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Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. 'Kyustendilska sinya' cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) have become an alternative light source to the fluorescent lamp (FL) for the maintenance of plant tissue cultures due to their low heat emission, low power consumption and the ability to fine-tune the light spectrum. In this study, the effect of LEDs on the growth and leaf stomata features of in vitro cultivated raspberries (Rubus idaeus L. 'Lloyd George') was examined. The plantlets were grown in vitro under a lighting system based on the Philips GreenPower LED research module. Four groups of LEDs emitting white (W), red (R), blue (B), and mixed (W:R:B: far red = 1:1:1:1) lights and FL (control) were used. As a second control (marked as EV), plants grown in the multiplication and rooting stage under fluorescent lamps and then acclimatized ex vitro in a greenhouse for 90 days in natural light were included. Relative growth rate (RGR), protein content as well as stomata morphology and density of the plantlets were analysed after three passages under corresponding light treatment. The results show that different LEDs specifically affect the growth and size of leaf stomata and density of in vitro cultured raspberry plants and can be applied as an effective modulator of morphogenesis during micropropagation. The combination of white, blue, red and far red LED stimulated the accumulation of biomass and proteins, as well as the formation of a higher number of stomata on the lower surface of the leaves, which would be a prerequisite for more effective control of water loss from plantlets during the ex vitro acclimatization. [ABSTRACT FROM AUTHOR]

The bacterial blight caused by the Gram-negative bacteria Pseudomonas sp. is a significant problem in stone fruit orchards. The resistance or tolerance of the cultivars is one important strategy for disease control. In the frame of a study conducted with the support of the BNSF, administrative contract KП-06 M 46/2, was compared the reaction of plum cultivars and rootstocks, after inoculation with the bacterial pathogen Pseudomonas sp. Flowers and shoots of the cultivars 'Topgigant Plus' and 'Jojo' grafted on the two rootstocks - 'Docera 6' (Prunus domestica L. x Prunus cerasifera Ehrh.) and the seedling myrobalan plum rootstock (Prunus cerasifera Ehrh) were artificially inoculated. In addition, two years old rootstocks 'Docera 6', seedling P. cerasifera and 'Myrobalan 29C' (Prunus cerasifera) also were inoculated with bacterial suspension. The cultivar 'Topgigant Plus' had lower susceptibility to flower infection when grafted on the seedling rootstock than 'Docera 6'. The reaction of rootstocks fourteen days after inoculation showed a lesion diameter of 400 mm on 'Docera 6', 433 mm measured on 'Myrobalan 29C', and 41 mm on the seedling rootstock P. cerasifera. [ABSTRACT FROM AUTHOR]

In recent years, the light emitting diodes (LED) have become an alternative to the fluorescence lamp source of light for plant tissue culture, due to their low energy consumption, low heat emission, specific wavelength irradiation etc. The aim of this study was to investigate the effect of LEDs on the growth of in vitro cultivated raspberry (Rubus idaeus L. 'Lloyd George'). The plantlets were cultivated in vitro under an illumination system based on Philips GreenPower LED research module. Four groups of LEDs emitting in white (W), red (R), blue (B), mixed (W:R:B:far-red=1:1:1:1) lights and fluorescent lamps (control) were used in our studies. Growth parameters, some physiological and biochemical characteristics of the plantlets were measured after three four weeks passages under corresponding light treatment. Our results indicated that different LEDs specifically influence the growth and development of in vitro cultivated raspberry plantlets and could be applied as an efficient lighting system for rapid in vitro micropropagation of Rubus idaeus L. The combination of blue, red, far red and white LEDs (1:1:1:1) stimulated the growth and biomass accumulation, as well as the intensity of net photosynthesis. For optimal results, it would be advisable to shorten the culture period to 3 weeks. This effective and affordable protocol would support the commercial micropropagation of raspberries and other soft fruits. [ABSTRACT FROM AUTHOR]

Acclimatization is one of the key steps in the success of micropropagation of woody plants. Improvement of acclimatization of micropropagated woody fruit plants could be achieved in different ways. The purpose of this study was to optimize the acclimatization of micropropagated sweet cherry rootstock GiSelA 6 (Prunus cerasus 'Schattenmorelle' x Prunus canescens) through application of biostimulators of natural origin in floating system. A new generation of plant growth biostimulators Regoplant and Charkor (Agrobiotech, Ukraine) contain metabolism products of symbiotic fungus-endophyte of ginseng roots, cultivated in vitro. Micropropagated and rooted plantlets from cherry rootstock GiSelA 6 (Prunus cerasus 'Schattenmorelle' x Prunus canescens) were acclimatized in a floating system with 100 µl L-1 Regoplant or Charkor. As control plantlets with no additional treatments served. Multi-cell bedding plant trays filled with peat: perlite 1:1 (v:v) were used for acclimatization. Plants were grown in a greenhouse under high humidity conditions for one week and then humidity was gradually decreased. Data on some growth, physiological and biochemical parameters were collected 45 days after transplanting to ex vitro conditions. Regoplant (100 µl L-1) led the highest plants survival rate (86%), also the greatest values for the growth determined parameters. [ABSTRACT FROM AUTHOR]

