Effect of Glycine Betaine Nanocomposite Coated with Chitosan and Moderate Salinity Stress on In vitro Microtuberization of Potato (Solanum tuberosum L.) cv. Agria

Potato (Solanum tuberosum L.) is an important food and cash crop having the first rank in the world from non grain crops to ensure food security. The tubers produced through the conventional propagation are characterized by low multiplication rate and susceptibility to pathogens. Microtubers are an ideal propagating material for producing high quality seed potatoes. Nowadays, the production, application, and biological risk assessment of nano-scaled products have attracted global concerns in various fields such as agricultural, biotechnological, medicinal, and plant sciences. Chitosan, a biocompatible polymer, has been widely utilized to improve the production of nano-chemicals, thereby improving crop growth, productivity, and immunity. Nanotechnology plays an important role in modern agriculture to address global challenges such as climate change, severity of plant diseases and the limited availability of important plant nutrients. Polymer-based nano-formulations have recently received the greatest attention with the key objectives of developing less harmful, plant growth promoting and protective agents of biodegradable and natural origin. Use of chitosan-based nanoparticles in agriculture field is still in a budding phase. Significant outcomes have been reported in in vitro and a few in vivo studies in plant growth and protection by chitosan-based nanomaterials.

MS medium containing 80 g of sucrose, containing glycine betaine at concentrations of 20 and 40 mg/l, chitosan at a concentration of 240 mg/l, glycine betaine 20 and chitosan 240 mg/l, glycine betaine 40 and chitosan 240 mg/l, 120 mg/l, glycine betaine nanocomposite coated with chitosan 120 and 240 mg/l and control treatment, as well as nonsalinity treatments with the same compounds and concentrations mentioned for salinity were cultured. The study was performed in randomized complete block design with three replications and sixteen treatment. Glycine betaine nanocomposite coated with chitosan were prepared at Maragheh University as follows. Chitosan, glycine betaine, and triphosphate are major consumables. First, chitosan was dissolved well with acetic acid under the influence of temperature. Then, a certain amount of glycine betaine was dissolved in distilled water and added to the chitosan. Tri-polyphosphate (TPP) was dissolved in distilled water at a certain volume ratio and added dropwise to the mixture of chitosan and glycine betaine. The precipitate obtained under the freeze-drying process lead to the preparation of its powder.

According to the comparison of the means, treatment of glycine betaine coated with chitosan nanocomposite at a concentration of 120 mg/l produced the highest number of microtuber during the experiment from the first month to the final month. The nanocomposite was more capable of improving growth and biomass than the bare ZnONPs in pepper. The application of the nanocomposite increased the concentration of chlorophylls (51%), carotenoids (70%), proline (2-fold), and proteins (about 2- fold). The supplementation of culture medium with the nanomaterials upregulated enzymatic antioxidant biomarkers (catalase and peroxidase) (Asgari-targhi et al., 2021). The highest mean microtuber weight was related to the nanocomposite treatment of 120 mg/l with a weight of 29 mg. In the microtuber diameter, this treatment had the highest value. The results of analysis of variance in Table 1 indicate that the effect of moderate salinity and the interaction of moderate salinity and nanocomposite treatments are not significant and the effect of experimental treatments is significant at the level of 5% probability. Due to the fact that the most important trait in the potato microtuberization is microtuber yield, so in the experiment, the highest microtuber yield was earned nanocomposite treatment with 131 mg and the lowest in control treatment with 87 mg. It seems that by using stress-reducing compounds such as glycine betaine and chitosan and nanocomposites, these compounds increase the amount of genes responsible for the formation of microtuber, and as a result, increasing the proteins involved in stresses induce more microtuberization. Also, nanocomposite materials, more assimilated materials may be transferred from the roots to microtuberization processes.

 The microtuber produced in the glycine betaine coated with chitosan nanocomposite treatment produced the highest number of microtubers in the first, second, third, and final months. In treatments with moderate salinity in the first, second, third and final months, the number of microtuber and eyes and sprouted microtubers had the highest amount compared to the treatment without moderate salinity. Also, plants treated with glycine betaine voated with chitosan nanocomposite in the microtuber trate showed a greater effect than chitosan and glycine betaine with chitosan. According to the findings of this study, it seems that the use of nanocomposite materials in increasing the microtuber and reducing the vegetative growth of potato shoots has been made in Agria cultivar.