Short-Term Storability of Alginate-Encapsulated Persian Violet Microshoots for Germplasm Exchange

Microshoots have been widely used for micropropagation. It may be necessary to store microshoots for a short period of time, for example in germplasm exchange needing transport to other research groups. Here, we investigated the short-term storability of alginate-encapsulated Persian violet (Exacum affine Balf. f. ex Regel) microshoots at 4 °C and 25 °C. After storage, the encapsulated microshoots were sown on basal Murashige and Skoog medium for germination and viability determination using tetrazolium chloride staining. The results showed that one or five microshoots encapsulated with a single alginate layer could be stored at 4 °C for up to 30 days, while the percentages of germination and viability of the microshoots encapsulated with two layers of alginate were greatly reduced upon storage. This is the first report on the storability of alginate-encapsulated multiple microshoots, which could be a more efficient way to encapsulate microshoots used for short-term cold storage.

Germination and Plantlet Regeneration of Encapsulated Microshoots of Aromatic Rice (Oryza sativaL. Cv. MRQ 74)

Plant tissues such as somatic embryos, apical shoot tips, axillary shoot buds, embryogenic calli, and protocom-like bodies are potential micropropagules that have been considered for creating synthetic seeds. In the present study, 3–5 mm microshoots ofOryza sativaL. Cv. MRQ 74 were used as explant sources for obtaining synthetic seeds. Microshoots were induced from stem explants on Murashige and Skoog (MS) medium supplemented with 1.5 mg/L benzylaminopurine (BAP). They were encapsulated in 3% (w/v) sodium alginate, 3% sucrose, 0.1 mg/L BAP, and 0.1 mg/Lα-Naphthalene acetic acid (NAA). Germination and plantlet regeneration of the encapsulated seeds were tested by culturing them on various germination media. The effect of storage period (15–30 days) was also investigated. The maximum germination and plantlet regeneration (100.0%) were recorded on MS media containing 3% sucrose and 0.8% agar with and without 0.1 mg/L BAP. However, a low germination rate (6.67%) was obtained using top soil as a sowing substrate. The germination rate of the encapsulated microshoots decreased from 93.33% to 3.33% after 30 days of storage at 4°C in the dark. Therefore, further research is being done to improve the germination rate of the synthetic seeds.

Microshoots encapsulation and plant conversion of Musa sp. cv. 'Grand Naine'

Synthetic seed technologies are useful tools for the field delivery of in vitro derived plantlets. In the present study, different encapsulation procedures and their efficacy in the plantlet regeneration using microshoots of banana cv. 'Grand Naine' were evaluated. Two encapsulation systems were evaluated: i) single encapsulation in beads or droplet hardening method; and ii) double layer or hollow beads. The use of different compounds to enhance the capsule conservation and the conversion to plantlets was also evaluated. The conversion capacity was assessed in vitro on water-agar culture medium or in ex vitro conditions with Gerbox® boxes. The single encapsulation system showed 80% conversion. The capsules with MS saline formulation treated with 100mM KNO3 showed 76% conversion. Capsules with 1.5g L-1 activated charcoal, and 0.5g L-1 benomyl sucrose-free capsules showed 75% conversion. The encapsulated and non-encapsulated microshoots exhibited 100% germination in response to MS culture medium, and polyethylene glycol after 10 days of storage at 4°C. Sucrose-free capsules showed significantly higher germination (83.3%) than those sucrose-enriched capsules (56.7%). The ex vitro conversion of encapsulated microshoots was 20% in the Gerbox™. These results indicate the feasibility using synthetic seeds in the large-scale micropropagation of banana cv. 'Grand Naine'.