PRODUCTIVITY OF EARLY AND MEDIUM EARLY APRICOT CULTIVARS IN THE BELGRADE AREA

Characteristics of productivity and growth (yield per tree, trunk cross-sectional area, yield efficiency and fruit weight) were studied in 40 apricot cultivars of early and medium early maturity in the Belgrade area during the six-year period (2009 – 2014). The cultivar ‘Hungarian Best’ was used as a control for comparison. The period of study was divided to initial bearing (age of trees three and four years) and full bearing (age of trees from five to eight years). Significant differences in yield between cultivars and years were found. Average yield in the period of initial bearing ranged from 0.3 to 11.3 kg per tree, and in the period of full bearing from 5.6 to 24.8 kg per tree. Compared with the control cultivar, significantly higher yield was obtained in 17 cultivars. Adverse weatherconditions resulted in significant reduction of yield in two out of six years of study. Cumulative yield efficiency varied from 0.17 to 0.87 kg/cm2 and in 19 cultivars it was significantly higher compared with the control cultivar. Fruit weight ranged from 27.7 to 80.1 g. Compared with control, fruit weight was significantly higher in nine cultivars, and significantly lower in 11 cultivars

POLLEN VIABILITY IN QUINCE CULTIVARS

Pollen viability of eight quince cultivars (ʻLeskovackaʼ, ʻVranjskaʼ, ʻMoravaʼ, ʻPazardzijskaʼ, ʻHemusʼ, ʻAsenicaʼ, ʻPortugalʼ and ʻTriumphʼ), was studied in the two-year period (2011-2012). Testing of pollen viability was performed using two methods: the staining of pollen with acetocarmine (indirect method) and pollen germination in vitro with sucrose and agar-agar (direct method). Studied cultivars differed significantly in terms of pollen viability. The lowest percentage of stained pollen grains was detected in ʻLeskovackaʼ cultivar (70.29%) and the highest in the cultivars ʻAsenicaʼ, ʻHemusʼ and ʻTriumphʼ (over 90%). Similarly to that, the lowest percentage of pollen germination was obtained in ʻLeskovackaʼ cultivar (62.86%) and the highest in the cultivars ʻMoravaʼ, ʻAsenicaʼ, and ʻTriumphʼ (over 80%). With the exception of ʻPortugalʼ cultivar, the values of pollen viability determined by staining with acetocarmine were higher for 3-15% compared to the pollen germination in vitro. However, values obtained using these tho methods are highly positively correlated. On the basis of obtained results, the both methods can be recommended as reliable tests for pollen viability of quince, although priority should be given to the method of pollen germination in vitro, because it is more accurate. All tested cultivars are distinguished for high pollen viability, and can be successfully used as male parents in hybridization. In addition, they also can be recommended as a good pollenisers when are planting new quince orchards

CHARACTERISTICS OF FRUITING SHOOTS OF SOME PEACH AND NECTARINE CULTIVARS

Morphological characteristics of fruiting shoots: length, diameter, internode length, length of the basal part without flower buds, number of flower buds (per shoot, node and 1 m of shoot length) were studied in 12 peach and 12 nectarine cultivars. The study was conducted at the Experimental farm “Radmilovac” of the Faculty of Agriculture in Belgrade during the two–year period (2016-2017). Control cultivar for peaches was ‘Redhaven’, and for nectarines ‘Stark Redgold’. For all studied traits statistically significant differences between cultivars were found. The average length of shoots varied from 62.4 to 76.8 cm, diameter from 5.9 to 8.0 mm, and internode length from 2.45 to 3.00 cm. The length of basal part of a shoot without flower buds was on average lower in nectarines (3.9 cm) than in peaches (9.1 cm). Peach cultivar ‘Tardibelle’ is characterized by the longest basal part of a shoot without flower buds (22.2 cm). All studied peach cultivars are characterized by lower flower bud density compared to control (‘Redhaven’). In nectarines, most of the studied cultivars had flower bud density similar to control (‘Stark Redgold’). Cultivars with higher flower bud density such as peaches: ‘Redhaven’, ‘Maria Marta’, ‘Autumn Glo’, and nectarines ‘Rita Star’, ‘Maria Carla’, ‘Orion’ require severe pruning in order to obtain better fruit size. On the other hand, cultivars with lower flower bud density e.g. ‘Tardibelle’, ‘Flavorcrest’, ‘Royal Glory’, ‘Bolero’, ‘Maria Lucia’ should be pruned slightly in order to obtain higher yield

