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Lower Giraffe Mapping Rate and Fewer SNPs Compared with BWA-GATK #1995

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@Sumit1331

Hi vg team,

I am comparing a Minigraph-Cactus/vg workflow with a BWA-GATK workflow for >500 isolates of a fungal pathogen.

The pangenome graph was built from 13 high-quality assemblies and includes the same reference genome used for the linear analysis. Using the same Illumina reads, BWA maps about 95% of reads, while vg giraffe maps about 89%. In addition, the vg workflow detects fewer SNPs than GATK.

Is this kind of result expected when comparing graph-based and linear-reference workflows, or does it more likely indicate an issue with graph/index construction, mapping, or variant calling?

I would especially appreciate guidance on how mapping rate and SNP count should be interpreted fairly between these two approaches.

Thank you!

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