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An R2R3-MYB transcription factor, CmMYB9a, activates floral coloration in chrysanthemum by positively regulating CmCHS, CmDFR and CmFNS, but inhibiting the expression of CmFLS. Chrysanthemum is one of the most popular ornamental plants worldwide. Flavonoids, such as anthocyanins, flavones, and flavonols, are important secondary metabolites for coloration and are involved in many biological processes in plants, like petunia, snapdragon, Gerbera hybrida, as well as chrysanthemum. However, the metabolic regulation of flavonoids contributing to chrysanthemum floral coloration remains largely unexplored. Here, an R2R3-MYB transcription factor, CmMYB9a, was found to be involved in flavonoid biosynthesis. Phylogenetic analysis and amino acid sequence analysis suggested that CmMYB9a belonged to subgroup 7. Transient overexpression of CmMYB9a in flowers of chrysanthemum cultivar 'Anastasia Pink' upregulated the anthocyanin-related and flavone-related genes and downregulated CmFLS, which led to the accumulation of anthocyanins and flavones. We further demonstrated that CmMYB9a independently activates the expression of CmCHS, CmDFR and CmFNS, but inhibits the expression of CmFLS. Overexpression of CmMYB9a in tobacco resulted in increased anthocyanins and decreased flavonols in the petals by upregulating NtDFR and downregulating NtFLS. These results suggest that CmMYB9a facilitates metabolic flux into anthocyanin and flavone biosynthesis. Taken together, this study functionally characterizes the role of CmMYB9a in regulating the branched pathways of flavonoids in chrysanthemum flowers.

Interaction of plants with beneficial microbes is one of the strategies for increasing growth and resistance under environmental stresses. In this study, the effects of a fungus, Piriformospora indica, on growth and salt resistance in gerbera (Gerbera jamesonii L.) seedlings were investigated. After co-cultivation with P. indica, the gerbera roots were colonized by the mature chlamydospores of P. indica. A large increase in plant biomass and enhanced photosynthesis were observed in the P. indica-colonized seedlings. Moreover, these seedlings also exhibited a strong tolerance to salt stress after the colonization. The wilting symptoms, the impairments in chlorophyll, carotenoids, and photosynthesis, and anthocyanin accumulation, that can be caused by salt stress, were alleviated in the P. indica-colonized plants. The malondialdehyde and hydrogen peroxide levels were lower in P. indica-colonized plants than in non-colonized plants under salt treatment, whereas both enzymatic and non-enzymatic antioxidants were not increased by P. indica colonization. Differential expressions of sodium transporter genes and aquaporin genes were found in gerbera plants after P. indica colonization. The P. indica colonization positively regulated the transcription level of genes involved in ionic homeostasis, such as NHX2 and SOS1, while most aquaporin genes were not induced in P. indica-colonized gerbera seedlings exposed to salt stress, except for NIP6;1 gene. These results demonstrate a strategy through plant–microbe interaction to promote Gerbera jamesonii performance under salt stress.

Gerbera is an important cut flower crop popular throughout the world. In summer months of 2016, gerberas grown in polyhouses of RHREC, GKVK, Bengaluru, Karnataka, India showed heavy infestation of thrips and displayed symptoms of viral infections. Infected plants displayed irregular chlorotic or necrotic spots or blotches, necrosis of veins, bronzing, crinkling and deformations of leaves; necrotic streaks on flower stalks; chlorosis or necrosis of flower petals; tip necrosis or death of young plants. The virus was identified as groundnut bud necrosis virus based on DAC-ELISA, RT-PCR and transmission studies, and it was characterized by cloning and sequencing of N gene and 3′ UTRs. Thrips associated was identified as Scirtothrips dorsalis and the virus was detected in individual thrips using DAC-ELISA. The virus could be efficiently transmitted to cowpea variety C-152 both by mechanical sap inoculation and vector transmission and to tulsi plants by vector transmission. Sequence of S-RNA segment of the virus from two independent gerbera samples was submitted under the accession numbers KX832986.1 and KX832987.1. The two isolates showed per cent identities of 97.1 and 98.5 at N gene and at 3′ UTRs, respectively, with each other and 92.9–99.1% at N gene with other GBNV isolates. Phylogenetically they clustered along with other GBNV isolates reported from different hosts and locations within the major clade of watermelon silver mottle virus serogroup. Differential response was observed in gerbera varieties with respect to incidence of GBNV disease (19.6–80.6%) and thrips (24.6–54.0 thrips/leaf) with the least incidence in the varieties Esmara and Orinaco.

Key message We review the main genes underlying commercial traits in cut flower species and critically discuss the possibility to apply genome editing approaches to produce novel variation and phenotypes. Abstract Promoting flowering and flower longevity as well as creating novelty in flower structure, colour range and fragrances are major objectives of ornamental plant breeding. The novel genome editing techniques add new possibilities to study gene function and breed new varieties. The implementation of such techniques, however, relies on detailed information about structure and function of genomes and genes. Moreover, improved protocols for efficient delivery of editing reagents are required. Recent results of the application of genome editing techniques to elite ornamental crops are discussed in this review. Enabling technologies and genomic resources are reviewed in relation to the implementation of such approaches. Availability of the main gene sequences, underlying commercial traits and in vitro transformation protocols are provided for the world’s best-selling cut flowers, namely rose, lily, chrysanthemum, lisianthus, tulip, gerbera, freesia, alstroemeria, carnation and hydrangea. Results obtained so far are described and their implications for the improvement of flowering, flower architecture, colour, scent and shelf-life are discussed. Electronic supplementary material The online version of this article (10.1007/s00299-020-02632-x) contains supplementary material, which is available to authorized users.

Fungal diseases are one of the major factors responsible for severe agricultural losses with a deep impact to the economy. An early detection of these diseases, preferably at the agriculture site itself could be useful so that appropriate counter measures can be taken against the pathogens. In our paper, we have focused on analyzing and characterizing phytopathogens. Foldscope—an origami-based paper microscope—was used for visualization of diseased leaves, fruits, vegetable parts, pathogenic fungal pure cultures, etc. We characterized fungal isolates acquired from various vegetable, fruit, and ornamental plants. Our main objective was to evaluate whether the paper microscope could be used as a preliminary tool for onsite observation of fungal diseases in crops, so that immediate measures can be taken by farmers against fungal infestation prevailing in their agricultural fields. This will thus ensure reduction in crop and revenue losses for the farmers. Ours is the first report wherein phytopathogenic fungi from broccoli, gerbera, guava, okra, and orange as host plants have been successfully identified with the Foldscope as a tool and studied to the extent where cell wall–degrading enzymes, pathogenicity, and ITS region sequencing have been established for these fungi.

Ninety five bacterial strains were isolated from the rhizosphere and soils of flower crops, specifically gerbera, carnation and tuberose, were preliminarily screened against Fusarium oxysporum f. sp. gerberae in vitro along with five elite strains Bbv 57, EPCO 16, EPC 5, EPC 8 and Pf 1 obtained from Department of Plant Pathology, TNAU, Coimbatore, India. The results revealed that the strain Bbv 57 had highest inhibition of 50.00% and showed the maximum value for the assays that is siderophore, hydrogen cyanide, IAA, GA3 and salicylic acid production (3.68 O.D. value; 14.05 µg ml-1; 44.40 µg ml-1; 25.28 µg ml-1 and 19.25 µg ml-1 respectively). It also showed resistance to antibiotics namely ampicillin, erythromycin, clindamycin. The highest exopolysaccharides, biofilm production was observed and had lowest protease production clearly indicated that it is non - pathogenic to plants. Further, the polymerase chain reaction using16S rRNA intervening sequencing showed 100% homology to Bacillus subtilis (KF718836) and showed positive for quorum sensing regulator genes of aiiA and comQ. Additionally, the culture filtrate assay also produced significant reduction in egg hatching capacity and juvenile mortality of root-knot nematode Meloidogyne incognita. Further, the HPLC study showed 91.69 µg µl-1 of surfactin with the retention time of 2.304 min and 0.453 µg µl-1 of Iturin with the retention time of 8.739 min at 205 nm. Whereas, GCMS analysis has detected the aliphatic hydrocarbons responsible for antifungal, antibacterial and nematicidal activity.