ROOTSTOCK INFLUENCE ON VIGOR AND GENERATIVE POTENTIAL OF YOUNG SWEET CHERRY TREES

The main goal of breeding and testing of rootstocks for sweet cherry is to obtain small and productive trees and to improve precocity. The objective of this study was to examine the influence of six rootstocks on vigor and productive characteristics of young sweet cherry trees. The experimental orchard is situated at the Experimental farm “Radmilovac”, of the Faculty of Agriculture (near Belgrade). Three sweet cherry cultivars: ‘Kordia’, ‘Karmen’ and ‘Regina’ were grafted on six rootstocks: Prunus mahaleb L. seedlings, ‘Colt’, ‘Ma×Ma 14’, ‘Gisela 6’, ‘Gisela 5’ and ‘Oblačinska’ sour cherry. During a two-year period (2015-2016) the following characteristics were studied: scion diameter above the grafting union, rootstock diameter under the grafting union, length and diameter of shoots, height of the tree and the number of spurs per tree. The resultsshowed different influence of rootstocks on the tree vigor, spur formation and precocity. The average diameter of the scion in all tested cultivars was the largest on the Mahaleb rootstock. The largest average number of spurs per tree in the second year was recorded on cherry trees grafted on the rootstocks ‘Gisela 6’ and ‘Oblačinska’ sour cherry (28 and 23 respectively). The lowest average number of spurs (6) was found on trees grafted on the rootstock ‘Colt’

The Phenolic Profile of Sweet Cherry Fruits Influenced by Cultivar/Rootstock Combination

The influence of three cultivars (‘Carmen’, ‘Kordia’ and ‘Regina’) grafted on six rootstocks (Mahaleb, ‘Colt’, ‘Oblacinska’, ‘M × M 14′, ‘Gisela 5′ and ‘Gisela 6′) on the phenolic profile of sweet cherry fruits was studied during a two-year period. All the individual phenolic compounds were detected using high-pressure liquid chromatography with diode-array detection coupled with mass spectrometry (HPLC-DAD-MSn). In all the examined samples, 54 compounds were identified and divided into five phenolic classes: anthocyanins (4 compounds), flavonols (7), flavanols (11), flavanones (4), and hydroxycinnamic acids (28). Anthocyanins (58%) and hydroxycinnamic acids (31%) showed the greatest amounts in all the examined fruit samples. PCA analysis revealed that among the cultivars, ‘Kordia’ showed the highest phenolic content. Regarding rootstocks, the lowest values of the most important phenolic compounds were obtained in fruits from trees grafted onto the seedling rootstock Mahaleb. Among the clonal rootstocks, the vigorous ‘Colt’ and dwarf ‘Gisela 5′ promoted the highest values of the evaluated phenolic compounds in the cultivars ‘Kordia’ and ‘Carmen’, while the dwarf ‘Oblacinska’ and semi-vigorous ‘M × M 14′ induced the highest values in the cultivar ‘Regina’. By evaluating the influence of cultivars and rootstocks on the phenolic content in fruit, it has been proven that the cultivar has the most significant influence. However, the rootstock also influences the content of a large number of phenolic compounds. The selection of an adequate cultivar/rootstock combination can also be a powerful tool for improving the phenolic content in fruits, and consequently the nutritional value of sweet cherry fruits. © 2022 by the authors

