Volume 31 (2019): Issue 1 (June 2019)

In this review, we present genetically modified (GM) horticultural events that have passed the regulatory process and have been approved for cultivation or food use in different countries. The first authorization or deregulation of a GM horticultural plant issued 25 years ago initiated a fast expansion of GM organisms (GMO) engineered by using gene transfer technology. The list of GM horticultural species comprises representatives of vegetables, fruit plants and ornamentals. We describe their unique characteristics, often not achievable by conventional breeding, and how they were developed, and the approval process. Information on the adoption of GM horticultural cultivars and sale is accessed if commercialization has occurred. The review comprises, among others, Flavr Savr^TM and other tomato cultivars with delayed ripening and improved shelf-life, insect-resistant eggplant (or brinjal), as well as virus-resistant squash, melon and the common bean, and also fruit trees, plum and papaya. Cultivation of the latter was particularly valuable to farmers in Hawaii as it ensured restoration of papaya production devastated earlier by the Papaya ringspot virus (PRSV). In contrast, a plum resistant to sharka (Plum pox virus; PPV) deregulated in the USA is still awaiting commercialization. GM events with improved quality include the recently marketed non-browning apple and high-lycopene pineapple. We also present orange petunia, blue ‘Applause’ rose and Moon-series carnations with a modified purple and violet flower colour. Finally, we discuss prospects of GM horticultural plants, including their development using promising new breeding technologies relying on genome editing and considered as an alternative to the transgenic approach.

The present study evaluated the effect of different organic fertilizers on the morphological parameters and yield in two different onion cultivars. Proper use of organic fertilizers in appropriate amounts could be helpful to growers from the economic point of view. Field experiments were conducted to study the effect of three different organic biofertilizers on yield and morphological parameters of two onion cultivars ‘Stuttgarter Riesen’ and ‘Rote Laaer’ during 2016 and 2017. The investigated treatments included: B-Stimul^® – a mixture of bacterial and algal extracts, EkoBooster 2^® – organic matter and NPK, and VermiFit A® – an extract of compost produced by Californian earthworms, peat, nutrients, plant hormones, enzymes, amino acids, and sugars. The following parameters of onion plants were evaluated: number of leaves, bulb diameter, bulb weight, marketable and total yields. The study showed that all the results were affected by the growing season (higher values were recorded in 2016). In ‘Stuttgarter Riesen’, EkoBooster 2^® application resulted in the highest bulb weight in 2016 (67.16 g) and in 2017 (55.17 g) and in the highest number of leaves in 2016 (6.66) and in 2017 (6.30), which led to the highest marketable bulb yield in 2016 (3.47 kg m⁻²) and in 2017 (2.53 kg m⁻²). In ‘Rote Laaer’ in 2016, EkoBooster 2^® application resulted in the highest number of leaves (7.06), bulb diameter (54.32 mm) and bulb weight (79.30 g). In 2017, the largest bulb diameter (54.13 mm) and the highest bulb weight (71.79 g) and marketable bulb yield (2.39 kg m⁻²) were determined after VermiFit A^® application. EkoBooster 2^® showed the best effect on parameters such as the number of leaves, bulb weight, and marketable bulb yield of the cultivar ‘Stuttgarter Riesen’ and positively affected the parameters of ‘Rote Laaer’ during 2016, while in 2017 VermiFit A^® showed better results as compared to the other treatments.

This study presents an efficient improvement in the in vitro propagation protocol for one cloned genotype of lentisk (Pistacia lentiscus L.) by assessing the effects of gibberellic acid (GA3) concentrations, different cytokinins and amino acids and their concentrations on shoot proliferation, the effects of shoot length on rooting and the effects of compost type (sterile and non-sterile) on acclimatization. The best growth medium for multiple shoot induction was the MS medium supplemented with a combination of 1 mg l⁻¹ BA, 100 mg l⁻¹ tryptophan and 0.5 mg l-1 GA3, which gave a mean shoot length of 1.64 ± 0.07 cm and a mean bud number of 5.46 ± 0.16. The best results in terms of root length, rooting rate and the number of roots per shoot were obtained with 2 cm long shoots. The rooted plantlets were readily acclimatized in the sterile compost. In conclusion, the micropropagation protocol developed in this study can be used for large-scale propagation of P. lentiscus L. in reforestation programmes.