Each species cultured in vitro has specific nutritional requirements on the culture medium. The use of silicon in culture can provide benefits to plants, such as increase of tolerance to water stress, increase of photosynthetic capacity and reduction in transpiration. These effects may be quite relevant for in vitro growth and development of plant and during acclimatization. However, the effectiveness of this nutrient may vary depending on the used sources. The aim of this study was to verify the ideal concentration of the MS culture medium and to evaluate the to evaluate the different sources as well as the function of silicon for in vitro development and acclimatization of gerbera plantlets. Shoots (4–6 cm) of gerbera (Gerbera jamesonii cv. Jaguar Cream) cultured in vitro were inoculated in MS medium with different concentrations of salts (MS ¼, MS ½, MS ¾, MS) supplemented with different silicon sources (potassium silicate, sodium silicate, calcium silicate and silicic acid) at concentrations of 0 (control), 0.25, 0.5, 0.75, and 1 mg L−1. The use of MS ¼ medium and the supplementation of 0.25 g L−1 calcium silicate provided better shoot development. The acclimatization rate was not affected by the origin of plants treated in vitro by different silicon sources, their concentrations, and the used culture medium. Thus, the use of silicon is beneficial for in vitro development of gerberas, however, the effectiveness depends on the used source. In vitro shoots of Gerbera jamesonii cv. Jaguar Cream regenerate better, shoots are taller and healthier, and root more effectively when are cultured on MS 1/4 supplemented with 0.25 mg L−1 calcium silicate.

Background Gerbera jamesonii Bolus ex Hooker f. (African daisy) is listed among the top five most important ornamental plants in the global floricultural industry. To satisfy its demand, the floriculture industry relies on reproducible and effective propagation protocol while retaining the genetic uniformity of G. jamesonii. The present study, for the first time, reports the potential of picloram for enhanced induction of organogenic calli from leaves of G. jamesonii and its high-frequency indirect regeneration. Results The fastest induction of calli with maximum fresh and dry weight was recorded in the Murashige and Skoog (MS) semisolid medium supplemented with 1 mg/l picloram. In addition, callus induction was observed in 2,4-dichlorophenoxy acetic acid- and α-napthaleneaceticacid-supplemented media but with delayed response and reduced fresh and dry weight. The proliferated calli were transferred to shoot induction media containing MS salt and 0.5–1 mg/l N6-benzylaminopurine, kinetin, or thidiazuron. A mean number of ~6 shoots per callus were developed after 5 days of culture in the MS medium supplemented with 1 mg/l kinetin, with a mean length of 5.2 cm. Successful rooting of shoots was achieved in the MS medium fortified with 1.5 mg/l indole-3-acetic acid, wherein the earliest root initiation (~5 days), as well as the maximum number (~9) and length (~4.8 cm) of roots, were recorded. Complete plantlets were primarily acclimatized in sand before being transferred to a mixed substrate (of soil, sand, tea leaf waste, and cow urine) that secured >90% survival and further growth of the plantlets. Eventually, clonal fidelity of the in vitro regenerants assessed via inter-simple sequence repeats (ISSR) primers exhibited a monomorphic banding patterns that suggested genetic integrity within the plantlets as well as with their mother plant. Conclusions The results of the present study should be of interest for commercial propagation and mutagenesis- as well as genetic transformation-related research.

Short vase life, capitulum wilting, neck bending, and postharvest chilling injury (CI) are major disorders have negative impact on quality and marketing of gerbera cut flowers. Low storage temperatures prolonging the vase life, but on the other hand leads serious CI which decreases the quality and consumer preferences. Spermine (SPER) and γ-aminobutyric acid (GABA) were identified as anti-aging factors delay the senescence and elevate the chilling tolerance in many species. Greenhouse-grown gerbera cv. ‘Stanza’ sprayed with 2 mM SPER and 1 mM GABA twice (2 T) or thrice (3 T). Cut flowers were stored at 1.5 °C and 8 °C postharvest to study the effects of GABA and SPER on senescence and CI. Vase life, CI and quality of cut flowers were improved by GABA and SPER treatments. No CI was observed in GABA-treated flowers at 1.5 °C; while, flowers sprayed with water showed severe CI. GABA treatments efficiently prolonged the vase life for 6–7 days more than the control (15 days). GABA and SPER increased the fresh weight, solution uptake, protein and proline contents, catalase, peroxidase, and superoxide dismutase activities, while decreased the electrolyte leakage, H2O2, and malondialdehyde contents, polyphenol oxidase, lipoxygenase, and phospholipase D activities. GABA and SPER significantly prolonged the vase life and prevented degradation of proteins and chilling damage and increased capacity of detoxifying and scavenging of H2O2 and reactive oxygen species (ROS), led to alleviate the negative consequences of the senescence and CI.

In January 2018, gerbera plants showed root rot symptoms were found in a greenhouse at Guizhou Horticultural Institute in Guiyang city, Guizhou Province in southwest China. Morphological and molecular identifications confirmed the isolation of Fusarium proliferatum. The pathogenicity was verified with Koch’s postulates. To our knowledge, this is the first report confirming root rot of gerbera caused by Fusarium proliferatum in China.

Carnation, gerbera and lisianthus are an important part of the cut flower market worldwide, but plant-parasitic nematodes (PPN) affect their production and quality. Therefore, rapid and accurate identification of PPNs is required for effective pest management programmes and crop rotation. In this study, a survey was carried out in the Antalya province of Turkey, an area where carnation, gerbera, lisianthus and chrysanthemum are commercially grown. A total of 79 soil samples were collected from greenhouses in the area, and 12 species-specific primers for identification of Meloidogyne, Pratylenchus and Rotylenchulus species were used for molecular detection. Pratylenchus thornei, M. incognita, P. neglectus, M. javanica, M. arenaria and M. hapla were detected in 98.73%, 88.60%, 65.82%, 34.17%, 22.78% and 5.06% of samples, respectively. Results showed combination of different PPN species in the soil of greenhouses where cut flowers were grown. These findings may be used to improve management practices, reducing losses in cut flower production.

