Hi GATK team, i would like to seek opinion from your team to find the best workflow that best fit my data. Previously i've been exploring both variant calling algorithms UnifiedGenotyper and HaplotypeCaller, and i would love to go for UnifiedGenotyper considering of the sensitivity and the analysis runtime. Due to my experimental cohort samples grows from time to time, so i've opt for single sample calling follow by joint-analysis using combineVariants instead of doing multiple-samples variant calling. However by doing so, i've experience few drawbacks from it (this issue was discussed at few forums). For a particular SNP loci, we wouldn't know whether the "./." reported for some of the samples are due to no reads covering that particular loci, or it doesn't pass certain criteria during variant calling performed previously, or it is a homo-reference base (which i concern this most and can't cope to lost this information).
Then, i found this "gvcf", and it is potentially to solve my problem (Thanks GATK team for always understand our researcher's need)!! Again, i'm insist of opt for unifiedGenotyper instead of haplotypeCaller to generate the gvcf, and reading from the forum at https://www.broadinstitute.org/gatk/guide/tagged?tag=gvcf, i would assume that as VCFs produced by "UnifiedGenotyper with --output_mode EMIT_ALL_SITES" to be something alike with the gvcf file produced by HaplotyperCaller. However i couldn't joint them up using either "CombineVariants" or "CombineGVCFs", most probably i think "UnifiedGenotyper with --output_mode EMIT_ALL_SITES" doesn't generate gvcf format.
Can you please give me some advice to BEST fit my need and with minimum runtime (UnifiedGenotyper would be my best choice), is there any method to joint the ALL_SITES vcf file produced by UnifiedGenotyper which i might probably missed out from the GATK page?