In vitro Secondary Metabolite Production from the Roots of Decalepis arayalpathra KMA 05 Clones and its Antimicrobial Potential using Methylobacterium sp. VP103 as an Elicitor

Decalepis arayalpathra KMA 05 clones were elicited with a bacterium, Methylobacterium sp. VP103 isolated from the leaves of ex-vitro established plantlets of D. arayalpathra KMA 05 clones, with the aim of increasing the production of root specific secondary metabolites. D. arayalpathra KMA 05 shoot tip cultures were triggered for root initiation by keeping the cultures for one month in ½ strength Woody Plant Medium (WPM)+Thidiazuron (TDZ) 0.3 mg/l. They were then shifted to ½ strength WPM supplemented with auxins [0.5 mg/l indole-3-butyric acid (IBA) + 0.05 mg/l Naphthalene acetic acid (NAA)] along with 40 mg/l activated charcoal with a fixed concentration (0.4 mg/l) of lyophilized bacterium powder (LBP) dissolved in 30% methanol. The effect of elicitation was studied on three root specific secondary metabolites, i.e. 2-hydroxy 4-methoxy benzaldehyde (MBALD), 2-methoxy-4-vinylphenol (2M4VP) and α-amyrin. The production of α-amyrin was found to be enhanced in all 12, 24 and 36 week old treated root extracts. Antibacterial activity was also found to be enhanced against all the bacteria selected from the 36 week elicited extracts among which Rhodococcus sp. UKS7 (34 ± 0.0 mm.) showed maximum inhibition. The findings provide an insight into the use of Methylobacterium sp. VP103 as an elicitor in the growth of the roots and enhanced production of α-amyrin.