Towards immunity from disease: 'Home Run'?

With the introduction of Bill Radler's 'Knockout' about ten years ago, hybridizers have placed greater emphasis on the creation of roses with greatly improved immunity to the typical diseases that trouble garden roses, namely Blackspot: Diplocarpon rosae. Its not an easy task; Blackspot resistance is complicated and may involve multiple genes to accomplish. Of course, it IS possible, but a breeder can easily take ten years or more to achieve reasonable results. Fortunately for many of us, the groundwork has been done by several breeders and we have several lines of hybrids we can incorporate into our work. One of the roses I am working with that I have found to impart superior Blackspot (and often Mildew) resistance is Ralph Moore's 0-47-19, the old R. wichurana X 'Floradora' hybrid. However, it tends to breed a lot of pinks and whites, which has so far been a rather limiting factor.

More recently I acquired Tom Carruth's shrub 'Home Run', bred from 'Knockout' and involving 'Baby Love' as a grandparent. The latter is a five-petaled yellow shrub rose that is often used in breeding for disease resistance. Like its pollen parent 'Knockout', 'Home Run' is a triploid and only somewhat fertile. Its pollen will take on a limited number of plants and seeds are frequently infertile. However, in 2007 I made a successful cross of the old red Hybrid Tea 'Roundelay' X 'Home Run'. Why 'Roundelay', you ask? Well, here in my cliate it is immune to Blackspot even when not treated with fungicide. It is a shapely shrub of about 4 X 4 feet and blooms in clusters of deep garnet red 4" blooms. It does have some fragrance, but not very strong to my nose. Mainly, the Blackspot resistance was the thing that appealed to me most.

As usual, there were very few seeds from the cross, and even fewer seedlings. Two survived by the end of the season and were in fact growing very strongly and making an impression on me. The best of the two is the seedling pictured here. (Photographed April 20, 2009) This seedling has dark red tinged green foliage that is quite large and very healthy so far. The plant branches freely from the base and blooms in clusters, much like its seed parent. The photo does not do the bloom justice; it is a dark black-garnet red much like 'Black Jade' at its very best. From a beautifully scrolled bud it opens to a slightly cupped, 12 petaled bloom about 3 inches across. There is a modest fragrance that I detect. I will propagate this from cuttings and by budding this year to multiply the plant and to evaluate its ease of propagation. Now the deal is to find out just how disease resistant it (and its sibling) really is.