Newsletter
- March 2002
Inside This Issue
Chairman’s Report to the Annual Meeting
Regina, Saskatchewan, August 13, 2001
- John J. Doornbos
This is the fifth Chairman’s report I have provided to the members
of the Poplar Council of Canada. We have been in our Edmonton
office for almost 3 years and are quite comfortable here.
Last year we worked with Poplar Council of the United to host
IPC 2000, the 21st Session of the International Poplar
Commission in Portland Washington. Jim provides a good overview
of the session in the Technical Director’s Report and details
of the tours are provided in the next issue of our newsletter.
In addition to the presentations and posters provided during the
session, it is worth noting that IPC 2000 served as the impetus
for the following publications:
- A special issue of the Forestry Chronicle containing
13 papers from the session,
- The book Poplar Culture in North America, a companion
book to Biology of Populus, (just going to print),
- A pre-conference publication containing over 200 abstracts,
- The Canadian report "Activities Related to Poplar and Willow
Cultivation, 1996-1999",
- Similar IPC member country reports (most are available from
our office).
The Annual Meetings of the Poplar Council have generally been
held across Canada and a conference and field tour have typically
been part of the main activities. Our membership base is small
and it is often difficult for our members to host these events
particularly if they return to an area every two or three years.
Consequently we have often held our meetings in cooperation with
other organizations. The members involved in organizing these
cooperative meetings are often members in both organizations.
This year we will be holding our Annual Meeting in conjunction
with the Seventh Biennial Conference on Agroforestry in North
America. The conference is being held in Regina, Saskatchewan
from August 12 to 15. Poplar Council will also be holding a workshop
on August 15 and 16, following the conference, to look at our
Technical Committees (additional information is provided later
in this report).
Holding our Annual Meetings together with other organizations
limits our flexibility in selecting the meeting location. We have
not have a meeting east of Manitoba since 1998. We have explored
the option of another joint meeting with the Poplar Council of
the United States in New York and Ontario for 2002. We have also
been asked to work with the Canadian Tree Improvement Association
on their Annual Meeting to be held during July 2002 in Edmonton.
We also have the option of holding our Annual Meeting by itself
and not in conjunction with a conference or field tour. We will
need some direction from our members on their preference during
this year’s Annual Meeting.
As I have mentioned before, our revenues do not cover the cost
of our operations. Last year we were fortunate enough to do some
outside project work which allowed us to balance our books last
year and this year. Based on our project cash flow for 2002, we
will run a small deficit. At this point there are no outside projects
under development. More details are provided in the Financial
Report.
In my report last year I mentioned Forest 2020 as an initiative
supported by the Canadian Council of Forest Ministers that could
have implications for Poplar Council. A secretariat has been established
that has conducted a series of extensive consultations that some
of you may have participated in (Poplar Council was asked to provide
some comments). They have also produced some background literature.
There has been no word yet on a definitive program.
The concept behind Forest 2020 appears to be a change in the
approach to forest management from a single level of extensive
management to a regime with increasing levels of management intensity.
The most intensive level of management would focus on high yield
plantations, likely on private land. Much of the discussion has
centered on hybrid poplars as one of the key species that could
be used. We will continue to monitor this initiative.
Last year at our Annual Meeting, a small ad-hoc group was tasked
with evaluating the eight Technical Committees of the Poplar Council
and with looking at ways to rejuvenate them. The committees have
generally been inactive for a number of years and those that have
been active were essentially committees of one.
The ad-hoc group met several times during the past year on the
phone and exchanged many e-mail messages. Through our deliberations,
it became apparent that to resurrect the Technical Committees
we needed to have a good understanding of the current research
activities, gaps and opportunities followed by some discussion
on the prospects for collaboration and coordination. We realized
that this discussion should involve as many Council members and
other interested people as possible and developed the workshop
which will be held following the Agroforestry Conference. From
the workshop we will provide a discussion paper summarizing the
presentations and a plan for future activities.
I should note that we continue to receive the strong support
of Canadian Forest Service directly through the provision of office
space and through the support they provide to our activities such
as the Canadian Report to IPC and the book on Poplar Culture in
North America. This support benefits the Council members and the
broader community involved in poplars and willows.
In closing I would like to thank Sandra and Jim for their continued
hard work and dedication to the Poplar Council of Canada and its
members. Myself as Chairman and all the members are well served
by our Technical Director and Executive Secretary.
