Two Agrobacterium-mediated Transformation Protocols of White Clover (Trifolium Repens) Through the Callus System

White clover (Trifolium repens) is one of the most widely cultivated livestock forage legumes co-cultivated worldwide with pasture grass in a mixed-sward setting, however, its persistence and aesthetic quality are severely affected by abiotic stresses. In this study, regeneration of white clover plants was conducted through a callus system for 4-5 months with a regeneration frequency of 36-41%. Inoculating 4-day-old cotyledons into MS media fortified with 0.4 mg·L-1 6-BA and 2 mg·L-1 2,4-D significantly increased the callus formation rate. Roots and cotyledons were better induced, followed by hypocotyls, leaves, and petioles. The development of differentiated structures performed effectively on MS supplemented with 1 mg·L-1 6-BA and 0.1 mg·L-1 NAA. Further, we determined factors affecting the Agrobacterium tumefaciens-mediated transient transformation for root-derived callus and 4-day-old cotyledons. The parameters that facilitated transient transformation were: Agrobacterium suspension density of 0.5 (OD600), 20 mg·L-1 AS, and 4-days co-cultivation duration. Subsequently, we developed two transformation protocols: transformation after callus formation in root segments (Protocol A) and transformation before callus initiation in 4-day-old cotyledons (Protocol B). The transformation frequencies varied from 1.92% to 3.17% in Protocol A and from 2.76% to 3.47% in Protocol B. We offer the possibility to regenerate multiple transgenic white clover from a single genetic background. In addition to assistance in identification of functional genes associated with yield, resistance and aesthetic quality, our research will also contribute to successful genetic manipulation and genome editing in white clover.

Pengaruh Jenis Eksplan dan Asam Amino pada Inisiasi dan Proliferasi Kalus Embriogenik Phalaenopsis Var. ‘Raiza Agrihorti’

<p><strong>(<em>The Effect of Explant Types and Amino Acids on Embryogenic Callus Initiation and Proliferation of Phalaenopsis Var. ‘Raiza Agrihorti’</em>)</strong></p><p>Penyiapan kalus embriogenik (KE) yang optimal memiliki peranan penting dalam menghasilkan benih bermutu Phalaenopsis skala komersial. Kendala utama yang dihadapi ialah inisiasi dan proliferasi KE yang masih rendah, serta akumulasi fenolik yang tinggi. Penelitian dilakukan di Laboratorium Kultur Jaringan Balithi dari Agustus 2019 hingga Juli 2020. Penelitian menggunakan Rancangan Acak Kelompok (RAK) pola split plot dan faktorial dengan lima ulangan. Percobaan-1: jenis eksplan (pucuk, pangkal, dan daun plantlet) sebagai petak utama dan perlakuan asam amino (tanpa asam amino, L-Proline, L-Glutamine, L-Cysteine, dan Casein-Hydrolisate) dengan konsentrasi 150 mg/l pada medium PC1 (1/2 MS + 1,0 mg/l TDZ + 0,5 mg/l BAP + 20 g/l sukrosa) sebagai anak petak. Percobaan-2: faktor-1 ialah jenis asam amino (L-Proline, L-Cysteine; L-Glutamine, dan Casein-Hydrolisate) dan faktor-2 ialah konsentrasi asam amino (0, 75, 150, 225, dan 300 mg/l). Hasil penelitian menunjukkan bahwa inisiasi KE Phalaenopsis var. ‘Raiza Agrihorti’ terbaik didapatkan dari pangkal plantlet dan 150 mg/l L-Glutamine dengan waktu inisiasi 18,3-24,0 hari, 80-100% pembentukan KE, dan ukuran KE 0,4-0,5 cm3. Proliferasi KE terbaik ditemukan pada L-Glutamine dengan konsentrasi 150 mg/l. Proliferasi KE mencapai 100% dengan penambahan berat segar sebesar 0,39 g, tingkat multiplikasi (MR) 4,55 kali dan pencokelatan 4,0%. Hasil penelitian ini berpotensi tinggi untuk diterapkan pada kultur starter Phalaenopsis hibrida lain.</p><p><strong>Keywords</strong></p><p>Phalaenopsis hibrid; Asam amino; Inisiasi; Kalus embriogenik; Proliferasi</p><p><strong>Abstract</strong></p><p>Setup of the optimum Phalaenopsis embryogenic callus (EC) is an important role in producing qualified-seedlings of Phalaenopsis in commercial scale. The main constraints that are still being faced are the low rate of culture proliferation and high phenolic accumulations. The research was carried out at the Tissue Culture Laboratory-Indonesian Ornamental Plants Research Institite, from August 2019 through July 2020. The split plot and factorial designs were arranged using a Randomized Completely Block Design (RCBD) with five replications. Experiment-1: explants type (shoot tip, basal part, and leaf of plantlet) was used as main plot and amino acids (amino acids free, L-Proline, L-Glutamine, L-Cysteine, and Casein-Hydrolisate) with 150 mg/l concentration on medium PC1 (1/2 MS + 1,0 mg/l TDZ + 0,5 mg/l BAP + 20 g/l sukrosa) as subplot. Experiment-2: the first factor was amino acids type (L-Proline, L-Cysteine; L-Glutamine, and Casein-Hydrolisate) and the second factor was amino acids concentration (0, 75, 150, 225, and 300 mg/l). Results of the studies revealed that the best EC initiation of Phalaenopsis var. ‘Raiza Agrihorti’ was produced by basal part of plantlet and PC1 medium containing 150 mg/l L-Glutamine with EC Initiation time was 18.3-24.0 days, 80-100% of EC formation and size of 0.4-0.5 cm3. The best proliferation of EC was found in L-Glutamine with 150 mg/l concentration. EC proliferation reached 100% with 4.55 EC multiplication rate, 0.39 g EC fresh weight added, and EC browning as low as 4.0%. The established method is high possibly applied for other Phalaenopsis hybrids.</p>

