Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
ORIGINAL ARTICLE
DOI: 10.2478/ffp-2020-0010
Isozyme polymorphism and seed and cone variability
of Scots pine (Pinus sylvestris l.) in relation to local
environments in Poland
Paweł Przybylski1 , Katarzyna Masternak2, Szymon Jastrzębowski1
1
Forest Research Institute, Department of Sylviculture and Forest Tree Genetics, Braci Leśnej 3, Sękocin Stary,
05-090 Raszyn, Poland, e-mail p.przybylski@ibles.waw.pl
2
University of Life Sciences in Lublin, Faculty of Agrobioengineering, Institute of Plant Genetics,
Breeding and Biotechnology, Akademicka 13, 20-950 Lublin, Poland
AbSTRAcT
Evolutionary processes lead to the survival of individuals best adapted to local environment. This gives rise to allele
polymorphism and genetic diversity of populations. Isoenzyme proteins, which are the product of gene expression,
are an effective tool for tracking these changes. On the other hand, the reproductive potential of a given population
can be assessed based on its ability to produce viable and efficiently germinating seeds. The present results combine
molecular analyses of isoenzyme proteins with anatomical and morphological studies of Scots pine seeds (Pinus
sylvestris L.). The study was conducted in 6 populations that are characteristic of this species occurrence range in the
country. The results confirm the correlation between seed weight and embryo size. They also show a population from
northeastern Poland had a higher effective number of alleles and seed with lower germinative energy and capacity.
There was genetic homogeneity in all except for the population from Woziwoda, which was significantly different
based on the Fst test. The genetic characteristics of Scots pine from Woziwoda may be associated with the lower levels
of rainfall that occur there during the growing season. The results improve our knowledge of Scots pine variability
and contribute to the discussion of the impact of local environment on genetic variability.
KEy wORDS
adaptive capacity, isoenzyme marker, Scots pine, seeds
InTRODucTIOn
Genetic variability is the sum of the differences in
phenotypes and genotypes amongst individuals, populations or species (Sztuba-Solińska 2005). Indices of
genetic variation in forestry are becoming more widespread, with the knowledge gained used in breeding
Received 19 July 2019 / Accepted 22 January 2020
forest trees and forest protection. Maintaining a high
level of genetic variation within and between populations is a basis for sustainable forestry (Food and Agriculture Organization of the United Nations 2014). Genetic variability is one of the most important attributes
of any population, because it determines its stability in
the face of possible changes in environmental condi-
© 2020 by the Committee on Forestry Sciences and Wood
Technology of the Polish Academy of Sciences
and the Forest Research Institute in S´kocin Stary
Isozyme polymorphism and seed and cone variability of Scots pine (Pinus sylvestris L.)…
tions (Reed and Frankham 2003). Intensive studies have
been conducted in forest science to analyse the correlation of selected molecular markers with phenotypic
characteristics. Some studies show that genetic markers
are not a good means of assessing plasticity and adaptability of trees. For example, Hedrick and Miller (1992)
claimed that molecular markers are selectively neutral
and the data obtained from genetic analyses describe
only a small part of the genome and, therefore, cannot be a good indicator of adaptive genetic differences.
Reed and Frankham (2001) added that the loss of genetic diversity does not necessarily have to reduce adaptive potential. Despite these arguments, many studies
indicate the usefulness of genetic markers, particularly
isoenzymes, to evaluate the adaptive potential of forest
trees. So far, research in this area has been conducted
for species of the genus Pinus (Blumenröther et al.
2001) and Picea (Seifert and Müller-Starck 2009; Masternak 2015).
Populations of forest trees adapt to the environment in which they live, which, as a result, results in
phenotypic and genetic variabilities. For pine, adaptive
variability has a unique significance because the species
occurs in a diverse set of ecosystems, whereas provenance-based studies show the adaptation of certain subpopulations to environment (Blumenröther et al. 2001).
