INFLUENCE OF LOW VIGOUR ROOTSTOCKS ON GROWTH AND FRUITING PROCESS OF ‘REGINA’ CULTIVAR

The aim of this paper was to study the influence of low vigor rootstocks on the 'Regina' cherry cultivar. The study was conducted at Research Institute for Fruit Growing Pitesti, Arges county, Romania between 2019 and 2021. A bifactorial experiment was set up, with A factor-the rootstock ('Gisela 3', 'Gisela 5', 'Gisela 12' and 'Weigi 2') and B factor-the study year (2019, 2020 and 2021). Fruiting and vegetative growth data (fruit production, the trunck cross-section area-TCSA, the annual increase of TCSA, the productivity index and the ratio between the fruit production and the annual increase of TCSA), as well as fruit quality data (fruit mass, firmness, pH, total soluble content, chromatic coordinates of epicarp color and chlorophyll fluorescence) were collected. 'Gisela 5' rootstock recorded the highest value of TCSA annual increase (11.46 kg/cm2) and had also the highest cromatic coordinates values: colour brightness (25.68), red pigment (15.61) and yellow content (4.12).The highest vigor of the cultivar 'Regina' was observed in 'Weigi 2' rootstock variant (with an TCSA value of 44.71 cm2), given that 'Weigi 2' TCSA annual increase was similar to 'Gisela 5'. 'Gisela 3' rootstock stood out for its fruit highest pH (3.97), fruit yield (13.51 t/ha), lowest vigor (TCSA=24.19 cm2), smallest annual TCSA increase (6.11 cm2), highest productivity index 0.219 kg/cm2) and highest fruit production to annual TCSA increase ratio (1.79 kg/cm2). Taking into account climatic accidents that marked the spring of 2021, on the average of the study years, the cultivar 'Regina' grafted on the rootstock 'Gisela 12' was distinguished by fruit weight (10.02 g), firmness (66.53 units HPE Bareiss) and TSS (16.03°Brix) on the background of the lowest fruit yield. A negative very signifficant correlation between fruit yield and fruit quality traits (weight, firmness and total soluble solids) was found.

The influence of rootstocks on the sensitivity of flower buds to frost and the main properties of the ‘Carmen’ sweet cherry cultivar

The study examined the influence of five vegetative rootstocks on the flower bud sensitivity to frost during the period of ecological dormancy and the most important biological and pomological properties of the ?Carmen? sweet cherry cultivar. The ?Carmen? cultivar was grafted on the following rootstocks: ?Colt?, ?Gisela 5?, ?Gisela 6?, ?MaxMa 14? and ?Oblacinska cherry?. Winter frosts occurred during the ecological dormancy of sweet cherry trees. The intensity of frost was between -5?C and -7?C. The percentage of damaged and non-damaged flower buds per fruiting branch was determined by counting (50 flower buds per tree were taken from every part of the canopy and fruiting branches). The highest rate of damage of flower buds was in trees grafted on ?Oblacinska cherry?, an average of 77.2% of flower buds, while the lowest was observed in trees grafted on ?MaxMa 14?, an average of 24.3% of total flower buds. The significantly higher sensitivity of flower buds was found in spur fruiting branches compared to lateral fruiting branches. The fruits of the ?Carmen? cultivar had the earliest ripening on rootstocks ?Gisela 5? and ?Oblacinska cherry?. The ?Carmen? cultivar had the highest yield per tree on the ?MaxMa 14? rootstock, while the lowest yield rate was observed in ?Oblacinska cherry?, 5.4 kg and 1.9 kg, respectively. The highest mass of fruits was noticed in trees grafted on ?Gisela 6?, an average of 11.6 g, while the smallest was recorded in trees grafted on ?Gisela 5?- an average of 9.4 g.

UTICAJ PROREĐIVANJA PUPOLJAKA NA KVALITET PLODOVA TREŠNJE (Prunus avium L.) SORTI ‘KORDIA’ I ‘SWEETHEART’

Thinning the buds of May flowers, as an pomotechnical measure, can significantly increase the average fruit size. The paper presents the results of thinning of buds of cultivars "Kordia" and "Dušice" on rootstocks "Gisela 5" and "Gisela 6" grown in the system of Vogel spindles. The examined cultivars reacted positively to the thinning of the buds by increasing the fruit weight, which was especially expressed in the cultivar 'Kordia'. Thinning of the buds had a positive effect on the presence of marketable fruits, although not to a significant extent.

Improving of Cherry Fruit Quality and Bearing Regularity by Chemical Thinning with Fertilizer

The study’s objective was to evaluate the influence of thinning on the quality and regularity of yield of ‘Regina’ cherries grown on a dwarf Gisela 5 rootstock. The experiments were conducted in the years 2009–2012 in Western Poland. Trees were thinned using a chemical agent, ammonium thiosulphate (ATS), at doses of 20 g ATS L−1, 30 g ATS L−1 and 40 g ATS L−1, and by hand, and the results of chemical and hand thinning were compared with those obtained for unthinned trees. The course of weather conditions in winter and during flowering had a significant impact on yield. Chemical thinning is known to be an effective method to regulate fruiting of pome trees, but it can also be successful if applied to cherry trees, as reflected by the alternate bearing index, which was the lowest after applying ATS at a dose of 40 g. ATS treatment improved fruit quality in full crop years. Thinning resulted in, among other things, larger and darker fruit and higher content of total soluble solids and titratable acidity. Treatment with 40 g ATS L−1 significantly stimulated the vegetative growth of trees.

