Identification of ISSR markers associated with valerenic acid content and antioxidant activity in Valeriana jatamansi Jones in the West Himalaya

Abstract

Valeriana jatamansi Jones, commonly known as Indian Valerian or Tagar (Family: Valerinaceae) is used in both traditional and modern systems of medicine. The plants of this species are known for their high content of valerenic acid, the main active constituent of valerian, and high antioxidant activity, and these characteristics have increased the demand for these plants by the pharmaceutical industry. At present, the demand for planting material is largely met from the harvesting of wild plants, which vary in quality and quantity of the active ingredient. Therefore, there is a need to identify individual plants/populations with a higher content of the active ingredients and higher antioxidant activity. We used inter-simple sequence repeats (ISSR) markers in 151 genotypes of 25 V. jatamansi populations to identify markers associated with valerenic acid and antioxidant activity. Of the 130 ISSR primers tested, 20 generated 159 bands, with an average of 7.95 bands per primer. Valerenic acid content was significantly (p < 0.05) higher in the Katarmal (aerial portion 0.57 ± 0.04 %) and Joshimath populations (root portion 1.80 ± 0.12 %). Antioxidant activity using these different in vitro assays varied among the populations and plant portions, with maximum antioxidant activity found in the aerial plant portion (8.63 ± 0.06 mM) and roots [8.36 ± 0.0 mM ascorbic acid equivalents (AAE)/100 g dry weight (dw)] of the Didihat and Katarmal populations, respectively, using the ABTS [2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic)] assay. The DPPH (2, 2-diphenyl-1-picryylhydrazyl free radical scavenging) assay revealed maximum antioxidant activity in the aerial plant portion (15.23 ± 0.09 mM) and roots (17.53 ± 0.04 mM AAE/100 g dw) of the Didihat population. The FRAP (ferric-reducing antioxidant power) assay showed that the roots of plants of the Ukhimath population had significantly higher antioxidant activity (12.71 ± 0.04 mM AAE/100 g dw) than those of other populations of V. jatamansi. Based on the stepwise multiple regression analysis, seven positive and six negative markers showed significant association with valerenic acid content. Antioxidant activity measured by the ABTS, DPPH and FRAP assays showed a positive correlation with 14, 13 and 10 markers, respectively (p < 0.001). These markers have the potential for application in breeding programmes in order to select lineages of V. jatamansi with higher biochemical attributes, especially when no other genetic information, such as linkage maps and quantitative trait loci is available.