In order to obtain the information on the genetic
basis of adaptation, research is conducted at various
stages of tree and stand development (Müller-Starck
89
1993; Starcke et al. 1996). Genetic markers have been
studied in relation to survivability (Bergmann and
Scholz 1989), growth (Durel et al. 1996; Wang 1996;
Furnier et al. 1991), wood properties (Wang et al. 2008;
Xiaet al. 2008), date of bud break and the resulting loss
of resistance to late frosts (Masternak 2015), resistance
to drought (Eckert et al. 2010) and fungi and insects
(Quesada et al. 2010), as well as resistance to environmental pollution (Bergmann and Scholz 1985; Konert
1993; Brus 1996; Müller-Starck 1989; Prus-Głowacki et
al. 2003).
For Scots pine clones, the correlation was observed
between the date of flowering and frequency at the locus Sdh-A (Prus-Głowacki et al. 2015). An analysis of
growth characteristics in common beech found a clear
correlation between breast height diameter (DBH) and
variation at loci Mdh-C, 6Pgdh-B and Aat-C (MüllerStarck et al. 2005). This was confirmed by previous research on Scots pine, which showed that heterozygosity
at specified loci is related to smaller tree size (Blumenröther et al. 2001). However, amongst spruce trees, variation at specified loci was more closely related to the
ability of trees to bear seeds (Seifert and Müller-Starck
2009).
The main objective of the present study was to
evaluate the genetic variability of pine populations with
isoenzyme markers. The anatomical and morphological
characteristics of seeds were also analysed. Evidence
was evaluated for the relation of phenotypic and genotypic differences amongst
populations to be the result
Table 1. Geographical location of the populations, their estimated age in 2016, area of the
stand and habitat, species composition of the analysed population with the height and width
of adaptation to environof studied trees
mental conditions.
Location
Latitude
(N)
Longitude
(E)
Area
Species
Age in
(ha) composition 2016
DBH
(cm)
Height
(m)
Międzyzdroje
53°55′44″ 14°54′40″
(Mi)
7.36
Pine 70%,
oak 30%
137
47.4 ± 7.7 31.6 ± 3.5
Strzałowo
(St)
19.6
Pine 80%,
spruce 20%
112
43.4 ± 6.7 36.0 ± 2.5
Białowieża
(Bi)
Pine 50%,
53°15′21″ 23°39′16″ 10.54
spruce 50%
158
52.9 ± 7.3 40.1 ± 2.1
Woziwoda
(Wi)
53°39′85″ 17°55′37″ 13.34
Pine 100%
149
45.3 ± 6.6 30.7 ± 3.0
Bolesławiec
(Bo)
51°20′20″
15°42′1″
12.01
Pine 100%
165
47.0 ± 6.1 29.1 ± 2.2
Józefów
(Jz)
50°57′38″ 22°54′49″
5.96
Pine 100%
125
42.2 ± 3.8 30.8 ± 3.0
53°41′
21°26′
MATERIAl AnD METhODS
Tree material
The study was conducted
using six Scots pine populations from different seed
zones covering the range
of the species in Poland
(Tab. 1). Selected locations
differed in the amount of
precipitation during the
growing season (Fig. 1).
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
90
Paweł Przybylski, Katarzyna Masternak, Szymon Jastrzębowski
From each selected tree, 10 kg of cones per populations
was collected, which, after seed extraction, was used
to evaluate the yield and quality of seeds. At the same
time as cones were collected, shoots with dormant winter buds were sampled from standing trees for laboratory analyses.
and 3 g of PVP K 25 in 100 mL of buffer) (Odrzykoski
and Gottlieb 1984). Whatman filter paper strips (31ET
4 mm x 11 mm) were soaked with the resultant solution
and stored at –80oC before analysis.
