Cytokinin application improving growth, sugar content, polyphenol and flavonoid content in Yacon tuberous roots

Abstract

Yacon is a tuberous crop that accumulates sugar in large quantities and has many valuable secondary compounds in medicine such as phenolic compounds and flavonoids. The objective of this study was to increase the size and content of sugars, polyphenols and flavonoids during the early growth of tubers. Therefore, early tuber stimulation and tuber size are important as they determine yield over time. Cell restructuring along with growth expansion as well as control of tuber reserves also takes place. This study investigated anatomy structure changes, fresh weight, dry weight, respiratory intensity and sugar content in different Yacon root types. A spray of N-benzyl adenine (BA) (0–25 ppm) is applied in the initial stage. Determining agronomic, physiological, and, biochemical indicators after 4 weeks of treatment, the sugar content of tubers determines the yield of tubers after 16 weeks of treatment. The results showed that Yacon crops at the stages of 5 to 9 weeks develop fibrous roots, thin fibrous roots and pre-tuberous roots at week 13, intermediate storage roots at week 17 and mature storage roots at week 17. BA 20 ppm application on Yacon crop week 13 increased the number of storage roots, fresh weight, dry weight tuber diameter, total sugar content, fructan content, total phenolic and flavonoid remarkably compared to controls, but reducing sugar content is lower than treating BA at 15 ppm. BA 20 ppm application on Yacon crop week 13 increased the parameters of sugar growth and accumulation, tuber yeild on a plant increased 2 times, dry weight increased 1.65 times, sugar content, total sugar 1.12 times, reducing sugar 3.01 times, fructan 1.36 times, total phenolic and flavonoid 1.36 and 1.26 times after 25 weeks of treatment.