Foliar Spraying of 6-Benzylaminopurine Promotes Growth and Flavonoid Accumulation in Mulberry (Morus alba L.)

Abstract

Mulberry ( Morus alba L.) leaf, a “source of both medicine and food”, contains antioxidant ingredients such as flavonoids, alkaloids and polyphenols. The effects of 6-benzylaminopurine (6-BA) treatment on plant growth and flavonoid contents in mulberry leaves were investigated in this study. The expression of rutin (Rut), chlorogenic acid (ChA), isoquercitrin (IQ) and astragaloside IV (Ast) related genes in the flavonoid synthesis pathways was investigated in mulberry leaves. The results showed that 6-BA treatment significantly promoted mulberry differentiation and growth as well as, increased the numbers of new shoots and buds compared to the control. In addition, 30 mg/L 6-BA significantly increased the contents of Rut, IQ and Ast, and it strongly induced the expression of flavonoid biosynthesis-related genes, including flavonoid 3- O -glucosyltransferase (F3GT), 4-xoumarate-CoA ligase (4CL), phenylalanine (PAL) and chalcone synthase (CHS). The dietary risk assessment of mulberry leaves was based on hormone residues 5 days after treatment with 30 mg /L 6-BA, and the results showed that the dietary exposure risk of 6-BA was extremely low without causing any health concern. Thus, treatment with 30 mg/L 6-BA is a new method to improve the medicinal quality and development of high-value mulberry leaf foods without any potential risk.

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