Callus of Curculigo latifolia Dryand. ex W.T. Aiton: initiation, regeneration, secretory structure and histochemistry

In Indonesia, Curculigo latifolia, popularly known as lemba, is used as traditional medicine for antihypertension, antidiabetic, and as a food and drink additive. Despite the high benefits, this plant is difficult to propagate due to its low seed viability. Tissue culture offers an alternative for plant propagation, thus providing a continuous source of bioactive substances. The study aimed to establish efficient methods of explant sterilisation, callus induction and its regeneration from leaf tissues for plant multiplication. The study also investigated histochemically secondary metabolites produced by the callus. Our results showed that sterilising agents in the lowest concentrations and the shortest duration was the most suitable for getting aseptic cultures. BAP (3 mg L−1) and IBA (5 mg L−1) were the highest callus initiation, shoots, and roots regeneration. The histological sections of fresh callus showed secretory structure in the form of secretory cavities surrounded by a layer of epithelial cells and idioblasts around the secretory cavities. The histochemical tests identified phenolic compounds and essential oils in organogenic callus. Idioblasts were detected containing essential oils too. The results will contribute to C. latifolia propagation and the development of callus as a producing source of secondary metabolites.

Induction of Somatic Embryogenesis and Organogenesis in Zimbabwean Sweet Potato (cv Brondal)

Somatic embryogenesis (SE) and organogenesis are crucial in the development of disease free plants and genetic engineering. An investigation was conducted on the ability of treatments containing a combination of 2,4-D and Kinetin to induce either SE or organogenesis from cultured sweet potato cv Brondal leaves. Ten treatments were evaluated and each treatment had an exclusive combination of 2,4-D (at 0.05, 0.1, 0.2, 0.5 or 1 mg/L) to kinetin (at either 0.1 or 0.5 mg/L). Callus initiation occurred earlier in treatments containing higher hormonal concentrations. The 2,4-D to Kinetin ratio had a highly significant ( p = 0.001 ) effect on callus growth and proliferation. Increasing 2,4-D to Kinetin ratio promoted profuse explant callusing while increasing Kinetin to 2,4-D ratio suppressed callusing but encouraged organogenesis, in particular shoot production (treatment containing 0.05 mg/L 2,4-D and 0.5 mg/L Kinetin). Embryogenic calli were formed seven weeks after leaf culture in the treatment containing 0.5 mg/L 2,4-D and 0.1 mg/L Kinetin. The embryogenic calli that developed from this treatment emerged from previously nonembryogenic calli. Plantlets produced via the SE pathway proved to be weak and unviable and died within four weeks of germination. In contrast, plantlets produced under organogenesis were strong, grew vigorously, and could be subcultured several times. This disparity may be accounted for by the fact that the cv Brondal embryos that developed under SE were not exposed to an embryo maturation staged before plantlet germination was initiated. The maturation stage would have assisted embryos to reach physiological maturity and a desired level of desiccation, both being critical elements in embryo to plantlet conversion. In this experiment, cv Brondal regeneration from leaf explants was successfully achieved via organogenesis using 0.05 mg/L 2,4-D and 0.5 mg/L Kinetin, and tentative steps towards development of SE based regeneration protocol were established using 0.5 mg/L 2,4-D and 0.1 mg/L Kinetin.