Electrophoretic separation was performed in
13% starch gel (Starch-Art) using two buffer systems,
A and C, whose composition was described by Odrzykoski and Gottlieb (1984) and Cieślewicz (2008). After electrophoresis, the gel was cut into 1.5-mm thick
layers and each layer was used to visualise isoenzymatic proteins. The location of proteins in the gel was
carried out according to the procedure described by
Conkl et al. (1982) and modified by applying an ‘agar
overlay’ for excluding loci: Got-A, Got-B and Got-C
(Manchenko 1994). The most variable enzyme systems
within the Pinus species were selected (Opracowanie
szczegółowych wymagań 2003). The list of examined
loci is shown in Table 2.
Table 2. List of enzymes with buffer systems used to
separate them
Figure 1. Geographical distribution of the population with
regard to the precipitation gradient during the vegetation
period (April–September). Location: 1, Bolesławiec; 2,
Józefów; 3, Międzyzdroje; 4, Woziwoda; 5, Strzałowo; 6,
Białowieża
Buffer
system
A
cone and seed assessment
Cones harvested from each tree were weighed, and
1,000 seeds from each population were subsampled to
evaluate the average cone weight, total yield of seeds
from cones, average number of seeds per cone and the
mass of 1,000 seeds. A sample of seed was dissected
to determine the length and width of the embryo and
length and width of the endosperm. Germinative energy
and capacity of seeds were determined in accordance
with international seed evaluation standards (ISTA
2013).
Analysis of genetic markers
Proteins were extracted from buds in a state of winter
dormancy. The buds, with bud scales removed, were
ground, and then extraction was carried out with 150
µL of extraction buffer (100 mM of Tris-HCl with pH
7.5, with the addition of 10 of mM 2-mercaptoethanol
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
C
E.C.
number
locus
Glutamic oxaloacetic
transaminase
2.6.1.1
Got-A
Got-B
Got-C
Diaphoresis
1.8.1.4
Dia-C
Enzyme
Glutamate dehydrogenase
1.4.1.2
Gdh-A
6-phosphogluconate
dehydrogenase
1.1.1.44
Pgd-B
Shikimate dehydrogenase
1.1.1.25
Sdh-A
Sdh-B
Malate dehydrogenase
of NAD-dependent
1.1.1.37
Mdh-A
Mdh-C
Statistical analysis
Cone and seed measurements were evaluated using the
Shapiro–Wilk test to determine those with a normal distribution. Homogeneity of variance was verified with
the Leven test. For features meeting the assumptions
of normality and homogeneity of variance, parametric
ANOVA tests were performed, followed by Tukey’s
test applied post hoc to identify significant differences
amongst populations. In other cases, the non-parametric
Kruskal–Wallis test was used to differentiate populations.
91
Isozyme polymorphism and seed and cone variability of Scots pine (Pinus sylvestris L.)…
The relationships between cone and seed attributes
were evaluated using the Pearson correlation method.
Relationships between geographic coordinates and genetic variability of populations, such as germinative
energy and capacity and seed production and seed quality features, were determined using the non-parametric
Spearman correlation method. Calculations were performed using Statistica ver. 9.0 (Stat Soft 2010).
The variation of isoenzymatic loci was analysed
using the GeneAlex 6.5 program (Peakall and Smouse
2006). Allele frequencies, the percentage of polymorphic loci, the average number of alleles at the locus (Ni)
and the observed heterozygosity (Ho) were calculated
(Wright 1969; Bergmann 1989). The effective number
of alleles at a locus (Ne) was calculated according to the
formula given by Wright (1969): Ne = 1/1 − He, where He
is the expected heterozygosity.
The genetic diversity of the consolidation coefficient (Fst) (Wright 1987), expressed by the formula
Fst = (HT − Hs)/HT, was also calculated, where Hs is
the ratio of heterozygous genotypes assuming random
mating in subpopulations and HT is the proportion of
heterozygous genotypes for the particular gene, assuming genetic equilibrium in the entire population. For Fst,
PCoA analysis was performed.
