Effects of abscisic acid, jasmonic acid and salicylic acid on the content of phytochemicals and their gene expression profiles and biological activity in turnip (Brassica rapa ssp. rapa)

Turnip (Brassica rapa ssp. rapa) is an important vegetable crop and produces valuable health-promoting phytochemicals which have been used for their nutraceutical value. The exogenous effects of abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) on the contents of glucosinolate, individual and total phenolic compound, carotenoid, chlorophyll and anthocyanin content and their gene regulation of metabolic biosynthesis, as well as antioxidant and antimicrobial activities were studied in turnip plants. The JA treatments significantly increased the amount of glucobrassicin, 4-methoxyglucobrassicin, neoglucobrassicin and 4-hydroxyglucobrassicin. Gluconasturtiin content was considerably increased by ABA treatment. Glucoallysin, sinigrin, progoitrin, gluconapin and glucobrassicanapin were highly increased in SA-treated plants. The content of lutein was higher in ABA and SA-treated plants compared with that in control plants. Carotenoid, chlorophyll and anthocyanin contents were significantly increased with ABA, JA and SA treatment. Individual phenolic (flavonols, hydroxycinnamic and hydroxybenzoic acids) and total phenolic, flavonoid content, antioxidant and antimicrobial activity were noticeably increased in ABA, JA and SA-treated plants. Furthermore, ABA, JA and SA-treated plants exhibited significantly increased expression of genes associated with the phytochemical production. Our results proved that ABA, JA and SA did significantly increase the concentration of health-benefiting phytochemicals and also increased biological activity in turnip plants.