The postharvest longevity of gerbera (Gerbera jamesonii) flowers has a critical importance in determining their commercial value; and therefore, there is a commercial demand for prolonging their vase life (VL). Here, we tested the efficacy of salicylic acid (SA, 150 µM) preservative in extending longevity of cut flower of two gerbera cultivars, namely the ‘Sunway’ and ‘Bayadere’, of which water-held ‘Bayadere’ has longer VL than water-held ‘Sunway’. The results indicated that exogenous SA could significantly prolong the VL of cut flowers of both ‘Sunway’ and ‘Bayadere’ cultivars, with better preservative effect being observed on ‘Sunway’. SA preservative was more effective in ameliorating relative water uptake and relative fresh weight in ‘Sunway’ than in ‘Bayadere’, which was accompanied by a greater decrease in proline accumulation. Application of SA prolonged the VL of two cut gerbera flower cultivars by inhibiting the activity of polyphenol oxidase involved in browning reaction, and decreasing oxidative stress through improving reactive oxygen species-scavenging antioxidant capacity, which included accumulation of total phenolic compounds and total flavonoids, and enhancement of enzymatic antioxidant activities. As a result, membrane lipid peroxidation levels were reduced in cut flowers of both cultivars, with higher reduction level being observed in ‘Sunway’ than in ‘Bayadere’. Additionally, SA preservative was more efficient in maintaining a greater content of total soluble proteins in ‘Sunway’ than in ‘Bayadere’. These findings clearly demonstrated that SA has higher preservative effects on extending VL of ‘Sunway’ than that of ‘Bayadere’. Taken together, SA can be recommended to farmers for postharvest treatments to maintain quality and delay senescence of gerbera flowers.

In this study, the effect of gamma irradiation in inducing resistance/tolerance towards powdery mildew disease was investigated in Gerbera jamesonii cv. ‘Harley’. In vitro shoot cultures were established through capitulum explants on Murashige and Skoog medium supplemented with 22.2 µM 6-benzyladenine (BA) and 2.53 µM indole acetic acid (IAA), followed by gamma irradiation of regenerated shoots (3–5 cm). Activity of four antioxidant enzymes i.e. superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase increased significantly as compared to the control and reached to highest level at the most stringent doses of mutagen. Ninety randomly selected irradiated plants (6 months old) and 100 control plants were inoculated with fungal conidial suspension, to screen for tolerance/resistance against powdery mildew. The severity of the disease was recorded on 0–4 scale with ‘0’ indicating highly resistant; ‘1’ indicating resistant; ‘2’ indicating medium resistance; ‘3’ indicating susceptible and ‘4’ indicating highly susceptible. Three plants (3.33%) irradiated with 5 Gy were found to be tolerant to powdery mildew as these plants showed slight and delayed development of fungal colonies on the leaves. The random amplified polymorphic DNA characterization showed that the irradiated plants had DNA patterns that were different from the control and mother plants.

Gerbera jamesonii cv. Dura is a well-known and economically important ornamental crop that is produced using micropropagation. This study aimed to evaluate the effect of various light wavelengths in six different light emitting diode (LED) treatments on biometric attributes and photosynthetic pigment content in gerbera plants grown in vitro. The LED treatments were B (100% blue), RB1 (50% red and 50% blue), RB2 (70% red and 30% blue), RBW (40% red, 40% blue, and 20% white), RBfR (49% red, 49% blue, and 2% far red), and R (100% red). Light quality was seen to significantly affect plant growth and development. The highest shoot multiplication rate was observed in plants grown under both RB1 and RB2. Plantlets grown under R displayed the greatest shoot elongation, and their petioles were three times longer than those grown under B. Both B and R resulted in reduced leaf blade area. Rooting of shoots was observed in plants grown under all light treatments; however, R stimulated adventitious root formation. The average number of roots produced by plants under all light treatments was calculated and found to match that produced under RB2. The RBfR treatment caused a reduction in leaf dry weight compared to that produced under B, which represented the highest leaf dry weight. Control fluorescent lighting, supplied by Philips TL-D 36W/54 lamps, had a positive effect on root dry weight. Photosynthetic pigment content was higher in the leaves of rooted plants compared to that in plants at the multiplication stage. RB2 resulted in higher concentrations of chlorophyll a and b and carotenoids, whereas lower accumulation of photosynthetic pigments was observed under R. These results demonstrate that light wavelength manipulation through LEDs can be strategically used for the rapid and large-scale propagation of gerbera. The outcomes of this study offer potential to improve micropropagation efficiency and reduce the costs of in vitro plant production.

Fungus gnats (FG) have been reported in Venezuelan greenhouses recently. Bradysia difformis Frey (Diptera, Mycetophilidae) was found attacking Daisy gerbera plants [Gerbera sp. L. (Asterales: Asteraceae)] and many other crops in the country causing serious damages. Heterorhabditis amazonensis Andalo et al. (Rhabditida: Heterorhabditidae), was used to assess the mortality of larvae and adults of FG, number of invader nematodes per larvae and to compare the mortality of FG using nematodes and/or ciromazine under laboratory conditions. In a commercial flower farm, different doses of these nematodes were applied for eight weeks to control FG. The results showed 95% of mortality of the B. difformis larvae under laboratory conditions and performed better in the field when 50,000 nematodes were applied in every pot as a base dose to initiate a control programme. According to our results, H. amazonensis has the potential to become a regular organism for controlling fungus gnat larvae in tropical greenhouses.

We investigated the effects of different NO3 −:NH4 + ratios in nutrient solution on the yield and growth of gerbera (Gerbera jamesonii) cut flowers in soilless culture. Two cultivars of gerbera (red ‘Stanza’ and yellow ‘Double Dutch’) were supplemented with four different NO3 −:NH4 + ratios (100:0, 80:20, 60:40, and 40:60). Replacing 20% nitrate in the nutrient solution with ammonium resulted in the higher number of leaves per plant, highest fresh and dry weights of roots and shoots, greatest number of flowers, highest flower stalk diameter and flower disk diameter, longest vase life, highest fresh and dry weight of inflorescences, and highest relative water contents in petals compared with the control. Decreasing the NO3 −:NH4 + ratio to 60:40 caused a considerable reduction in plant growth and biomass. The chlorophyll and carotenoid contents, as well as catalase (CAT) and peroxidase (POX) activity, increased with increasing proportion of ammonium-to-nitrate in the nutrient solution. The results suggest that a NO3 −:NH4 + ratio of 80:20 should be used for gerbera cut flower production to achieve the highest growth and quality.

In the global flower industry, gerbera (Gerbera jamesonii Bolus ex Hooker f.) is ranked within the top 10 cut ornamental flowers. Commercially, micropropagation is more important than seed or vegetative propagation. This study assessed the viability of using a temporary immersion bioreactor (TIB; BIT®) to propagate shoots in vitro. Factors such as immersion frequency (6, 8 and 12 h), additional ventilation (1 min every 2 h) and the length of duration of shoot culture (14, 21, 28 and 35 days) were tested. Immersion every 8 h with additional ventilation produced more shoots with better morphology than the control. The average multiplication rate was 9 shoots/explant across treatments. However, when shoots were immersed every 6 h, shoots had higher fresh and dry weight, but displayed hyperhydricity. No differences in shoots were found when immersion frequency was 8 or 12 h. Additional ventilation (12 min/day) reduced shoot hyperhydricity to 5.24% as compared to the ventilation-free control (31.37%). Shoots receiving additional air supply every 8 h had lower fresh and dry weight with an 89.8% decline in relative water content. The number of shoots/explant increased as culture time increased, 6.7 after 28 days, and 6.1 after 35 days (statistically equal). After 7 and 14 days, shoots were induced to root in the TIB using the same medium but supplemented with IAA. Plantlets were subsequently acclimatized. More than 87% of plantlets survived in a zeolite and sugarcane filter cake (1:1) substrate. This protocol allows for the mass production of gerbera shoots in a simple TIB, with effective rooting and acclimatization. This is the first documented TIB for gerbera.

