25 Years of Breeding for Disease Resistance
(and it's still 99 % luck and only one percent planning!)

Reading in one of the forums on the Internet, "Mildew on seedlings, and how to prevent it", inspired me to write about my experiences since 1974. Mildew is enemy number one here in the Pacific Northwest.

Curiously I became interested in hybridizing roses in 1968, before I had learned much of rose culture. In the spring of 1969 I joined the local rose society hoping to possibly find a hybridizer and learn more about the subject. I was out of luck and had to learn everything out of books. I did my first crosses that same season. Some of the top rosarians in our local rose society thought I was crazy to start from the "top" down. However, I soon learned more about the culture and care of roses and that they had to be sprayed regularly. I was lucky and happy to get my first few dozen seedlings in the spring of 1970. When the first mildew appeared I of course sprayed regularly with a fungicide. In 1974 I had about a dozen seedlings of a cross of Blanche Mallerin X Pascali planted close together in the same box. One of them stood out from the crowd. Every other one was covered with mildew, but this one was completely clean. It was then that I learned that some roses are disease resistant. I only kept this one, and when it went outside it could go 3 months without spraying. Incidently, in 1980 this one would become ‘Canadian White Star’® (CWS®) and was my first rose to be introduced.

Before getting back to my main topic, there is a very interesting discovery I made about CWS on the internet. Out of curiosity I searched (on GOOGLE) for ‘Canadian White Star’®. Boy, was I surprised with the results! Out of 28 different sites listed, three were about disease resistance in roses. One was about mildew resistance and CWS was among the top 42 hybrid teas listed as having excellent mildew resistance. For blackspot there were 2 sites listed. Most of us know that there are not many varieties that are really blackspot resistant. Again, I was surprised as CWS was one of only 21 hybrid teas listed as being blackspot resistant. Starting in 1975 I did not spray my new seedlings any more, and those with excessive mildew were thrown out even before I had seen their first blooms. In 1975 I also started to use CWS as seed and/or pollen parent. Only one in 20 crosses would take as a female, so I used its pollen extensively. It did not produce any seedlings worth keeping, so I gave up on CWS.

Some hybridizer friends have told me I should not be so radical in throwing out mildewed seedlings, as I might throw out a possible All-America Rose Selections (AARS) winner. I know from a friend who lives near an AARS test garden that roses there are sprayed regularly. Not knowing at the time that AARS test gardens get sprayed regularly, I bought every AARS winner for hybridizing purposes until the early eighties. I finally realized that most were more susceptible to diseases than any of my own seedlings that I had kept over the years. I never ever spray my roses (95 % are my own seedlings) as often as most other rosarians do, and by July/August my roses are still the cleanest of any local gardens I regularly visit. My roses are only sprayed 7 to 8 times per season. Once in mid April and mid May, twice in June and July, then once in early August. After that, I wait until late September to October when blackspot appears. Those seedlings covered in blackspot are also thrown out, and in some years only one out of a hundred seedlings are left.

Since 1990 I have been working with miniatures only, and just during the past 3 years I have started using most of the top ten miniatures as seed and/or pollen parents. However, I have found that some of the “Top Ten” cannot go more than 2 weeks in the fall without spraying. In order to keep mildew and blackspot from spreading to my other roses, I will now have to spray those more regularly.

Finally, onto my main topic...

Only two or three of the top miniatures I am presently hybridizing with from other breeders are very disease resistant here in the Pacific Northwest. Only one, Hot Tamale™, never ever had mildew or blackspot since I first grew it and began using it as a seed parent in 1998. As it sets seed readily, I went all out in 1999 and did hundreds of crosses on about 40 plants of it growing in 2 gallon pots. For every one of those crosses I used my own ‘Rubies 'n' Pearls’ as the pollen parent. As ‘Rubies 'n' Pearls’ is also very mildew resistant, I thought it would be a very good combination to produce some very disease resistant seedlings. My crosses produced nearly 4,000 seeds, but only about 500 germinated. I waited with great anticipation for the results of my all out effort. Exactly the opposite happened from what I had expected, and it was the greatest disappointment of my 30 years of hybridizing roses. When the seedlings were 2 weeks old, mildew started on just a few, and within 2 weeks it spread like wildfire to about 95 % of the plants. Just like in previous years, I grew the seedlings in my basement under grow lights.

Again, I started to throw out seedlings by the dozens, but this time I threw out only those with stems covered by mildew and bent over. Half of my seedlings went into the trash can within a month after germination, and for the first time in years I started spraying them until I had seen their first blooms. It was against my own policy, but I wanted to see those that were left come into bloom. In the end, I kept a total of 15 seedlings with good vigor, color, and form. Ten of them still had a little mildew and 5 did not show any sign of mildew. I was hoping for improvement when these were moved outside during May in 1 gallon pots.

Again, another big disappointment! Even with my own regular spray program (see first page), 12 out of the 15 were covered in mildew. A couple extra fungicide sprays on just these seedlings did not improve their condition either. Now my whole theory of using two disease resistant parents to produce resistant seedlings went up in smoke. On some of those 15 seedlings I could not keep the mildew under control, and there are only 8 left now at the end of the 2000 season. For my 2000 crosses I did not abandon Hot Tamale™ as seed parent and gave it one last chance. This time I did not use Rubies 'n' Pearls for pollen parent. Instead, I used every lower growing mini I have (eg. June Laver™, Behold™, Incognito, Golden Beryl...) as well as some of my smaller mini seedlings. Besides lots of mildew, Hot Tamale™ also gave me nothing but very tall seedlings with blooms too big for a mini 90 % of the time. Hopefully I will get some better seedlings in 2001. If not, Hot Tamale™ will be just another exhibition rose.

What did I learn from my setback?
I learned not to be discouraged from this experience, as I have had many LOW POINTS in 31 years of rose breeding. There is always another season I say to myself and to friends. Also, it confirms what I always say to any rosarian friend who becomes interested in hybridizing, "Remember it's 99 % luck!!!"

What will I do different in the future? For seed and/or pollen parents I may only select those varieties that have good vigor, good form and substance, as well as specific colors I am looking for. Also, I may give Hot Tamale™ another last try as a pollen parent only. For a change I will completely ignore disease resistance in seed and pollen parents and I might just be lucky to have a better crop of seedlings in 2002. Before changing directions, I will have to wait for my new crop of seedlings in spring of 2001. Who knows... possibly my hundreds of hips on Hot Tamale™ with a dozen different pollen parents might give better results. Whatever happens, I may report about it in summer or fall 2001.

George Mander
October, 2000

(first published in The Rose Hybridizer's Association newsletter, in Winter 2000/2001)