Volume 29 (2017): Issue 2 (December 2017)

Tea (Camellia sinensis) is an important beverage crop cultivated in the tropics and subtropics under acid soil conditions. Increased awareness of the health-promoting properties of the tea beverage has led to an increase in its level of consumption over the last decades. Tea production contributes significantly to the economy of several tea-cultivating countries in Asia and Africa. Environmental constrains, particularly water deficiency due to inadequate and/or poorly distributed rainfall, seriously limit tea production in the majority of tea-producing countries. It is also predicted that global climate change will have a considerable adverse impact on tea production in the near future. Application of fertilizers for higher production and increased quality and quantity of tea is a common agricultural practice, but due to its environmental consequences, such as groundwater pollution, the rate of fertilizer application needs to be reconsidered. Cultivation of tea under humid conditions renders it highly susceptible to pathogens and pest attacks. Application of pesticides and fungicides adversely affects the quality of tea and increases health risks of the tea beverage. Organic cultivation as an agricultural practice without using synthetic fertilizers and other chemical additives such as pesticides and fungicides is a sustainable and eco-friendly approach to producing healthy tea. A growing number of tea-producing countries are joining organic tea cultivation programmes in order to improve the quality and to maintain the health benefits of the tea produced.

As a result of its domestication, breeding and subsequent commercialization, African violet (Saintpaulia ionantha H. Wendl.) has become the most famous and popular Saintpaulia species. There is interest in producing cultivars that have increased resistance to pests and low temperature, in the introduction of novel horticultural characteristics such as leaf shape, flower colour, size and form, and in improved productivity and enhanced flower duration in planta. In African violet, techniques such as the application of chemical mutagens (ethylmethanesulfonate, N-nitroso-N-methylurea), radiation (gamma (γ)-rays, X-rays, carbon ion beams) and colchicine have been successfully applied to induce mutants. Among these techniques, γ radiation and colchicine have been the most commonly applied mutagens. This review offers a short synthesis of the advances made in African violet breeding, including studies on mutation and somaclonal variation caused by physical and chemical factors, as well as transgenic strategies using Agrobacterium-mediated transformation and particle bombardment. In African violet, Agrobacterium-mediated transformation is affected by the Agrobacterium strain, selection marker, and cutting-induced wounding stress. Somaclonal variation, which arises in tissue cultures, can be problematic in maintaining true-to-type clonal material, but may be a useful tool for obtaining variation in flower colour. The only transgenic African violet plants generated to date with horticulturally useful traits are tolerant to boron (heavy metal) stress, or bear a glucanase-chitinase gene.

Biostimulants are commonly used in horticulture, primarily to increase yield quantity and quality, as well as plant tolerance to stress. The purpose of the study was to determine the effect of amino acid-based biostimulants and amino acids in combination with Ascophyllum nodosum filtrate, applied during the growing season on the phenolic content in broccoli heads both after harvest and after long storage in a cold store. The seedlings were planted in mid-July, and heads were harvested from September to October in each year of the study. Ascophyllum nodosum filtrate at a concentration of 1% was used during seedling production. The plants were watered with biostimulants twice, in the fourth and fifth week after sowing. They were also sprayed with amino acid-based biostimulants (1.5 dm3 ha-1) three times, i.e. after the second, fourth and sixth week after planting. The biostimulants were not used in the control treatment. After harvest, the heads were stored for three weeks in a cold store at 1-2°C and 95% RH. Chemical analyses of total phenolic, caffeic, ferulic and sinapic acids, and of quercetin and kaempferol were carried out on samples of fresh broccoli and after the first, second and third week of storage. It was found that the application of biostimulants resulted in a significant increase in the total phenolic content, sinapic acid content, as well as quercetin content. Both in the control treatment and in the plants treated with the biostimulants, the concentration of all the tested phenolic compounds increased with the duration of storage.

