I think when lilies are compared to daylilies, the daylilies win where it comes to ease of breeding. Most cultivars cross easily, seeds are big, no need to maintain a little bulb. The fat roots of daylilies are much easier to maintain. I'm not familiar with diseases of daylilies, other than rust. Lilium fields must be chemically fumigated prior to planting a crop of bulbs. Then there is virus and botrytis, lily beetle and so forth to be concerned about.
I think that if lilies were as easy as daylilies then there would be more backyard lily hybridizers.