A strong antibiotic producer, Bacillus subtilis strain Bbv 57 (KF718836), has been utilized for the management of wilt-nematode complex (Fusarium oxysporum f. sp. gerberae, Meloidogyne incognita) in gerbera under greenhouse conditions in the Department of Floriculture, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The strain strongly inhibited F. oxysporum f. sp. gerberae (KM523669) mycelial growth to an extent of 44.33 and 63.33%, at 10 and 100 μl, of culture filtrate, respectively. Further, the culture filtrate at 100% concentration exerted lethal effect on nematode eggs (7.00 hatched) and juveniles (87% mortality) compared to control. The analysis of TLC revealed that Bbv 57 showed the cyclic antimicrobial peptides surfactin and iturin that were confirmed by PCR. Strain Bbv 57 was able to produce antifungal and anti-nematicidal activity with reduced wilt incidence (15.33%) and thus holds a great potential for use in the biocontrol of Fusarium wilt-root-knot nematode disease complex in gerbera under greenhouse conditions.

We analyzed the expression of anthocyanin biosynthesis genes and transcription factors (TFs) in the Gerbera hybrida cultivars ‘Bintang’ and ‘Alliance’ that exhibit different coloration patterns. Differential expression of biosynthesis genes and TFs was associated with variable anthocyanin content at different flower developmental stages (S1–S3) in both cultivars; higher anthocyanin content was correlated with higher levels of gene expression. Exposure to different temperatures (6 and 22 °C) also resulted in different anthocyanin content levels: the lower temperature (6 °C) enhanced anthocyanin content compared to the higher temperature (22 °C). However, the increased anthocyanin content of ‘Bintang’ compared to ‘Alliance’ was the result of higher levels of expression of all detected genes, regardless of flower stage and temperature conditions. Therefore, we conclude that transcriptional control of the detected genes is associated with the mechanisms of anthocyanin biosynthesis and coloration patterns in gerberas; however, further studies of the key genes are needed.

Purpose This study was performed to investigate the impact of various agricultural wastes as potting media on growth, yield, and quality flower production of Gerbera jamesonii L. cv. hybrid mix, and to estimate hazardous impact of chemical fertilizers. Method The effect of four agricultural substrates viz. farm yard manure, coconut coir dust, Lahore compost (local produce), and leaf compost combined with conventional media i.e., garden soil, sand, and silt in equal proportion was studied for commercial production of gerbera. All the treatment combinations were arranged into completely randomized design with three replicates. Result Visible variations in morphological characters were evidenced among conventional medium and agricultural waste as substrates with significant superiority of flower quality and plant growth. The presented results showed that treatment combination of silt, coconut coir dust, and top soil (SCT) produced maximum plant height while mixture of silt, Lahore compost and top soil (SLT) gave maximum number of leaves per plant and maximum flower stalk thickness. The highest values for leaf area, number of roots, flower fresh to dry weight ratio and number of flowers per plant were achieved in combination of silt, farm yard manure, and top soil (SFT) whereas silt, sand, and top soil (SST) presented maximum flower diameter, maximum fresh, and dry weight of flowers. Chemical characteristics of growing media showed superiority of silt, farm yard manure, and top soil (SFT) and silt, sand, and top soil (STL) for available phosphorus and potassium with values of 27.0 and 500 ppm, respectively. Conclusion It was concluded that the application of waste materials in combination with silt provided positive results for vegetative and reproductive growth of Gerbera jamesonii plants.

Identification of distinct allelic versions for dihydroflavonol 4-reductase in gerbera cultivars reveals that gerbera DFR enzymes have strong substrate preference in vivo that is not reflected to the activity in vitro. Flavonoids in the model ornamental plant Gerbera hybrida consist of flavones, flavonols and anthocyanins. Anthocyanins accumulate in the adaxial epidermis of petals and give the different cultivars their characteristic red and violet colour. Both pelargonidin and cyanidin derivatives are found in gerbera, but none of the cultivars contain delphinidin. ‘Ivory’, a cultivar with white petals, is a sport of the pelargonidin-containing pink cultivar ‘Estelle’, i.e. it originates from an acyanic branch of ‘Estelle’. In this work, four different alleles encoding dihydroflavonol 4-reductase (DFR) were identified in gerbera cultivars. We found that, in contrast to ‘Estelle’ with the functional allele GDFR1-2, ‘Ivory’ carries a mutation in this gene that results in an inactive enzyme. Interestingly, ‘Ivory’ also expresses a second, nonmutated allele (GDFR1-3) in petal epidermi, leading to extractable DFR activity but not to anthocyanin biosynthesis. The second allele encodes a protein identical in amino acid sequence to the DFR of the cyanidin-containing variety ‘President’. Pelargonidin-containing cultivars do not react to the flavonoid 3′-hydroxylase inhibitor tetcyclacis, but cyanidin-containing cultivars lose their colour, instead of starting to synthesise pelargonidins, indicating the specificity of GDFR1-3 for the cyanidin pathway. This explains why petals of ‘Ivory’ are white, even when it has lost only one of the two enzymatically functional DFR forms, and shows that anthocyanin biosynthesis in gerbera is under more complex regulation than earlier thought.

An intergeneric hybrid between Hippolytiakaschgarica (maternal plant) and Nipponanthemum nipponicum (paternal plant) was produced without emasculation for the first time. This proves a close relationship between Hippolytia and Nipponanthemum, once again. The hybrids could be identified by nuclear ribosomal DNA internal transcribed spacer (ITS) sequences and morphological characteristics. The composition of the hybrid capitulum was a mix between both parents. It was basically similar to the maternal plant (Hippolytia) with yellow (actinomorphic) tubular florets, but supplemented with 5–13 white tetramerous, or pentamerous tubular florets bursting out in the outer whirl, being more distinctive and bigger. Instead of ligulate white ray florets of the paternal plant (Nipponanthemum), they were tubular (actinomorphic). The same phenomenon recently appeared in the intergeneric hybrid between Cancrinia maximowiczii (tubular) and the interspecific hybrid of Chrysanthemum naktongense × Chrysanthemum ×morifolium ‘Aifen’ (ligulate, daisy-like). The shape of the achenes of our new hybrid is quite similar to that of the paternal parent with pappus of separate unequal subulate scales, or awns. In the maternal parent, pappus is absent. Similarly to the referred intergeneric hybrid, this new viable hybrid might be used as bridge for breeding multi-generic hybrids within the Compositae tribe Anthemideae. Since the molecular mechanism behind the novel phenotype of the new hybrid has not been explored in Chrysanthemum, this is discussed here with recent findings in Senecio, Gerbera and Helianthus. One of the CYCLOIDEA-like genes that control floral symmetry, CYC2c is required for zygomorphy in normal ligulate ray florets. In novel intergeneric hybrids, ray florets remain actinomorphic (tubular), however. Some causes are tackled.

The present report describes an original protocol for in vitro direct induction of roots from leaf explants of gerbera for the first time. Since gerbera has immense potential as a premium cut-flower, the major attempts were made on in vitro mass propagation chiefly through in vitro multiple shoot proliferation or callus regeneration. Nevertheless, rhizogenesis could be impending an unattempted method with its yet-to-be known advantages. In our study, the optimum conditions for direct root induction from leaf explants were assessed employing tissue culture technique. Leaves were inoculated to MS medium containing no or variable auxin sources and concentrations namely, 2,4-dichlorophenoxyacetic acid, indole-3-acetic acid (IAA), indole-3-butyric acid or α-naphthaleneacetic acid for root induction. It was evident that the maximum root induction (with a frequency of 92.6 %) occurred on MS media fortified with 1.5 mg l−1 IAA, wherein root induction was observed as early as 11 days of culture and an average of ~19 roots with ~13 mm length was obtained from 4 cm2 leaf segment after 45 days of culture. Stereo microscopic observation revealed the induction of roots and gradual developmental stages of rhizogenesis. The efficiency of direct root induction without any interim growth stages (such as, callus or shoots) in our study offers a reproducible system that could provide a model protocol for more comprehensive developmental studies on root growth.