Perennial wall-rocket (Diplotaxis tenuifolia) belongs to the Brassicaceae family. It has spread worldwide due to its functional properties, and has long been known in folk medicine of native populations in areas of the Mediterranean and western Asia. In the past, Diplotaxis tenuifolia was a herbaceous plant harvested and consumed as a spontaneous herb, but today it is an important leafy vegetable in ready-to-use salads, with an increasing impact in the national and international vegetable retail markets. The leaves of perennial wall-rocket have valuable nutritional properties because of the amounts of antioxidant compounds they contain, in particular glucosinolates, vitamin C, as well as flavonoids, which make their consumption beneficial for preventing some types of cancer and cardiovascular disease. In the current review, major pre-harvest factors of Diplotaxis tenuifolia production, such as cropping systems, fertilization, as well as water management and irrigation, are addressed with respect to crop productivity and leaf quality.

To gain insights into the regulatory networks of miRNAs related to golden colour formation in Ginkgo biloba leaves, we constructed an sRNA library of golden-green striped mutant leaves. A total of 213 known miRNAs comprising 54 miRNA families were obtained, and 214 novel miRNAs were identified in the mutant leaves. We further constructed a normal green leaf sRNA library as a control and compared the expression of miRNAs between mutant and normal leaves. We found 42 known and 54 novel differential expression candidate miRNAs; 39 were up-regulated and 57 down-regulated in mutants compared to normal leaves. Our transcriptome analysis and annotation of the predicted targets indicated that the potential roles of miRNAs in G. biloba leaves included involvement in the ‘Glutathione metabolism’, ‘Plant circadian rhythm’, and ‘Phenylalanine metabolism’ categories. miRNAs and their targets were further validated by qRT-PCR. The expression of miR159a and miR159c, in particular, was significantly higher in mutant leaves than in normal leaves, while their potential target gene CLT3, which is associated with chloroplast development, displayed the opposite expression pattern. In addition, the expression of miR396g-3p and miR396h was also significantly higher in mutant leaves than in normal leaves, while the target genes ABP1 (auxin-related gene) and PPR32 (chloroplast RNA editing protein), respectively, showed the opposite expression pattern. Combined with the transcriptome analysis, these data suggest that miR159, miR396, and their targets may participate in chloroplast development and hormone metabolism to regulate colour formation in G. biloba leaves.

The southern African geophyte Lachenalia with an enormous number of species and cultivars is nowadays a commercially important plant material. There is a need for research on the optimization of growing conditions to obtain a satisfactory visual quality of potted plants, which may boost its production on the international ornamental market. Our research can be considered as an innovative study on supplemental irradiation with various light spectra in relation to flower quality of Lachenalia spp. The main objective was to examine the usefulness of LED lighting in extending the length of the natural day to a 16/8 h photoperiod in order to control the development of Lachenalia ‘Rupert’ inflorescence during greenhouse cultivation in Central-European winter time. Three light treatments were applied with red (660 nm) and blue (440 nm) light in different ratios: 100% red (100/0), 90% red mixed with 10% blue (90/10) and 80% red with 20% blue (80/20). The PPFD at the plant leaf level was approx. 150 µmol m⁻² s⁻¹. The most favourable spectrum, 90/10, induced the longest inflorescences characterized by the highest stem diameter with simultaneously the highest number of florets. Additionally, blue light increased the anthocyanin content in the corolla by about 35%, compared with plants exposed to 100% red light and non-irradiated ones (control plants). This first study on the wavelength ratios is aimed to increase the production quality of Lachenalia and indicates the need for continuation.

The aim of this study was to identify the molecular and morphological characteristics of Turkish pea accessions (Pisum sativum L.). The genetic diversity among 130 Turkish landraces and 2 commercial varieties in a total of 132 pea accessions was assessed with 14 simple sequence repeat (SSR) markers. Forty-eight (48) polymorphic alleles were identified using 14 SSR markers. The pairwise Dice coefficients of similarity between accessions ranged from 0.091 to 0.960. The polymorphism information content (PIC) value ranged from 0.585 to 0.861. Overall, 50 morphological traits were evaluated. Cluster analysis was carried out on a matrix of Euclidean distances. The accessions were divided into three main groups. Principal component analysis (PCA) was used to identify the weight of each morphological characteristic. According to the results, the highest eigenvalue was observed in PC-I (13.88) followed by PC-II (11.42), and PC-III (7.32). The first fifteen PCs with eigenvalues > 1 explained 74.08% of the variability. The results showed that the molecular markers were useful and polymorphic, sufficient to allocate all the evaluated accessions. This research has provided significant insights into the genetic variability of Turkish pea accessions.

