Synthetic seeds and their role in agriculture: status and progress in sub-Saharan Africa

Dicot seeds are commonly characterised by the rapid loss of moisture, vigour and longevity that cause adverse physiological and biochemical effects. Such changes reduce seed viability, germinability and seedling vigour in most agronomic legume crops. Thus, this paper evaluates the potential role of synthetic seed production as an avenue to achieve genetic variability, avert recalcitrance and fleet seed viability challenges experienced in recalcitrant legume species. Synthetic seeds, also known as synseeds or artificial seeds produced via somatic embryogenesis are crucial for the successful establishment of plants, and serve as an important determinant of plant productivity, especially for crops such as soybean. The potential use of synseeds could serve a fundamental role in ensuring cheap and rapid supply of new genetic resources and seed propagules for both breeders and farmers. This approach will ultimately maximise crop yield and offer a tremendous potential for micropropagation and germplasm preservation of recalcitrant species in sub-Saharan Africa. This review reports on a variety of applications and benefits of plant biotechnology in the African context and highlights important advantages such as genetic uniformity, simplified handling, storage, efficient distribution etc. that could be of immeasurable benefit to the seed value chain in agriculture, particularly for rural communities in these developing countries.

Impact of Encapsulation on Plantlet Regeneration from in vitro Grown Shoot tips of Citrus aurantifolia (Lime)

In order to conserve diverse species of citrus, an experiment on in vitro micropropagation and production of synthetic seeds from in vitro regenerated plant propagules of the species; Citrus aurantifolia (Lime) was carried out in which shoot tips were found to be suitable for excapsulation of artificial seeds. Highest rate of germination was obtained from the shoot tips when MS was supplemented with 1 mg/l BAP. Beaded shoot tips produced maximum germination (81.43%). Germinated synthetic seeds with well established roots and shoots were were taken out from the culture bottles and transferred in plastic cups containing a mixture of sterile soil: sand and farmyard manure at a ratio of 1:1:1. Seedlings were further shifted in earthen pots and kept in a partial shed net house for 7 days. Those seedlings were finally transferred under the field conditions for acclimatization. Plant Tissue Cult. & Biotech. 31(1): 43-49, 2021 (June)

Abscisic acid in preservation of Taraxacum pieninicum in the form of synthetic seeds in slow growth conditions

Taraxacum pieninicum Pawł. is listed as critically endangered species, for which currently applied protection methods are insufficient. The aim of this study was to investigate the possibility of T. pieninicum storage in the form of synthetic seeds under slow-growth conditions in combination with ABA treatment, as one of the ex situ protection methods of this species. The obtained results indicated that darkness was much more favorable condition for synseed storage and did not generate additional stress during cold exposure in contrast to the light conditions. The preculture of shoot tips on the medium supplemented with ABA led to a decrease in the shoots proliferation rate and inhibition of their growth. ABA clearly inhibited growth of the encapsulated shoot tips also during cold storage. Biochemical parameters showed that ABA effectively reduced the negative effect of the cold stress, what was found on the basis of analyzes of H2O2 and TBARS levels in the stored material. Moreover, synseeds stored under light conditions and treated with ABA exhibited decreased level of endogenous jasmonic acid what indicated interaction between those two phytohormones at a low temperature. The study also demonstrated that in vitro culture, cold storage and ABA treatment had no effect on the flowering process of this species after acclimatization to ex vitro conditions.

Synthetic Seed Technology Development and Production Studies for Storage, Transport, and Industrialization of Bracken Spores

Bracken fern (Pteridium aquilinum var. latiusculum (Desv.) Underw. ex A. Heller) has long been grown industrially in South Korea. Conventional propagation methods, including planting rhizomes and in vitro seedling culture, are labor intensive and expensive, and thus not commercially suitable. We aimed to develop a system to produce synthetic seeds using fern spores (SFS). Synthetic seeds were prepared by mixing bracken spores and alginate matrix. Spore germination and gametophyte and sporophyte growth and development from SFS proceeded normally. Spore density affected gametophyte and sporophyte numbers. SFS prepared using cold (4 °C) long-term storage spores (even 7-year-old spores) could effectively form sporophytes. The highest germination was observed at 25 °C. Soaking-treated SFS successfully formed sporophytes, even after 30 days of storage at 4 °C; indeed, sporophytes formed even after five days of storage at 25 °C during transport conditions. SFS were sown in plug trays for commercial use. Young sporophytes grown from plug seedlings were greenhouse cultivated, and transplanting within eight weeks was effective for root growth and growing-point formation. Developing synthetic seeds is a feasible solution for facilitating efficient transport and the handling of small-sized fern spores; furthermore, this SFS technology provides the basis for fern seedling culture and fern spore industrialization.

