Read Groups without known barcodes

Dear all,

I am working with some barley accessions but the barcodes for the samples are not known (not publicly available). However, because the addition of the read groups is a prerequisite for BQSR and HaplotypeCaller, I wonder if I can I use the AddOrReplaceReadGroups command by substituting the barcodes with Ns? RGPU=NNNNNNNN-NNNNNNNN? Thank you in advance.