After conducting two-year observations in nurseries in the Małopolska province, Poland, the species of shrubs on which symptoms of discoloration and withering of the leaves/needles and shoots, and sometimes of whole plants, occurred most frequently were selected for further study. The species included juniper (Juniperus horizontalis ‘Wiltonii’, rose (Rosa ‘Star Profusion’), yew (Taxus × media ‘Hillii’) and highbush blueberry (Vaccinum corymbosum ‘Patriot’). The predominant fungus isolated from the diseased plants was Alternaria alternata (Fr.) Keissl. A pathogenicity test performed in the laboratory confirmed the pathogenic effects of A. alternata on all of the tested species of shrubs. In 2011-2014, a field experiment was conducted with A. alternata inoculum introduced into the growth substrate. The presence of the pathogen reduced considerably the annual growth of all the shrubs tested. The applied mycorrhizal inocula had an effect on some morphological characteristics of plants, such as height and number of shoots. Moreover, the plants whose roots had been treated with the mycorrhizal inocula and were grown in the substrate inoculated with the pathogen also achieved greater increases in growth in comparison with the plants treated with the pathogen as well as relative to the control. The protective role of mycorrhizal inocula against the damaging effects of the pathogen was evident in all the species of shrubs.

The publication presents the current state of knowledge regarding the importance of mulching in the cultivation of Cucurbitaceae (cucurbit, or gourd family) vegetables. The intensifying climate change – mainly decreasing rainfall – combined with large-scale production of cucurbit vegetables worldwide prompt the application of methods that reduce evaporation and weed infestation. One of the widespread methods is mulching of the soil. The most important advantages of this treatment include the efficient use of water, the reduction in soil erosion and in the leaching of nutrients to the deeper layers. In addition, mulching improves the physical and chemical properties of the soil, and positively affects the surrounding microclimate of the plant. The report includes descriptions of the characteristics of various types of organic, mineral and synthetic mulches used. The results of studies on the environmental conditions forming in mulched soil are presented. Also, the results of research into the physico-chemical properties of mulch-covered soil are collated. The effect of mulching on cucurbit vegetables was evaluated in terms of plant growth and development as well as fruit yield and its biological value. The monograph also deals with the effect of mulching on weed infestation, as well as the occurrence of harmful and beneficial organisms.

Berry skin colour is a crucial determinant of red/black grape berry quality. We investigated the effects of combination treatments with amino acids and a low concentration of ABA on anthocyanin accumulation in grapes. Among the amino acids tested, isoleucine and phenylalanine resulted in high anthocyanin contents in grape cell cultures. The combination treatments with isoleucine or phenylalanine, and a low concentration of ABA enhanced anthocyanin accumulation in grape cells and detached grape berries. The combination treatment with isoleucine, but not with phenylalanine, and ABA upregulated MybA1 expression. Field-grown grapevines received combination treatments with isoleucine or phenylalanine, and ABA in two growing seasons. In the 2015 growing season, the combination treatments with isoleucine or phenylalanine, and a low concentration of ABA accelerated anthocyanin accumulation in grape berry skins of field-grown grapevines on days 10 and 31 post treatment. The effects on anthocyanin accumulation became negligible at harvest. The effect of the combination treatment with phenylalanine and a low concentration of ABA on anthocyanin accumulation was masked in the 2017 growing season due to the unexpected stimulation of anthocyanin accumulation by the low concentration of ABA, although the combination treatment accelerated anthocyanin accumulation on days 3 and 10 post treatment. Taken together, the results suggested that exogenous isoleucine and phenylalanine interacted with ABA-mediated anthocyanin accumulation in grape berry skins of field-grown grapevines when the activity of ABA used to treat the grapevines was inadequate.

