The sweet chestnut (
The species is thought to have survived in several refuges during the last ice age in southern Europe, northeastern Turkey and the Caucasus (Pereira-Lorenzo et al. 2010; Lang et al. 2007; Conedera et al. 2004).
In Bosnia and Herzegovina, this species has a small disjunctive areal. It can be found in the northwestern part (around Cazin, Velika Kladuša, Bužim, Bosanska Kostajnica), south (Neretva and Rama valleys, around Jablanica, Konjic, Prozor, Mostar and Trebinje) and northeastern part (around Srebrenica, Goražde and Bratunac).
There are not much studies on this species in Bosnia and Herzegovina so far. Mujić et al. (2010) and Skender (2010) studied pomological traits, Mujić et al. (2006) researched chemical composition of the fruit, Treštić et al. (2009) studied diseases, and Mujagić-Pašić and Ballian (2012, 2013a, 2013b), Ballian et al. (2012–2013), Daničić et al. (2018) and Tuğ et al. (2020) researched morphological traits.
Several authors used correlation analysis to determine the correlation among traits of sweet chestnut. Atar and Turna (2018) obtained high values of correlation coefficient for fruit traits from eight natural populations of sweet chestnut in Turkey. Grygorieva et al. (2018) investigated 28 genotypes of sweet chestnut in Ukraine in a sample of 800 fruits. The obtained results indicated a high correlation of the investigated traits. Also, Serdar et al. (2006) researched the width, length and surface of leaves in sweet chestnut populations in Turkey. The obtained results showed a high correlation among these leaf traits. Ertan (2007) found significant correlations among the pomological traits of fruits and among the characteristics of leaves of the sweet chestnut populations in western Turkey. Yıldız et al. (2009) studied the correlations among length, width, thickness and weight of the chestnut fruit from the populations of the Black Sea region of Turkey and found correlations among them. There have been no studies on the correlations among the morphological traits of fruits, leaves and cupules of sweet chestnut in Bosnia and Herzegovina so far.
This research aims to determine the correlation of the analysed morphological traits in a significant Bosnia–Herzegovinian sweet chestnut population. It is expected that the results of this research would contribute to the knowledge of morphological traits of sweet chestnut in Bosnia and Herzegovina and help in the choice of activities for the selection, breeding and protection of its indigenous gene pool.
Within the natural populations of sweet chestnut (
List of researched subpopulations
Location | Subpopulation label | Longitude | Latitude | Altitude (m) |
---|---|---|---|---|
Vrnograč (Velika Kladuša) | V1 | 45°10′11″ | 15°56′07″ | 268.80 |
V2 | 45°09′56″ | 15°58′13″ | 262.10 | |
V3 | 45°09′54″ | 15°58′12″ | 252.10 | |
V4 | 45°10′06″ | 15°58′13″ | 258.60 | |
V5 | 45°10′02″ | 15°58′19″ | 285.20 | |
Zaradostovo (Bužim) | B6 | 45°04′44″ | 16°03′42″ | 282.60 |
B7 | 45°04′44″ | 16°03′53″ | 271.10 | |
B8 | 45°04′40″ | 16°03′43″ | 319.60 | |
B9 | 45°04′35″ | 16°03′38″ | 323.30 | |
Gornja Koprivna (Cazin) | C10 | 44°58′47″ | 15°57′35″ | 503.00 |
C11 | 44°58′44″ | 15°57′40″ | 490.10 | |
C12 | 44°58′49″ | 15°57′39″ | 484.10 | |
C13 | 44°58′59″ | 15°57′45″ | 498.80 | |
C14 | 44°59′08″ | 15°57′46″ | 486.40 | |
Ck15 | 44°58′52″ | 15°57′41″ | 498.60 | |
Ck16 | 44°58′47″ | 15°57′35″ | 492.00 |
In this research, the following traits of sweet chestnut fruits were measured: fruit length (FL; in mm), fruit width (FW; in mm), fruit thickness (FT; in mm), hilum width (HW; in mm), hilum length (HL; in mm) and fruit weight (FWG; in g). The following traits were assessed according to the international descriptor for sweet chestnut (UPOV, 1989): fruit shape (FS); fruit embryony (FE) and penetration of seed coat into embryo (PSCiE). The following parameters were calculated (according to the method given by Furonez-Pérez and Fernández-López 2009): FL/FW ratio, relative size of the hilum (RSH): HW × HL.