Fst is related to the inbreeding coefficient (Fis),
which determines the proportional reduction of het-
erozygosity because of inbreeding, compared to the
population as a whole, and is expressed by the formula:
Fis = (Hs − HI)/Hs, where HI is the probability that a gene
in an inbred individual is heterozygous.
The statistical significance of differences in the level of deviation from Hardy-Weinberg equilibrium was
tested using the chi-square test (ɣ2).
Differences in aspects of genetic variation depending on origin were determined with the Kruskal–Wallis
test using Statistica ver. 9.0 (Stat Soft 2010).
RESulTS
Evaluation of seed production and seed quality
Average attributes of the seed production and seed
quality from the populations are presented in Table 3.
Seed performance was lowest in the Józefów population, whereas the highest performances were in those
from Międzyzdroje and Woziwoda. The average mass
of 1,000 seeds ranged from 5.49 to 6.60 g. The lowest
weight and embryo size were observed for seeds from
Białowieża, whereas the highest weight and embryo size
were in the population from Woziwoda, where the mean
length of the embryo was 3.04 mm and the width was
0.51 mm. Overall, the highest variation was exhibited
by attributes such as the average number of full seeds
Yield of seeds
per cone (%)
The mass of
a single cone (g)
The mean
number of seeds
in a cone
Mass of 1000
seeds (g)
Germination
capacity (%)
Energy of
germination (%)
Embryo length
(mm)
Embryo width
(mm)
Endosperm
length (mm)
Endosperm
width (mm)
Table 3. Mean performance indicators and statistic significant of seeding and seed quality
Bi
1.30
5.28
13
5.49
95.70
94.70
2.81
0.50
3.17
1.86
Bo
1.96
5.67
19
5.88
97.90
97.40
2.91
0.50
3.27
1.88
Origin
Jz
1.12
4.55
9
5.82
97.40
96.30
2.87
0.50
3.20
1.87
Mz
1.99
6.54
21
6.23
98.40
98.30
2.97
0.51
3.32
1.90
St
1.29
6.12
13
6.05
94.80
93.50
2.92
0.51
3.28
1.88
Wi
1.89
6.71
19
6.60
98.90
98.60
3.04
0.51
3.37
1.97
Mean
1.59
5.81
16
6.01
97.18
96.47
2.92
0.51
3.27
1.89
SD
0.40
0.82
4.68
0.38
1.60
2.04
0.08
0.01
0.07
0.04
V%
24.84
14.04
29.85
6.32
1.65
2.11
2.72
1.08
2.27
2.10
P-Value
0.0000
0.0000
0.0000
0.0001
0.0000
0.0000
0.0005
0.1599
0.0216
0.0146
Significance at the level of *** 0.001,
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
92
Paweł Przybylski, Katarzyna Masternak, Szymon Jastrzębowski
genetic distance of the Woziwoda population from all
the others (Tab. 4).
Białowieża
0.000
Bolesławiec
0.015 0.000
Józefów
0.016 0.011 0.000
Woziwoda
Strzałowo
Międzyzdroje
The mean number of alleles per locus ranged from 1.8
to 2.1. The highest mean number of alleles was found in
the population from Józefów, whereas the lowest was
in the population from Woziwoda. The highest effective number of alleles was observed in populations from
Strzałowo and Białowieża. The lowest values were observed in the population from Woziwoda. Heterozygosity (Ho) in the populations ranged from 0.24 to 0.32,
whereas the expected heterozygosity (He) was greatest
in populations from Strzałowo and Białowieża, with the
population from Józefów being the least variable despite
having the highest number of alleles (Fig. 2). In the populations from Józefów, Międzyzdroje and Strzałowo, an
excess of heterozygotes was demonstrated, but differences among all populations were not significant.
The highest degree of genetic variation was demonstrated between the Międzyzdroje and Woziwoda populations (Fst = 0.108). Populations from Białowieża and
Strzałowo were least divergent (Fst = 0.005) (Tab. 4).