Influence of Chemical Thinning of Apple Cultivars on Yield and Fruit Quality

U radu je ispitivan uticaj hemijskog proređivanja plodova na zametanje plodova, prinos, kvalitet ploda i povratno cvetanje kod sorti jabuke Zlatni delišes klon Rajnders, Gala rojal bjut, Red kep i Red džonaprins u 2014. godini. Zasad je podignut u proleće 2013. godine sa „knip“ sadnicama. Hemijsko proređivanje je vršeno sledećim sredstvima: naftil-sirćetna kiselina (NAA), 6-benziladenin (6-BA), karbaril, metamitron i kombinacijom ovih sredstava. Najintenzivnije proređivanje plodova kod svih sorti bilo je kod tretmana sa metamitronom i tretmana sa kombinacijama metamitron + NAA i 6-BA + NAA. Usled smanjenja broja plodova po stablu kod ovih tretmana je zabeleženo najveće povećanje mase ploda u poređenju sa kontrolom. Primena bioregulatora u dvogodišnjem zasadu imala je efekat na cvetanje jabuke narednog proleća. Kod sorti Gala rojal bjut i Red džonaprins, efekat hemijskog proređivanja na cvetanje narednog proleća nije bio značajan, za razliku od sorti Zlatni delišes i Redkep. Kod sorte Zlatni delišes broj plodova preko šest po cm2 površine poprečnog preseka debla (PPPD) uticao je na izostanak diferenciranja cvetova, dok je kod sorte Red kep kritičan broj plodova bio tri po cm2 PPPD.This experiment was designed to investigate effects of chemical thinning on fruit set, yield, return bloom and fruit quality of apple cultivars ‘Golden Reinders’, ’Gala Royal Beaut’, ’Red Cap Deliciou’' and ’Red Jonaprince’ in 2014. The orchard was established in spring 2013 with high-quality 2-year-old nursery trees that contained 7 or more lateral branches (except the cultivar ’Red Cap Delicious’). For chemical thinning the following chemicals were used: auxine naphthaleneacetic acid (NAA), cytokinin 6-benzyladenine (BA), insecticide carbaryl (‘Sevin’) and photosynthesis inhibitor metamitron (‘Brevis’) and their mix combinations. The most intensive fruit thinning for all cultivars were obtained in treatments with metamitron used either alone or in combination with NAA, and in the combination BA + NAA. Due to the decrease in the number of fruits per tree, in these treatments was recorded the largest increase in fruit weight compared with the control. Application of bioregulators in two-year old orchard depending on the cultivar had a greater or lesser effect on apple bloom in the next spring. Effect of chemical thinning on flowering in the next spring was not significant in cultivars ‘Royal Gala Beaut’ and ‘Red Jonaprince’. In the cultivar ‘Golden Reinders’ number of fruits over 6 per cm2 of trunk cross-sectional area (TCSA) resulted in absence of flowers, while in the cultivar Red Cap that number was 3 per cm2 of TCSA

Pollen tube growth and fruit set in quince (Cydonia oblonga Mill.)

Aim of study: To determine the self-compatibility level of eight quince cultivars.Area of study: The region of Belgrade (Central Serbia).Material and methods: Pollen tube growth in vivo and fruit set in two pollination variants (self- and open-pollination) were studied in eight quince cultivars. The quantitative parameters of pollen tube growth (average number of pollen tubes in the upper and middle third of the style, base of the style and in the ovary; the dynamics of pollen tube growth through these parts of the pistil) was determined using the fluorescence microscopy.Main results: The parameters of pollen tube growth and fruit set were primarily dependent on the genotype and variants of pollination. All studied parameters were significantly higher in the open-pollination variant compared with the self-pollination in all cultivars. In the self-pollination variant, ʻLeskovackaʼ and ʻVranjskaʼ had the highest number of pollen tubes that penetrated the ovary (2.10 and 0.54 in average, respectively), as well as the largest percentage of pistils with the penetration of pollen tubes in the nucellus of ovules six days after pollination (40.09% and 14.74%). Also, they had the highest percentage of initial fruit set (17.01% and 28.52%) and final fruit set (9.32% and 9.86%). Based on this, ʻLeskovackaʼ and ʻVranjskaʼ can be classified as self-compatible cultivars, while the others are self-incompatible.Research highlights: The majority of quince cultivars were self-incompatible. When establishing new orchards with these cultivars, care should be taken about the choice of pollenisers in order to achieve high yields

Influence of Prohexadione-Calcium and Ethephon on Vigor of Sweet Cherry Cultivars