FWG was measured in a fresh condition immediately after fruit collection, using an analytical balance with an accuracy of 0.01 g. Other traits were measured using a digital caliper with an accuracy of 0.01 mm.
The following traits of sweet chestnut leaves were measured: leaf blade length (LBL; in mm), leaf blade width (LBW; in mm) and leaf petiole length (LPL; in mm). The following traits were assessed according to the international descriptor for sweet chestnut (UPOV, 1989): leaf blade shape (LBS) (sharp, blunt, serrated) and leaf edge shape (LES) (mucronate, dentate). The following parameters were calculated according to method given by Serdar et al. (2011): total leaf length (TLL) (TLL = LBL + LPL), LBW/LBL ratio and LBW/TLL (blade + petiole).
Measurements were performed using a graph paper with an accuracy of 1/10 mm.
The following traits of sweet chestnut cupules were measured: cupule width (CW; in mm) and cupule height (CH; in mm). The following traits were assessed according to the method given by Pereira-Lorenzo (1996): needle length (NL) (long, medium, short) and number of fruits in cupule (NfiC). The following parameters were calculated according to the method given by Serdar et al. (2011): relative size of cupule (RSC) (CW × cupule height CH).
The measurement of these traits was performed using a digital caliper with an accuracy of 0.01 mm.
A linear correlation was calculated using Pearson correlation coefficient
In this paper, the investigated traits of fruits, leaves and cupules of sweet chestnut were analysed to determine the existence or absence of significant correlations and to find whether the regression factor was positive or negative at the level of significance (Sig. < 0.0001) for most analysed traits.
The correlation coefficient (
Correlation coefficients and labels of significant differences for the fruit traits
Variables | FL | FW | FT | HW | HL | FWG | FS | FE | PSCiE | FL/FW | RSH |
---|---|---|---|---|---|---|---|---|---|---|---|
FL | 1 | 0.766**** | 0.567**** | 0.557**** | 0.531**** | 0.794**** | −0.173**** | 0.007 | −0.006 | 0.139**** | 0.575**** |
FW | 1 | 0.617**** | 0.666**** | 0.725**** | 0.877**** | −0.054*** | −0.014 | −0.029 | −0.521**** | 0.734**** | |
FT | 1 | 0.651**** | 0.582**** | 0.796**** | −0.120**** | −0.031 | −0.042* | −0.198**** | 0.652**** | ||
HW | 1 | 0.723**** | 0.699**** | −0.047** | −0.012 | −0.033** | −0.278**** | 0.923**** | |||
HL | 1 | 0.694**** | −0.009 | −0.012 | −0.028 | −0.403**** | 0.915**** | ||||
FWG | 1 | −0.103**** | −0.023 | −0.045** | −0.290**** | 0.748**** | |||||
FS | 1 | 0.070**** | 0.418**** | −0.149**** | −0.033** | ||||||
FE | 1 | 0.133**** | 0.030 | −0.015 | |||||||
PSCiE | 1 | 0.035* | −0.033** | ||||||||
FL/FW | 1 | −0.351**** | |||||||||
RSH | 1 |
FL, fruit length; FW, fruit width; FT, fruit thickness; HW, hilum width; HL, hilum length, FWG, fruit weight; FS, fruit shape; FE, fruit embryony; PSCiE, penetration of seed coat into embryo.
The correlation coefficient (
Correlation coefficients and labels of significant differences for the leaf traits
Variables | LBL | LBW | LPL | LBS | LES | TLL | LBW/LBL |
---|---|---|---|---|---|---|---|
LBL | 1 | 0.616**** | 0.294**** | −0.035 | −0.001 | 0.989**** | −0.366**** |
LBW | 1 | −0.177**** | 0.036 | −0.012 | 0.553**** | 0.492**** | |
LPL | 1 | −0.041 | −0.114**** | 0.434**** | −0.527**** | ||
LBS | 1 | 0.185**** | −0.039 | 0.083 | |||
LES | 1 | −0.019 | −0.022 | ||||
TLL | 1 | −0.427 | |||||
LBW/LBL | 1 |
LBL, leaf blade length; LBW, leaf blade width; LPL, leaf petiole length; LBS, leaf blade shape; LES, leaf edge shape; TLL, total leaf length.