The effects of mineral nutrient were examined on in vitro growth of Gerbera hybrida (G. jamesonii × G. viridifolia), specifically Gerbera hybrida cv. Pasadena. Four types of experiments were conducted to quantify the effects of mineral nutrients on four in vitro growth responses (quality, shoot number, leaf number, and shoot height) of gerbera and included groups of mineral nutrients (macros/mesos, micros, and Fe), individual salts (CuSO4·5H2O, MnSO4·4H2O, ZnSO4·7H2O, and Fe/EDTA), and the specific ions NO3−, NH4+, and K+. Experiments included mixture-amount designs that are essential for separating the effects of proportion and concentration. Highly significant effects were observed in all experiments, but the mineral nutrients with the largest effects varied among the four growth responses. For example, leaf number was strongly affected by the macronutrient group in one experiment and by NH4+ and K+, which were in the macronutrient group, in the NO3−/NH4+/K+ ion-specific experiment, whereas quality was strongly affected by the micronutrients ZnSO4 and Fe/EDTA. Because mineral nutrient effects varied significantly with the response measured, defining an appropriate formulation requires a clear definition of “optimal” growth.

Marigold (cv. Lemon Gem), castor bean, ornamental pepper (cv. Black Pearl and Purple Flash), gerbera daisy (cv. Festival), feverfew, and sunflower (cv. Choco Sun) were evaluated for their suitability as banker plants (BP) for Orius insidiosus (Hemiptera: Anthocoridae) in commercial greenhouses. Oviposition, egg hatch, nymphal development to adulthood, and population increase were quantified in laboratory trials. Assessments of oviposition and egg hatch indicated that all plants tested were equally accepted by O. insidiosus. Nymphal development to adulthood and survival tests indicated that gerbera may be a suitable BP as survival was the highest (58.1 %), whereas marigold would not be an acceptable BP as only 10.7 % of nymphs survived to adulthood. Nymphal development time differed by only one day among all plants. In greenhouse cage experiments, Purple Flash pepper supported the greatest population growth over a ten week period. Based on the combined results from all tests, Purple Flash pepper appears to have the greatest potential as a BP species for O. insidiosus.

Biological control in ornamental crops is challenging due to the wide diversity of crops and cultivars. In this study, we tested the hypothesis that trichome density on different host plants influences the behavior and performance of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Behavioural observations of this predator in the presence or absence of prey (western flower thrips, Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) were done on leaf squares of ornamental plant species differing in trichome density (rose, chrysanthemum and gerbera) and compared to a smooth surface (plastic). Tomato leaves were used to observe the influence of glandular trichomes. The performance of A. swirskii was assessed by measuring predation and oviposition rate. Behaviour of A. swirskii was influenced by plant species. Up to a certain density of trichomes, trichome number had a negative effect on walking speed. It was highest on plastic, followed by rose. No differences were found among chrysanthemum, gerbera and tomato. Walking speed was slightly higher on disks without prey. Proportion of time spent walking was the same on leaf disks of all plant species, with and without prey. No effect of glandular trichomes on tomato leaves was seen. Most thrips were killed and consumed on gerbera, and least on rose. Predation rates on chrysanthemum and plastic were intermediate. In contrast, no differences in oviposition rate were found among plant species. The results of this study indicate that trichome density can explain some of the variability in efficacy of A. swirskii on different crops. Release rates of A. swirskii may need to be adjusted depending on the crop in which it is used.

The basal salt formulation of a medium is a vital but often overlooked component in many in vitro applications, as it regulates the growth and morphology of plant tissues by providing essential nutrients. The MS and B5 formulations are the two most widely used basal media, yet they are suboptimal for many species. The objective of this study was to evaluate the BDS (modified B5) basal salt formulation for in vitro growth and development using rice, maize, soybean, cotton, onion, tobacco, muscadine, raspberry, and gerbera daisy as test species. The responses measured for each species included callus growth (biomass production), plant regeneration, micropropagation rate, hairy root growth, and production of secondary metabolites. BDS was compared to MS, B5, and BABI, a high-calcium version of BDS (440 mg/l CaCl2). For the majority of the species and responses measured, the results obtained with BDS and/or BABI were equal to or better than those obtained with MS or B5. Because of the wide range of plant species and in vitro systems included in this study, we conclude that BDS—or simple variations of BDS, such as BABI—are better balanced for a variety of uses in plant biotechnology, research, and production systems than either MS or B5.

One of the alternatives to autoclaving culture media is chemical sterilization, which may cause fewer changes to the chemical composition of the media. In this study, the effect of chemical sterilization by inclusion of chlorine dioxide (ClO2) in the culture medium on the in vitro development of gerbera (Gerbera jamesonii) cv. AL101, cultured at different stages of micropropagation, was evaluated. The following five concentrations of ClO2 were tested: 0%, 0.0025%, 0.0050%, 0.0075%, and 0.010%. Autoclaved medium was used as the control. ClO2 in the culture medium reduced contamination at rates comparable to autoclaving when tested at three stages of the culture process: in vitro establishment, multiplication, and rooting. Plantlets grown in culture media sterilized with ClO2 showed similar or better development than those grown in autoclaved culture medium. Use of 0.0025% ClO2 to sterilize the culture medium resulted in better plantlet development than autoclaved medium, regardless of the stage of micropropagation.

Plant MADS box transcription factors play key roles in many developmental processes, including the transition to reproductive phase and determination of floral meristem and organs identity. Here we describe the obtaining and characterization of transgenic Nicotiana tabacum L. plants with constitutive expression of Asteraceae MADS box genes CDM111, CDM41, CDM8,CDM77, CDM44 (Chrysanthemum morifolium L.) and HAM92, HAM75 (Helianthus annuus L.). Phylogenetic analysis confirmed that CDM111, HAM75 and HAM92 belong to APETALA1 (AP1), CDM41 and CDM8—FRUITFULL (FUL), CDM44—SEPALLATA3 (SEP3), and CDM77—ASTERACEAE.SEP3 (AST.SEP3) clades. Overexpression of Chrysanthemum and HelianthusAP1/FUL-like genes in tobacco plants resulted in early flowering, shortened stem and decreased number of leaves, which confirmed the functional similarity of Asteraceae AP1/FUL-like factors to AP1 and FUL. This observation testified the conservatism of processes taking place in different plants including Asteraceae. The yeast GAL4 two- and three-hybrid analysis of interactions between CDM77 and other CDM proteins revealed that CDM77 shares similar interaction map with Gerbera SEP-proteins GRCD1 and GRCD2. Overexpression of CDM44 in tobacco caused early flowering without any alterations in vegetative tissues, while overexpression of CDM77 did not reveal any visible developmental changes, which verified the functional similarity between CDM44 and SEP3, and assumed the unique role of CDM77 as whorl- and flower-type specific C-function partner.

To induce variation through chromosome doubling in Gerbera jamesonii Bolus cv. Sciella, two-week-old in vitro grown shoots were treated with various concentrations of colchicine (0.01, 0.05, 0.10, 0.50 or 1% w/v) for 2, 4 or 8 h. Treated shoots were then cultured on Murashige and Skoog (MS) medium supplemented with 8.8 μM 6-benzyladenine (BA) and 155 μM adenine sulphate (ADS), and subsequently transferred to fresh MS medium containing 2.85 μM indole-3 acetic acid (IAA) for rooting. When shoots were treated with 0.1% colchicine for 8 h, 64% of recovered plantlets were tetraploid. Ploidy of plantlets was confirmed by flow cytometry, stomatal analysis, and morphological characters. Tetraploid plantlets displayed slower proliferation along with higher vigor and thickened broad leaves. Moreover, tetraploid plants developed larger flowers, longer stalks, and have improved vase-life, all contributing to higher ornamental value of gerbera.