 Top
Technical
Director’s Report to the Annual Meeting
Regina, Saskatchewan, August 13, 2001
Jim Richardson
Background
This is the fifth annual report to the Poplar Council membership
from the Technical Director, a position that was created by the
Executive Committee in April1997. The general objectives of the
Technical Director are to supply technical services and advice
to the Council, to promote awareness and support for the Council
and to increase membership. More specifically, the particular
responsibilities initially established for the technical director
were:
a. to take the lead role on behalf of PCC in the development
and co-ordination of the proposed Canadian Poplar Biotechnology
and Genetics Association linking industry needs to research capabilities
and pursuing research funding;
b. to develop contract/partnership opportunities to raise
the profile of PCC and promote the objectives of the PCC and,
through fee-for-service work or contract administration fees,
generate revenues for PCC;
c. to respond to technical enquiries using E-mail, phone,
fax and mail; contributes to the PCC Newsletter and participates
in the PCC Annual meeting; and
d. to provide services to members of a technical rather than
purely administrative nature.
Although the general objectives are still appropriate, at least
the first two specific responsibilities could bear revision and
updating in light of changing times and other developments, as
other parts of this report will show.
Recognizing the limited budget of the Council, the services of
the technical director are provided for a minimal level of compensation.
I work out of my home office, whose co-ordinates are given at
the end of this report. I devote on average two days a week to
Poplar Council business, but the actual time commitment varies
greatly depending on the tasks at hand.
IPC 2000
My last report to the Council was presented almost at the mid-point
of the 21st Session of the International Poplar Commission
(IPC 2000) which was jointly hosted by the US and Canada near
Portland, Oregon September 24-30, 2000. Along with Jud Isebrands
of the US Forest Service and the Poplar Council of the US, I co-chaired
the organizing committee for that major international event, which
was generally considered a great success. Winding up the affairs
of IPC 2000 and following through with related activities, particularly
publications, has taken considerably more time this year than
I had anticipated, and it has continued to be the major focus
of my work. However, there are numerous benefits from this to
the Poplar Council, both directly and in support of Council objectives.
Financially, IPC 2000 broke even. All the bills have been paid,
but this would not have been possible without the considerable
direct and in-kind contributions of the US Forest Service, and
specifically the North Central Research Station at Rhinelander,
WI, where Jud Isebrands is based. The financial support of the
Canadian Forest Service was also invaluable, covering a direct
contribution to the Council for involvement in IPC 2000, a contract
for the preparation of the Canadian national report to IPC, and
the cost of publishing the book 'Poplar Culture in North America'
by NRC Research Press. The total CFS support amounted to $42,000.
Immediately following the IPC Session, three separate field tours
took place. With the help of our Executive Secretary, I organized
and led one of these through southern British Columbia and Alberta.
Referred to as Tour C, this exposed more than 40 international
poplar experts to our successes and concerns with poplar and aspen
in western Canada over a period of 5 days. Hosts for major tour
stops included Scott Paper Co., Kalamalka Research Station of
the B.C. Forest Service, Jasper National Park, Canadian Forest
Service Northern Forestry Centre, and Alberta-Pacific Forest Products.
A more complete report of the tour is featured in the current
issue of the Council's newsletter.
Completion of the "Poplar Culture in North America" book has
taken longer than originally anticipated, but that is apparently
not unusual for a multi-author publication. This one has 27 contributing
authors, of whom 10 are Canadian. When published, it will provide
a comprehensive guide to poplar growing and management in North
America. It will also feature succinct descriptions and illustrations
of 47 of the most useful poplar clones and cultivars in North
America. By the time this report is presented, I expect the final
pieces of the book will have been submitted to the National Research
Council of Canada Research Press and the published book should
appear in the fall. As originally planned, a copy of the book
will be sent to each participant in IPC 2000. Copies will also
be available for general sale. Production of the book is a joint
project of the Poplar Councils of Canada and the US, who will
be named on the cover. I have acted as managing editor for the
project, which involved securing funds, co-ordinating relations
between authors, editors and NRC, and reviewing drafts of most
of the chapters.