Dust pollution can negatively affect plant productivity in hot, dry areas with high insolation during summer. To understand the effect of water-deficit and its interaction with dust pollution on vegetative and physiological changes in grapevine ʻBidaneh Sefidʼ, two-year-old plants were subjected to drought stress (-0.1 and -1 MPa) and dust treatment in a greenhouse during 2013 and 2014. The results showed that dust had a significant negative effect on the number of leaves, shoot length, root and shoot dry weights, and total dry weight under both drought and well-irrigated conditions. Dust, when applied in combination with drought, caused severe growth reduction. Leaf relative water content (RWC) and membrane stability index (MSI) were reduced under dust and drought stress, while soluble carbohydrate, proline, malondialdehyde (MDA) and H₂O₂ concentrations increased. Furthermore, dust application resulted in characteristics similar to those induced by water-deficit stress and intensified vegetative and physiological changes when applied together. Dust and drought treatments increased peroxidases and ascorbate peroxidase activities when compared to the control. The results indicate that dust has an adverse effect on the growth and physiology of grapevine and plays a negative role in the response of grapevine to drought stress.

Sugar beet is recalcitrant to in vitro tissue culture. Usually, proliferation of in vitro cultured rosette explants is a prerequisite for micropropagation. Although hormonal treatments can induce proliferation in sugar beet rosette explants, they may also result in some side effects. In vitro culture of sugar beet explants and some hormonal treatments make them more prone to hyperhydricity. Effects of media with different concentrations of 6-benzylaminopurine (BAP) and kinetin (Kin) on the proliferation and hyperhydricity of haploid sugar beet explants were investigated. It was observed that 0.2 mg L^-1 Kin, with a reasonable amount of proliferation and minimum rate of hyperhydricity, performed better than BAP in different concentrations and combinations. The effect sizes of the treatments on the dependent variables were large. The correlation between proliferation and hyperhydricity of the treated explants was statistically negative and the association was large. However, the hormonal treatments without BAP or with the lowest amount of it produced the highest proliferation rate with the least hyperhydricity. The coefficient of determination was R² quadratic = 0.885. The results suggest that, in comparison with BAP, Kin is a potent plant growth regulator for the proliferation of sugar beet haploid explants that causes the least hyperhydricity. Although explants proliferated better in the presence of 0.01 mg L^-1 BAP in combination with Kin than under Kin alone, the hyperhydricity of the proliferated explants decreased their suitability for in vitro propagation.

The study was carried out in 2014 and 2015, and aimed to determine some important biochemical and antioxidant characteristics of the fruits of mulberry (Morus spp.) cultivars and genotypes found in Malatya (Turkey). Phenolic compounds (protocatechuic acid, vanillic acid, ellagic acid, rutin, quercetin, gallic acid, catechin, chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid, o-coumaric acid, phloridzin and ferulic acid), organic acids, sugars, vitamin C and antioxidant capacity were analyzed in sampled fruits. The results showed that most of the biochemical content and antioxidant capacities of the cultivars and genotypes were significantly different from one another (p < 0.05). Among the phenolic compounds, rutin (118.23 mg 100 g^-1), gallic acid (36.85 mg 100 g^-1), and chlorogenic acid (92.07 mg 100 g^-1) were determined to have the highest values for most of the fruit samples. Malic acid and citric acid were dominant among the organic acids for all the cultivars and genotypes except 44-Nrk-05. Glucose was measured as a more abundant sugar than fructose and sucrose in all samples. Antioxidant capacity, on the other hand, varied between 6.17 and 21.13 μmol TE g^-1 among the cultivars and genotypes analyzed.

In the study, micropropagation of three varieties of Lavandula angustifolia was developed, and the appearance of trichomes, antioxidant activity of extracts and antimicrobial activity of essential oils isolated from plants growing in field conditions and in vitro cultures were compared. The study evaluated the number of shoots, and the height and weight of the plants grown on media with additions of BAP, KIN and 2iP. The greatest height was attained by the lavenders growing on MS medium with the addition of 1 mg dm^-3 2iP - ‘Ellagance Purple’. The greatest number of shoots was developed by the ‘Ellagance Purple’ and ‘Munstead’ plants growing on the medium with 2 mg dm^-3 BAP. The highest weight was attained by the plants growing on the medium with the highest concentration of BAP - 3 and 5 mg dm^-3. Moreover, the present study determined the influence of media with the addition of different concentrations of IBA and media with a variable mineral composition (½, ¼, and complete composition of MS medium) and with the addition of IBA or NAA for rooting. The majority of the media used had a positive influence on the development of the root system. The longest root system was observed in ‘Ellagance Purple’ growing on the medium composed of ¼ MS with 0.2 mg dm^-3 NAA. All the examined oils exhibited activity towards S. aureus, S. epidermidis, P. aeruginosa, E. coli and C. albicans. The majority of the essential oils isolated from the plants propagated in vitro exhibited stronger antimicrobial activity than the field-grown plants. The plants propagated under in vitro conditions demonstrated considerably higher antioxidant activity as compared with the field-grown plants, which was determined using the DPPH, FRAP and ABTS assay.