The effect of gibberellic acid (GA3) and benzyladenine (BA) on the postharvest quality and vase life of gerbera cut-flowers was investigated. Freshly cut flower stems of gerbera cultivar ‘Good Timing’, with four outer disc florets open, were put in vases containing 0, 50, 100, 150, 200, or 300 mg·L−1 GA3 and 0, 10, 25, 50, 100, or 150 mg·L−1 of BA for 48 hr and then held in vases containing 2.5% ethanol and 3% sucrose. Vases were placed in chambers at 25°C with a relative humidity about 70% and were arranged in a Completely Randomized Design with three replicates. Data were recorded for vase life, fresh weight, solution uptake, membrane stability, total soluble solid over time and analyzed statistically. GA3 50 mg·L−1 and BA 50 mg·L−1 were the most effective treatments on vase life, fresh weight, solution uptake, membrane stability and total soluble solids of gerbera cut flowers. Cytokinins and gibberelins have potential to enhance post harvest quality of cut gerbera flowers.

The genetic fidelity of in vitro-raised gerbera clones was assessed by using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers. Out of 35 RAPD and 32 ISSR primers screened, only 12 RAPD and 10 ISSR primers produced clear, reproducible and scorable bands. The 12 RAPD primers produced 54 distinct and scorable bands, with an average of 4.5 bands per primer. The number of scorable bands for ISSR primers varied from 3 (ISSR-14) to 9 (ISSR-07), with an average of 5.5 bands per primer. The number of bands generated per primer was greater in ISSR than RAPD. All banding profiles from micropropagated plants were monomorphic and similar to those of the mother plant. A similarity matrix based on Jaccard’s coefficient revealed that the pair-wise value between the mother and the in vitro-raised plantlets was 1, indicating 100% similarity. This confirmed the true-to-type nature of the in vitro-raised clones.

Gerbera (Gerbera hybrida) is one of the most important cut and pot flowers marketed worldwide. Few molecular markers and no SSR (simple sequence repeat) markers were available for gerbera breeding and genetic studies. Through in silico analysis of 8,670 unigene sequences assembled from 16,998 gerbera expressed sequence tags (ESTs) in the GenBank, we identified 893 SSR loci, corresponding to 10.3% of the gerbera unigene sequences or one SSR in every 5.16 kb of the ESTs in the gerbera transcriptome. The majority of SSR loci contain dinucleotide (42.8%) or trinucleotide (25.6%) repeats, while fewer contain tetranucleotide (6.4%), pentanucleotide (9.1%) and hexanucleotide (16.1%) repeats. AG (37%) and AAT (7.3%) were the most abundant motifs identified. Out of 115 primer pairs designed, 99 (86.1%) amplified discrete PCR products of the expected sizes, while 67 (67.7%) detected polymorphism among seven gerbera cultivars representing three plant types (cut flower, pot, and garden) propagated by two methods (seed or tissue culture). The number of alleles at these SSR loci ranged from 2 to 6, with an average of 2.7 alleles per locus. The PIC value of 67 polymorphic SSR markers was 0.13–0.80, with an average of 0.51. Sixty-eight ESTs targeted by the 115 SSR markers have putative gene functions, and two marker loci may have potential to be associated with disease resistance or flowering time. The availability of these gerbera EST-SSR markers should facilitate the use of molecular markers in gerbera breeding and genetic studies.

GASA-like genes form multigene families in diverse plant species and encode the proteins with a unique cysteine-rich domain (GASA domain). In our previously work, we cloned a GASA-like gene PRGL (Proline-rich GASA-like) from gerbera. Here we report the expression profiles of PRGL and the subcellular localization of PRGL protein. Multiple sequence alignment of the GASA domains indicates that PRGL shows the highest homology to AtPRGL (73.3% of amino acid identity) from Arabidopsis. Phylogenic analysis based on the full amino acid sequences indicates that PRGL and AtPRGL belong to a novel subfamily of GASA proteins. Northern blot assay showed that PRGL is highly expressed in young flower, young leaf and young root, whereas hardly detected when these organs became mature. Furthermore, in young inflorescence, PRGL transcript accumulation only occurred in the fast elongation organs such as scape, ray floret petal and disc floret petal. Western blot and immunolocalization assay revealed that PRGL protein is located in cell wall and high level accumulation of PRGL was found to correlate with the fast organ elongation in scape. Our results suggest that PRGL participates in the regulation of cell elongation during the development of Gerbera hybrida plant.

Three trials were carried out during the years 2002–2005 at the Agricultural Experimental Center of Albenga (northern Italy) on gerbera plants grown in a closed soilless system. The efficacy of slow sand filtration and UV treatment in eliminatingFusarium oxysporum f.sp.chrysanthemi (Foc) propagules, naturally present or artificially added to the recirculating nutrient solution, was evaluated. These techniques were tested alone and in combination with the application into the soilless system of different antagonistic strains ofFusarium spp. andTrichoderma spp., isolated from gerbera rhizosphere, and of a commercial formulation ofStreptomyces griseoviridis. The role of the nutrient solution pH in reducingFoc infections was also evaluated. Results showed that slow sand filtration, alone and in combination with the application of biocontrol agents, and a nutrient solution pH higher than 6.0, may induce a significant reduction inFoc infections on gerbera plants grown in closed soilless systems.

Gerbera jamesonii H. Bolus ex Hook (Family: Asteraceae) has been successfully acclimatized from temperate to subtropical North Indian plains of Lucknow through in vitro propagation. Flower heads were collected from greenhouse, segmented into 4–16 pieces and cultured in Murashige and Skoog’s medium (MS) (Physiol Plant 15:472–497, 1962) supplemented with 2.87 μM indole-3-acetic acid (IAA) and 8.88 μM N6-benzyladenine (BA) for shoot regeneration. Shoots were subcultured on growth regulator free MS medium. Apical shoot meristems from in vitro plantlets of gerbera were tested in MS medium with different combination of cytokinins [BA, kinetin, and thidiazuron (TDZ)] alongwith 2.68 μM 1-naphthaleneacetic acid (NAA) for shoot multiplication. The optimum results were obtained with 8.88 μM BA. Regenerated plants with well-established root system were transferred to pots containing soil and sand (1:1 v/v) and were kept in humidity chamber with 80–90% relative humidity for 0, 5, 10, 15, 20, and 25 days before they were transferred to field (during October, 2005 to February, 2006). Survival percentage was higher when regenerated plantlets were kept under humidity chamber for 15 days. An attempt was made to obtain basic information on different biochemical changes during acclimatization process of in vitro raised plantlets. Increased lipid peroxidation and high H2O2 content in early stages of acclimatization process reflected a similar process of oxidative stress. Our work suggests that tissue-cultured plants develop antioxidant enzymatic protective system which determine the ability to survive in oxidative stress and up regulation of these enzymes would help to reduce the built up of reactive oxygen species (ROS).

