Abstract. For accelerated development of fertility restorer lines with imidazolinone tolerance in sunflower (Helianthus annuus L.), the gamma-induced parthenogenesis, which combines classical breeding approaches and in vitro techniques, was applied. As initial materials six imidazolinone-tolerant hybrid combinations (F1203, F1216, F1246, F1248, F1295 and F1332)Keywords: sunflower, double haploid fertility restorer lines, embryo culture, gamma-induced parthenogenesis AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 9, No 3, pp -3, 2017 190 19 DOI: 10.15547/ast.2017 IntroductionThe herbicide-tolerant sunflower hybrids are generally preferred by agricultural producers in Bulgaria and this determines the main directions of contemporary sunflower breeding. Imidazolinone (IMI) and sulfonylurea (SU) tolerance to herbicides transferred to cultural sunflower from wild species is most often used (Kaya et al., 2012).The development of parental components for the hybrid is a necessary prerequisite for the production of sunflower hybrids tolerant to herbicides. The classical breeding approach for developing lines that can be included as parental components of hybrids comprises inbreeding of plants for at least 5 -6 years. To accelerate this process, a number of researchers have directed their attention towards non-traditional approaches for production of homozygotic lines. The development of plant biotechnologies opened new opportunities in this respect. One of the methods for accelerated development of haploid and double haploid lines is the gamma-induced parthenogenesis (Todorova et al., 1997;Gok Guler et al., 2015;Blasco et al., 2016;Wang et al., 2016). The use of this method significantly shortens the time necessary to develop parental lines for heterosis breeding in sunflower Ivanov, 1999, 2000). The properties of the double haploid lines obtained through this method are determined by the genetic potential of the initial material they were derived from. In spite of the unquestionable benefits from the use of biotechnology methods for acceleration of the breeding process, there are many cases in which they are influenced by the genotypic responsiveness of the investigated plant material (Sauton, 1989;Bouvier et al., 1993;Faris et al., 1999;Todorova et al., 2004;Taşkın et al., 2013;Drumeva and Yankov, 2015). Therefore, additional investigations and certain modifications of the standard methodologies are necessary depending on the specific requirements of the genotype.This study was aimed at investigating the genotypic responsiveness of sunflower hybrid combinations with expressed herbicide tolerance to the application of the gamma-induced parthenogenesis method for accelerated production of imidazolinones-tolerant fertility restorer lines. Material and methodsAs initial materials for parthenogenetic induction six imidazolinone-tolerant hybrid combinations (F1203, F1216, F1246, F1248, F1295 and F1332), obtained from Dobrudzha Agricultural Institute, General Toshevo, were used. For initiation of parthenogenetic embryo devel...

The investigation was carried out on slightly leached chernozem soil type during 2014 -2016. The effects of different soil tillage methods for sunflower on the vertical distribution of the seeds in the soil layer and the development of the plants were followed -ploughing at 24-26 cm, chisel ploughing at 24-26 cm, disking with disk harrow at 10-12 cm and no-tillage. The highest percent of sunflower seeds in the zone of the soil layer optimal for sowing (5-7 cm) were significantly placed in the areas cultivated with chiselploughing (62.1%). Under the other types of soil tillage, their amount decreased. When sowing was performed at a mean diurnal air temperature close to the norm (10.1 °С), the emergence of the plants in the variants with chisel ploughing, disking and no-tillage occurred significantly slower in comparison to ploughing. At higher mean diurnal air temperature (12.0 °С), only at the beginning of sunflower emergence some delay was observed depending on the type of the applied soil tillage. Under these conditions, a significant difference in the occurrence of the phenophases was determined in the variants with disking and direct sowing, as compared to the areas with ploughing. With the minimizing and exclusion of the soil tillage, the growth of the sunflower plants was significantly retarded at the initial stages of their development. At phenophase flowering, the plant height and the stem diameter were lowest in the areas cultivated with disking. The investigated types of soil tillage did not have a significant effect on the diameter of the sunflower heads.

Although in Bulgaria there is a sub-law from the Law of Tourism regulating the security and safety of the users of the ski slopes in Bulgaria, not enough attention is paid to the point of view of reasons for the accidents, feedback, and prevention of injuries in the snow sports. Another argument underlying the relevance of the topic is the more frequent intervention of experts in snow sports from NSA “Vassil Levski”, which has been invited as an experts in the preparation of sports-technical expertise for occurred accidents on the slopes. This study aims to research the type of accidents and traumas in ski zone Borovets for 2019/ 2020 year on various indications – an hour of occurrence of the trauma, slope complexity, type of the trauma, and type of ski or snowboard equipment. The tasks reviewed as determine the type of trauma with ski and snowboarding. Methods used: frequency analysis, analysis of documents, comparative analysis. Summary of results: the total number of accidents on the slopes of ski zone Borovets for season 2019/2020 is 455. The skiing accidents are nearly 8 times as many as the snowboarding ones. We distributed the traumas into four sub-groups: head, body, legs, and arms. It appeared that the biggest number of traumas is the ones of the legs, followed by those of the arms. In slope accidents, the most common trauma is on the knee joints, followed by shoulder and lower leg injuries. From those traumas, we reviewed the most severe traumas – the fractures. The most registered fractures are the ones of the lower leg and the collarbones. Conclusions: Borovets is in second place in incidents in Bulgaria for the period. The highest percent of the traumas are the ones of the lower limbs, registered in the alpine ski. The incidents occur mainly on blue slopes.

