Биолошке и производне карактеристике популација дивљег кестена (Aesculus hippocastanum L.) секундарног порекла / Biological and production characteristics of horse chestnut (Аesculus hippocastanum L.) secondary populations

Horse chestnut (Aesculus hippocastanum L.) is endemic to the southern part of the Balkan Peninsula. It is a very interesting deciduous species for the study of secondary populations thriving on green spaces in Serbia, as well as a valuable source for the production of planting material for horticulture and landscape architecture. The study aim is identification of horse chestnut genotypes from secondary populations developed on the green spaces of Vojvodina in a form of alleys, as individual trees or in group formations. Criteria for genotype evaluation as a horticultural seed resources are based on the work of Stilinović and Tucović (1977). Biological characteristics of genotypes should provide focus for the production criteria of quality horse chestnut planting material, adaptability to urban environment conditions and res Genotypes BDS1 and BDS2, in the three-year observation period, were characterized by significantly earlier occurrence of leafing and flowering phases, while the genotypes BP4, SK4 and SK7 exhibited later onset of both phases. Experimental trees, as separate seed sources for the use in horticulture and landscape architecture, produced regular and abundant yield. Based on the morphological seed characteristics, genotypes P6 (with high values for length /29.83 mm/, width /35.56 mm/ and thickness /30.92 mm/ and P3 (with high values for weight of seeds /17.63 g/) could be singled out. Seeds for the needs of nursery production were stored in a cold chamber in controlled conditions, at a temperature of 4 to 6 °C. Sowing was carried out in the spring. The seed material of 17 genotypes, in the three-year period, exhibited very high field germination rate, averaging from 80.94% to 85.64%. Seedling percentage survival, determined at the end of the vegetation period and the beginning of a successive vegetation stage, ranged from 78.96% to 82.98%. By measuring the growth indicators of one-year-old seedlings, average values for tree height (12.26 cm), root collar diameter (10.04 mm), root length (12.87 cm), tree weight (3.62 g), root mass (5.34 g), and number of I order roots (26.49) were determined. BDS1 genotype could be distinguished due to the high values of measured indicators (19.20 cm for height, 17.51 cm for root length, 4.40 g for tree weight and 6.80g for root mass). According to the growth indicators of two-year-old seedlings, genotypes BDS1, BDS2 and SK4 could be singled out based on height (30.20cm, 35.80 cm and 35.68 cm). The highest tree base diameter values were measured for genotypes BDS1 (19.20 mm) and BDS2 (19.33 mm). The average value of the above-ground height and tree base diameter for the three-year-old plant genotypes were 81.45 cm and 26.81 mm, respectively. In the third year of the horse chestnut seedling in situ development in the Rimski Šanĉevi nursery, maximum values for height and tree base diameter were found for genotypes BDS1 (92.00 cm and 29.55 mm), BDS2 (90.80 cm and 31.27 mm) and SK4 (91.30 cm and 28.45 mm). Two-year-old seedling growth rate distinguished genotypes BDS1, BDS2 and SK4, which also exhibited a remarkable growth in the third year of development in nursery. On two- and three-year-old seedlings of genotypes BP4, BP5, BDS1, BDS2, P5, P6, SK1 and SK4, grafting of red chestnut hybrid was performed. Scion-rootstock compatibility was evident, and the average graft uptake was 82.36%. The applied English grafting technique produced good results, as a vegetative technique for red chestnut hybrid planting material production. From the seed extract of these horse chestnut genotypes, 16 fatty acids were isolated and determined. A high proportion of unsaturated fatty acids, oleic in particular, was noted. The highest content was found in the seeds of genotype BDS1 (59.10%). Genotypes P5 and SK1 are characterized by the highest values of quercetin (0.538 µg/g and 0.806 µg/g, respectively) and kaempferol (0.227 µg/g and 0.429 µg/g, respectively), while high levels of rutin were also found in genotype P5 (25.784 µg/g). Escin was present in the seeds of all tested genotypes, with the highest average content in the seeds of genotypes BP2 and P5 (4,04%). In the seed sample, heavy metal analysis revealed a high average zinc (10.11 µg/g) and copper (9.23 µg/g) content. The P5 genotype can be distinguished due to the highest average seed content of aluminum (2.88 µg/g) and chromium (0.1 µg/g), while the highest values of copper (13.0 µg/g), iron (13.2 µg/g), manganese (3.2 µg/g), nickel (0.8 µg/g) and zinc (18.1 µg/g) were recorded in the seeds of genotype P1. In the soil samples taken along the Bulevar Jaše Tomića in Novi Sad, lined by horse chestnut trees, soluble salts and heavy metals were identified. Average salt content values in the samples probed in April were 0.10% and 0.11%, at the 0-30 and 30-60 cm depth, respectively, which is below the established upper limit. The soil samples probed in August 2012 had higher than allowed content, owing to the ascending salt movement due to drought. As a consequence of the high salt content, leaf chlorosis, necrosis, repeat flowering and reduced tree vitality occurred. Heavy metal (Fe, Zn, Mn, Cu, Cd, Co, Ni, Pb and Cr) analysis of the soil samples showed their presence in both readily available and overall form, albeit within the allowable limits for the Novi Sad environmental conditions.