INFLUENCE OF THE PROPAGATION METHOD OF THREE SEMIDWARF ROOTSTOCKS ON THE GROWTH AND ACTIVITY OF THE PHYSIOLOGICAL PROCESSES OF MAIDEN SWEET CHERRY TREES IN A NURSERY

Rootstocks that reduce the vigor of sweet cherry trees are currently in high demand in orchard production. However, their suitability for nursery production is not fully verified. There are also difficulties in the method of their obtaining, mainly through in vitro cultures, which is associated with high prices. The experiment compared the growth of maiden trees of four sweet cherry varieties on rootstocks that reduce their vigor, ‘Gisela 5’, ‘Krymsk 5;, and ‘Pi-ku 1’. In addition, rootstocks produced by cheaper means using shoot cuttings were evaluated compared with those from in vitr o. The lower efficiency of maiden trees was obtained on the ‘Krymsk 5’ rootstock than on the other two rootstocks. In contrast, the vigor of maiden trees on this rootstock was significantly more potent. Generally, rootstocks derived from in vitro yielded a higher percentage of maiden trees. Additionally, for most of the varieties and years tested, the rootstocks obtained in this way improved the growth of the trees as determined by their diameter and length of the lateral shoots. The activity of the physiological processes of the maiden trees varied with the rootstock used. Maiden trees on the ‘Krymsk 5’ rootstock were most often characterized by the lowest levels of the three tested parameters (E, C, and I CO2). Meanwhile, the net photosynthetic intensity was lowest on the ‘Pi-ku 1’ rootstock.

A steady improvement in the intensification of production has characterized the cultivation of sweet cherries in Poland over the last two decades. The sweet cherry fruit harvest oscillates from approximately 90 000 tons, depending on weather conditions, to just 20 000 in 2019. This fact does not discourage producers from growing trees of this species. This is because the price obtained for sweet cherries is several times higher than that for apples. The dominant rootstock is 'Colt', whose qualified maiden tree produc-tion share was 88% in 2020. There are also changes in the selection of rootstocks for the production of maiden sweet cherry trees in favor of those reducing the vigor of sweet cherry trees, of which 'Colt' is not one. Many studies have confirmed the influence of rootstocks on the growth characteristics of sweet cherry trees [Baryła and Kapłan 2005, Gonçalves et al. 2005, Jimenez et al. 2007, Sitarek and Grzyb 2010, Cantín et al. 2010, Sitarek and Bartosiewicz 2012, Baryła et al. 2014, Zec et al. 2017.

INTRODUCTION MATERIAL AND METHODS
The nursery experiment comprised two cycles of production (2018-2020) of one-year-old maiden trees of four sweet cherry varieties ('Bellise', 'Earlise', 'Lapins', 'Vanda') on rootstocks obtained from propagation by shoot cuttings and the in vitro method. The number of combinations was 24 (four varieties, three rootstocks, two propagation methods). Each combination was represented by 20 maiden trees in four replications. On rootstocks planted in a nursery in spring at a spacing of 90 × 30 cm, the "letter T" method of shield budding was applied. The plants were grown in a nursery on podzolic soil, bonitation class IVb. The mineral content of the soil was as follows: phosphorus-107, potassium-145, calcium-520, and magnesium 96. The soil had a pH of 6.5. Before nursery establishment, the following fertilization was applied at the following pure nutrient doses: 40 kg⸱ha -1 phosphorus and 140 kg⸱ha -1 of potassium. Nitrogen fertilization at a rate of 120 kg⸱ha -1 was applied in three split doses. To prevent weed growth, the soil herbicide Sencor 80 WG was applied once immediately after planting the rootstocks at a dosage of 0.25 kg⸱ha -1 . Preventively, from mid-May to mid-August, plants were sprayed every fortnight against cherry leaf spots. For this purpose, the following preparations were applied alternately: Zato 50 WG, Score 250 EC, Syllit 65 WP, and Topsin M 500SC in recommended doses. The nursery was not irrigated in all years of experience. The rainfall in individual years was 2018 -320 mm, 2019 -409 mm, and 2020 -443 mm.
After the completion of maiden tree growth, measurements and observations of maiden tree growth were carried out on 15 randomly selected maiden trees in 4 replications. They were measured for height (cm), trunk diameter (mm) at 20 cm above the shield budding site, and length of lateral shoots (cm). At the end of the growing season, the maiden trees were dug out of the nursery, and the number of first-order roots was determined. In addition, the percentage of the maiden trees obtained concerning the shield-budded rootstocks was calculated.
In 2020, the following parameters were measured with a CI-340 aa Handheld Photosynthesis device (CID Bio-Science Inc., USA): net photosynthetic rate (Pn, μmol CO 2 ·m -2 ·s -1 ), transpiration rate (E, μmol H₂O·m -2 ·s -1 ), stomatal conductance (C, mol H 2 O· m -2 ·s -1 ), and intracellular CO 2 (I CO 2 , mol CO 2 ·mol -1 ). The research was conducted at a constant intensity of photosynthetically active radiation (PAR; 1000 µmol·m -2 ·s -1 ) supplied to the plants and at a constant concentration of carbon dioxide (CO 2 ; 390 µmol CO 2 ‧ mol -1 of air). Mature, healthy leaves growing on the middle part of the long shoots from the illuminated part Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024 of the crown of four randomly selected plants for each combination were selected for measurements.
Statistical calculations were performed using 'Statistica 13.1'. The Duncan test was used to perform the analyses at a significance level of α = 0.05. The results were subjected to a two-factor analysis of variance (rootstocks, method of propagation) separately for each variety and year (growth parameters).

