When crossing modern type roses to ‘Tigris’, most seedlings are once blooming and will not bloom during the first year. Some of the seedlings will not have a blotch, while some will have a light blotch and still others will have a good sized dark blotch. This later group seem often to be triploids in the way that they behave. When crossed again with modern tetraploids, most of the seedlings are non-remontant, however, a few will be repeat blooming and will bloom like normal modern rose seedlings after 8-10 weeks from germination. Most of these repeat blooming seedlings will lack the blotch, but a few will show a blotch. In my experience, all of these with blotches will be more attenuated as compared to the best F1 ‘Tigris’ seedlings.
The next step though changes things. If a repeat blooming dim blotched Hulthemia hybrid is crossed with another, there will be a few seedlings in the next generation that exhibit good blotches with intensity comparable to the best F1 ‘Tigris’ seedlings. It is these seedlings that appear to have 2 of the homologous chromosomes having the blotch gene(s).
Finally, when these seedlings with good blotches are crossed with regular modern roses, some of the resulting seedlings will get the 2 dose effect and will have good blotches. Below is an example of a cross that surprised me. It appears to be a regular HT in bud form, but when the petals are removed, you can see the blotch. This is a cross of ‘Gemini’ X “L83-4”.