This paper aimed at studying the effect of different types of soil tillage systems on the change of total carbon (C) and nitrogen (N) in the soil structural units of different size after dry structural analysis of soil. The research was carried out in a 6-field rotation system (grain maize-wheat-sunflower-wheat-bean-wheat) at the end of the 2nd rotation. Six out of 24 soil tillage systems were selected; they were applied independently and in combination in the crop rotation. After that, they were compared to the system with constant deep plowing. So a total of seven soil tillage systems were investigated. The selected systems for main soil tillage were the following: plowing (control variant), disking, cutting, nil tillage (direct sowing), plowing-disking, plowing-nil tillage, disking-nil tillage. Three depths of 0-10, 10-20 and 20-30 cm were studied, as well as soil structural units were of the following sizes: > 10 mm, 10-5, 5-3, 3-1, 1-0.25 mm and < 0.25 mm. As a result of systematic implementation of different soil tillage systems, higher N and C concentrations were established by the layers according to constant plowing. Constant disking and its alternation with nil tillage increased the total N concentration with 15.6% and 11.1%, respectively, in comparison with the constant plowing. The same was valid for C concentration in soil, but the highest increase was established in the variants with constant cutting and nil tillage. The exceeding was with 14.0% and 13.2%, in comparison to constant plowing. The redistribution of N and C depending on the structural soil units was most expressed in the 0-10 cm and 10-20 cm layers. The highest amounts of C and N were found in the soil units with size less than 5 mm, mainly in the < 0.25 mm fraction. At depth of 20-30 cm, the role of the size of soil structural units for C and N redistribution decreased strongly. The values of C/N ratio were moderate only under the use of constant disking. This index was low under all other soil tillage systems. The correlation of total N with C in soil was high, positive and significant depending on the size of structural soil units and the tillage systems, as average for the investigated factors in this experiment. The minimal tillage and the tillage without turning of soil, used independently and in combination, had the highest contribution to preserving the organic matter in the haplic Chernozems of Dobrudzha region.

Abstract. The investigation was carried out in the trial field of Dobrudzha AgriculturalInstitute on slightly leached chernozem soil. In order to clarify the effect of some types of pre-sowing soil tillage for wheat on the crop structure and certain yield components, the following variants of a stationary field experiment were analyzed: double disking at depth 10-12 cm (check variant); ploughing at 14-16 cm + disking; no-tillage (direct sowing) -pre-sowing Keywords: wheat, pre-sowing tillage, crop structure, yield components AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 9, No 2, pp , 2017 DOI: 10.15547/ast.2017 Introduction square meter after direct sowing, averaged for three years.According to López-Bellido et al. (2000), the various types of soil tillage used in growing of wheat do not significantly influence the Wheat is a main cereal crop in Bulgaria and occupies the number of grains in spike. Małecka et al. (2015) reported higher greater part of the agricultural areas. The obtaining of stable yields values of this index in the variant with direct sowing. These authors and quality production from wheat under the conditions of the pointed out that grain weight per spike was mainly affected by the contemporary intensive agriculture is directly related to a complex of meteorological conditions. breeding (Chamurliyski et al., 2015; Kirchev and Delibaltova, 2016; The aim of this investigation was to follow the effect of some Raykov et al., 2016;Tsenov et al., 2017) and agronomy (Delibaltova ways of pre-sowing tillage of soil for wheat on crop structure and and Kirchev, 2010; Ivanova and Tsenov, 2010;Ivanova and Tsenov, yield components under the conditions of slightly leached 2012; Delchev, 2013; Georgiev, 2015) practices, soil tillage being a chernozem soils in Dobrudzha region. major one. The various ways and tools for soil tillage have different effects on the soil properties, the emergence, growth and development of the plants and the size of the produce (Klochkov, 1983; Boydaș and Turgut, 2007; De Vita et al., 2007; Fernández et al., 2007; Bakirov, 2008; D'Haene et al., 2008; Arvidsson et al., 2014). Material and methodsThe investigation was carried out during 2008 -2011 in the trial The fast and full germination of the wheat seeds and the uniform field of Dobrudzha Agricultural Institute -General Toshevo. The emergence of the plants are prerequisites for good yields (Nasr and effect of the different types of soil tillage on the development and the Selles, 1995). The different ways used for preparation of the soil productivity of the agricultural plants, and some physical and influence the formation of the planting beds of the seeds and hencechemical characteristics of the slightly leached chernozem soil the emergence of the crops (Mohanty and Painuli, 2004). The plants (FAO, 2002) have been investigated in a stationary field trial initiated emerging earlier contribute more to the formation of the yield in in 1987. The agricultural crops typical for this region (wheat, grain comparison to those emergi...