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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) | |