Cilj ovog rada je bio ispitivanje uticaja kombinovane primene dva bioregulatora: proheksadion-kalcijuma i etefona na bujnost sorti trešnje. Ipitivanja su obavljena u proizvodnom zasadu trešnje u Grockoj na pet sorti: Burlat, Karmen, Sanberst, Kordija i Regina okalemljenih na podlozi Kolt. Tretman bioregulatorima je obavljen u proleće u dva navrata: početkom i krajem maja. Na kraju vegetacionog perioda izmereni su sledeći parametri: dužina i prečnik letorasta, broj nodusa, dužina internodija i površina lista. Svi ispitivani parametri bujnosti su, u manjoj ili većoj meri, imali manje vrednosti na stablima na kojima je obavljeno tretiranje bioregulatorima. Pored toga, bioregulatori su uticali na značajno povećanje broja formiranih majskih buketića kod svih ispitivanih sorti, osim kod sorte Burlat.In Serbia, in the majority of sweet cherry orchards, vigorous rootstocks (Mazzard and Mahaleb seedlings and clonal rootstock ‘Colt’) are used. Cherry trees grafted on these rootstocks are characterized by vigorous growth and the subsequent late coming into bearing. The aim of this study was to examine the effect of the combined use of two bioregulators: Prohexadione-calcium and Ethephon on vigor of sweet cherry cultivars. Studies were carried out in a cherry orchard in Grocka (near the Belgrade) on five cultivars: ‘Bigarreau Hatif Burlat’, ‘Sunburst’, ‘Carmen’, ‘Kordia’ and ‘Regina’ grafted on the rootstock ‘Colt’. There were two treatments with Prohexadione-calcium (250 mg/l) and Ethephon (175 mg/l). The first treatment was done when the shoots were 8-10 cm long, and the second one three weeks later. At the end of the growing season were conducted measurements of the following parameters: length of shoots, diameter of shoots, number of nodes per shoot, leaf area, and the number of spurs per tree. All parameters of vigor had less values on the trees treated with bioregulators. Length of the terminal shoots on treated trees was lower by 24-35% comparing to control. In addition, bioregulators influenced significant increase in the number of spurs (by 12-74%) in all tested cultivars, except for the cultivar ‘Burlat’

The Phenolic Profile of Sweet Cherry Fruits Influenced by Cultivar/Rootstock Combination

The influence of three cultivars (‘Carmen’, ‘Kordia’ and ‘Regina’) grafted on six rootstocks (Mahaleb, ‘Colt’, ‘Oblacinska’, ‘M × M 14′, ‘Gisela 5′ and ‘Gisela 6′) on the phenolic profile of sweet cherry fruits was studied during a two-year period. All the individual phenolic compounds were detected using high-pressure liquid chromatography with diode-array detection coupled with mass spectrometry (HPLC-DAD-MSn). In all the examined samples, 54 compounds were identified and divided into five phenolic classes: anthocyanins (4 compounds), flavonols (7), flavanols (11), flavanones (4), and hydroxycinnamic acids (28). Anthocyanins (58%) and hydroxycinnamic acids (31%) showed the greatest amounts in all the examined fruit samples. PCA analysis revealed that among the cultivars, ‘Kordia’ showed the highest phenolic content. Regarding rootstocks, the lowest values of the most important phenolic compounds were obtained in fruits from trees grafted onto the seedling rootstock Mahaleb. Among the clonal rootstocks, the vigorous ‘Colt’ and dwarf ‘Gisela 5′ promoted the highest values of the evaluated phenolic compounds in the cultivars ‘Kordia’ and ‘Carmen’, while the dwarf ‘Oblacinska’ and semi-vigorous ‘M × M 14′ induced the highest values in the cultivar ‘Regina’. By evaluating the influence of cultivars and rootstocks on the phenolic content in fruit, it has been proven that the cultivar has the most significant influence. However, the rootstock also influences the content of a large number of phenolic compounds. The selection of an adequate cultivar/rootstock combination can also be a powerful tool for improving the phenolic content in fruits, and consequently the nutritional value of sweet cherry fruits