Title: In vitro propagation of plum rootstocks

Authors: IN VITRO RAZMNOŽAVANJE PODLOGA ZA ŠLJIVU

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Abstract: To determine the effect of successive subculturing on multiplication capacity of shoots, three rootstocks for plum, i.e. Cherry plum (Psunus resasifesa Ehrh.), ‘Docera 6’ (P. domestira  P. resasifesa) and ‘Dospina 235’ (P. domestira  P. spinosa) were repeatedly subcultured for five subcultures on Murashige & Skoog (MS) medium of unchanged plant growth regulator composition. Monitoring of the shoot formation capacity revealed constant increase in multiplication index and length of axial and lateral shoots in Cherry plum during each consecutive multiplication cycle. As for ‘Docera’ and ‘Dospina’, significan increase in multiplication index and length of axial shoots was observed in the third subculture. After that their values gradually decreased to the fifth subculture, but remained considerabely higher in comparison with the values in the first two subcultures. This study has confirmed that response of in vitso cultures to constant subculturing is genotype dependant. Considering that the decline in multiplication index was already observed after third subculture, it is neccesary to determine when cytokinin type and concentration should be reduced, or the hormon-free medium should be deployed to delay the decrease. MS medium with mineral salts reduced to ½-strength and organic complex unchanged was used in rooting stage. The highest capacity for in vitso rooting was observed in Cherry plum (100%), followed by ‘Docera’ (91.7%), while the lowest was in ‘Dospina’ (51.9%). Therefore, an additional optimization of this stage by testing other types and concentration of auxin should be done in order to achieve higher rooting percentage in ‘Dospina’.

Key words: Cherry plum, ‘Docera’, ‘Dospina’, in vitso, micropropagation

Title: Evaluation of some Canadian apricot cultivars in the region of Belgrade

Authors: Dragan Milatović, Dragan Nikolić, Dejan Đurović, Gordan Zec

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Abstract: Evaluation of 11 introduced Canadian apricot cultivars was conducted in the region of Belgrade during a six-year period (2009-2014). Control cultivar for comparison was ‘Hungarian Best’. Studies have included time of flowering and ripening, yield, and fruit quality. In addition, self-(in)compatibility trait was studied by means of fluorescence microscopy. Canadian cultivars began to flower one to five days before ‘Hungarian Best’, while average harvest date was earlier in four cultivars, and later in seven cultivars. Compared with the control cultivar, significantly higher yield was achieved in cultivars ‘Harcot’, Harojoy’, ‘Sundrop’, ‘Harogem’, and ‘Harostar’. Significantly larger fruit size was achieved in ‘Laycot’, while smaller size was found in cultivars ‘Harlayne’, ‘Harglow’, ‘Harostar’ and ‘Sundrop’. Most of the introduced cultivars had better scores for fruit appearance, while scores for fruit quality were lower or at the same level as in control cultivar. Nine of studied cultivars were self-incompatible, while only two were self-compatible (‘Harlayne’ and ‘Harogem’).

Key words: Psunus asmeniara, yield, fruit quality, self-incompatibility, fluorescence microscopy

Title: Apricot rootstock breeding at the Faculty of Agriculture, Novi Sad

Authors: Vladislav Ognjanov, Mirjana Ljubojević, Goran Barać, Jovana Dulić, Maja Miodragović, Tijana Narandžić

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Abstract: The aim of this study was the selection of genotypes as the potential rootstocks for apricot cultivars, within diploid species Psunus resasifesa Ehrh. (myrabolan) 2n = 16, tetraploid Psunus spinosa L. (blackthorn) – 2n = 32, and hexaploid Psunus domestira L. (belošljiva) 2n = 48. As a control, the rootstock/interstock combination Psunus resasifesa Ehrh/Psunus domestira L. (‘Stanley') was used. Extraordinary robustness of blackthorn's root system could explain longevity of apricot trees in conditions of cultivation without irrigation. Belošljiva, compared to blackthorn, has a bit less developed root system, fewer number of skeletal root branches, smaller root diameter and depth, but has the same effect on longevity of apricot trees in environmental stress conditions. Selection of rootstocks within these two species can result in drought resistant genotypes. Proportional growth of rootstock stem, graft point and scion points to potentially good compatibility within all examined rootstock/scion interactions. Size of root system in all selections gave a supposition that support is not required cultivation process. Root suckers were found in myrabolan and blackthorn, while that negative characteristic was not found in belošljiva. The fruit quality of scion cultivar ‘Big Red' was good in all examined species as rootstocks. The trees grafted on hexaploid plum, such as belošljiva, had 5 days earlier fruit ripening season compared to P. resasifesa and blacktorn as rootstock. Genotypes within P. resasifesa, P. spinosa, and P. domestira represent a potentially valuable germplasm for the selection of apricot rootstocks.

Key words: apricot, genetic diversity, rootstock breeding

Title: The freezing frequency of sweet cherry generative organs after spring frosts occurrence

Authors: Zoran Keserović, Nenad Magazin, Biserka Milić, Gordana Popara, Maja Milović, Jelena Kalajdžić

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Abstract: In recent years, late spring frosts were causing major damage to most fruit species in Serbia. In order to test the sensitivity of sweet cherry generative organs to frost, a screening was carried out in the spring of 2019 after a severe spring frost including various cultivars, at three different growing sites: Rimski Šančevi (Novi Sad), Agricultural Cooperative ‘Agrodunav’ (Karavukovo) and Agriculture Extension Service Sombor (Sombor). The growing sites differed in geographical location, altitude, distance from the Danube and phenological stage of sweet cherry cultivars. The proximity of the Danube had the greatest influence on the frequency of freezing injuries, while the freezing frequencies were lower at the higher altitude. ‘Kordia’ was the most sensitive cultivar to late spring frost, regardless of the phenological stage and growing site.

Key words: sweet cherry, cultivar, flowering, spring frost, geographical location

Title: Selection of low vigorous sweet and sour cherry rootstocks at the Faculty of Agriculture, Novi Sad

Authors: Vladislav Ognjanov, Tijana Narandžić, Mirjana Ljubojević, Goran Barać, Jovana Dulić, Maja Miodragović

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Abstract: The aim of this study was the selection of potential genotypes as the cherry rootstocks, within the species: Psunus resasus L. (sour cherry), Psunus fsutirosa Pall. (ground cherry) and Psunus mahaleb L. (mahaleb cherry). As a control, the low vigorous rootstock 'Gisela 5' was used. Clonal progeny of the examined germplasm was obtained by the rooting of softwood cuttings under the mist system. A significant variability of the examined germplasm was determined, out of which it was possible to allocate a few very interesting genotypes of ‘Oblačinska’ sour cherry ST1 and OV12 NC, and mahaleb cherry GM1, as a very uniform low vigorous sweet and sour cherry rootstocks. Selections within ground cherry were vigorous, and produced large number of suckers. Proportional growth of rootstock stem, graft point and scion points to good compatibility among all examined interactions of rootstock/scion. The results clearly point to the potential within the examined germplasm of genus Psunus sp. as new cherry rootstocks.

Key words: sweet cherry, sour cherry, germplasm, rootstock breeding