We investigated the impact of inundative releases of the parasitoid, Encarsia formosa Gahan (Hymenoptera: Aphelinidae), for control of greenhouse whitefly, Trialeurodes vaporariorum (Westwood), on cut gerbera (Gerbera jamesonii L.) under controlled greenhouse conditions. Experimental units consisted of ten plants covered and separated from other units by gauze tents. We assessed three release rates of the aphelinid parasitoid: a 7-week experiment with a standard release rate (10 m−2/14 days), and a subsequent 3-month trial with high (100 m−2/week) and very high (1,000 m−2/week) release rates. Experimental units without release of parasitoids served as control treatment. Gerbera plants were infested initially with 50–100 juvenile and 50–70 adult whiteflies in the first experiment, and in the second experiment with less than 50 juveniles per plant and 50–70 adults. Whitefly and parasitoid population density were assessed in weekly intervals using infestation and activity categories. Results show that parasitized whiteflies were present in all treatments within 2 weeks after initial release. Unfortunately, it was not possible to control whiteflies with standard release rates of E. formosa. Although parasitism rates slightly increased, the effect on whitefly populations was negligible. Large amounts of honeydew and growth of sooty mold fungi caused the termination of the first experiment. In a second experiment, E. formosa was tested at 10–100 times higher release densities. In contrast to the first experiment, whitefly densities increased steadily during the first 8 weeks, but remained constant until the end of the experiment in both treatments. Parasitism by E. formosa reached its maximum after 8 weeks. We discuss possible reasons for the low efficiency of E. formosa as a whitefly antagonist in greenhouse production of gerbera.

Orange- to red-colored flowers are difficult to produce by conventional breeding techniques in some floricultural plants. This is due to the deficiency in the formation of pelargonidin, which confers orange to red colors, in their flowers. Previous researchers have reported that brick-red colored flowers can be produced by introducing a foreign dihydroflavonol 4-reductase (DFR) with different substrate specificity in Petunia hybrida, which does not accumulate pelargonidin pigments naturally. However, because these experiments used dihydrokaempferol (DHK)-accumulated mutants as transformation hosts, this strategy cannot be applied directly to other floricultural plants. Thus in this study, we attempted to produce red-flowered plants by suppressing two endogenous genes and expressing one foreign gene using tobacco as a model plant. We used a chimeric RNAi construct for suppression of two genes (flavonol synthase [FLS] and flavonoid 3'-hydroxylase [F3'H]) and expression of the gerbera DFR gene in order to accumulate pelargonidin pigments in tobacco flowers. We successfully produced red-flowered tobacco plants containing high amounts of additional pelargonidin as confirmed by HPLC analysis. The flavonol content was reduced in the transgenic plants as expected, although complete inhibition was not achieved. Expression analysis also showed that reduction of the two-targeted genes and expression of the foreign gene occurred simultaneously. These results demonstrate that flower color modification can be achieved by multiple gene regulation without use of mutants if the vector constructs are designed resourcefully.

In the present work, the pigmentation regulated by light was investigated in ray floret (rf) of Gerbera hybrida. When inflorescences from stage 1 were covered with aluminium foil in vivo the pigmentation of the rf petals was strongly blocked and the gene expression of CHS (Chalcone synthase) and DFR (Dihydroflavonol-4-reductase) was inhibited. Similar results were obtained when the detached rfs were cultured in vitro. Covering of the leaves on the plants resulted in reduced pigmentation compared with the covering of inflorescences in vivo. Removal of the green bracts did not affect the pigmentation significantly and the anthocyanin concentration was maintained at a level similar to that of the control. The ultrastructure of the plastids in rf petals was examined to investigate the possible role of photosynthesis in light regulation of flower pigmentation. Plastids within rf epidermal cells showed a characteristic chloroplast morphology in flowers at stage 2, which deteriorated by stage 3. They then changed to a chromoplast-like structure in fully opened rf petals (stage 6). Similar chromoplast-like structures were observed in the plastids of the rf petals from inflorescences both shaded in vivo and in vitro. Additionally, DCMU, a photosynthetic inhibitor, did not show a significant effect on light-induced anthocyanin accumulation. Our data suggest that light is an important factor for pigmentation of rf petal in Gerbera and the petal itself acts as a light sensor site to perceive the light signal. From the different light qualities evaluated, blue light promoted gene expression of CHS and DFR, and red light enhanced the gene expression of CHS, indicating the photoreceptors responding to blue and red light involved in the photoregulation of flower pigmentation in Gerbera.

The interactions between the NH4-N/total-N supply ratio (N r) and the pH of the nutrient solution delivered to the plants regarding the nutrient availability and its influence on plant growth and yield were investigated in a gerbera crop grown in pumice. Four treatments obtained by combining a low and a high N r (0.02 and 0.13 on a molar basis, respectively) with two different levels of nutrient solution pH (5.0 and 5.8, respectively) were compared in a long-term glasshouse experiment. The low N r resulted in significantly higher pH levels in the rhizosphere, as indicated by the values measured in the drainage water. A high nutrient solution pH further increased pH in the root zone at low N r but had no influence on it at the higher N r level. The high pH in the root zone restricted significantly the Cu, Mn, and Zn uptake as indicated by both analytical results and visual symptoms, which were typical for Cu- and Mn-deficiencies. Mn-deficiency was induced only when a low N r was combined with a high nutrient solution pH. The Cu-deficiency symptoms appeared earlier, were more severe and occurred also when the low N r was combined with a low nutrient solution pH, but to a lesser extent. As a result of these nutrient deficiencies, both the growth and the flower yield were severely restricted when N r was low. These results indicate that gerbera is prone to Cu- and Mn deficiencies at pH values above 6 in the rhizosphere. The maintenance of root zone pH below this level in soilless culture is most successfully attained by properly adjusting the NH4-N/total-N supply ratio rather than the pH of the nutrient solution delivered to the plants.

Spread of Phytophthora root and crown rot in three pot plant species was studied on ebb-and-flow benches where the nutrient solution was recirculated. The plant species and their respective pathogens were: Saintpaulia ionantha – P. nicotianae, Gerbera jamesonii – P. cryptogea, and Spathiphyllum wallissii – Phytophthora spp. Ebb-and-flow benches were infested with the pathogen using different methods: 18–25% of the plants on a bench were inoculated or potted in soil infested with the pathogen or the nutrient solution was infested by either zoospores or mycelium fragments. More than 80% of the inoculated Saintpaulia plants and 22% of plants potted in infested soil developed disease but no spread of the disease was observed. Infestation of the nutrient solution did not result in any diseased Saintpaulia plant. More than 70% of the Gerbera plants developed disease as a result of spread of the pathogen irrespective of the infestation method used. No significant spread of the disease was observed with inoculated Spathiphyllum plants nor from plants potted in infested soil. A few Spathiphyllum plants developed disease symptoms after infestation of the nutrient solution with zoospores. In one experiment, nearly all Spathiphyllum plants were diseased after infestation of the nutrient solution with mycelium fragments. The presence of an irrigation mat significantly reduced the spread of the Phytophthora disease in Gerbera and Spathiphyllum. The possibility of an irrigation mat acting as a filter for zoospores is discussed.