There has not in the past been a tradition of formal publication
of the proceedings of IPC Sessions. However, for IPC 2000, the
Organizing Committee undertook to arrange the refereed publication
in a recognized forestry journal of a collection of keynote and
invited papers from the Session. A total of 12 such papers were
published in the March/April 2001 issue of The Forestry Chronicle,
for which Dr. Stefano Bisoffi, the new chair of the IPC Executive
Committee, prepared a guest editorial. An additional paper appeared
in the subsequent issue. A total of 40 authors was involved, of
whom two are Canadian. The special issue, which was produced in
the name of the Poplar Councils of Canada and the US, forms an
excellent overview of the poplar sector and of poplar and willow
science worldwide. The Poplar Council was able to purchase a quantity
of copies of the special issue at a greatly reduced price and
these are available free of charge to paid-up members. I co-ordinated
the publication process, providing liaison between authors, reviewers
and the journal editor, and personally reviewing each paper in
detail.
I believe the Poplar Council can be proud of both these publications,
produced in its name, as well as the Canadian national report
to IPC 2000 prepared by Cees van Oosten. The latter is also available
from the Council as a separate publication. All three should be
valuable references and sources of information for the future.
Other activities
Our website continues to be well used, with 3-4000 visits a month
on average. I have maintained the site throughout the year. However,
I regret not having been able to keep its contents as timely as
I would have liked. In the past month, billing irregularities
with the web hosting service we have been using for the past 2˝
years (since we moved from the Canadian Forest Service server
to our own domain name (www.poplar.ca))
have prompted us to switch to a different host. Visitors to the
website should not notice any difference, but a fair amount of
work has been required 'behind the scenes'. The switch should
be complete by mid-August.
Progress continues to be slow with the development of a directory
of Canadian poplar scientists. The groundwork has been laid to
develop such a directory as a subset of an effort of the Canadian
Forest Service in Victoria to establish a directory of Canadian
forest researchers. Both directories are intended to grow by self-registration,
which is perhaps the simplest method of developing an Internet-based
directory, but is initially a slow process, until the project
achieves a certain critical mass of entries.
The technical director deals with a regular stream of technical
enquiries - on average, 2-3 per week - most of which are received
through the website and dealt with by E-mail. When I am unable
to provide the information requested myself, I involve other Council
members who are experts in different fields. Whenever possible,
advantage is taken of the opportunity to promote Council membership
in responding to enquiries from non-members. However, the point
is fast being reached when we may need to limit the provision
of free information to non-members, particularly when these are
potential corporate members and provision of an adequate response
requires more than a minimal amount of time.
I make regular contributions to the Council's newsletter. The
most recent contribution was a report on the Canadian post-IPC
tour. Finally, I have been actively involved in the planning and
program preparations for this year's annual meeting, participating
in the ad hoc planning group which conducted a brief survey of
poplar research across the country, and preparing a presentation
for the technical program.
Future
In the coming year, activities related to IPC 2000 should be
completed within a month or two. These will mostly involve the
final stages of publication and distribution of the book on "Poplar
Culture in North America". Once it is released, I would like to
find a suitable occasion to present a copy - on behalf of his
colleagues in the Poplar Council and IPC - to Louis Zsuffa, to
whom the book is dedicated.
With the present climate of increasing interest, and potential
government program support, for intensive management, it seems
likely that surveying, helping to co-ordinate and promoting poplar
research will be a strong focus for the future. The outcome of
the annual meeting this year may provide direction for my work
in that regard. This may include the further development of the
directory of Canadian poplar scientists. Considerable effort needs
to be devoted to improving and updating the material on the website,
in part to reflect the above focus, but also because the website
is the chief means by which people come in contact with the Poplar
Council. I will also continue to write material for the newsletter
and deal with technical enquiries.
I would like to thank John Doornbos and the Council's Executive
for their support and confidence throughout the year. I also express
sincere appreciation to the Council's dedicated and hard-working
Executive Secretary, Sandra Williams, who, with the help of activities
like the post-IPC Canadian tour, continues to learn about poplars
and has become a real pro at managing the logistics of organizing
and running meetings and conferences - a valuable asset to the
Council.
Top
Executive Secretary’s
Report
- Sandra J. Williams
In my second report to the members of the Poplar Council, I will
briefly address the Secretariat’s workload, PCC membership, and
Tour C.
The PCC has not been directly involved with a conference since
IPC 2000 at Vancouver, Washington in September. However, work
has been steady at the Poplar Council Secretariat for the year
2001.