Leaf traits which had a low value of the correlation coefficient (around zero) were LES and LBL (
Table 4 shows the correlation coefficients (
Correlation coefficients and labels of significant differences for the cupule traits
Variables | CW | CH | NfiC | NL | RSC |
---|---|---|---|---|---|
CW | 1 | 0.750**** | 0.613**** | −0.042 | 0.916**** |
CH | 1 | 0.508**** | 0.076** | 0.935**** | |
NfiC | 1 | −0.069* | 0.584**** | ||
NL | 1 | 0.007 | |||
RSC | 1 |
CW, cupule width; CH, cupule height; NfiC, number of fruits in cupule; NL, needle length.
The correlation coefficient (
Correlation coefficients and labels of significant differences for the traits of fruit and leaf
Variables | LBL | LBW | LPL | LBS | LES | TLL | LBW/LBL | LBW/TLL |
---|---|---|---|---|---|---|---|---|
FL | −0.070 | −0.178 | 0.225 | 0.011 | −0.080 | −0.031 | −0.131 | −0.165 |
FW | −0.092 | −0.186 | 0.211 | 0.008 | −0.062 | −0.053 | −0.119 | −0.153 |
FT | −0.073 | −0.156 | 0.161 | −0.001 | −0.033 | −0.043 | −0.107 | −0.131 |
HW | −0.079 | −0.167 | 0.170 | 0.030 | −0.023 | −0.048 | −0.113 | −0.140 |
HL | −0.099 | −0.187 | 0.171 | 0.014 | −0.057 | −0.066 | −0.113 | −0.143 |
FWG | −0.060 | −0.170 | 0.215 | 0.002 | −0.031 | −0.023 | −0.133 | −0.163 |
FS | −0.024 | −0.001 | −0.040 | −0.053 | 0.039 | −0.029 | 0.015 | 0.019 |
FE | −0.022 | −0.039 | −0.008 | −0.037 | 0.001 | −0.022 | −0.015 | −0.014 |
PSCiE | −0.002 | −0.044 | 0.070 | −0.007 | −0.043 | 0.010 | −0.055 | −0.062 |
FL/FW | 0.046 | 0.050 | −0.029 | 0.006 | −0.012 | 0.039 | 0.011 | 0.020 |
RSH | −0.086 | −0.182 | 0.180 | 0.025 | −0.030 | −0.053 | −0.122 | −0.151 |
FL, fruit length; FW, fruit width; FT, fruit thickness; HW, hilum width; HL, hilum length, FWG, fruit weight; FS, fruit shape; FE, fruit embryony; PSCiE, penetration of seed coat into embryo; LBL, leaf blade length; LBW, leaf blade width; LPL, leaf petiole length; LBS, leaf blade shape; LES, leaf edge shape; TLL, total leaf length.
Table 6 shows the correlation coefficients (
Correlation coefficients and labels of significant differences for the traits of fruit and cupule
Variables | CW | CH | NfiC | NL | RSC |
---|---|---|---|---|---|
FL | −0.087 | −0.020 | −0.077 | 0.134 | −0.052 |
FW | −0.040 | 0.009 | −0.031 | 0.210 | −0.013 |
FT | −0.053 | 0.034 | −0.058 | 0.180 | −0.007 |
HW | −0.016 | 0.027 | −0.055 | 0.174 | 0.018 |
HL | −0.012 | 0.002 | −0.051 | 0.181 | −0.001 |
FWG | −0.062 | −0.004 | −0.051 | 0.192 | −0.032 |
FS | 0.067 | −0.030 | 0.023 | 0.153 | 0.013 |
FE | −0.046 | −0.025 | −0.025 | −0.042 | −0.033 |
PSCiE | −0.007 | −0.069 | −0.016 | 0.074 | −0.040 |
FL/FW | −0.067 | −0.056 | −0.063 | −0.138 | −0.064 |
RSH | −0.022 | −0.002 | −0.057 | 0.177 | −0.004 |
FL, fruit length; FW, fruit width; FT, fruit thickness; HW, hilum width; HL, hilum length, FWG, fruit weight; FS, fruit shape; FE, fruit embryony; PSCiE, penetration of seed coat into embryo; CW, cupule width; CH, cupule height; NfiC, number of fruits in cupule; NL, needle length.
