Yes, these things have been tested according to Maurice.
And easy to test in your own garden. You just need to graft a daylily with stripes to a plain one. If an infection agent (e.g. virus) is responsible the new daylily will become infected and act accordingly (become striped).
However, ELISA would be useless unless there was a known antigen to ELISA for. PCR would be much more logical, perhaps using degenerate primers that can "fish" for similar sequences.
Since stripes are passed on to kids at some ratio your hypothesis must then be that virus can hide inside pollen, and thus seeds?
I suspect Purple Leopard is a genetic or genomic mutant, and will not pass any blotches on to kids. The creator has never mentioned a single seedling with blotches despite all the years working with it. He should be the first to see anything. But I bought it anyway. If anything, that makes it even more rare and unique than before.