A great deal of my time earlier this year was spent on the accounting
end of the various projects the Poplar Council pursued in the
previous year. I have spent the remainder of my time on general
office duties, managing the Poplar Council accounts and investments,
gathering information for and setting up two newsletters, membership
invoicing and support, handling and relaying information requests,
and preparing for the Poplar Council Workshop in Regina, Saskatchewan
on the 15th and 16th of August.
In my last report to the members I mentioned that Revenue Canada
was in the process of reviewing a Poplar Council GST claim. Revenue
Canada has informed us that the Secretariat is required to collect
GST on all conference registrations even though we are not required
to collect GST in association with membership fees. In the future,
the PCC will include GST in registration fees for conferences.
In early April, 2001, John Doornbos and me attended an organizational
meeting for the 2002 CTIA (Canadian Tree Improvement Association)
conference at the University of Alberta. A decision to hold the
PCC annual meeting in conjunction with the CTIA as well as WFGA
(Western Forest Genetics Association) was made in mid-September.
The event will take place July 22 - 25, 2002, at the University
of Alberta in Edmonton. PCC Chairman, John Doornbos, has offered
his budgeting/financial expertise while I will manage the conference
registrations and finances.
Information requests, via the PCC web site, are being conveyed
to the Secretariat with increasing frequency. Types of requests
range broadly from employment inquiries, poplar research information,
wood lot management, poplar-growing advice, to poplar biology
for children’s projects. Jim Richardson deals with the bulk of
the knowledge requests while I respond to some of the information
requests.
I have received about 8 new member submissions, originating from
several continents, on the web site. These uses of the PCC web
site demonstrate that the site is a valuable and convenient connection
for both information seekers and the Poplar Council.
The PCC membership count for the year 2001 is very close to the
year 2000. The membership is comprised of 17 Corporate members,
61 Affiliate members, and 65 Individual members. The latter group
consists of 43 members with one-year memberships, 18 members with
three-year memberships, one student, and 3 Associates. Associates
include the executive members of the U.S. Poplar Council. I also
maintain a mailing list of approximately 40 libraries across Canada.
Membership renewal notices were mailed out in March and to date
the Secretariat has received about 99% of all membership payments
due this year.
After having spent months preparing for Tour C, I was somewhat
disappointed that the tour went by in a blink. However, I am pleased
to report that everything progressed as planned, even with the
rigorous itinerary we adhered to in order to cover such a great
distance in so little time.
I express my sincere appreciation to everyone involved with Tour
C, including Scott Paper Limited, Kalamalka Research Centre, Jasper
National Park, Canadian Forest Service - Northern Forestry Centre,
and Alberta-Pacific Forest Industries. Our international guests
thoroughly enjoyed Canadian hospitality. They were especially
impressed to receive home-cooked lunches at several of the tour
stops. Thanks also to Daishowa-Marubeni International Ltd. and
Weyerhaeuser for their financial contributions to the tour. In
addition, I thank the organizers of IPC 2000, especially Kathy
Heise, from the US Forest Service in Rhinelander, Wisconsin, for
taking care of Tour C registration.
John and Jim never hesitate to share their forestry knowledge
with me. I am very grateful for this as it keeps my job interesting.
Thanks guys! We’ve had a very productive year and I look forward
to the productive year ahead.
Top
A Brief History of the Poplar Council of Canada, and of the
Poplar Culture Related to its Establishment and Growth
- Dr. Louis Zsuffa, Professor Emeritus, Faculty of Forestry,
University of Toronto
The Poplar Council of Canada is 25 years old this year. The council
was established at the annual meeting of the North American Poplar
Council, which was held in Eastern Ontario in 1977. The North
American Poplar Council had been, since 1950, a committee of the
IPC, International Poplar Commission, which in turn is a Statutory
Body of the FAO, Food and Agricultural Organization of the United
Nations.
The history of the PCC is closely related to the history of poplar
culture in Canada. One cannot discuss it without referring to
the history of poplar cultivation. Poplar culture came first,
so I will address it first.
A Brief History of Poplar Culture in Canada
In the US as well as in Canada there were several periods of
industrial interest in hybrid poplar planting and utilization,
the first one being with Dr. E. Schreiner, the hybrid poplars
in Arnold Arboretum, and the wood industry in Northeastern US
(Oxford Paper). However, poplars and willows were planted and
cultivated for the benefit of mankind around the world for thousands
of years before that.
Poplars and willows belong to the same botanical family, the
Salicaceae. Poplar and willow wood demonstrate similarities
in key characteristics.
