Saturday, June 2, 2012

Hulthemia Fertility - Update on Seedling "O352"

If you are familiar with the Hulthemias, it is easy to see why I wanted to use "O352" in further breeding:  It has one of the largest blotches that I have ever seen; the blotch is heat stabile (doesn't fade in the summer like most Hulthemias); it is fully remontant (blooms all summer); it doesn't get any powdery mildew; and, unlike the often vicious armor (thorns) seen with most Hulthemias, this one appears to be completely thornless (even the rachis are prickle free).
Note "O352" was mentioned in an earlier post The Largest Blotch A Dead End?

Time and time again, however, I had tried to get pollen from this particular seedling to use in breeding, but to no avail.  There was just no pollen released.  It is sterile as a pollen parent.

So, what do you do when you have a rose/Hulthemia that is pollen sterile?

Well, one of the wonderful things about roses is that they can be used as either a pollen parent (male parent), or a seed parent (female parent).  The very first Rose-Hulthemia hybrid that proved to be fertile was 'Tigris' (a once bloomer and a fairly weedy type plant),  but it too was pollen sterile.  It only worked as a seed parent.  Fortunately for all of us, when pollen was applied to 'Tigris' blooms, hips formed, yielding viable seeds. All of the new Hulthemia hybrids get their characteristic darker central blotch from 'Tigris'.

In the photo below, you can see some pollen spilling onto the petals of "O352".  Knowing that it does not produce pollen, you have probably guessed that I played the bee in this case, slopping pollen onto the stigmas.  You will notice too, that tags were hung from the peduncles, identifying the pollen parent(s).




In the second photo below, you can see that like 'Tigris', "O352" appears to be fertile as a seed parent.  Right now, there are many hips devoloping on it.  I am hopeful that the seeds forming within the hips will germinate when they are planted this coming winter.



You may be able to make out the writing on the tag as "Rx".  I use the "Rx" designation to indicate Radler genetics (Bill Radler is the breeder of the Knock Out series of roses known for their strong resistance to many of the fungal diseases that attack roses).  Rather than make many different crosses using the various pollens that I have from the Bill Radler group ('Knock Out', 'Double Knock Out', 'White Out', 'Sunny Knock Out', 'Carefree Sunshine', and 'Milwaukee's Calatrava'), I mix the pollen.  For me, the crucial thing is bringing in the genetics of cleanliness from these roses, rather than knowing the specific pollen parent.  "Rx" seemed to me to be a good description too, since Radler genetics are the right prescription for better health in roses (and Hulthemias)!

4 comments:

  1. It's great to see that you can move forward with this one, Jim. It's an amazing blotch! I probably wouldn't want the blotch any bigger, however, or it will end up looking like an ordinary picotee ;)

    Is this the first time you've tried to pollinate this one? So far, out of the 6 seedlings I got from your seed, I have noticed that they don't seem very self-fertile. Whether this is due to non-functioning pollen or some kind of selfing barrier I don't know but none of the flowers have ever set an OP hip. The instant I put cross-pollen on them, however, I get hips (see; http://rosebreedingdownunder.blogspot.com.au/2012/06/keeping-eye-on-progress-here.html). Does the ability to form OP hips take a while to kick in with these seedlings or is this a pattern you see a bit?

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  2. Hi Simon,

    Thank you for your comments! I am very happy with this one. This is brand new from 2011, so I hadn't gotten to use it until now. I do remember trying a cross on it as a new seedling and it formed one hip. It was sown with other small lots, so I don't know if it germinated.

    Regarding fertility in the Hulthemias - there are many that are very self fertile, so it doesn't seem that there is a class effect of poor self fertility. What I am finding is that I need to go back and check fertility on some with better blotches when used as seed parents, that hadn't ever set hips. There is another that I have with a great blotch that has been a dead end - no pollen and never sets OP hips. I went ahead and tried mixed pollen on it and it is setting hips wonderfully.

    I should mention that K206 is very self fertile.

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  3. Hi Aprille,

    Thank you! I am so happy that O352 is setting hips. If the seeds germinate, I would expect some fun seedlings from this one.

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