The correlation coefficients (
Correlation coefficients and labels of significant differences for the traits of leaf and cupule
Variables | LBL | LBW | LPL | LBS | LES | TLL | LBW/LBL | LBW/TLL |
---|---|---|---|---|---|---|---|---|
CW | 0.028 | 0.023 | −0.081 | −0.028 | 0.025 | 0.017 | 0.003 | 0.015 |
CH | −0.008 | −0.009 | −0.024 | −0.036 | −0.046 | −0.010 | −0.001 | 0.002 |
NfiC | 0.031 | 0.064 | −0.061 | −0.007 | 0.022 | 0.022 | 0.045 | 0.054 |
NL | −0.036 | −0.019 | −0.143 | 0.021 | −0.015 | −0.052 | 0.000 | 0.017 |
RSC | 0.014 | 0.010 | −0.063 | −0.031 | −0.002 | 0.006 | −0.002 | 0.008 |
CW, cupule width; CH, cupule height; NfiC, number of fruits in cupule; NL, needle length; LBL, leaf blade length; LBW, leaf blade width; LPL, leaf petiole length; LBS, leaf blade shape; LES, leaf edge shape; TLL, total leaf length.
This paper presents the correlations between the investigated traits of fruit, leaf and cupule of sweet chestnut (
Atar and Turna (2018) studied the correlation of the traits of sweet chestnut fruit from eight natural populations (Adapazarı, Artvin, Aydın, Balıkesir, Bartın, Izmir, Kütahya and Sinop) in Turkey. They analysed four characteristics of the fruit: FL, FW, FT and shape of the fruit (length/width ratio). For the FL/FW ratio, they found a high value of the correlation coefficient, which varied between 0.8 and 0.9. Also, a statistically significant positive correlation was found at a significance level of 99% between the length, width, thickness and weight of 1,000 fruits.
Grygorieva et al. (2018) investigated 28 genotypes of 30-year-old sweet chestnut trees in Ukraine, which were produced from seeds from the Czech Republic, the Carpathians and Kyrgyzstan. In a sample of 800 fruits, the traits of fruit mass, FL, FW and FT, and HL and HW were measured. The obtained results indicated a high correlation between the following investigated traits: FW and FL (
The most significant conclusion of this study is the high value of correlation coefficients for the traits of FL, FW, FT and FWG, HL and HW, leaf lamina length and width, TLL, CW and CH, and NfiC. Also, mutual correlations of traits of fruit, leaf and cupule showed statistically significant correlation values. Statistically most significant correlations were found between the measured fruit traits with leaf lamina width, LPL and NL on the cupule. High and statistically significant values of the correlation coefficient for the traits of NfiC and the length of the needles with the traits of leaf lamina width and petiole length were also observed. The highest positive correlation was shown by the measured traits of the fruit, and they can be used in further selection and breeding of this species in Bosnia and Herzegovina. The exception is the trait of FE, which was not statistically significantly related to other investigated traits of the fruit, and therefore, does not represent an important indicator of genetic variability of the studied populations. Since this is the first correlation analysis of the traits of the fruit, leaf and cupule of sweet chestnut in Bosnia and Herzegovina, it is necessary to expand the research to a larger number of samples in different habitats to draw more concrete conclusions.
The correlated traits can be distinguished as important for further selection and breeding of sweet chestnuts. The research results indicate that the genetic material of sweet chestnut is a rich source of genetic diversity and can be used in selection to obtain new varieties and cultivars in Bosnia and Herzegovina and for the protection of the indigenous gene pool.