The PCoA analysis (Fig. 3) for two main components of Fst (84.48% variability) indicates a significant
Białowieża
Variability and genetic variation of populations
Józefów
Table 4. Wright’s (1987) coefficient of genetic diversity (Fst)
Bolesławiec
in a cone, the yield of seeds per cone and average cone
mass. Significant (0.001–0.05) differences amongst genetic parameters such as Ne, Ho and He for the two origins were obtained for germinative capacity and energy.
Międzyzdroje 0.024 0.030 0.015 0.000
Strzałowo
0.005 0.020 0.023 0.036 0.000
Woziwoda
0.085 0.096 0.094 0.108 0.079 0.000
correlations between traits
There was a significant correlation between the mass
of seeds and the length of both embryo and endosperm
(r = 0.7). The average cone weight was positively correlated with the yield, the number of seeds per cone and
the mass of 1,000 seeds (r = 0.8). On the other hand, the
mass of 1,000 seeds and the dimensions of the embryo
and endosperm did not depend on the number of seeds
that were in cones or the yield of seeds per cone.
Table 5 shows the Spearman correlation coefficients amongst indicators of productivity, seed produc-
0.40
2.5
0.35
2.0
0.25
Mean
1.5
0.20
1.0
0.15
Heterozygosity
0.30
0.10
0.5
0.05
0
0
Strzałowo
Bolesławiec
Białowieża
Józefów
Międzyzdroje
Woziwoda
Na
Ne
No. Private Alleles
No. LComm Alleles (≤50%)
Na Freq. ≥ 5%
I
No. LComm Alleles (≤25%)
He
Figure 2. The average number of alleles (Na), effective number of alleles (Ne), Shannon index (I) and expected heterozygosity
(He)
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
−0.609
−0.500
−0.588
−0.677
−0.382
0.088
−0.088
−0.676
−0.600
−0.543
−0.486
−0.314
0.257
−0.257
−0.507
−0.942**
−0.886*
−0.828*
−0.714
−0.371
0.371
−0.507
−0.942**
−0.886*
−0.828*
−0.714
−0.371
0.371
−0.676
−0.600
−0.543
−0.486
−0.314
0.257
−0.257
−0.676
−0.371
−0.257
−0.257
−0.028
0.314
−0.31
−0.676
−0.600
−0.543
−0.486
−0.314
0.257
−0.257
−0.676
−0.600
−0.543
−0.486
−0.314
0.257
−0.257
93
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
Significance at the level of *** 0.001, ** 0.01 and * 0.05.
−0.845*
−0.486
−0.428
−0.600
−0.143
0.371
−0.371
0.338
0.486
0.600
0.371
0.485
0.028
−0.028
−0.507
−0.086
−0.200
−0.314
−0.028
0.828*
−0.828*
−0.607
−0.428
−0.543
−0.657
−0.371
−0.028
0.028
0.657
0.657
0.428
0.657
0.657
0.706
0.600
−0.657
0.143
0.657
0.657
0.657
0.428
0.657
0.657
0.706
0.600
−0.657
0.657
0.657
−0.714
0.657
−0.714
0.600
−0.542
0.657
−0.714
Endosperm
width
Endosperm
length
Embryo
width
Embryo
length
0.143
The quantity and quality of seeds produced have a significant influence on population’s stability and the
likelihood of breeding features being expressed. Scots
pine starts yielding good cone crops from the age of
35 years and produces seeds until death (Załęski 1995).