This study aimed at investigating the antiviral activities of biocides made of formulated essential oils. These were derived from five plant species: fennel, oregano, peppermint, thyme and ginger. The potencies of these preparations were tested against local infection with the Tobacco necrosis virus (TNV) on common bean (Phaseolus vulgaris L.) and against systemic infection with the Cucumber mosaic virus (CMV) on cucumber (Cucumis sativus L.). After the determination of the most effective concentration, the formulated biocides were tested in protective and curative manners (before and after virus inoculation) against the growth of plants. The obtained results showed that the peppermint-derived biocide had the greatest effect on reducing the infectivity of the TNV virus (100% growth inhibition at 4000 ppm), whereas the biocide from thyme was the most effective against the infectivity of the CMV virus, as it induced a complete growth inhibition at 3000 ppm. The results of the protective and curative experiments revealed that the formulated biocides exerted high protection and curative effects against the two viruses. The observations revealed that the biocides were able to enhance plant defences against viral infection, as indicated by the increased levels of total chlorophyll, protein and phenols. Moreover, the levels of the oxidative stress markers including peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were improved compared to the control settings. In conclusion, the formulated biocides progressively present a favourable alternative to chemically synthesized pesticides in crop protection.

Ensete ventricosum (enset) has been cultivated in Ethiopia since ancient times. It is a multipurpose, drought tolerant and food security crop. When burying enset corms for vegetative propagation, manure is usually placed on the soil surface. However, there is no research-based evidence to justify this practice. We hypothesised that enset sucker production would be enhanced by placing manure in the corm burial hole. We tested this hypothesis, investigated manure application rates per buried corm and tested the effect of supplying a small amount of inorganic fertilizer. Three enset cultivars (Endale, Gewada and Yanbule) were used. Ninety corm halves were buried in separate holes (N = 3), resulting in 1,389 individually recorded suckers. There were significantly more suckers and a larger total biomass when manure was placed with the corm than when spread on the top of the soil, thus corroborating the main hypothesis. The number of suckers and the biomass increased with increasing amounts of air-dried cow manure up to 4.0 kg DW per burial hole, while the size of the three largest suckers per buried corm increased further with 6.0 kg DW of manure. Supplying a smaller amount of manure (2.0 kg DW) or equal nitrogen amount from inorganic fertilizer increased the production, compared to the treatment with no fertilizer. In conclusion, we recommend that farmers should ideally bury the corm with 7-11 dm³ of air-dried pulverized manure, thoroughly mixed with field soil; if manure is in short supply, burying even a small amount of it with the corm is beneficial.

Quality of fresh produce is the most critical issue in the economics of a vegetable enterprise. In order to investigate the effect of biochar amendment and deficit irrigation on tomato fruit quality, experimental research was conducted under a rain shelter in southern China during the 2017 and 2018 growing seasons. The experiment consisted of five treatments. Crops were irrigated to 100% of field water capacity at all growth stages as treatments T1 and T2. The other treatments received 30% less irrigation water than T2 when its soil water content reached 70% of field capacity, and were designated as treatments T3, T4 and T5, applied at the vegetative (stage I), flowering and fruit development (stage II), and fruit ripening (stage III) stages, respectively. Treatment T1 included no biochar, while the other treatments included 10% biochar by weight. The results showed that the total soluble solids (TSS) content, sugar-to-acid ratio (SAR), vitamin C (VC) content, and colour index (CI) increased in the deficit irrigation treatments depending on the phenological stage, the fruit ripening stage in particular. Meanwhile, single fruit weight was significantly (p < 0.05) reduced by water deficit at stages II and III, subsequently affecting the total fruit yield. Biochar improved soil moisture conservation and had a positive effect on fruit quality as evidenced by better single quality attributes (p < 0.05) of T2 over T1. The GRA and TOPSIS appraisal methods were used to conduct the comprehensive quality analysis. Eventually, treatment T5 ranked the best in both seasons, and this was also confirmed by the combinational evaluation method.

