Sunday, November 10, 2013

Moving Toward Cleaner Minis

Miniature roses are not known for their cleanliness.  There is much room for improving the health of this class of roses.  This has been a goal of mine for several years, but initially I was only addressing powdery mildew resistance.  One of my favorite mini seedlings is named 'Pearl Sanford'.  Although it has very good powdery mildew resistance, like most minis, it is very susceptible to black spot.

Therefore, 'Pearl Sanford', which happens to be an excellent seed parent, has been crossed with two lines of roses that have very good black spot resistance.  The first shown below is a cross of 'Pearl Sanford' X "Basye's Thornless" (aka "Basye's Legacy").  This is a brand new seedling from this year.  It only has 8-10 petals, but has taller buds than most "Basye's Thornless" seedlings and it's petals unfurl nicely.  It sets hips very readily and this coming year I will be testing it's germination rate.

The second seedling is a cross of 'Pearl Sanford' X 'Double Knock Out'.  I didn't expect to get much from this cross, however, this seedling has very full blooms with fairly good form.  It gets some powdery mildew when conditions are right, but does not get severe infections.  It appears to not set hips, however, it produces at least some pollen.

I am hoping that by combining these two lines, I will be able to get an exhibition mini that combines good powdery mildew resistance with better horizontal black spot resistance.  Since I will not be making crosses between these two until next Spring, the first seedlings will not sprout until 2015.  This hobby has a way of developing patience!


  1. Looks like great form to me. I love when they produce sprays. Very full. "horizontal" black spot resistance? Now if we could just get roses to develop seeds in a month or two like gladiolus do.

  2. Hi Dave, thanks! Horizontal resistance refers to a deeper level of resistance factors/genes and long term is better than "vertical" resistance where only one gene may be involved and can easily be overcome by mutation of the pathogen.

    I forgot to mention that the first seedling appears to have excellent powdery mildew resistance and is thornless. Now the challenge is to try to combine the best traits together of both seedlings.....

  3. Thanks. For further clarification of "horizontal" "long term" would this be like having disease resistance in both parents and in its grandparents and great grandparents etc. What was it in the second bloom that made you feel that it would be a good one to cross with when it does get a little PM and has a hard time with hip development and some pollen production. Was it the fullness and color of the seedling? Why would you not want to use your clean seedlings like Heather Sproul, Forgiveness, Jolene Adams, First Impression or back breeding with Pearl sanford or your "First Impression" seedling (Gemini x First Impression) or your Pearl Sanford x (Gemini x First Impression). Thanks for your time.


  4. To understand horizontal resistance you need to think of it like a battle in a war (against the combined forces of rose diseases). If I went into battle against these dark armies with just one really strong strategy then it would hold them off well but eventually they would find a way to get around it, over run me, and I would be defeated. Roses like 'Baby Love' have excellent vertical resistance but because disease organisms are constantly changing to get around the changes roses make to try and protect themselves from the attacks of the marauding disease armies then it doesn't take long for them to find a way around it and they succumb. On the other hand, if I went into the battle with lots of strong strategies, like strong genetic resistance from multiple genes, physical resistance from a hard waxy coat that resisted the attempts of fungal spores to breach the dermal layer, chemical defences so that I exuded chemicals to deter insect pests that would eat me but also pass on pathogens, etc, then I have strong horizontal resistance and it would take the disease troops a lot longer to work out a way around my defences and I would be more successful in warding off their attack for much longer. By combining roses with various disease resistance attributes you potentially bring these individual strategies together into a single rose and theoretically a rose with better horizontal resistance. This is why we want to go back to the species drawing board to see what we can incorporate from these roses into modern roses so that we can temporarily get he upper hand against disease and give us some breathing room to keep developing these new roses and use new species to try and stay a few steps ahead of disease. The Knock Out roses go back to Rosa moyesii, Baby Love goes back to Rosa davidii var. elongata, Basye's roses go back to Rosa carolina (and others) and can all of them can owe their health to their recent species ancestors. Apart from the Basye roses, who also seem to have excellent horizontal resistance already, the others have only vertical resistance and when they crash they crash in a big way. Bring them together and this may be a different story. Combine them with other modern roses, which bring genes from roses such as Rosa gigantea, Rosa chinensis, Rosa multiflora etc , then some ground might be made against these rose diseases and efforts can then be made to incorporate new genes from new species to further the advantage.

    Hope this helps.