Pine seeds exhibit high germinative capacity, often
up to 100% (Załęski 1995). Mast years occur every
3–4 years, although some trees bear seeds every year
(Tyszkiewicz 1949). In our study, the mean individual
cone mass was 5.81 g, which was lower than the mean
cone mass of 6.30 g reported for Poland by Bodył and
Załeski (2005). Seed mass per 1,000 seeds from Polish
forests ranged from 4.0 to 8.5 g, averaging 6.2 g (Antosiewicz 1970). In the present study, 1,000-seed mass
averaged 6.01 g, similar to that found for the East European Plain (Mameav 1972). The embryo dimensions in
0.771
−0.657
Traits of cones and seeds
-
DIScuSSIOn
-
The mean number of alleles at a locus was negatively correlated with the average cone weight. Moreover,
a negative correlation between a population’s latitude of
origin and seed yield per cone and the average number
of seeds per cone was demonstrated. Geographic variation at the locus A of glutamate dehydrogenase was
confirmed (Tab. 5).
Latitude
Longitude
Germination
capacity
Germination
energy
Na
Ne
I
Ho
He
GA allel1
GA allel2
Figure 3. PCoA analysis of the variability of two main
components for the Fst of studied populations
The mass
Germination Germination
of 1000
capacity
energy
seeds
0.657
0.142
0.142
−0.714
-0.657
−0.657
Międzyzdroje
The number
of seeds
per cone
0.618
−0.883*
Woziwoda
Seed
yield per
cone
0.486
−0.828*
Józefów
Longitude
Strzałowo
Białowieża
Bolesławiec
Latitude
Principal Coordinates (PCoA)
Feature
tion, seed quality and geographic origin, as well as the
genetic variation of the studied Scots pine populations.
There is a strong negative correlation between germinative energy and capacity and measures of genetic variation, such as the effective number of alleles at a locus,
Shannon index and the observed heterozygosity.
Table 5. Spearman correlation coefficients amongst indicators of seed bearing efficiency, seed quality, location and the genetic variation of the investigated pine stands
Isozyme polymorphism and seed and cone variability of Scots pine (Pinus sylvestris L.)…
94
Paweł Przybylski, Katarzyna Masternak, Szymon Jastrzębowski
this study did not differ from mean values found for the
Polish climate. The mean length of the embryo in this
study was 2.92 mm, with a width of 0.51 mm and an
endosperm length of 1.89 mm. In comparison, the average embryo length in another study of Scots pine from
Poland is 3.02 mm, width is 0.52 mm and endosperm
length is 0.94 mm (Załęski 1995).
In this study, we did not observe a significant correlation between the geographical location of stands
and seed weight. This contradicts studies performed
for the entire range of the species (Staszkiewicz 1993;
Reich et al. 1994) that show decreased seed mass for
more northerly provenances. This probably results from
severe winters and low growing season temperatures.
According to Cherepnin (1964) and Pravdin (1969), the
weight of pine seeds may also depend on local habitat
and stand density.
Many positive correlations have been shown
amongst the seed size and mass with germinative capacity, germination energy (Cicek and Tilki 2007;
Singh and Sofi 2011) and also size and vigour of seedlings (Cicek and Tilki 2007; Gonzáles-Rodriguez et
al. 2011). We also showed significant relationships
between the seed mass and dimensions of the embryo
and endosperm. This correlation did not impact the
germinative energy or ability of seeds to germinate.
This confirms similar studies performed using Polish
pine populations (Załęski 1995). However, based on Jovanovic’s observation (1960), one-year-old black pine
seedlings (Pinus nigra Arn.) grown from larger seeds
exhibited greater seedling height, root length and dry
mass compared to those grown from smaller seeds.
Similar results were obtained by Vojčal (1961), who
examined the vigour of pine seedling growth. Consistent with Jovanovic (1960) and Vojčal (1961), Novoselce
(1968) observed a correlation between the pine seedling growth and seed weight. Studies have shown that
the germination of seeds less than 4 mg in weight was
only 12%, but when seeds weighed 5 mg, the germination was 83.8% (Novoselceva 1968). Novoselceva
(1968) pointed out that particularly large seedling size
was reached when pine seeds weighed more than 8 mg.
