Oaks represent the most important forest resource in Europe. Despite their economic and ecological importance, they have received little attention concerning their genetic improvement. There is a general consensus that no genetic breeding programme can be conducted for long lived species such as oaks. Therefore, the material used for regenerating naturally or artificially will come exclusively from existing stands. Thus knowledge of the genetic variation existing in actual forests becomes of primary importance.
Contrary to other major forest species, there has been no wide range study of the genetic variation in the oak forests. The lack of knowledge in this field has resulted in unanswered problems that the forester has to face:
the identification of the species, hybrids or populations;
the transfer of reproductive material between different regions of provenances or countries.
Taxonomic questions are still open in oak forests. Hybrids do exist and usually occupy specific ecological niches, however there is no specific genetic marker available yet. Flowering and fruiting is irregular and heterogenous and seed often have to be transferred for plantation. The identification of provenances and their adaptation in the new environment is of critical importance in this context.
The present project aims at answering these two questions by assessing both gene markers and adaptive traits in several populations of oak forests.
The project concentrated on describing genetic variation in oak populations by means of molecular markers and adaptive traits. The work was done mainly on sessile and pedunculate oak, although several other species were also studied. As a result of the project, taxonomic identification (Q petraea and Q robur) based on molecular markers on an individual tree basis is now possible. The results also contribute to a better understanding of the evolutionary biology of the oaks in Europe and of the transfer of reproductive material among different regions and countries.
The project resulted also in important methodological breakthroughs including:
the cloning of the recombinant deoxyribonucleic acid (rDNA) unit in Q robur and Q cerris;
the finding of several pairs of primers permitting amplification of polymorphic zones in the chloroplast genome;
the development of a methodology for frost resistance in oaks.
Despite of their sylvicultural and eco
nomical importance oaks have not recei
ved significant efforts for their gene
tic improvement. Seed stands have been
identified in all european countries,
and the population variation is still
the only one used in selection scheme
s. The present project aims at a genet
ic description of different oak popula
tions and at the assessment of their a
daptative abilities. The technics used
will offer reliable basic information
at a juvenile stage (seedlings) and r
esults can directly be applied in fore
1- VARIATION OF MOLECULAR MARKERS DNA
markers have been recently identified
in oak species. Studies will be conduc
ted on various species (Q. robur, Q. p
etraea, Q. suber and Q. cerris). In a
first step variation occuring at the t
otal genome will be described: percen
tage of repeated sequences, rate of me
thylation. In a second step, restricti
on fragment length polymorphims will b
e assessed in cytoplasmic DNA (mitocho
ndrial-mtdna- And chloroplast -cpdna-)
and nuclear DNA (ribosomal -rDNA- and
minisatellites)by means of the southe
rn blot hybridisation technique with h
eterologous and homologous probes. Spe
cific studies of these markers concern
: inheritance in F1 inter and intrasp
ecific crosses, DNA fingerprinting, cl
oning of rDNA genes, species and popul
ation variation. In a third step, a li
brary of CDNA (complementary DNA) will
be established in Q. robur After extr
action and purification of messenger R
NA from apical buds and leaves. By add
ressing both coding and non coding gen
es, these markers will provide a signi
ficant description of DNA polymorphism
in the genus Quercus. Allozyme variat
ion on a european scale will be analys
ed in Q. petraea.
2- INTRASPECIFIC VARIATION OF ADAPTATI
VE TRAITS On most species studied so f
ar phenological traits exhibited impor
tant geographic variation. The studies
conducted in oaks (Q. petraea and Q.
rubra) will focus on the different com
ponents of phenology: bud flushing, b
ud set and growth rhythm.
* Bud set and bud flushing will be rec
orded in the nursery * Growth rhythm w
ill be studied in controlled chambers.
Particularly the occurrence of severa
l flushes (polycyclism) will be follow
ed and related to other phenological t
raits, rate of growth and duration of
Variation in phenology traits lead to
differential sensitivity to frost. Spe
cific studies will be conducted on fre
st hardiness and chill requirement to
bud burst in controlled chambers.
These traits and markers will be asses
sed on various populations and species
(see next paragraphs). Results expect
ed from these studies will have both p
ractical and theoretical consequences.
on the one hand they will contribute
to define seed transfer rules between
the different european countries. On t
he other hand assessing geographic var
iation of adaptative and molecular cha
racters will provide a better understa
nding of the distribution of genetic v
ariation in oak populations, and basis
information for further tree improvem
Funding SchemeCSC - Cost-sharing contracts
EH26 0QB Penicuik