Enhancement of In Vitro Production of Volatile Organic Compounds by Shoot Differentiation in Artemisia spicigera

Callus initiation, shoot formation and plant regeneration were established for Artemisia spicigera, a traditional medicinal plant growing in Armenia, Middle-Anatolia and Iran, and producing valuable volatile organic compounds (VOCs) that are mostly represented by monoterpenoids. Optimal callus initiation and shoot production were obtained by culture of hypocotyl and cotyledon explants on MS medium comprising 0.5 mg L−1 naphthalene acetic acid (NAA) and 0.5 mg L−1 6-benzyladenine (BA). Consequently, the shoots were transferred onto the MS media supplemented with 1 mg L−1 of indole-3-butyric acid (IBA) or 1 mg L−1 of NAA. Both types of auxin induced root formation on the shoots and the resulting plantlets were successfully grown in pots. The production of VOCs in callus tissues and regenerated plantlets was studied by gas chromatography–mass spectrometry (GC-MS) analysis. Although the potential of undifferentiated callus to produce VOCs was very low, an increased content of bioactive volatile components was observed at the beginning of shoot primordia differentiation. Intriguingly, the volatiles obtained from in vitro plantlets showed quantitative and qualitative variation depending on the type of auxins used for the rooting process. The acquired quantities based on total ion current (TIC) showed that the regenerated plantlets using 1 mg L−1 NAA produced higher amounts of oxygenated monoterpenes such as camphor (30.29%), cis-thujone (7.07%), and 1,8-cineole (6.71%) and sesquiterpene derivatives, namely germacrene D (8.75%), bicyclogermacrene (4.0%) and spathulenol (1.49%) compared with the intact plant. According to these findings, in vitro generation of volatile organic compounds in A. spicigera depends on the developmental stages of tissues and may enhance with the formation of shoot primordia and regeneration of plantlets.

Early Low-Fluence Red Light or Darkness Modulates the Shoot Regeneration Capacity of Excised Arabidopsis Roots

In plants, light is an important environmental signal that induces meristem development and interacts with endogenous signals, including hormones. We found that treatment with 24 h of low-fluence red light (24 h R) or 24 h of darkness (24 h D) following root excision greatly increased the frequency of shoot generation, while continuous low-fluence red light in callus and shoot induction stages blocked the explants’ ability to generate shoots. Shoot generation ability was closely associated with WUS expression and distribution pattern. 1-N-naphthylphtalamic acid (NPA) disrupted the dynamic distribution of the WUS signal induced by early 24 h R treatment, and NPA plus 24 R treatment increased the average shoot number compared with early 24 h R alone. Transcriptome analysis revealed that differentially expressed genes involved in meristem development and hormone signal pathways were significantly enriched during 24 R or 24 D induced shoot regeneration, where early 24 h R or 24 h D treatment upregulated expression of WOX5, LBD16, LBD18 and PLT3 to promote callus initiation and formation of root primordia, and also activated WUS, STM, CUC1 and CUC2 expression, leading to initiation of the shoot apical meristem (SAM). This finding demonstrates that early exposure of explants to transient low-fluence red light or darkness modulates the expression of marker genes related with callus development and shoot regeneration, and dynamic distribution of WUS, leading to an increased ability to generate shoots.

Introduction to in vitro culture and callus initiation in Salvia hispanica L. (chia)

Aim. Preparation of aseptic seedlings Salvia hispanica L., callus initiation in vitro and establishment of primary explants suitable for the callus production. Methods. Seeds are sprouted on our own modification of conventional methods. The non-hormonal Murashige-Skoog agarized nutrient medium was used as basic medium for the experiments. Parts of one-month seedlings (roots, hypocotyl, cotyledon leaves) were used as explants for the use of the colza. We added growth regulators (BAP, 2,4-D) in different concentration combinations into the nutrient medium for callus initiation. Statistical processing was performed in Microsoft Office Excel. Results. Aseptic S. hispanica seedlings have been obtained. The callus growth was initiated on all types of explants, the dependence of the callus intensity on the type of explants and the growth regulators content in the nutrient medium was established. Morphogenic callus and root-regenerants have been obtained. Conclusions. Hypocotyl was the most suitable primary explant for callus growth. Seedlings, leaves and roots showed low morphogenetic capacity. The nutrient medium with an elevated 2,4-D content was the most effective for initiation of callus genesis and proliferation of non-morphogenous callus. A high concentration of 2,4-D in the medium improves S. hispanica callus growth but suppresses its morphogenic ability.Keywords: Salvia hispanica (Chia), in vitro culture, callus.