A few possible breeders

General Discussion
1

A recent graduate thesis (Wu, cited below) gives clues to a few roses having greater genetic diversity than most and which may, then, be useful as breeders.

Dr. Wu studied DNA markers associated with a blackspot resistance gene, RDR1, among a group of 121 rose cultivars. For the most part the cultivars turned out to be nearly indistinguishable from one another (with respect to this particular gene) but a small number did stand apart from the rest (pdf page 56).

The outlayers are:

CANA2 - David Thompson - 'David Thompson' Rose

CANA5 - Jens Munck - 'Jens Munk' Rose

CANA8 - John Davis - 'John Davis' Rose

EU19 - Crown Princess Margareta - 'Crown Princess Margareta ®' Rose

EU79 - Summer Song - 'Summer Song' Rose

EU88 - Wild Edric - 'Wild Edric' Rose

It’s important to note that this does not necessarily mean anything with respect to better or worse blackspot resistance, although it could. Rather, I interpret this as meaning that they are probably less heavily introgressed than the others and so are worth a look for that reason alone.

Wu’s thesis covers more than just the use of DNA markers to differentiate cultivars, which is the second portion of the research. The first part is a complex analysis of inheritance mechanisms in tetraploid roses. A discussion on pdf pages 13-15 introduces the concepts of autopolyploidy and allopolyploidy in the context of disomic vs tetrasomic inheritance. The key idea for us is that certain re-assortments of chromosomes during meiosis can lead to the phenomenon of double-reduction. This is the way that a unique gene on a single chromosome gets to become present (with luck) on all four sets of chromosomes (say, four times the color or scent, or across-the-board recessives for remontancy).

The thesis is:

Chromosome segregation analysis for disomic and tetrasomic inheritance in K5 tetraploid rose population

by Enjun Xu,

Department of Plant Breeding

Wageningen University

September 2010

http://edepot.wur.nl/150716

2

I wonder if these are the David Austin roses related to the induced tetraploid rugosa line. One clearly has tetraploid foliage.

3

I was reading this earlier today before I had to finish other stuff.

I knew Jens Munk was special among rugosas, which is why I have continually mentioned it here on RHA. I didnt know it was that special though, so it is great to read.

The Austin trio was from left field though. I recall CPM being very healthy. I bought it as like 2 dollar nursery trash (September) and revived it to give it away the following summer. I recall it being free of disease, stable in color and very noisette-ish in growth and general feel. It did not have much in common with Abraham Darby, which defoliates here and is bolt upright just like Aloha is. I can say for sure that it had superior foliage to Abraham Darby… and very different. The photos on HMF match my memory, which is that the leaflets were very thick yet wispy/slightly serrated in a very aesthetic way. They were of a much lighter green too.

Wild Edric caught me off guard. I ignored it like I ignore many Austins because they have the habit of repeating the same generic patterns year after year in terms of what they introduce. I thought it was red austin #2097172. I did not even look deep enough to know it looks very beautiful and healthy. It looks like it is worth our time as breeders in digging deeper.

Summer Song looks to have beautiful blooms. I can only hope it doesnt have a plant like Pat Austin.

Not only do I wonder if these trio all have some relation to Rosa rugosa, but also to Rosa roxburghii.

Also, as a personal side note, Jubilee Celebration is remarkably superior to Golden Celebration’s disease resistance (awful blackspot here). It has not had one speck of bs in its 4 years with me. It has also escaped the octopus-itis syndrome that many Austins share :slight_smile:

4

Thanks for posting the information Don.

I found CPM to be disease free in my garden for the two seasons I grew it. Not a spot of disease. I was disappointed that it wouldn’t set hips for me and none of the crosses of using her pollen worked either so it got tossed to make room for something more fertile. Great color, bloom form and superior disease resistance on this one.

Wish I could get a hold of Summer Song to try that one.