In Canada, the culture of poplars and willows has a long history.
The planting and utilization of these trees may have been practised
by natives for millennia. The spread of some balsam poplar trees,
such as the "Balm of Gilead" and the "Western Balm" and willows
used for medicinal purposes provide indications of this. Much
later, but still centuries ago, the white people brought with
them, along with the many plants and trees they found useful in
their previous home, poplars and willows. Lombardy poplar and
silver poplar are examples of these poplars. Weeping willow, cracking
willow, and basket willow are good examples of the willows they
brought. These trees and shrubs were planted around new settlements
and farms and appreciated for their usefulness.
Many of the introductions from Europe were of a single type,
and even of a single clone (most poplars and willows propagate
by twigs or root pieces as clones). Such was the case with Lombardy
poplar, silver poplar, and crack willow.
The movement of trees with the settlers from Europe also went
in the opposite direction: when returning home settlers took with
them many of the useful plants they found in the New World. Thus,
eastern cottonwood trees were taken from Canada and planted in
France in the 17th century. These trees, when flowering,
hybridized spontaneously with the native European black poplar
(Populus nigra). Many of the hybrid seedlings grew well
and formed into nice trees. Gardeners selected some of the best
and named them "Canadian poplars" because the seed from which
the trees grew were collected from mother trees brought from Canada.
Thus a new Canadian poplar which did not even exist in Canada
appeared with the scientific name of Populus canadensis.
This Canadian hybrid poplar became very popular in many European
countries and provided the foundation for a widely spread culture
of poplar in Europe.
Varieties of these Canadian poplars did not exist in Canada until
the beginning of the twentieth century when several clones were
imported from Europe and propagated under different names. Of
these imports the so-called "Carolina poplar" was the most successful.
It has been planted so extensively in Ontario, Québec and
the Lake states that in people’s minds it became one of the native
poplars. (Working with poplars I often hear people assert that
they do not want exotic poplars, they want to plant our native
Carolina poplar!). This single hybrid poplar clone has been propagated
by commercial nurseries as well as by government forest nurseries.
Since the 1950’s, in Ontario alone, more than half a million plants
(rooted cuttings) were sold or distributed annually and its planting
has continued to present times. Naturally only a portion of the
trees survived. Those planted in poor sites and in bad cultural
conditions succumbed. However, enough Carolina poplar trees survived
to make it a typical tree of Ontario’s landscapes, farms, and
roadsides.
As witnessed by the widespread cultivation of poplars, the trees
have been very popular with the people of Canada. In most of Europe
and Asia poplars and willows have been noted as cultivated trees
since biblical times. The Latin, hence scientific, name for poplar
is Populus, which literally means "the people" in Latin.
Thus the name Populus for the tree signifies "the people’s
tree".
Poplars and willows are easy to grow; a twig stuck in the ground
grows into a new tree in no time. In this way, by rooting cuttings,
trees chosen for desired form and other qualities were and are
easy to duplicate and perpetuate. Such trees include, for example,
the Lombardy poplar and the weeping willow, both of which originated
in Asia millennia ago and have spread by cultivation throughout
the world. This means also that the bodies of these trees have
been alive for thousands of years! We know poplars and willows
as short-lived trees. However, they possess a tremendous capacity
for regeneration, they re-grow from roots, and from stumps and
twigs, and are often indestructible, living and re-growing for
many generations. The same is true for aspen which regenerate
from root suckers.
In parts of the world that are deficient in wood, poplars are
considered very useful. Not so in Canada, where foresters are
concerned with traditional timber species of high commercial value.
In a few cases however, some industries showed interest in hybrid
poplar for specialty products such as paper, veneer boards, matches,
fruit boxes, and composite boards.
Poplar breeding and cultivation started in Ontario in the mid
1930s as the result of an upswing in industry interest. However,
the decisive factor was the presence of a poplar enthusiast, breeder
and scientist, Dr. Carl Heimburger. Heimburger’s work in selection
and breeding resulted in fast-growing and excellent varieties
and laid the foundation for a poplar culture. Heimburger represented
Canada on the North American Poplar Council prior to the establishment
of the PCC.
Since the 1970s the Canadian hybrid poplar culture has been focused
in Ontario and Québec, as well as in parts of British Columbia.