The study evaluated some agro-morphological (fruit weight, fruit flesh ratio, fruit skin colour, number of fruits per raceme, number of racemes per bush), biochemical (vitamin C, soluble solids content, organic acids), and bioactive (total phenolics, total anthocyanins, total flavonoids, and antioxidant capacity) characteristics of the fruit of a number of selected European Cranberrybush (Viburnum opulus L.) genotypes grown in the Sivas province of Turkey. To evaluate the antioxidant capacity, ferric reducing antioxidant power (FRAP) assays were performed. The results showed genotype-specific differences in most of the agro-morphological, biochemical and bioactive characteristics. The range of fruit weight, number of fruits per raceme, and number of racemes per bush was between 0.67 and 0.82 g, 40.7 and 57.1, and 470 and 581, respectively. The highest vitamin C and soluble solids contents were found in the fruits of genotypes SIV-9 and SIV-6 as 39 mg per 100 g and 12.6%, respectively. Tartaric acid was the main organic acid in all the genotypes; it ranged from 120 to 144 mg per 100 g of fruit FW. Total phenolic, total anthocyanin and total flavonoid contents ranged from 621 to 987 mg gallic acid equivalents per 100 g, 15 to 51 mg cyanidin-3-rutinoside equivalents per 100 g, and 202 to 318 mg rutin equivalents per 100 g, respectively. Genotype SIV-10 had the highest antioxidant capacity (34.90 μmol Trolox per g, based on FRAP assays). The present study shows the potential of the evaluated European Cranberrybush genotypes for improving the nutritional value through germplasm enhancement programmes.

This study was conducted to investigate the effect of various horticultural substrates (compost, peat-coconut, peat TS1, flower soil, lowmoor peat) and a foliar spray of chlormequat (at a concentration of 1380 mg dm^-3) on the growth and flowering of the marigold cultivars belonging to two species: Tagetes erecta - ʻMarvel Mixtureʼ and ʻTaishan Orangeʼ, and Tagetes patula - ʻDurango Redʼ and ʻBonanza Flameʼ. The obtained results show that the plants grown in peat TS1 and peat-coconut were taller, had longer internodes and leaves, and thicker stems than the plants grown in the other substrates. Chlormequat significantly reduced the height of ʻMarvel Mixtureʼ (in peat TS1), ʻTaishan Orangeʼ (in lowmoor peat) and ‘Bonanza Flameʼ (in peat-coconut). The use of chlormequat also accelerated the development of flower heads in ʻTaishan Orangeʼ (in lowmoor peat).

‘Regina’ sweet cherry fruit (Prunus avium L.) harvested from trees grown on vigorous and semi-dwarfing rootstocks was stored in normal atmosphere (NA) at 8°C and 2°C, and in a controlled atmosphere (CA) 3% O2 + 5% CO₂ at 2°C for two weeks. At harvest time, the fruits differed in the measured quality parameters (firmness, soluble solids content - SSC, titratable acidity - TA) depending on the rootstock. The storage conditions and the rootstocks significantly influenced the fruit quality parameters after storage. Generally, reduced fruit firmness and TA, and higher SSC and SSC/TA ratio were observed at the end of the storage period. Among the rootstocks, the lowest soluble solids content was found in the fruit from trees on the vigorous F12/1 rootstock. The lower storage temperature decreased the SSC independently of the storage atmosphere composition. Firmer fruit was found in CA 2°C compared with the other two treatments. The greatest loss of weight was found after fruit storage in NA 8°C. The extent of fruit decay depended on the season, storage conditions and the rootstock. Storage in NA 8°C of the fruit grown on F12/1 rootstock resulted in the highest percentage of fungal decay. The best retention of the green colour of the peduncle was noted in CA 2°C. The findings on how the rootstocks affect sweet cherry fruit properties can be useful for sweet cherry breeding programmes, as well as for sweet cherry crop production and storage technologies.