The object of the experiment was the walnut cultivar Izvor 10, grafted on a walnut rootstock (Juglans regia L.). The plants were propagated by the "Hot Callus" method and grown in containers (50 l) with peat-pearlite mixture (2:1). The impact of nitrogen fertilization on the growth and the physiological characteristics of young walnut plants was studied. Variants of the experiment were: Control (not-fertilized), Variant II - 2 g N / container and Variant III - 4 g N container. The height of the fertilized plants varied from 86 to 107 cm and the stem diameter - from 12.76 to 13.61 mm, while the control plants reached average values of 49.33 cm in height and 10.53 mm in stem diameter and the differences were statistically proven. It was found that fertilization with ammonium nitrate (NH4NO3), in the range of 2 - 4g N/container contributes to a more efficient development and structuring of the photosynthetic apparatus, which, on the other hand, is a prerequisite for more intensive photoassimilation and biomass accumulation. It was concluded that fertilization is mandatory for the production of walnut planting material in containers. [ABSTRACT FROM AUTHOR]

Rooting in vitro is considered one of the main problems in the micropropagation of woody species. The aim of the present study was to optimise the rooting and acclimatization of micropropagated pear plants through applying a new plant-growth biostimulator of natural origin, Charkor (Agrobiotech, Ukraine). Charkor contains metabolism products of symbiotic fungus-endophyte of ginseng roots, cultivated in vitro. Microshoots of pear rootstock OHF 333 (Pyrus communis L. 'Old Home' x 'Farmingdale') were rooted on DKW (Driver and Kuniyuki, 1984) media supplemented with Charkor (0.1 ml l-1, 0.3 ml l-1 or 0.5 ml l-1) and 10 µM indolyl-acetic acid (IAA; alone or in combinations). Plantlets cultivated on a medium free of growth regulators served as a control. After three weeks on rooting media, plants were transferred for acclimatization in pots (peat: perlite 2:1). Data on fresh weight of leaves, roots, stems and dry matter, leaf area, mean number of leaves per plant, stem and root length, chlorophyll fluorescence and net photosynthetic rate were recorded 20 days after acclimatization. The best result was obtained with plants treated with10 µM IAA (alone) and in combination with 0.5 ml l-1 Charkor. [ABSTRACT FROM AUTHOR]

Helichrysum italicum (Roth) G. Don is a Mediterranean vegetal species from the Asteraceae family. The ornamental value of the flowers and the properties of its essential oils contribute to its popularity. The aim of the present study was to compare the effect of different cytokinins on the multiplication of Helichrysum italicum and to develop a reliable protocol for in vitro micropropagation of this medicinal and ornamental plant. Nutrient media based on both MS (Murashige and Skoog, 1962) or DKW (Driver and Kuniyuki, 1984) formulations were used. They were enriched with different cytokinins - BAP, Kinetin, or Zeatin (5µM). The best multiplication rate was achieved on DKW medium, supplemented with 5µM Kinetin. A high percentage of rooting was achieved on the control treatment and the nutrient media, supplemented with IBA. [ABSTRACT FROM AUTHOR]

Recently, cold atmospheric plasma (CAP) is under investigation for possibility to be applied for inactivation of pathogens in medicine, food technologies, water cleaning technologies and agriculture. The aim of the current study is to investigate the effect of CAP on microplants, propagated in vitro from plum tree (Prunus domestica L., cv. 'Kyustendilska sinya') naturally co-infected by M and D strains of Plum pox virus (PPV) and in that respect the possibility for CAP application for virus inactivation. In the present work, we have used two types of plasma sources for biological systems treatments: a surface-wave-sustained Argon plasma torch and an underwater diaphragm discharge. These enabled several variants of plasma treatment to be performed. Based on the data of IC-RT-PCR tests of the microplants on the third subculture after treatment, it was found the most effective variant was the reiterated plasma torch tip treatment to nodal segments without leaves in gas medium. The strain specific RT-PCR analysis results of PPV positive CAP-treated microplants showed that only PPV-M strain was identified after treatment, although the starting material was co-infected by both strains. The results obtained from IC-RT-PCR and strain specific RT-PCR of the acclimatized ex vitro plants have been in agreement with the data from molecular analyses of the microplants tested. These are the first experiments on CAP ability for inactivation of PPV from tissue of living woody plants even if in in vitro conditions. The completed estimation of this approach for obtaining of PPV-free plum plants will be made after more prolonged observation and testing of the ex vitro plants. [ABSTRACT FROM AUTHOR]