A detailed analysis of seed weight in relation to their
anatomy was conducted by Wrześniewski (1982). The
author showed a strong positive relationship between
the weight and dimensions of the embryo and endosperm. The dry matter of the seed coat, endosperm
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
and embryo increased proportionally with the weight
of the seeds, but their percentage contribution to the
dry mass of the seeds was almost the same in all weight
classes. The mean length of the embryo was smallest in
seeds with the lowest weight and increased proportionally with seed weight. For heavy seeds, the length of
the embryo was similar. In our research, we showed
significant relationships between the seed weight and
dimensions of the embryo and endosperm. Seed weight
did not affect seed germinative energy or capacity in
this study. Different results were obtained by Załęski
and Gozdalik (1994), who observed a significant correlation between the germinative capacity and germinative energy in pines, and the length of the embryo
and endosperm. Załęski and Gozdalik (1994) assumed
that embryos with a width of less than 0.46 mm suffer
significantly poorer germination. Owing to discrepancies in published results, additional research in this
field is important, because container seedling nurseries
require high seed quality. The application of the ‘one
seed – one seedling cell’ method requires that germination be close to 100%. Most research on the viability
of Scots pine seeds in Poland comes from the past century, with unfortunately no new publications known
concerning seed research in this country. Studies concerning seed properties must also take into account the
effects of climate change.
genetic variability of Scots pine populations
A lower number of alleles per locus was observed in
this study than that has been reported previously for
Scots pine populations in Europe, for example, PrusGłowacki and Stephan (1994) reported 2.77 alleles per
locus and Scaltsoyiannes et al. (2009) reported 2.48 alleles. The highest average number of alleles per locus
was reported by Kosińska et al. (2007). A lower number of alleles can occur if the sample size analysed is
small, because this reduces the likelihood of detecting
rare alleles. The high number of effective alleles for the
two populations from northeastern Poland is noteworthy. This region of Poland is important because of the
fact that Scots pine populations growing there have the
best-preserved genetic structure in the country. This
probably reflects the absence of planting of trees from
uncontrolled trade in tree seeds in the nineteenth century, which occurred commonly in the west and south
of Poland.
Isozyme polymorphism and seed and cone variability of Scots pine (Pinus sylvestris L.)…
Genetic variability (He) of the populations in this
study does not differ from the average for European Scots
pine populations analysed using similar loci (Burczyk
1990; Prus-Głowacki et al. 1993; Prus-Głowacki and
Stephan 1994; Scaltsoyiannes et al. 2009). Genetic variability in this study ranged from 0.5% to 10.8%, demonstrating that 90% of genetic variability is contained
within a single population, which is compatible with
the results obtained by other authors (Prus-Głowacki et
al. 1993; Goncharenko et al. 1994; Prus-Głowacki and
Stephan 1994; Hu and Li 2001; Kosińska et al. 2007).
This is typical for wind-pollinated conifers with a wide
geographic range (Loveless and Hamrick 1984). Attention should be paid to the fact that the highest genetic
variability was recorded for populations located in relatively close proximity to one another, whereas populations separated by greater distance were more closely
genetically related. It seems justified to suppose that
it is local climate that determines a given population’s
genetic structure, not distance from other populations.
According to our results, the crucial climate component
for Scots pine is the amount of rainfall during the growing season, because other climate factors for populations tested were not sufficiently discriminative.
The PCoA analysis performed for Fst provided significant separation of the populations in this study. The
Woziwoda population is separated from other populations, which agrees with the hypothesis that growing
season rainfall has strong effects on genetic variability.
Woziwoda receives significantly lower growing season precipitation than other locations in this study. It
should be noted that these results might be influenced
by a history of uncontrolled seed transfer in Poland in
the nineteenth century. However, evidence to support
this hypothesis is lacking.