However, the prairie windbreaks could not have existed without
the poplar development work of the PFRA Shelterbelt Centre starting
as early as 1900. By the late 1970s the foundation existed for
a countrywide interest in poplar culture and utilization and the
situation was ripe for the establishment of the Poplar Council
of Canada.
Poplar Council of Canada – Organization and Purpose
The Poplar Council of Canada is a national group of corporate
and individual members who are concerned with developing, harvesting,
utilizing and renewing the poplar and willow resources of Canada.
PCC members are from industry, woodlot owners, universities, research
establishments, and provincial and federal governments. The word
poplar in the name of the PCC includes all members of the poplar
and willow family.
The mission statement of the Poplar Council reads as follows:
"The Poplar Council of Canada will develop, collect, maintain
and disseminate information on the poplar resource of Canada and
will promote the sound management of and wise use of this resource
for the benefit of all Canadians."
The objectives of the PCC are: 1) to facilitate the development
and exchange of information and materials on poplar in the national
and international arena; 2) to organize meetings, workshops, seminars
and technical sessions on poplar for landowners, industry and
other users, scientists, and government bodies and to increase
the awareness and understanding of the general public; 3) to promote
the sound management and wise use of the poplar resource, including
recognition of its environmental role as well as its capacity
to rehabilitate water courses; and 4) to evaluate current knowledge
of poplar and to identify, encourage and undertake needed research.
The organization of the PCC: The Council has dealt with
its objectives via technical committees, and discussions of the
reports submitted to its annual meetings. Since 1991 the PCC has
published a periodical newsletter. The technical committees were
in economics, genetics, protection, and utilization. There was
also a business meeting held annually in conjunction with the
annual meeting at which a nominating committee was struck and
the positions of the Chair, secretary-Treasurer and Technical
Committee chairs were reviewed.
The first elected chair of the PCC was Russell Johnson, Woodlands
Manager, Domtar and I was his assistant. At the time I was working
for OMNR, at the Maple Research Station. Russell Johnson and me
are the founders of the Poplar Council of Canada and the PCC committees.
I became chair in 1979, the same year the Poplar Council became
incorporated. Since the inception of the PCC there have been several
different people in the chair, all very capable contributors to
the objectives of the PCC. The Secretariat of the PCC has moved
from province to province with the headquarters of the chair,
and so went the Secretary-Treasurer.
The initial objective of poplar culture and utilization has expanded
to include agroforestry, biomass, aspen plantations and shelterbelts,
establishment, management and utilization.
The technical committees dealt with many important issues such
as the financial returns from poplar culture, the introduction
and identification of new clonal varieties, identification of
poplar diseases and damaging insects, the wood qualities and utilization
of the wood of aspen and balsam poplar varieties, and of the newly
introduced and developed clones, the silvics and growth of aspen
sucker stands, short rotation and minirotation poplar and willow,
management and growth of old poplar and willow coppice stands,
problems with Septoria canker, growing poplar and willow
in sewage-sludge-inundated soils, and many others.
Literature:
Fayle D.C.F., L. Zsuffa and H.W. Anderson, eds. 1977. Poplar
research, management, and utilization in Canada. Proc. North American
Poplar Council Annual Meeting, Brockville, ON. Sept., 1977. For.
Res. Inf. Paper no. 102, OMNR, Canada.
Top
The In vitro Technology
for Large Scale Propagation of Populus tremuloides Michx.
(Trembling Aspen)
- Andrzej Stolarz
Introduction
In vitro culture methods, techniques and technologies are an
essential part of forest biotechnology. The plant cells, tissues
and organ cultures of herbaceous and woody plant species have
the capacity to regenerate new plants under defined, sterile conditions
of an artificially created environment.
There are three general pathways of plant regeneration and in
vitro multiplication: (1) via shoot morphogenesis and subsequent
root formation (2) through somatic embryogenesis or (3) via organogenesis.
The process of shoot morphogenesis in vitro refers to plant multiplication
by the shoot tip and nodal culture methods. In both instances
propagation proceeds by repeated development of shoots from shoot
tips or axillary buds stimulated by the presence of plant growth
hormones in the culture medium. The shoot cultures can be maintained
in vitro almost indefinitely, without any changes in their ability
to supply, in reproducible manner, uniform and healthy seedling-like
plants throughout the year.
