ANALYSIS OF INTRAPOPULATION VARIABILITY OF BALD CYPRESS ( Taxodium disTichum L . RICh . ) IN A SEED STAND NEAR BAČKA PALANKA USING MORPhOMETRIC MARKERS

In this paper are presented the results of an analysis of intrapopulation variability using morphometric markers of 20 Bald cypress test trees originating from seed stand S 01.10.01.01 near Bačka Palanka. The morphometric characters of cones (length, width and number of grains) and seedlings (root collar diameter and height of seedling) that were produced by this seed were analyzed. A mutual biological similarity or distance of mother trees depending on the analyzed characters was tested. The determined values of the dimensions of cones and seedlings indicate the good genetic and adaptive potential of this species, which can be a starting point for the mass production of Bald cypress seed and planting materials in Serbia.


INTRODUCTION
The Bald cypress is a monoecious, long-lived, deciduous conifer.It belongs to the family Taxodiaceae and genus Taxodium that includes three species (Vukićević, 1987).In Serbia, there is only Taxodium distichum (L.) Rich.The capability of the Bald cypress to establish forest cultures on lowlands and floodplains in Serbia was recorded in the 1950s (Petrović, 1951;Špiranec, 1959, 1966).At the beginning of the 1980s, Stilinović and Tucović (1970) concluded that in our environmental conditions, the Bald cypress could be considered as a species that exhibits rapid growth and one of the few conifer species that may be suitable for introduction on lowland and floodplains where it can achieve high productivity.
On the territory of the Republic of Serbia, this species has practically never been out of the range of horticultural activities.Researches on the variability and adaptive potential of the Bald cypress in our conditions published to date refer to trees that grow individually and in smaller or larger groups mainly in the city green areas (Dražić, Batos, 2002;Ninić-Todorović, Ocokoljić, 2001, 2002;Tucović, Ocokoljić, 2005).The possibility of a wider application of Bald cypress as a forest species should be based on an assessment of its genetic and adaptive potential, as well as quantity and quality of yield, primarily at the level of the existing Bald cypress seed stand.

MATERIALS AND METHODS
Research was conducted in a Bald cypress seed stand in Bačka Palanka, registration number S 01.10.01.01, which is managed by FE Novi Sad, FA Bačka Palanka.The seed stand is within the MU "Palanačke Ade -Čipski poloj", Department 11, Sec-tion a, with an area of 0.22 ha and 111 trees.Its origin is artificial, aged about 70 years, with measured taxation values of mean diameter ds = 51.7 cm and mean height, hs = 26.5 m.It is located on flat ground with an average altitude of 80 m, with a uniform slope and without clear exposure.Flooding is not present, but it is heavily influenced by underground wetting.The site on which the seed stand is located belongs to the coeno-ecological group of White willow and Populus (Salicion albae) forests on undeveloped semi-gley soils.
On the basis of phenotypic characteristics and abundance of yield in 2010, 20 test trees were selected and 200 cones were collected from each tree.The cones were placed in separate bags.By the method of random sampling, 50 cones per tree were taken for processing at the laboratory of Institute of Forestry.Cone opening was done in a dryer at a temperature of 40°C, and seed cleaning was done manually.The basic morphometric parameters of each cone (length and width) were measured by a caliper with an accuracy of 1 mm.In addition, after cone opening the number of grains was determined for each cone.
In April 2011, seed sowing was performed in 12 Bosnaplast containers, with 10 containers for each test tree.In October 2011, by the method of random sampling, 50 seedlings per each half-sib line were selected and the height and root collar diameter were measured for each of them.Measurements were made by a caliper with an accuracy of 1 mm in the measurement of height, and 0.01 mm in the measurement of root collar diameter.
The obtained data were processed in a computer program Statgraph 5.0.

