Jostas are crosses of black currant and gooseberry. They were made tetraploid by using Colchicine. Josta is completely spineless due to genes from black currant. My idea is to cross Josta with gooseberry to obtain triploid plants of low fertility and then backcross these plants again with gooseberry to obtain completely spineless gooseberries. Did anyone already tried this? E. Keep did crossings between Josta and black currant successfully, so also crossings with gooseberry should be successful.