The effects of explant rotation, medium types, JA and GA3 additions on in vitro microtuber production from potato (Solanum tuberosum L.)
Abstract
This study investigates the effects on the in vitro microtuber formations of Solanum tuberosum L. cv. Marfona species, effected by the direction of planting the explants (horizontal or vertical), the type of medium (solid or two-phase), adding Jasmonic acid (JA) (0.0, 10 ng/L, 1 µg/L and 0.2 mg/L) and Gibberellic acid (GA ) (0.0 and 0.2 mg/L). The cultures 3 were incubated in a climate chamber at 22-25 oC, and were subjected to a light intensity of 145 µmol m-2 s-1 for 8 hours in light and 16 hours in dark photoperiods (short day) for 4-6 weeks. Microtuber production was inhibited when GA was 3 added. The maximum number of microtubers was observed when the explants were planted vertically and were grown in two-phase medium which did not contain GA and had 10 ng/L JA present. It was determined that two-phase medium with 3 0.2 mg/L JA but without GA was the most favourable medium for tuber growth (for both height and width). The best 3 microtuber formation on single node explants were observed to occur in the short day photoperiod (8 hours light/16 hours dark) in a two-phase medium that contained 0.2 mg/L JA without the addition of GA . The results shows that the effect 3 caused by JA works antagonistically with that of GA thus causing the resulting microtuber formation observed. 3
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Introduction
The potato (Solanum tuberosum L.) is the fourth most important vegetable after rice, wheat, and corn in food and industry amongst the food sources for the world’s population [1, 2]. When potato tubers are grown by vegetative propagation using conventional methods, the viruses on the main plant are easily transferred on to the new vegetative organs and tubers and causes serious damage to potato production. Due to seed tuber growth being significantly affected by environmental conditions, and that the possibility of disease becomes high in addition to high costs, microtubers are emphasized as an alternative seed source [3]. The microtubers that are produced from seedlings with no viral infections that were obtained from meristem cultures and propagated in vitro are considered to have significant advantages in potato seed production.
The success of in vitro microtuber production in the studies conducted in this field is based on a series of factors. Amongst these, nutrient media solutions, the chemicals used (like activated charcoal), sucrose concentration, growth regulators (such as Gibberellic acid, Jasmonic acid) and temperature, environmental factors like light intensity and genotype factors can be included [4-12]. In literature, it is emphasized that due to the plant growth regulators Gibberellic acid (GA ), Abscisic acid 3 (ABA), Ethylene, (2-chloroethyl) trimethylamonium chloride (CCC), and Jasmonic acid (JA) acting on each other and on environmental factors they are effective on the formation and development of vegetative storage organs like tubers [13-16].
The physiological mechanisms and their related hormones that determine potato tuber growth and development are still not fully known.
The gibberellins that are effective in many physiological processes, including plant stem development, seed germination, breaking of bud dormancy, and fruit growth, also effect the development of potato tubers. Environmental factors, like photoperiod and temperature regulate gibberellin biosynthesis [15].
In recent years, the effect of Jasmonic acid and methyl esters on tuber stimulation has been the focus of studies [17-19]. In addition to acting as a signal molecule for activating an immune response in case of pathogen invasions, JA also acts as a regulator for many physiological and developmental (such as root development, tuberization, ageing, and pollen development) processes. Jasmonates are also potential stimulators for the expression of vegetative storage protein genes [20].
It is also reported that JA’s are effective during in vitro microtuberization in addition to playing an important role in the development of vegetative storage organs [16, 19, 21-24]. However, JA’s influence on microtuber development and its relationship with other growth regulators are still not fully elucidated. In the studies conducted, the time taken for microtuber development, the medium conditions for growing microtubers and which hormones, chemicals etc. need to be applied in what doses could not be fully determined [18, 19, 22, 25-27]. To include JA when commercially producing microtubers, more information is needed on the effect of this substance on tuberization and its relationship with other hormones.
In this study, the relationship between the planting of explants (either horizontally or vertically), the type of medium (either solid or two-phase), the addition of Jasmonic acid (0.0, 10 ng/L, 1 µg/L and 0.2 mg/L), and Gibberellic acid (0.0 and 0.2 mg/L) into the media and how they affect the development of microtubers growing in vitro on the economically valuable Solanum tuberosum L. cv. Marfona is investigated.
Conclusion
To summarize the results:
- The best medium type for microtuber formation was a two-phase medium,
- GA addition to the medium inhibited microtuber formation, 3
- JA addition to the medium resulted in positive effects on microtuber formation and this effect resulted from working antagonistically with GA , 3
- In regards to JA-GA interaction and medium type, a two-phase medium with 0.2 mg/L JA but without any GA 3 3 was found to be the optimal medium.
In future studies, different substances that encourage tuberization will be beneficial for researching about other and their relationship with photoperiods in developing mechanisms in the production of microtubers.