Relationship of local growing conditions to seed
characteristics and genetic variation
The relationship between latitude and the frequency of
occurrence of alleles at the locus A of glutamate dehydrogenase was observed. This enzyme has strong
diagnostic importance for forest trees. For example,
for Picea abies, its variability is considered because of
a history of long-term isolation in refugia that had different environments. Locus Gdh-A in spruce is characterised by high polymorphism in northeastern Europe;
however, in the southern part of the range, this locus
95
is practically monomorphic (Gömöry 1992; Lewandowski and Burczyk 2002). A similar result was described by Fourier and Adams (1986), who confirmed
that there are differences in the frequencies of alleles at
the locus A of glutamate dehydrogenase in Pinus jefferyi. These differences seemed to be a consequence
of adaptation of P. jefferyi to ultramafic soils. Fourier
and Adams (1986) argued, however, that the adaptation of plants to soil conditions is not associated with
latitude or longitude of the geographical location, but
with non-clinal features of the ecosystem. Therefore,
the geographical selection of locus A of glutamate dehydrogenase depends on stand adaptation to local environmental conditions, as demonstrated for P. abies
(Gömöry 1992; Lewandowski and Burczyk 2002). This
is supported by the metabolic function of glutamate dehydrogenase, which catalyses the synthesis of glutamic
acid, that incorporates ammonium ions. Damage to
this mechanism or its reduced effectiveness may lead
to the accumulation of excess ammonia in plant cells
and, consequently, lead to the death of trees. Glutamate
dehydrogenase is also closely related to the availability
of zinc. In order to explain the observed genetic variation in glutamate dehydrogenase, additional studies on
a larger number of populations should be conducted,
which should include soil analyses.
Germinative capacity and energy decreased with
increased heterozygosity of the populations. This phenomenon has been seen previously in pine (Goncharenko et al. 1994) and was described for Pinus ponderosa
(Hu and Li 2001), Pinus radiata (Kosińska et al. 2007)
and Pinus sylvestris (Loveless et al. 1984). It is possible
that the reduction in the frequency of heterozygotes is
related to the elimination of allele forms that are not
adapted to a particular environment. Previous research,
however, compared mature trees with young stands,
whereas our study shows that selection occurs during
seed formation. In particular, in the case of the population from Białowieża, the diverse genetic structure of
the parent stand will not be passed on to subsequent
generations, because of poor seed production.
These results show negative relationships between
germinative energy and capacity and the effective number of alleles. In this context, we note the age of the
analysed stands and the high probability that they originated from trees that had previously grown on the same
area, so that selective pressure affected the gene pool.
Folia Forestalia Polonica, Series A – Forestry, 2020, Vol. 62 (2), 88–99
96
Paweł Przybylski, Katarzyna Masternak, Szymon Jastrzębowski
On the other hand, selective factors favour homozygotes in specific loci, preserving positive adaptations
(Whitlock 2002). The results might also be interpreted
as being a consequence of the decrease of seed mass
and germinative energy in pines in more northerly locations, which was not found in the present research. This
phenomenon was also described by Cherepnin (1964)
and Pravdin (1969).
cOncluSIOnS
Variability in seed traits and isozymes in six Scots pine
populations in this study is representative for the entire range of the species in Poland. Despite significant
geographical distance amongst the studied populations,
the main site environmental differences are mainly the
amount of rainfall received during the growing season.
Published information suggests that other environmental factors in Poland do not sufficiently differ between
the studied populations to exert an influence on population variability.
The results of seed analysis confirm the expected correlation between seed mass and embryo size,
although size did not impact germination. Instead, the
results indicated a higher effective number of alleles
in northeastern populations, compared to other populations; at the same time, northeastern populations are
characterised by lower germinative energy and capacity. In the present study, there was no direct link between
geographical distance and genetic variability. On the
other hand, based on the PCoA analysis for Fst, as well
as climates maps, we hypothesise that rainfall during
the growing season creates selective pressure affecting
the genetic variability of Scots pine.
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