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VARIATION OF DROUGHT TOLERANCE OF
HYBRID LARCH IN GREENHOUSE EXPERIMENTS
Dr. María del Carmen Dacasa Rüdinger
1
, Dr. Heino Wolf
1
1
Staatsbetrieb Sachsenforst, Department of Forest Genetics and Forest Plant Breeding
Bonnewitzer Straße 34, 01796 Pirna, Germany
Maria.Dacasa@smul.sachsen.de
Background
Hybrid larch resulting from crosses between
European and Japanese larch (
Larix decidua
x
Larix kaempferi
) has been shown to display
heterosis for several relevant commercial traits
like growth and stem form and to thrive well on a
broader range of ecological conditions than its
parents (Pâques, Ann. sci. for. 1989, 46). This
makes hybrid larch especially interesting for its
use in reforestation and afforestation programs as
well as in short rotation management systems.
Testing in the greenhouse
Three important questions arise in the attempt to
breed Larch varieties with enhanced tolerance to
drought:
Are there differences in drought stress tolerance
among hybrid progenies of Larch?
Which physiological aspects are the most
suitable to evaluate the response of Larch to
drought?
Are there trade-offs between relevant features
like growth of the breed varieties and their
tolerance to drought?
To address these issues, five hybrid larch full sib
families, all derived from tested seed, have been
assessed for their drought stress tolerance.
Seedlings of the parental species of the hybrids,
European (ELA) and Japanese (JLA) larch, were
included as a reference. A total of 50 one year-old
seedlings per variety and parental line were used
and divided into a control and a treatment group,
the first being regularly watered during nine
weeks until the end of the experiment. The
treatment group was left without watering during
the whole period. In addition, the stress tolerance
of 21 hybrid larch clones derived from somatic
embryogenesis was determined using ten ramets
per clone, half of which used as controls as
above. The clones represent five full sib families,
descending from basic material of the category
“tested”. Plants were evaluated by determining:
plant vitality evolution,
height growth under drought stress,
photosynthetic efficiency using a portable
chlorophyll fluorometer.
Förderkennzeichen 22034914
Laufzeit: 2012-2018
The challenge
There exists a large variation among hybrid
families regarding the extent of the heterosis
effect. This fact has to be considered in
breeding programs in order to maximize the
genetic gain for the desired traits. The public
enterprise Sachsenforst is working on larch
improvement since about 70 years and in view
of the predicted rise of temperatures has now
included the resilience against drought stress in
its breeding program as a feature to look for
along with the classical targets growth, stem
straightness and branching.
Phenotyping
doesn‘t cost,
it pays!
Detecting superior
genotypes
at family and
individual level
Variation in response to drought
There are differences among families and
among clones from the same family. After 9
weeks of drought it was possible to find all
three vitality scores among individuals of the
same family (Fig. 1). Only one of the five
hybrid families resulted less tolerant than the
parental lines (Fig. 2)
Assessment of plant vitality seems to be a
stable indicator of tolerance as it render
similar ranking results as obtained in previous
experiments.
The three most vital families after nine weeks
of drought present the largest growth under
control conditions (Fig. 3). No correlations
between growth under drought stress and
vitality scores has been found (Fig. 4).
1
2
3
Figure 1: Vitality scores
1 No damage or just slight damage
2 Intermediate damage
3 Severe damage or dead
Vitality scores
1 2 3
Cunnersdorf II Fichtelberg Graupa 68 Graupa I
Graupa II
JLA
ELA
1 2 3
1 2 3
1 2 3
1 2 3
1 2 3
1 2 3
Figure 2: Percentage of vitality scores
Cunnersdorf II Fichtelberg Graupa I Graupa II ELA Graupa 68
JLA
Figure 3: Growth of the control groups
Figure 4: Percentage of growth under drought conditions relative to
the respective control group
4
7
9
Weeks without watering
JLA
ELA
JLA
ELA
JLA
ELA