We investigated whether volatiles produced by spider mite-damaged plants of four gerbera cultivars differ in attractiveness to Phytoseiulus persimilis, a specialist predator of spider mites, and how the mite-induced odor blends differ in chemical composition. The gerbera cultivars differed in resistance, as expressed in terms of spider mite intrinsic rate of population increase (rm). In order of increasing resistance these were Sirtaki, Rondena, Fame, and Bianca. To correct for differences in damage inflicted on the cultivars, we developed a method to compare the attractiveness of the blends, based on the assumption that a larger amount of spider mite damage leads to higher attraction of P. persimilis. Spider mite-induced volatiles of cultivars Rondena and Bianca were preferred over those of cultivar Sirtaki. Spider mite-induced volatiles of cultivars Sirtaki and Fame did not differ in attractiveness to P. persimilis. Sirtaki plants had a lower relative production of terpenes than the other three cultivars. This was attributed to a low production of cis-α-bergamotene, trans-α-bergamotene, trans-β-bergamotene, and (E)-β-farnesene. The emission of (E)-β-ocimene and linalool was lower in Sirtaki and Fame leaves than in Bianca and Rondena. The importance of these chemical differences in the differential attraction of predatory mites is discussed.

An effective system for in vitro regeneration of adventitious shoots from callus for the transformation or mutation of gerbera was developed. Callus was produced from petioles of the youngest 3–4 leaves detached from auxillary shoots produced in vitro. Induction medium, on which leaves were incubated over 3 or 6 days, contained 2.3 μM thidiazuron and 0.53 μM α-naphthaleneacetic acid. Explants were than transferred to one of three regeneration media with lower levels of growth regulators. Regeneration was quantified over four (4-weeks each) passages at the time of explant transfer to fresh medium. Direct shoot regeneration occurred during the first 4 weeks, and after these shoots were discarded a semi-compact organogenic callus was produced. Effectiveness of shoot regeneration depended on four criteria: the cultivar (three cultivars were tested), the sequence of passage on regeneration medium, the growth regulators in regeneration medium and the duration of the induction period. Regeneration potential from calli of all cultivars increased from the first to the fourth passage. Duration of the incubation period on induction medium (3 or 6 days) influenced regeneration to varying degrees, depending on the cultivar used and the regeneration medium contents. There were no differences between two of the regeneration media – B, containing 2.2 μM 6-benzyladenine and 0.3 μM indole-3-acetic acid and C, containing 4.4 μM 6-benzyladenine, 4.6 μM zeatin and 0.6 μM indole-3-acetic acid. Cultivar Mariola was the most productive and regenerated more than seven shoots per callus in the fourth passage. Regeneration on medium B was further evaluated on four additional gerbera cultivars.

The effects of season, genotype and their interaction on haploid production were evaluated on four genotypes responsive to gynogenesis. Naked mature unfertilised ovules, collected from April to October, were cultivated on modified MS basal medium plus 0.88 μM 6-benzyladenine and 0.57 μM indol-3-acetic acid. After 30–60 days, recovered calli were transferred to a MS basal medium with 8.8 μM BA and 0.57 μM IAA for regeneration. Genotype and season of ovule collection substantially interact in the recovery of haploid calli. Between the four genotypes analysed, two gave more calli in the spring, one in the autumn and the fourth showed only weak differences between seasons. Shoot recovery depended upon both the season of ovule collection and the genotype but no significant interaction was shown by our data. The ability to produce haploid callus is not predictive for efficient shoot regeneration.

When leaves of the ornamental crop Gerbera jamesonii are damaged by the spider mite Tetranychus urticae, they produce many volatile compounds in large quantities. Undamaged gerbera leaves produce only a few volatiles in very small quantities. In the headspace of spider mite-damaged gerbera leaves many terpenoids are present, comprising 65% of the volatile blend. In addition, a number of nitrogen containing compounds, such as oximes and nitriles, are produced. We studied the attraction of P. persimilis to the volatiles from spider mite-damaged gerbera leaves and how attraction is affected by starvation and previous experience. Phytoseiulus persimilis that were reared on spider mites (T. urticae) on Lima bean were not attracted to spider mite-induced volatiles from gerbera. Starvation did not influence the predator's response to these volatiles. In contrast, predators that were reared on spider mites on gerbera leaves were strongly attracted to volatiles from spider mite-infested gerbera. This was found also for predators that originated from a culture on spider mite-infested bean and were offered six days of experience with spider mites on gerbera leaves.

Insight into the foraging behavior of the parasitoid Encarsia formosa Gahan for whitefly hosts was gained by continuous observation of individual parasitoids on leaves of the ornamental plant Gerbera jamesonii, until females left the leaf. Comparison of the parasitoid behavior on three cultivars gave similar results. Mean searching time on uninfested G. jamesonii leaves of three cultivars was 1 h 30 min and the mean percentage of walking activity of the total observation time on those cultivars was 61%. Both parameters were not influenced by different leaf structures of Gerbera cultivars. Encounters with hosts arrested the parasitoids on the leaves. The walking activity and the percentage of host encounters that resulted in an oviposition decreased with decreasing egg load of the parasitoid. In comparison with tomato, where biological control of whiteflies is successful, only minor differences in the foraging behavior occur, except for the residence time of females, which was about three to four times longer on G. jamesonii leaves, but these leaves are about seven times larger than tomato leaves. The facts that (1) the foraging behavior of E. formosa on G. jamesonii is independant of the cultivar and (2) the foraging behavior is, in many aspects, similar to that on tomato suggest that biological control of whitefly on this ornamental plant is a potential option.

A sample of 36 flower traits consisting of six morphological categories in the Davis population of gerbera was restructured into phenotypic and genetic principal component traits. The first 5 phenotypic principal component traits accounted for 62% of the total phenotypic variance of the 36 traits and have moderate to high heritablities. The first 5 genetic principal component traits account for 97% of total genetic variance and all have high heritability. Morphological structure of these component traits suggest an underlying process identified by the first genetic principal component involving largely trans and disk floret traits. The results of this study indicate that the quantitative genetic structure of the gerbera flower is controlled by a few independent components and that principal component analysis is a useful tool to reveal variation in this structure. These composite traits are heritable and are expected to respond to selection.

Increased copper concentration in the nutrient solution was used as a means for reducing the severity of root rot caused by Phytophthora cryptogea in Gerbera jamesonii in three experiments. Plants were grown in pots on ebb-and-flow benches with separate systems for recirculating nutrient solutions. Eight nutrient solutions with two concentrations of copper ions (0.07 and 0.28 ppm), two electrical conductivity values (1.5 and 2.2 mScm-1), and two iron sources (FeHEEDTA or FeSO4) were combined in a factorial design. Plants were inoculated with zoospores of P. cryptogea via the recirculating nutrient solution. Disease incidence was significantly reduced in inoculated plants grown on nutrient solution with 0.28 ppm copper compared with 0.07 ppm copper, when FeSO4was introduced as the iron source. No effects of increased copper concentration was observed when iron was added as FeHEEDTA. The change in electrical conductivity from 1.5 to 2.2 mScm-1 without changing the Cu2+ concentration did not influence the disease severity in these experiments. The results suggest that increased copper ion concentration in the nutrient solution could be a component of disease management strategy for ebb-and-flow systems. Possible management of the cupric ion concentration in the nutrient solutions is discussed.

Gynogenetic plants of pot gerbera (Gerbera jamesonii) were successfully produced from cultures of unpollinated ovulesin vitro. Genotypic variations in the number of ovules that formed callus were found among the lines tested. One particularly responsive genotype was found among 17 genotypes tested where the frequency of callus-forming ovules was 17.5%. Four genotypes formed no callus at all. The frequency of shoot formation from the callus varied from 0-19.6% in nine genotypes. Ploidy was determined by flow cytometry, and 37 (80.4%) regenerants were haploid, seven (15.2%) were diploid, and two (4.3%) were mixoploid with both haploid and diploid cells. The doubling of chromosomes was achieved by treatment with 0.05% colchicine for 2-6 din vitro, and 24.2-34.1% of treated haploid plants were found to have been diploidized.