Cones and seeds
The variability in cone morphometric characters of 20 Bald cypress test trees is presented on Table 1.
Based on the statistical indicators (Table 1), it can be concluded that the highest mean value of cone length is shown by the test tree marked number 1 (31.56 mm), while the smallest mean value of cone length is tree 11 (28.41 mm).The highest mean value of cone width is that of tree 1 (28.67 mm) and the smallest mean value of cone width is that of tree 11 (25.27mm).The highest mean value in the number of grains is that of tree 1 (28.5 pieces), and the smallest mean value in the number of grains is that of tree 15 (25.2 pieces).Tree 1 stands out as the best for all three characters, while tree 11 has the smallest mean value of cone length and width, but not number of grains.The values of the analyzed characters coincide with the values that were obtained by other authors.In the Bald cypress from the Motovun forest in Croatia, the cone diameter ranges from 20 to 25 mm; one cone contained from 18 to 30 grains (Špiranec, M. 1959.).Under Belgrade's environmental conditions, cone diameter range from 20 to 30 mm (Dražić, D., Batos, B. 2002).Under the environmental conditions of Bulgaria, cone diameters go up to 30 mm, cone lengths range from 20 to 40 mm, and cones contain approximately 20 to 25 grains (Milev, M., et al. 1999).In the Bald cypress population on the Veliko Ratno ostrvo island, cone diameters range from 22 to 39 mm; cones contain from 10 to 32 grains and on average about 20 grains (Šijačić-Nikolić, M., et al. 2011.).In its natural habitat, the Bald cypress reaches a cone diameter of 25 mm, and cones contain up to 30 grains.(Harvey, E., Kennedy, Jr. 1972).
The coefficient of variation can be used as an indicator of statistical set homogeneity.By analyzing the values of this coefficient, we can conclude that for the cone length character the most homogeneous is tree 16 (7.76),and the most heterogeneous tree no.7 (20).For the cone width character, the most homogeneous is tree 20 (6.25), and the most heterogeneous is tree 9 (23.95).For the number of grains, the most homogeneous is tree no. 1 (5.28), and the most heterogeneous is tree 8 (14.82).
Analysis of variance shows that the differences between the mean values of cone width of the 20 Bald cypress test trees are statistically significant at the confidence level p <0.05.The examined trees were grouped into 5 homogenous groups and this confirmed the variability of cone width of the trees.
In the homogeneous group with the greatest cone width are trees 1 and 2, and in the group with the smallest cone width are trees 11 and 16 (Table 2).
Analysis of variance shows that the differences between the mean values of cone length of the 20 trees are statistically significant at a confidence level p<0.05.The trees are grouped into 5 homogenous groups, confirming the variability of the trees' cone lengths.In the homogeneous group with the greatest cone length are trees 1, 2 and 5, and in the group with the smallest cone length are trees 11, 15 and 13 (Table 2).
Analysis of variance shows that the differences between the mean values in the grain numbers of the 20 Bald cypress trees are statistically significant at the confidence level p<0.05.The trees are grouped into 9 homogenous groups, confirming the variability in the numbers of grains.In the homogeneous group with the greatest number of grains are trees 1, 4 and 3, and in the group with the smallest number of grains are trees 15, 8 and 10 (Table 2).
Based on cone length, cone width and number of grains, cluster analysis was performed for all three observed characters together (Fig. 1).With this analysis we tested the mutual biological similarity or distance of these three characters.We concluded that the greatest distance was between trees 1 and 3, while the shortest distance was between trees 8 and 10.

