UPDATE OF DOUGLAS-FIR ROOTSTOCK BREEDING
Donald
L.
Copes• Pacific Northwest Research Station, Corvallis, Oregon
Introduction
The present rootstock breeding work by the Pacific Northwest Research Station Is based entirely upon results
use It Is possible
of graning stuciles initiated between 1964 and 1975. The breeding program Is successful
to accurately Identify Incompatible grafts of Douglas-fir at an earty age, and the Incompatibility trait has a high
herttabllity.
.·
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-ldeptilicatlon of Incompatible unions Is done by examining stained cross-sections of unions under a micro­
scope. Sacrificed graft unions are preserved In fixative, sectioned Into thin cross-sections, stained with
safranin 0 and fast green, and mounted upon microscope slides for viewing (Copes and Gnose 1975). Incom­
patible stock-scion combinations have unions that contain characteristic regraft zones In the wood. The
presence or absence of those regraft zones Is used to denote Incompatible or compatible grafts, respectively
(Copes 1970).
The history and status of past and current breeding efforts at Corvallis for both coastal and Interior Douglas-fir
are presented below.
Coastal Douglas-Fir
Research into genetic control of graft compatibility in coastal Douglas-fir indicated a very strong inheritance
pattern (Copes 1974). Field testing of both control- and wind-pollinated famUies and rooted cutting of clones
was done in five orchards in Oregon, Washington, California, and British Columbia (Copes 1983). The strong
genetic control of compatibility permitted development of highly graft-<;0n1patible rootstock families by cross­
pollinating highly graft-compatible parents. The parent clones used in the pollinations were trees with highest
compatibility found in several populations that had been screened previously for compatibility (Copes 1981).
In addition, a number of the best surviving clones from seed orchards in Oregon and Washington were sub­
jected to additional graft compatibility tests, and the trees that were 90+ /- percent compatible were used as
parent trees for breeding (Copes 1973). A total of 31 clones were selected from the first cycle of breeding and
graft testing.
The basic design for breeding and testing was to produce at least ten control-pollinated families of each
selected parent tree and graft test seedling of those families under field conditions. Testing included growing
50 seedlings of each family In our nursery beds In Corvallis, field planting those trees at our outplanting site
near Monmouth, Oregon, and grafting each of the 50 seedlings from each famQy with a different scion clone.
Graft unions were sacrificed for incompatibility determination after two growing seasons, and the unions were
processed in the microtechnique laboratory as previously described (Copes and Gnose 1975). Families that
tested at least 90 percent compatible were made
. available for general use in production orchards. Our screen­
ing work on the original group of 31 selections will be completed within 2 years, and a technical report wUI be
issued that will list for each family the following family data: compatibilities, first-and second-year heights, and
vegetative bud burst rankings. The ready availability of seed of numerous highly graft-compatible rootstock
families Is the final product resulting from field testing more than 300 families.
An additional twelve coastal clones were added later to the breeding program. Clones were included from
geQgraphic areas where we had few or any selections. This Included areas in northern California, southern
Oregon, and northern Washington. A different breeding procedure will be used with these selections since the
original method of making ten separate crosses for each parent tree and testing seedling of each cross re­
. quired many years and much work. In 1991, the new clones were control pollinated with a pollen mix consist­
ing of equal volumes of pollen from eight of the most highly compatible clones of the first 31 clones. Either a
50- or 100-seedling field test of each poly cross family will be field grafted in 1995 with 50 or 100 different scion
clones and the 2-year-old graft unions sacrificed and examined under a microscope for the presence of incom­
patibility symptoms. Compatibility Information from the tests will be available In 1996.
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Oone banks of the first 31 clones were established from 1971 through 1975 at the PNW Tree Improvement
Team's outplantlng site near Monmouth, Oregon. Those trees are periodically topped to limit maximum tree
height to approximately 20 feet. Only seed from control pollinations are used In seed orchard establishment,
so It Is necessary to limit tree size so the trees can be easny reached from 12- to 16-foot ladders. The soils at
the Monmouth site are often too wet during pollination time to permit use of mechanical lifts. A second clone
bank was establlsned 1n 1986 at a different location on the Monmouth site. The new clone bank was estab­
lished so the new 12 selections and the original 31 clones are together In same breeding area.. Another reason
toi e8tabllshlng the second breeding area was protection against catastrophic fire loss. We have had several
g1"95t..lires at the site In the past 10 years but have not lost trees In the rootstock breeding areas. In future
yea . the Seed Orchard Managers Association may want to address the possibility of establishing additional
done banks composed of the best clones. Scion material wUI be avaDable to all who desire to preserve the
clones.
Such action wm ensure future seed supplies.
