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:The aim of the present study was to establish the growth characteristics of the red-leaf peach hybrid No. 9-205, grown in a nursery, targeting its submission in future for recognition as a new vegetative rootstock for peach and nectarine cultivars. The traditional seedling rootstock 'Elberta' and the vegetative one GF-677 were included in the study. Hybrid No. 9-205 was selected from a population obtained at the FruitGrowing Institute in Plovdiv by open pollination of Rutgers Red Leaf seedling rootstock for peach, used in the past. It is characterized by high drought resistance and good resistance to diseases and pests. It is easily propagated under in vitro conditions and shows weaker growth compared to GF-677 rootstock. 18 cultivar/rootstock combinations were studied, including two cultivars of each peach type: for fresh consumption, for processing and of the nectarine type. 'Laskava' cultivar for fresh consumption, the processing cultivar 'Spasena' and the cultivar 'Gergana', which is of the nectarine type, are newly established in result of the implementation of the breeding programme at the Fruit-Growing Institute -Plovdiv. They were officially recognized in the period 2009-2012. The percentage of survival and of grafted bud shooting is high enough and meets the requirements of the production practices in nurseries. The planting material of the vegetative rootstock No. 9-205 is uniform in plant height and stem width and it fully complies with the quality standards.

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