Regeneration of plants via somatic embryogenesis may occur either
directly or indirectly, and is accomplished when the somatic cell
or group of cells of explant tissue behaves like a zygote with
the ability to perform a developmental program characteristic
of embryogenesis in vivo. Direct embryogenesis from somatic tissue
without an intervening callus phase is a rare phenomena and has
been described only in a few species (Stolarz et al. 1991). In
most instances regeneration proceeds indirectly through an embryogenic
callus phase or from embryogenic cell suspension cultures. For
extensive review on somatic embryogenesis in forest tree species,
see the most recent publication by Jain et al. (1995). Plant regeneration
through organogenesis refers to de novo formation of adventitious
shoots, roots or leaves directly from defined tissue or through
competent callus cultures.
The first attempts to regenerate in vitro plants of Populus
tremuloides were made by Mathes (1964), Winton (1968) and
Wolter (1968). The authors were able to regenerate very few plants
from friable callus cultures induced on stem explants of triploid
P. tremuloides. Plant regeneration occurred when callus
cultures were grown on the medium supplemented with BA (0.2-0.9
uM) in total darkness after 2-3 months (Winton 1968) or under
low light intensity with a 16 h photoperiod and with the same
concentration of BA (Wolter 1968). For almost 20 years after the
first paper was published, there was no interest in doing in vitro
experiments on plant regeneration of P. tremuloides until
Ahuja (1983) published his report on plant regeneration of aspen.
The report unfortunately, does not contain any information on
plant regeneration of P. tremuloides. Out of 48 clones
of P. tremula and P. tremuloides used in this study,
only 10 clones show some degree of regeneration and the rest of
the clones, including 4 clones of P. tremuloides, grew
poorly or not at all. In a last report Noh and Minocha (1986)
were successful in obtaining regeneration of plants from callus
cultures developed from leaf tissues of P. tremuloides.
After induction (0.1 mg/L BA + 0.5 mg/L 2,4-D), small callus clumps
were removed from the leaves surface and cultured in a liquid
medium for 35 days. Differentiation of shoots occurred when calli
were transferred on an agar medium supplemented with BA (0.5 mg/L).
An average regeneration efficiency of 6 plants per callus piece
was obtained.
Finally, there are two reports on Agrobacterium-mediated
transformation which are also related to plant regeneration
of P. tremuloides (Tsai et al. 1994; Hu et al. 1999). Genetically
transformed plants were regenerated from callus cultures originating
on leaf segments after co-cultivation with Agrobacterium
strains carrying GUS and NPT II marker genes or Pt4CL1gene responsible
for lignin synthesis in xylem tissue. Plants transformed with
the plasmid construct carrying reverse orientation of cDNA coding
sequence of Pt4CL1 gene fused to duplicated CaMV 35S promoter
have shown substantial reduction of lignin synthesis in 10 month
old plants. In some trees antisense inhibition reduce the lignin
synthesis up to 45% and increase cellulose synthesis by 15 %.
It would be very interesting to see how the developmentally regulated
expression of CaMV 35S promoter will affect the lignin synthesis
in much older trees and whether there will be sufficient activity
of this promoter to maintain similar reduction of lignin synthesis
in aging trees. For more information on genetic transformation
of poplars and what genes are already introduced to the genome
of Populus species and hybrids see Han et al. (1996).
In vitro propagation of Populus tremuloides
Highly efficient in vitro plant regeneration and multiplication
technology for rapid clonal propagation of Populus tremuloides
was developed and tested on several clones including superior
aspen clone AW-30 (Weyerhaeuser Company) a native to the province
of Alberta. The experiments on in vitro regeneration were initiated
on different aspen clones from arboretum of Alberta Horticulture
Center, Edmonton in 1992.
Similarly to other plant species propagated in vitro the protocol
for regeneration and multiplication of aspen consist of the following
stages:
Stage I.
To establish in vitro culture, actively growing shoots from greenhouse
grown plants were used in spring to mid-summer. The shoots from
healthy and vigorously growing plants were prepared for sterilization
and in vitro culture initiation. The growth of cultures during
the first stage is not uniform, some buds begin the growth almost
immediately while others require 6 to 8 weeks to commence the
growth. The first stage is completed when sterile explants show
visible bud growth and possibly some shoots proliferation.
Stage II.
Actively growing explants are transferred on multiplication media
to induce adventitious bud formation from the meristematic tissues
of axillary buds. This system of multiplication allows the regular
transferring of aspen shoots 2-2.5 cm long onto fresh medium every
4 to 6 weeks. The process of proliferation may be continued almost
indefinitely, until the required number of shoots is produced.