RESULTS
A higher percentage of maiden sweet cherry trees of the tested varieties was obtained for the 'Pi-ku 1' and 'GiSelA 5' rootstocks than for 'Krymsk 5' (Tab. 1). Four times the best values were obtained for the 'Piku 1' rootstock. For 'Bellise', the average for the propagation methods was not significantly different. For 'Earlise', the in vitro method only gave a better result in the study's first year. For the other two varieties, a higher percentage of maiden trees was confirmed for the in vitro method in both series.
Two years after the experiment, the maiden trees of the first three considered varieties grown on 'Krymsk 5' rootstock were characterized by greater height (Tab. 2). Moreover, those varieties produced on rootstocks from shoot cuttings were significantly higher in one series. Only in one year of research were higher maiden trees 'Vanda' obtained on 'Krymsk 5' rootstock and for rootstocks propagated in vitro.
Only the 'Krymsk 5' rootstock for 'Bellise' and 'Lapins' produced a larger trunk diameter in one series (Tab. 3). More frequently, the method of propagation by in vitro (four times) produced better diameter results than the second method (two times).  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci.  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci.  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22 (4) Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22 (4) The sum of shoot lengths for the two varieties 'Bellise' and 'Lapins' was more remarkable for the 'Krymsk 5' rootstock (Tab. 4), while for 'Bellise', this was the case only in the first year. The 'Earlise' maiden trees on the 'Pi-ku 1' rootstock had longer lateral shoots in both years and 'Vanda' and 'Bellise' had longer lateral shoots only in the second year. The in vitro propagation method gave better results in half of the combinations considered than the other shoot-cutting methods.
For the three varieties, the number of roots on the 'Krymsk 5' and 'Pi-ku 1' rootstocks was higher than that on the 'GiSelA 5' rootstock (Tab. 5). The 'Lapins' tended to have more roots on the ‚Pi-ku 1' rootstock and the 'GiSelA 5' rootstock in the first year of the experiment. The rootstock propagation method did not affect the number of roots.
The net photosynthetic rate (Pn) of the 'Bellise' and 'Earlise' maiden trees had a better average value for the 'GiSelA 5' and 'Krymsk 5' rootstocks (Tab. 6). Different propagation methods were applied, in favor of the in vitro method for the first variety and in favor of shoot cuttings for the second. The highest average value of Pn for the 'Lapins' was obtained for the 'Krymsk 5' rootstock, and the lowest was for 'Pi-ku 1'. Meanwhile, for the last variety, the best value was obtained for the 'GiSelA 5' rootstock and the worst for 'Pi-ku 1'. The two rootstock propagation methods did not differ in the average Pn for these varieties.
The average value of the transpiration rate (E) of the 'Bellise' and the 'GiSelA 5' rootstock was the best, while the 'Krymsk 5' rootstock was the worst (Tab. 7). 'Earlise' had the highest E for the 'Pi-ku 1' rootstock and the lowest for 'Krymsk 5'. For the 'Lapins', only the average for the 'GiSelA 5' rootstock had a significantly higher E value than the other two. With the in vitro method, a higher transpiration rate of the maiden trees was found for 'Earlise' and 'Lapins'. For the last 54 https://czasopisma.up.lublin.pl/index.php/asphc Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci.  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. According to Duncan's test, data followed by the same letters separately for each variety and year do not differ significantly at p = 0.05.  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024  Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024 1.14 a Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024 Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. Pol. Hortorum Cultus, 22(4), 47-66. https://doi.org/10.24326/ asphc.2023.5024 Świerczyński, S. (2023). Influence of the propagation method of three semidwarf rootstocks on the growth and activity of the physiological processes of maiden sweet cherry trees in a nursery, Acta Sci. variety tested, the average E had the highest value for the 'GiSelA 5' rootstock and the lowest for 'Pi-ku 1'. The propagation method did not differentiate the average results E of the 'Bellise' and 'Vanda'. The 'Bellise' and 'Earlise' in combination with the 'Pi-ku 1' and 'GiSelA 5' rootstocks had a better value of stomatal conductance (C; Tab. 8). For the 'Lapins' and 'Vanda', only the average for the 'GiSelA 5' rootstock had a higher C value. The averages for propagation methods did not differ for all varieties.
Higher intracellular CO 2 (I CO 2 ) for the first three varieties was found for the 'GiSelA 5' rootstock and lower for 'Krymsk 5' (Tab. 9). For the last variety, the averages for the 'GiSelA 5' and 'Pi-ku 1' rootstocks were better than those for 'Krymsk 5'. The average for the in vitro method had a higher I CO 2 value for 'Bellise' and 'Vanda'. No differences were found for the other two varieties.