Seedlings
In Table 3 is shown the variability of morphometric characters of one-year-old seedlings at the level of 20 half-sib lines of Bald cypress.
Based on the statistical indicators (Table 3), it can be concluded that the highest mean value for the root collar diameter was that of the half-sib line number 1 (4.23 mm), while the smallest mean value was that of half-sib line 3 (3.36mm).The highest mean value for seedling height has the half-sib line number 6 (52.1 mm), and the smallest mean value has the half-sib line number 2 (40.7 mm).The values of the analyzed characters, root collar diameter and height of seedling, coincides with the values that were obtained by other authors.The results of Vann Graph 1 -Dendrograms of cluster analysis for 20 test trees based on the cone characters and Megonigal, (2002) show that one-year-old seedlings attain a height of about 50 cm and a diameter of about 4 mm.Mazher et al. (2006) stated that oneyear-old Bald cypress seedlings attain heights up to 35 cm.By analyzing the coefficients of variation as indicator of statistical set homogeneity, we conclude that for the root collar diameter, the most homogeneous is the half-sib line 6 (13.1302), and the most heterogeneous is the half-sib line 7 (26.5335).For seedling height, the most homogeneous is the half-sib line 1 (10.9613), and the most heterogeneous is the half-sib line 7 (24.6596).
Analysis of variance shows that the differences between the mean values of root collar diameter of 20 Bald cypress half-sib lines are statistically significant at a confidence level p<0.05.Half-sib lines are grouped into 6 homogenous groups, confirming the variability of the root collar diameters in the half-sib lines.In the homogeneous group with the greatest root collar diameter are half-sib lines nos. 1, 15, 20, 17, 10, 13, 6, 16 and 14, and in the group with the smallest root collar diameter are half-sib lines 3, 5, 19, 2 and 18 (Table 4).
Analysis of variance shows that the differences between the mean values of seedling height in half-sib lines are statistically significant at a confidence level p <0.05.Half-sib lines are grouped into 10 homogenous groups and this confirmed the variability of seedling heights in the half-sib lines.In the homogeneous group with the greatest seedling height are half-sib lines 6, 10, 14, 17, 15, 7, 20 and 1, and in the group with the smallest seedling height are half-sib lines 2, 18, 5, 3, 19 and 8 (Table 4).
Based on the root collar diameter and seedling height, cluster analysis was performed for both observed characters together (Fig. 2).The mutual biological similarity or distance regarding these two characters was tested.It was concluded that the greatest distance was between half-sib lines 1 and 5, while the shortest distance was between half-sib lines 9 and 11.Variability in the quantity and quality of the yields of more important tree species has been the subject of research in forest science and profession for some time.However, examination of the genetic variability of the quantity and quality of forest trees seed yields, and the possibility of its optimal use in our country is still below actual needs, and is not in accordance with commercial importance.Thanks to the research results of Tucović, A. (1975), Mrva, F. (1976Mrva, F. ( , 1984)), Popnikola, N. (1978), Tucović, A., Stilinović, S. (1982), Tucović, A., Isajev, V. (1985), Isajev, V. (1987), Tošić, M. (1991), Mataruga, M. (2003), Lučić, A. (2007), Lučić, A. (2012) etc., our knowledge is gradually completing, and the relationships between the genetic constitution of populations and environmental conditions has been explained, as well as the morphological and physiological characters of the seeds.
The results obtained from the analysis of variability of morphometric characteristics of cones in 20 test trees and one-year-old seedlings of 20 half-sib lines of Bald cypress originating from a seed stand near Bačka Palanka, have contributed to a better understanding of the relationships of the analyzed characters, as well as of the influence of the analyzed characters on the differentiation of the test trees.Based on these results, differences were observed in the values of the characters for each test tree individually.Tree no. 1 stands out with the highest value for all three observed characters; tree 11 has the smallest value for the characters cone length and cone width, while the smallest value for the number of grains is that of tree 15.When it comes to the seedlings, the greatest values for the character root collar diameter is that of the half-sib line 11, while the smallest values are those of the seedlings of half-sib line 3.The greatest values for the character seedling height are those of the seedlings of the half-sib line 6, while the smallest values are those of the seedlings of half-sib line 2.
Comparative analysis of the obtained results in the study of the variability of the morphometric characters of cones, seeds and seedlings of the Bald Graph 2 -Dendrograms of cluster analysis for 20 half-sib lines based on the seedling characters.cypress suggests that there is considerable intrapopulation variability that is directly dependent on the type of analyzed character.This suggests that the obtained results need to be supplemented and verified using genetic methods that are based on the use of biochemical and molecular markers.

Table 1 .
-Variability in cone morphometric characters of 20 tested Bald cypress trees.

Table 2 -
Analysis of variance for cone width, cone length and number of grains.

Table 3 -
Variability of morphometric characters of one-year-old seedlings at the level of 20 half-sib lines of Bald cypress.

Table 4 -
Analysis of variance for root collar diameter and height of seedlings.