An average multiplication rate of 5 to 6 (often more) shoots per
culture per month can be obtained; this would suggest that more
than 500,000 plants per year could be produced from one initial
bud. However, in practice, in vitro culture space and nursery
facilities are the limiting factors. The number of proliferating
cultures, depending on production facilities, can be kept at a
constant level by subculturing 90% of the shoots to stage III
and placing the remaining 10% back onto a fresh multiplication
medium.
Stage III.
The elongation stage. The plant growth substances present in
multiplication medium facilitate the extensive axillary branching
but at the same time inhibit the natural growth. The transfer
of aspen plantlets on media without growth substances allowed
them to return to natural growth. At this stage the plantlets
should elongate to the size of 2-3 cm before the transfer on rooting
medium.
Stage IV.
At this stage shoots 2 to 3 cm long are cultured on medium supplemented
with rooting hormones. The basal medium for root initiation can
be reduced to half concentration of that used for multiplication.
The aspen plantlets kept under a 4000-5000 lux with a 16-hour
photoperiod formed the roots with high efficiency after 12-14
days.
Stage V.
The in vitro rooted plantlets were transferred to 18 mm forestry
pellets that very well facilitate adaptation to new growing conditions.
After transfer the plants should be kept in a mist chamber for
7-10 days. It is very important to control water loss by maintaining
very humid conditions as the plantlets fresh from in vitro cultures
are very sensitive and are not able to remain turgid. After hardening
the plants should be held on an unmisted bench for a week or two
and finally transferred into styroblocks and grown in the greenhouse
until the size of 30-40 cm. Before the field planting the plants
must be hardened outside in a shaded place.
The in vitro technology described here was successfully used
to produced
12,000 plants, including 7500 plants of superior aspen AW-30
up to now. It is also well suited for plant multiplication of
hybrids such as P. tremuloides x P. tremula, P.
alba x P. tremuloides and other poplar hybrids. This
technology can also be applied in breeding programs for rapid
multiplication of F1 progeny (from single seed) to
required number of trees for further testing. Once the technology
was developed the main efforts are concentrated on designing and
developing an automation system which will reduce the time and
labor required for transferring in vitro rooted plantlets to forestry
pellets and then to any other containers facilitating optimal
growth of plants in greenhouse conditions.
Acknowledgement
The author would like to thank Weyerhaeuser Company and personally
Tim Gylander and Bruce Macmillan for providing the Aspen Clone
AW-30 and allowing it to be used for experimentation and production.
Literature
Ahuja, M. R. Somatic cell differentiation and rapid clonal propagation
of aspen. Silvae Genet. 32: 3-4 (1983)
Han, K.H., Gordon, M.P. and Strauss, S.H. (1996). Cellular and
molecular biology of Agrobacterium-mediated transformation of
plants and its application to genetic transformation of Populus.
In Stettler, R.F. et al. (Eds.) 201-222 (1996)
Hu, W.J., Harding, S.A., Lung, J., Popko, J.L., Ralf, J., Stokke,
D.D., Tsai, Ch.J. and Chiang,V.L. Repression of lignin biosynthesis
promotes cellulose accumulation and growth in transgenic trees.
Nature Biotech. 17:808-812 (1999)
Jain, S. M., Gupta, P. K., and Newton, R. J. Somatic Embryogenesis
in Woody Plants. Kluwer Academic Publishers, Dordrecht (1995)
Mathes, M.C. The culture of isolated triploid aspen tissue. For.
Sci. 10:35-38 (1964)
Noh, E.W., Minocha, S.C. High efficiency shoot regeneration from
callus of quaking aspen (Populus tremuloides Michx.). Plant
Cell Rep. 5: 464-467 (1986)
Stolarz, A., Macewicz, J., and Lorz, H. Direct somatic embryogenesis
from leaf explants of Nicotiana tabacum. J. Plant Physiol.
v. 137, 347-357 (1991)
Tsai, C.J., Podila, G.K., and Chiang, V.L. Agrobacterium-mediated
transformation of quaking aspen (Populus tremuloides)
and regeneration of transgenic plants. Plant Cell Rep. 14:94-97
(1994)
Winton, L.L. Plantlets from aspen tissue culture. Science 160:
1234-1235 (1968)
Wolter, K.E. Root and shoot initiation in aspen callus culture.
Nature 219: 509-510 (1968)
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