No abstract

Background Potato (Solanum tuberosum L.) is one of the most economically important annual vegetable crops. Microtubers can be produced, stored around year and directly transported to market without transferring to fresh media and without acclimatization. Thus reducing the field cycle to obtain sufficient number of seed potatoes and a high level of healthy materials. The aim of this study was to investigate effects of different combinations and concentrations of growth regulators i.e., kinetin (2.5 mg/l) and coumarin (20, 40 and 60 mg/l) alone or in addition to varied concentrations of sucrose (30, 60 and 90 g/l) on in vitro tuberization of potato (Solanum tuberosum) cv. Diamount. Results The plantlets were propagated using single-node cuttings cultured on Murashige and Skoog medium containing 0.04 mg/l kinetin and 1.0 mg/l IAA. Shoots (6–7 nodes) from the previous step were cultured into medium supplemented with a factorial combination of sucrose concentrations (30, 60 and 90 g/l), coumarin concentrations (0, 20, 40, and 60 mg/l) and two concentrations of kinetin (0 and 2.5 mg/l). Our results showed that kinetin – induced medium have slightly effect to improve tuberization in vitro. But when kinetin was combined with sucrose, this effect was better when raised sucrose concentration from 30 or 60 to 90 g/l. The highest percentage of tuberization after 8 weeks, highest number of microtuber were obtained with high concentration of sucrose (90 g/l) together with dark condition, at 18–20 °C. Also, the highest concentration of sucrose significantly increased the fresh weight of microtuber. In case of coumarin, results revealed that it has important effect on tuber initiation especially with concentrations 20 mg/l and 40 mg/l; otherwise, the initiation period was minimized after adding kinetin. So, the plantlets must be continuously incubated in coumarin –induce medium plus kinetin for 8 weeks to affect the tuberization response. Also, all the other characters of tuberization process on coumarin-inducing medium could be improved by increasing sucrose concentration to 9 g/l. Conclusions Generally, results pointed out that the treatment which consists of kinetin (2.5 mg/l) plus 90 g/l sucrose and 20 mg/l coumarin has the best characteristics of in vitro micro-tuberization.

Background Citrus is an important fruit crop worldwide; artificial seeds are through encapsulation techniques of somatic embryos having many applications such as large-scale propagation and germplasm conservation. The aim of this study is the investigation of the viability of encapsulated citrus somatic embryos after different storage periods and to convert them into plantlets. Results Cotyledonary-stage somatic embryos (5–7-mm size) regenerated from stigma explants of Washington navel orange (Citrus sinensis L.) were encapsulated individually in 3% sodium alginate. After different preservation periods (1, 2 or 3 months) at 10 °C, the encapsulated somatic embryos were cultured on Murashige and Skooge (MS) medium solidified with 7 g/l agar and supplemented with 50 g/l sucrose for germination. Percentage of regrowth, germination percentage, number of plantlets, plantlets height and number of leaves/shoot were recorded after different recovery periods. The germination percentages of encapsulated embryos were 90, 62.5 and 40% with storage for one, two and three months, respectively. Encapsulated somatic embryos preserved for 1 month developed the highest number of plantlets, while those preserved for 2 months developed the highest length of plantlets and the highest number of leaves/shoot after a recovery period of 10 months. Molecular analysis was performed of plantlets recovered from somatic embryos after preservation by encapsulation, and the results showed that the percentages of polymorphism were 7.7% with the two primers in all treatments. Conclusions It could be concluded that callus developed from stigma explants was able to regenerate indirect somatic embryogenesis after 3 months. Cotyledonary-stage somatic embryos of citrus were successfully preserved by encapsulation using 3% sodium alginate. Frequencies of germination of encapsulated somatic embryos increased with increasing the recovery period on the germination medium. A maximum recovery frequency of 60.8% was obtained from encapsulated somatic embryos cultured on germination medium for up to 10 months. Also, recovery frequency of 62.5% was noticed from encapsulated somatic embryos preserved for 2 months at 10 °C. In addition, results indicated that recovered somatic embryos obtained from encapsulated somatic embryos were able to convert to normal plantlets.