DISCUSSION
An important factor in determining the suitability of rootstocks for nursery production is the high percentage of maiden sweet cherry trees obtained [Baryła et al. 2013]. Our experiment obtained the lowest number of maiden trees on the 'Krymsk 5' rootstock, depending on the variety, from 53.5 to 62.4%. The studies by Janes and Pae [2004] are consistent with this result, indicating a low yield of three varieties of maiden sweet cherry trees grown on 'GiSelA 5' and 'Krymsk 5' (VSL-2) rootstocks. The authors obtained a higher percentage on the 'GiSelA 5' rootstock (approx. 60%) than on 'Krymsk 5' (approx. 33%), except for one variety, for which the result was 68%. Similarly, in the experiment, maidens' efficiency was consistently higher on the 'GiSelA 5' rootstock than on the 'Krymsk 5' rootstock. The percentage of maiden trees obtained by the abovementioned authors was, on average several percent lower than the own percentage. However, the authors indicated that the low percentage of maiden trees may have been influenced by adverse weather conditions such as a prolonged dry period and high summer and low winter temperatures. Such unfavorable conditions were not recorded in the experiment under consideration, especially temperature drops in winter to -32°C, but only to -15°C. It could have resulted in a frosting of the leaf buds formed and, consequently, in lower maiden tree yields.
In the experiment, better results for the percentage of maiden trees were obtained on the 'GiSelA 5' (60-85%) and 'Pi-ku 1' (66-85%) rootstocks. Different results for the percentage of maiden trees were obtained by Baryła et al. [2013] during three series of experiments; in only one year, they obtained a high percentage of maiden trees of the 'Regina' variety on the 'GiSelA 5' rootstock, amounting to 90.8%. In the other two years, it did not exceed 60%. Meanwhile, Bujdosó and Hrotkó [2006] noted the variable efficiency of maiden sweet cherry trees on the 'GiSelA 5' rootstock. Depending on the variety, it ranged between 56% and 86%, similar to the result obtained in the experiment.
In the experiment, except for 'Vanda', the highest number of maiden sweet cherry trees was obtained on the 'Krymsk 5' rootstock. In contrast, lower maiden tree height was found on the 'GiSelA 5' and 'Pi-ku 1' rootstocks. Similar results for the height of maiden sweet cherry trees on the 'GiSelA 5' rootstock were obtained by Bujdosó and Hrotkó [2006], who, depending on the seven varieties tested, obtained a height ranging from 103 cm to 149 cm. A greater height of the 'Lapins' on the 'GiSelA 5' rootstock was obtained by Sitarek and Grzyb [2007], amounting to approx. 145 cm. However, the trees of this variety obtained by these authors were significantly taller than the other varieties tested, with similar heights.
In the experiment, trees grown on rootstocks obtained from shoot cuttings were mainly taller than those from in vitro. Only in the case of the 'Vanda' was an opposite relationship found. It suggests that the suitability of rootstocks from this method of propagation is not inferior to those from the in vitro method. It is not easy to refer to the results of other authors, as they did not use rootstocks other than those obtained from the in vitro method.
Maiden trees grown on 'GiSelA 5' and 'Pi-ku 1' rootstocks had similar trunk diameters. It is not fully in line with the opinion of Sitarek and Rozpara [2008], who found that 3-year-old 'Regina' cherry trees on the 'Pi-ku 1' rootstock grew significantly less than those on the 'GiSelA 5' rootstock. However, the differences could be due to the different ages of the trees tested. The reduction in the vigor of sweet cherry trees grown on the 'GiSelA 5' rootstock, as assessed by trunk diameter measurements, has been confirmed by several