I am a beginner of Galaxy.Because I need to analyze large-scale NGS data and the pubic Galaxy serve did not work out,I installed linux(the first time to use linux) and set up the local galaxy instance in my computer. It seemed everything worked fine until I tried to use Tophat to align the reads to the reference genome.The problem is although I have already downloaded the Refgenome from UCSC,when I use the Tophat,"select a reference genome"option is empty(please see the attached file).