Improving of Cherry Fruit Quality and Bearing Regularity by Chemical Thinning with Fertilizer

The study’s objective was to evaluate the influence of thinning on the quality and regularity of yield of 'Regina' cherries grown on a dwarf Gisela 5 rootstock. The experiments were conducted in the years 2009-2012 in Western Poland. Trees were thinned using a chemical agent, ammonium thiosulphate (ATS) at doses of 20g ATS × L-1, 30g ATS × L-1 and 40g ATS × L-1, and by hand, and the results of chemical and hand thinning were compared with those obtained for unthinned trees. The course of weather conditions in winter and during flowering had a significant impact on yield. Chemical thinning is known to be an effective method to regulate fruiting of pome trees, but it can also be successful if applied to cherry trees, as reflected by the alternate bearing index, which was the lowest after applying ATS at a dose of 40g. ATS treatment improved fruit quality in full crop years. Thinning resulted in, among other things, larger and darker fruit and higher content of total soluble solids and titratable acidity. Treatment with 40g ATS × L-1 significantly stimulated the vegetative growth of trees.

Long-term evaluation of rootstock effects on cropping and tree parameters of selected sweet cherry cultivars

The cropping of six sweet cherry cultivars that originated in the Research and Breeding Institute of Pomology at Holovousy, and a standard one, ‘Burlat’, were evaluated on three rootstocks in the period of 2007–2017. Trees planted in a spacing of 1.5 m × 5.0 m were trained as tall spindle axes utilising their natural tendency to develop a central leader. On the standard rootstock, P-TU-2, ‘Tim’ was the most productive with a mean total harvest of 47.6 kg per tree. ‘Sandra’ yielded the most on the PHLC rootstock with 56.2 kg per tree and ‘Helga’ yielded the most on Gisela 5 with a mean total harvest of 55.9 kg per tree. The mean impact of the rootstock on the tree vigour, measured upon the trunk cross section area, ranged from 148.4 cm2 on the standard rootstock P-TU-2 to 114.1 cm2 on the PHLC and 125.2 cm2 on Gisela 5 . On the standard rootstock P-TU-2, the most vigorous one according to this criterion was ‘Jacinta’ (178.0 cm2) whereas ‘Justyna’ (109.7 cm2) was the least vigorous. On the PHLC, the most vigorous was ‘Sandra’ (147.2 cm2) and the least was ‘Amid’ (94.0 cm2). The other tree characteristics were mainly dependant on the cultivar and minimally, or not at all, influenced by the rootstock vigour.

Micropropagation of rootstocks of stone fruit cultures in vitro

The usage of the method of clonal micropropagation of plants is currently the most promising for obtaining virus-free plant material, including clonal rootstocks of stone fruit cultures. The introduction of clonal rootstocks of stone fruit cultures PK SK1, PK SK 2, AI 1 into invitro culture is best doneduring the active shoot growth period in the second decadeof May. During this period, the highest level of explants regeneration was noted: in the rootstock PK SK 1 – 94,6 %, in the rootstock AI 1 78.2%, in PK SK 2 80.4%, in Gisela 5 (control) 85,7%. From the third decade of May, the survival rate of explants begins to decline. At the stage of multiplication on the Murashige-Skoog medium, with the addition of 6-BAP 1 mg/L, the average multiplication factor of clonal rootstocks to the fourth passage was 1: 12 for PK SK1, for Gisela 5 and for AI 11: 8.

Physiological basics of sweet cherry productivity depending on rootstocks, interstems and plant density

Optical and physiological parameters in sweet cherry tree canopies at different plant density and rootstock-interstem-scion combinations were studied in order to identify the combinations that would ensure optimal passage of photosynthesis and increase yield and fruit quality. It was shown that cherry cultivars react differently to varying plant density depending on their growth habit and thus require different planting schemes. Leaves in the periphery of tree canopy had higher dry matter content per unit of leaf surface area (LSA) and increased net photosynthetic productivity (NPP) compared to leaves in the center of the canopy. This can be related to higher light interception (LI) levels in peripheral zones of the tree. Trees on interstems had higher yield than trees on own-root clonal rootstock. The complex of photosynthetic and yield indices allowed to select the best scion-rootstock-density combinations: for ‘Melitopolska chorna’ cultivar – Krymsk 5 and Gisela 5 interstems with 5 x 3 m planting scheme; for ‘Krupnoplidna’ cultivar – Gisela 5 interstem (5 x 3 m) and Krymsk 5 interstem (5 x 4 m).

EARLY PERFORMANCE OF FOUR SWEET CHERRY CULTIVARS GRAFTED ON GISELA 5 AND COLT ROOTSTOCKS IN A HIGH DENSITY GROWING SYSTEM

Growing the sweet cherry on different vigor rootstocks, such as Colt and Gisela 5, in a high-density orchard, causes differences in growth and productivity and later imposes the need to change the growing system including pruning, flower and fruit thinning, irrigation and fertilization. In the present research, four sweet cherry cultivars (Summit, Kordia, Lapins and Regina) grafted on Colt and Gisela 5 rootstocks were assessed for morphological traits and productivity. The parameters investigated were: vegetative growth, bearing potential, fruit set, precocity, productivity, fruit growth habit and quality attributes. Compared to Colt, the trees on Gisela 5 had smaller TCSA and the length of two-year-old branches, in the fifth season after planting. Trees on Gisela 5 had a higher number of flower buds per may bouquet compared to Colt, which confirms that bearing potential is highly affected by the rootstock. Growing the sweet cherries on Gisela 5 induced a higher fruit setting in all cultivars except in Kordia. Fruit physical attributes were affected by the cultivar, growing system and experimental year. For all tested cultivars, the yield per tree was significantly lower on Colt compared to Gisela 5. Gisela 5 performed better than Colt, which suggests that Gisela 5 should be used as a rootstock in high density sweet cherry production systems.