can be found under the file path:\
/usr/local/illumina/consumables/ILMNStrandedmRNA/3/recipe.xml
For 25B flow cells (requires control software v1.2), this recipe can be found under the file path:\
`/usr/local/illumina/consumables/ILMNStrandedmRNA/4/v2/100/recipe.xml/usr/local/illumina/consumables/ILMNStrandedmRNA/4/v2/200/recipe.xml/usr/local/illumina/consumables/ILMNStrandedmRNA/4/v2/300/recipe.xml`
**Mixed Library Runs not using the Dark Cycle Recipe**
For mixed library runs where the other libraries are not compatible with the Illumina Stranded RNA dark cycle recipe, use the default recipe for sequencing. The default recipe will be automatically selected if any additional library types are added to the run configuration. Lanes containing Illumina Stranded RNA libraries must have at least 5% PhiX spiked-in to mitigate the low diversity caused by the first T base, when on Control Software v1.3 and above. On control software v1.2.2 or lower, 10-15% PhiX spike-in is recommended.
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| *For any feedback or questions regarding this article (Illumina Knowledge Article #8394), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000008394%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |
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