The main goal of the research conducted in the Lednice chateau park was to map the current spectrum of host trees and shrubs. The aim of the investigation was also to record changes in the host species, namely between the years 1985 and 2016, and to get an overview of the extent and degree of mistletoe infection on the most significant tree species present in the park. Furthermore, the occurrence of mistletoe across the developmental stages of woody species was monitored. Apart from taxonomic changes also the quantitative extent and the degree of infection reported in the last 31 years, and the impact on the development stages of woody plants in the past 20 years were analysed. Among the most frequently infected taxa are currently: Acer campestre, Acer platanoides, Acer pseudoplatanus, Crataegus monogyna, Robinia pseudoacacia, Tilia cordata and Tilia platyphyllos. The average share of infected specimens of the above host species amounts to 34.28%. A distinctive change in frequency and infection degree was recorded in the aggregate spectrum of hosts. The presence of mistletoe was recorded in a total of 1,362 specimens (almost 12% of the trees growing in the area). Compared to 1985, the occurrence of mistletoe was newly recorded in a total of 13 families (+3), 19 genera (+5) and 42 species (+18). In Aesculus ×marylandica, Fraxinus biltmoreana, Magnolia hypoleuca ×tripetala or Malus ×moerlandsii, it was probably described for the first time ever. At the moment, the most existentially endangered taxon is Tilia cordata.

During two seasons of observations, 244 specimens of hoverflies belonging to 16 species and four trophic groups were collected from herb flowers. Predatory species constituted about 50% of all the registered species and from 55% (2010) to 64% (2011) of all the specimens found. The most numerous flower-visiting species within this group were small, poor flyers, typical of communities with low plants - Sphaerophoria scripta (Linnaeus 1758) (19.6% in 2010 and 23.5% in 2011) and Eupeodes corollae (Fabricius 1794) (13.4% and 12.1%, respectively). Both species were classified to the eudominant group. Syrphus vitripennis (Meigen 1822) and Melanostoma mellinum (Linnaeus 1758) were classed as dominants. Non-predatory saprophagous species from the subfamily Eristalinae constituted about 25% of all collected species; the phytophagous group was scarce represented by Eumerus funeralis (Meigen 1822), E. strigatus (Fallen 1817) and Merodon rufus (Meigen 1838). Of the coprophagous species, only Syritta pipiens (Linnaeus 1758) was collected (6.8-8.0%). There were clear differences between flowers in terms of feeding visits by adult hoverflies. Matricaria chamomilla L. and Thymus vulgaris L. were the most attractive flowers, whereas Origanum vulgare L., Carum carvi L., Lavandula angustifolia L. and Hyssopus officinalis L. were of an intermediate visit status and Ocimum basilicum L. was relatively under-visited.

The present study has described a simple protocol for efficient plant regeneration of Asparagus densiflorus ‘Sprengeri’ and ‘Myriocladus’ using single-node spear explants, and indirect organogenesis via callogenesis induced on internode explants. The results showed that the genotypes ‘Sprengeri’ and ‘Myriocladus’ regenerated to complete plants via nodal cultures and callus tissue, but the plant regeneration response was higher in secondary explants on MS medium with NAA + kinetin (1+1 mg dm^-3) after transfer onto a multiplication medium with IAA+BAP (1+4 mg dm^-3), and then onto a rooting medium supplemented with IBA (10 mg dm^-3) or NAA + kinetin (1+1 mg dm^-3). Primary explants of both cultivars showed high regenerative potential (via the callus stage) on MS medium with IAA+BAP. The cultivar Sprengeri also regenerated via somatic embryogenesis. Both kinds of ‘Meyeri’ explants have a morphogenetic potential for the formation of shoots, which, however, were not capable of rooting. This confirms that the explant, genotype and culture medium are determining factors in the in vitro plant regeneration system.

We evaluated the effects of spraying different concentrations of citric and malic acids on stock plants in the greenhouse prior to the propagation and rooting of rose (Rosa × hybrida ‘Love Letter’) cuttings. Malic and citric acids (3, 6 and 9 mM) were sprayed several times at 14-day intervals on rose plants in a commercial cut flower producing greenhouse. Single-node cuttings taken from flowering stems were rooted under misty conditions, and the rooting parameters including root count and dry root weight were measured. A distinct change was observed in rooting features in response to the applied organic acids. Malic acid significantly enhanced rooting at the intermediate concentration while retarding it at both the higher and lower concentrations. On the other hand, the effect of citric acid was best at the highest concentration applied. We conclude that in softwood cuttings taken from rose plants these organic acids can act as a potential alternative to the currently applied methods of promoting rooting.