The ability of salicylic acid and jasmonic acid to suppress post-harvest infection with green mould Penicillium digitatum and blue mould P. italicum on three citrus species Citrus reticulata ‘Kinnow’, C. limon ‘Meyer Lemon’, and C. limetta ‘Mosambi’ was evaluated in a dose-response study. Salicylic acid (SA) and jasmonic acid (JA) were applied to the fruits as a post-harvest dip treatment followed by wound inoculation with the pathogens. Both resistance inducers caused a significantly lower disease severity compared with the infected but non-treated control, whereas disease incidence was not significantly lower than in the control. The efficacy of both SA and JA in reducing disease severity was concentration-dependent; the use of higher concentrations resulted in a greater degree of suppression. All the Citrus species tested in this study showed different responses in terms of disease development. C. limon ‘Meyer Lemon’ showed the highest disease development, and C. limetta ‘Mosambi’ the lowest. To get an insight into the mechanisms underlying the increase in resistance, the activity of defence-related enzymes – peroxidase (POD) and polyphenol oxidase (PPO) – was recorded in SA- and JA-treated fruit peelings. The activity of both enzymes was directly proportional to the concentration of the SA and JA applications. The highest activity of PPO and POD was observed in C. reticulata ‘Kinnow’ and the lowest in C. limon ‘Meyer Lemon’ fruits. This study is the first to document an increase in the activity of PPO and POD in SA- and JA-treated Citrus species in the presence of blue mould and green mould pathogens.

Planting ornamental species can help to create pollinator-friendly habitats. In the present study the flowering phenology and floral reward (nectar and pollen) in two cultivars of Prunus serrulata (‘Kanzan’ and ‘Amanogawa’) were evaluated in 2014-2015 in the city of Lublin (south-east Poland). On average, the onset of flowering of P. serrulata occurred in the first ten days of April (‘Kanzan’) or at the end of April (‘Amanogawa’), and lasted 8-17 days. In each year of the study, P. serrulata ‘Kanzan’ started flowering 11-18 days earlier than P. serrulata ‘Amanogawa’. The double flowers of P. serrulata ‘Kanzan’ offered only tiny amounts of nectar and pollen. The total mass of sugars was 0.59 mg per flower and that of pollen 0.08 mg per flower. The semi-double flowers of P. serrulata ‘Amanogawa’ produced 4.5 mg of sugars per flower and 0.17 mg of pollen per flower. The frequency of pollinator visits to flowers was low in P. serrulata ‘Amanogawa’ and very low in P. serrulata ‘Kanzan’. Therefore, if pollinator-friendly arrangements are made in urban areas, these cultivars should not be planted.

Ornamental plants growing in urban areas are often exposed to salt stress that negatively affects their decorative value. Enhancement of their salt resistance to retain a high decorative value despite salt stress has therefore high practical importance. In our study, the exposure of Plectranthus scutellarioides (L.) R. Br. to NaCl-induced moderate (40 mM) or severe salt stress (80 mM) resulted in a number of stress responses including reduced growth parameters, decreased concentration of photosynthetic pigments, and an increase in the accumulation of anthocyanins and free proline. These changes were partially compensated for by the application of selenium (5 µM as Na₂SeO₄) to the growth medium. However, the beneficial effect of selenium on the growth and physiological parameters of P. scutellarioides was manifested only at the moderate level of salt stress. Under the severe salt stress, the application of selenium was not able to alleviate the phytotoxic effect of NaCl.

Iron deficiency induces a yellowing in the aerial part of plants, known as iron chlorosis, and reduces the growth, yield, and quality of the fruits. Understanding plant response to iron deficiency is essential for agronomic management. This study decoded the temporal response of tomato plants (Solanum lycopersicum L.) to iron deficiency by quantifying different vegetative parameters. Subapical root swelling in the first 2.0 mm and several shoot and root growth parameters were measured in plants grown in a nutrient solution with and without Fe, on different dates designated as days after transplantation (DAT). Correlations between the total chlorophyll concentration in young leaves and 22 morphological and physiological parameters were also calculated. The plants grown in the absence of Fe had a higher number of secondary roots at 3 DAT, compared to control plants. On the same date, subapical root swelling was also observed, particularly at 1.5 and 2.0 mm from the root tip. Those plants also had a lower chlorophyll content in young leaves and a higher ferric-chelate reductase activity (FCR; EC 1.16.1.17) in the roots. At 9 DAT, the overall vegetative performance (plant height, fresh weight of stems and leaves) was negatively affected. At the end of the experiment (14 DAT), significant correlations were found between chlorophyll and the studied parameters. In conclusion, tomato plants experienced a cascade of responses to Fe deficiency throughout nine days: firstly, root lateralization increased; later, root swelling was observed, and a decrease in leaf chlorophyll content was registered associated with an increase in root FCR. At the end, the biomass of tomato plants decreased.