Annual seed and seedling needs of west coast orchards have ranged from 50,000 to 75,000 per year for the
past or 8 to 1O years. This seed has been sent to Oregon, Washington, California, British Columbia, four
European countries, and New Zealand. A three-person crew can produce the amount of seed needed. It re­
quires approximately 35 to 40 person-days every 2 or 3 years to Isolate and pollinate flowers In 500 to 900
bags and to collect, clean, and package 100,000 to 200,00 viable seeds produced by the pollinations. There
are more than 100,000 seeds of 90+/- percent compatible families and another 100,000 seeds of families that
tested less than 90 percent compatible stored In the freezer at Corvallis. Some assistance with pollinations or
seed work may be requested In future years if adequate supplies are to be maintained.
Interior Doualas-Fir
Research In the 1960's and 1970 at Corvallis indicated that the same incompatibility symptoms (regraft zones)
detected in coastal Douglas-fir were present in grafts of trees of interior origin (Copes 1974). The same screen­
ing and testing procedures could be used with either variety (Fouchee and Fins 1991 ). Work In establishing a
clonal base of highly graft-compatible parent trees for breeding rootstock has been quite limited due to the
late start of tree Improvement In the interior region. A test of 50 clones from the Colville National Forest
resulted In Identification of a number of highly graft-compatible trees. Scions from 20 selected trees were
grafted in a clone bank at PNWs outplanting site near Monmouth, Oregon, and at the Warm Springs Reserva­
tion Badger Seed Orchard In 1987. Trees at the Monmouth site were grafted on compatible coastal rootstock
families, while grafting at Warm Springs Seed Orchard was done on east-side Douglas-fir families of unknown
graft compatibility.
The clone bank near Monmouth now has trees that are approximately 6 to 9 feet tall. Attempts in 1990 and
1991 to stimulate the trees Into cone production by applying bark girdles and fertilizer (200 lbs. nitrate per
acre) were not successful. In April 1992 we wUI attempt to stimulate the Initiation and development of floral
buds with GA 4/7. In 1993, the flowers wUI be pollinated with a pollen mix of an undetermined number of Inte­
rior trees. A limited amount of pollen from the best Colville trees Is in -135° storage in Corvallis. Graft testing
of the seedling families should be done at typical Interior seed orchard sites rather than in the coastal Douglas­
fir zone. The Canadian Forest Service researchers at Vernon, British Columbia, have expressed an interest In
participating In future graft testing since they have just a few clones under test at this time and would like to
expand their parental base. Several additional clones might be obtained for testing from the Potlatch Com­
pany at Lewiston, Idaho.
The clone bank on the Warm Springs Reservation may be a more reliable source of seed In the future, but
groWlh is much slower at that Interior site than at Monmouth. The trees in the Badger Seed Orchard are said
to -Oelust 1 to 2 feet tall at this time. It is possible that the future health and vigor of the Monmouth grafts is
questionable because foliage diseases normally cause significant problems in future years when the trees from
the Interior get older. Annual spray treatments with copper solutions or other chemicals may be necessary if
the trees are to remain healthy.
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Summary
Existing suppiies of graft compatible seed for coastal Douglas-fir seed orchards are adequate. A new breed­
ing clone bank with 43 clones Is just beginning to produce significant quantities of seed. Help may be re­
quested In the future with pollinations and cone and seed processing If adequate seed supplies are to be main­
tained. Unfortunately, adequate seed supplies ol highly graft-compatible families do not exist for Interior Douglas-fir or
s. An eariy elimination ol this shortage Is not likely because graft compatibility .testlLJ.g ol the seedling families will not be completed for at least five more years. Clone banks are established at two locations and
flc:mei:.lnitiatlon will be stimulated for the 1993 cone crop. Testing cannot begin untU control-pollinated famUies are produced. Literature Cited
Copes, Donald L 1970. Initiation and development of graft Incompatibility symptoms In Douglas-fir. SUv.
Genet 19(2/3):101-107.
Copes, Donald L 1971. Seed source graft compatibility In Douglas-fir. For. Sci. 17(4):499.
. Copes, Donald L 1973. Inheritance of graft compatibility in Douglas-fir. Bot. Gaz. 134(1):49-52.
Copes, Donald L 1974. Genetics of graft rejection In Douglas-fir. Can. J. For. Res. 4(2):186-192.
Copes, Donald L 1981. Selection and propagation of highly graft-compatible Douglas-fir rootstocks - a case
history. Res. Note PNW-376, U.S. Dept. of Agric., For. Serv., Pacific NW. For. Res. Stn. 8 p.
Copes, D. L. 1983. Field tests of graft compatible Douglas-fir seedling rootstocks. SUv. Genet. 31 (5/6):183­
187.
Copes, Donald L and C. E. Gnose. 1975. Improved laboratory methods for testing graft compatibility in
Douglas-fir. Res. Note PNW-265, U.S. Dept. of Agric., For. Serv., Pacific NW. For. Res. Stn.
Fouchee, David and Lauren Fins. 1991. Testing graft incompatibility detection procedures on Interior Douglas­
fir. W. J. Appl. For. 6(2):3942.
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