RHA Newsletter 6(2)
TIPS ON CHOOSING PARENTS
What should we do to get that new seedling that is good enough to name and introduce to the public? This question is asked more than any other in the RHA. True, some don't bother to ask but look in Modern Roses and check the parentage on their favorite rose and then proceed to try and duplicate what the original hybridizer did. I find it hard to duplicate some of my own crosses. I wonder how often the correct parents are listed? Then there is the person who likes to work with royalty. Like crossing Royal Highness with Queen Elizabeth or King of Hearts.
Maybe you will get that desired rose using any of the above methods, but usually better than 99% of the offspring will have little value. That is if we decide to discard those that didn't meet our expectations.
We cross two varieties with hopes of obtaining seedlings that retain the best characteristics of both parents. It sounds easy, doesn't it? But somewhere along the way, some of the good features are lost. The following suggestions may help us find these lost qualities.
We shouldn't be too hasty to discard all of our seedlings that we consider worthless. True, most are worthless, but there are a certain few that have value. Let's assume we make the cross Queen Elizabeth x Gypsy Moth. Queen Elizabeth has a straight up bush that is very tall and fairly healthy. The bloom is a nice pink, and the form is just ordinary. Gypsy Moth has a short bush with stiff stems and the bloom is much larger with thick petals and a high canter. What we want and hope for in our seedlings is one or more that have a Queen Elizabeth bush, only a bit shorter, with blooms the size of Gypsy Moth and its same thick petals pad high center. This is a lot to expect, and we probably won't get it in one attempt.
But why toss all the seedlings away after a short testing period. One or more may have possibilities as a parent. Let's take a closer look at those seedlings and see what qualities they have. I would select the seedling that has an upright plant as a seed parent, even if the bloom is semi-double. It may be crossed with pollen of Gypsy Moth, which didn't exert itself in this seedling. This second shot of Gypsy Moth should improve the bloom quality and size considerably. This same seedling should also be crossed with pollen of some of the seedlings that have blooms showing Gypsy Moth influence. I would also suggest gathering pollen from all the seedlings of the original cross that have large blooms of fair quality. Mix this and pollinate the tall seedling that was selected as a seed parent.
I followed a similar method when I made the rose Sea Foam. The only variation from the above suggestions was to raise self seedlings from the seedling that had the best shape of plant and healthiest foliage.
I would like to clear one point here. On page 2 of the Spring, 1975, newsletter, there is this statement: "Do not think you can combine the good qualities of several parents by placing pollen of several different varieties…" Roy Shepherd's statement is correct, and so is my statement. I have been mixing pollen for well over fifteen years, and it works fine. However, each individual seed in a hep is only crossed with one variety, but in each hep, there are seeds which all have the same seed parent but each seed may have different pollen parents.
CybeRose note: The use of pollen mixtures can improve the chances of successful cross-pollination, particularly where the pollen of a prospective father is not compatible with the seed parent. Compatible pollen tubes can "blaze a trail" for the incompatible pollen tubes to follow. In addition, diversity of pollen tubes may stimulate the seed parent to invest more heavily in all the seeds within the fruit.
American Journal of Botany. 1999; 86:261-268.
The effects of pollen load size and donor diversity on pollen performance, selective abortion, and progeny vigor in Mirabilis jalapa (Nyctaginaceae).
Richard A. Niesenbaum
The influence of pollen competitive environment on pollen performance (pollen germination, stigmatic penetration, and pollen tube growth rate), the maturation or abortion of initiated fruit, seed size, and seedling vigor was explored by manipulating the size and diversity of stigmatic pollen loads on Mirabilis jalapa. All aspects of pollen performance significantly increased with the number of pollen grains on a stigma or pollen tubes in a style, but was not influenced by the diversity of pollen donors. Plants tended to mature single-ovulate fruits that came from flowers where pollen load size and diversity were greatest and aborted those where these were lowest. No plants from seeds resulting from pollinations with a single pollen grain survived, but other fitness measures were mostly determined by maternal plant.