Abstract
The flowers of Pyrethrum (Chrysanthemum cinerariaefolium) are known to contain Pyrethrins that are naturally occurring potential insecticide. Hairy roots were induced from leaves of C. cinerariaefolium using Agrobacterium rhizogenes strain A4. The root clones were characterized in to four groups i.e. thick, unbranched (D2 and D5), thin, highly branched (D3), thick, branched (B2) and thick, highly branched (D1, D6). Six established hairy root clones showed the presence of pyrethrin and were selected for elicitation studies. Growth kinetics studies revealed highest growth index in hairy root clone D1 (592.0) followed by D6 and D3 on dry weight basis after 40 days of culture. The maximum pyrethrin content was found in the clone D3 (7.2 mg/g dw) which is comparable to the flowers obtained from the variety "Avadh". Hairy root clone D2 (5.2 mg/g dw) and D6 (1.3 mg/g dw) contained pyrethrin but in less amount as compared to clone D3. The PCR analysis showed the presence of rol B and rol C genes in all the six hairy root clones while rol A was detected only in D2 clone. The methanolic extract of D3 clone showed antifungal activities against phytopathogenic fungal strains which were found maximum against Curvuleria andropogonis followed by Colletotrichum acutatum and Rhizoctonia solani. Hairy root clones D2, D3 and D6 were elicited with culture filtrate of endophytic fungus (Fusarium oxysporum) and bacteria (Bacillus subtilis). The culture filtrate (4.0 %v/v) of both the fungal and bacterial origin was found to be effective in enhancing the pyrethrin content in all the tested hairy root clones. Clone D3 showed maximum pyrethrin content on elicitation with F. oxysporum (9.7 mg/g dw) and B. subtilis (9.7 mg/g dw) culture filtrate, which is 32 % higher than the non elicited D3 hairy roots (7.2 mg/g dw). F. oxysporum also enhanced the hairy root growth resulting into the higher biomass yield of D3 (50 %) and D2 (76 %) in comparison to control non elicited hairy root clones of D3 and D2, respectively leading to higher pyrethrin yield.