Effect of Bead Composition, PVS Type, and Recovery Medium in Cryopreservation of Bleeding Heart ‘Valentine’—Preliminary Study

Bleeding heart (Lamprocapnos spectabilis (L.) Fukuhara) is a valuable ornamental and medicinal perennial. To date, there are few studies focused on cryopreservation of this species, although it could be useful in storage and breeding. This research is aimed at analyzing the effect of bead composition, type of plant vitrification solution (PVS), and the recovery medium of cryopreservation of bleeding heart. Shoot tips of L. spectabilis ‘Valentine’ were used in the study. The explants were precultured on modified Murashige and Skoog medium (MS; 1962), supplemented with 9% sucrose, 1.0-mg·L−1 kinetin (KIN), and 2.62-mg·L−1 abscisic acid. Next, in the first experiment, the shoot tips were embedded in 3% calcium alginate, based either on an MS medium or distilled sterile water. The produced synseeds were inoculated on the recovery medium with 3.0-mg·L−1 KIN, 0.5-mg·L−1 6-benzyladenine (BA), or cytokinin–free control. Based on the results of the first study, in the second experiment, precultured shoot tips were embedded in 3% calcium alginate based on MS medium and dehydrated with PVS2 or PVS3 for various durations. The pre-treated explants were plunged in liquid nitrogen and, after rewarming, inoculated on the recovery MS medium with 0.5-mg·L−1 BA. PVS3 was more effective in securing the shoot tips than PVS2. The highest recovery level (68.3%) was reported after a 150-min pretreatment with PVS3. Explants from this experimental combination also proliferated the highest number of shoots, as well as those with the greatest length. On the other hand, a higher share of dry weight was found in PVS2-derived shoots (13.5–18.2%) compared with plants produced after PVS3 treatment (10.6–11.4%). The obtained results here can serve as a good basis for further studies related to synthetic seeds and cryopreservation of bleeding heart.

Preparation of Synthetic Seeds of Citrus jambhiri Using in vitro Regenerated Multiple Plantlets

Biotechnological tools are useful for true-to-type propagation. Shoot tips encapsulation is potential for plant development from pre-existing meristematic tissue. MS medium fortified with 1 and 2 mg/L of BAP (6-bezylaminopurine) was found to be suitable for in vitro mass-multiplication of plantlets (10.18 and 13.05 plantlets/explant, respectively) of Citrus jambhiri from nodal segments. Nodal segments were more appropriate than the shoot tips for in vitro multiplication of plantlets. Synthetic seeds were prepared using 2.5% sodium alginate dropping into 3.0% CaCl2 solution. Maximum germination was recorded when beaded shoot tips were cultured on MS medium fortified with 1 and 2 mg/L of BAP (96.67 and 100.00%, respectively). However, the germination of synthetic seeds was found to be comparatively high than the earlier findings. The results support the use of encapsulated unipolar explants for synthetic seed preparation. These type of capsules could be useful in exchange of sterile material between laboratories, germplasm conservation and direct plant propagation.

Study on the germination of nano - TiO 2 synthetic seeds and the physiology of Dendrobium officinale regenerated plants

Synthetic seed of biological technology has been suggested as an effective strategy to improve breeding. Nano-TiO2 is a photosemiconductor material widely used in life science and agriculture. Nano-TiO2 has been recently shown to improve photosynthetic function, promote plant growth and development，but the physiology mechanism is still unclear. The aim of the current study was to confirm whether or not nano-TiO2 synthetic seed has an effect on germination and physiology of Dendrobium officinale. Using D. officinale protocorm models, we demonstrate that appropriate nano-TiO2 leads to growth and development of germination seedlings, and improves the root activity, nitrate reductase activity and antioxidant system activity. Our data also provide a basis for the improvement of the preparation process and practical production of D. officinale synthetic seeds.