Fungal elicitor-mediated enhancement in growth and asiaticoside content of Centella asiatica L. shoot cultures

Abstract

Effect of fungal elicitors on biomass and asia- ticoside production in multiple shoot cultures of Centella asiatica was studied in a dose- and culture age- dependent manner. Addition of 3 % v/v Trichoderma harzianum culture filtrate (CF) in the growth medium on 10th day of 35 days culture cycle resulted in 9.63 mg g -1 dry weight content and 1.15 mg dry weight culture -1 yield of asiati- coside that was 2.53 and 2.35 times higher than in the un- elicited control shoots, respectively. The elicited cultures also registered 1.24 folds more biomass over the control with a growth index (GI) of 7.67, calculated as fresh weight increment over the initial inoculum weight. Elicitation of shoots with mycelial extract (ME) of the fungus Colleto- trichum lindemuthianum (1.5 % v/v, added on 0 day) on the other hand, though favored highest biomass accumu- lation amongst all the elicitation treatments (GI = 16.10) resulted in a decreased asiaticoside content of 1.10 mg g -1 dry weight that was nearly 3.5 and 8.7 times lower than in the control or T. harzianum CF-treated shoots, respectively. Treatments with mycelial extract of Fusarium oxysporum (0.5-1.5 % v/v), in general, proved inhibitory for shoot growth if added on 0 day of the culture cycle with GI = 4.85-8.45 in comparison to 11.11 in the control with a poor asiaticoside yield of only 0.18-0.42 mg dry weight culture -1 . Though the shoot biomass accumulation was marginally improved (GI = 5.68-11.94) over the untreated control when F. oxysporum ME (0.5-1.5 % v/v) was added in the medium on the 30th day of culture but the asiati- coside yield (0.18-0.94 mg dry weight culture -1 ) remained low. The results presented here demonstrate for the first time the potential application of T. harzianum CF in up- regulating the asiaticoside biogenetic pathway in C. asiatica.