Two way analysis of variance for performance of <i>H. armigera</i> on various days feeding on tomato and <i>O. kilimandscharicum</i> leaves.

<p>DF = Degrees of freedom, SS = Sum of squares, MS = Mean square, n = numerator, d = denominator, p = probability of significance, α = 0.05.</p

Metabolic changes in leaves of <i>O. kilimandscharicum</i> following <i>H. armigera</i> infestation.

<p>Heat map representing relative expression of a sub-set of volatiles elicited in leaf tissue during <i>O. kilimandscharicum</i>-<i>H. armigera</i> interaction; comparison between metabolite profiles of local (L) and systemic (S) leaf tissue in <i>O. kilimandscharicum</i>, 12 h and 24 h after feeding by <i>H. armigera</i>, and also on days 3 (D3) and 6 (D6), compared to control (C) plants.</p

Insecticidal Potential of Defense Metabolites from <i>Ocimum kilimandscharicum</i> against <i>Helicoverpa armigera</i>

<div><p>Genus <i>Ocimum</i> contains a reservoir of diverse secondary metabolites, which are known for their defense and medicinal value. However, the defense-related metabolites from this genus have not been studied in depth. To gain deeper insight into inducible defense metabolites, we examined the overall biochemical and metabolic changes in <i>Ocimum kilimandscharicum</i> that occurred in response to the feeding of <i>Helicoverpa armigera</i> larvae. Metabolic analysis revealed that the primary and secondary metabolism of local and systemic tissues in <i>O. kilimandscharicum</i> was severely affected following larval infestation. Moreover, levels of specific secondary metabolites like camphor, limonene and β-caryophyllene (known to be involved in defense) significantly increased in leaves upon insect attack. Choice assays conducted by exposing <i>H. armigera</i> larvae on <i>O. kilimandscharicum</i> and tomato leaves, demonstrated that <i>O. kilimandscharicum</i> significantly deters larval feeding. Further, when larvae were fed on <i>O. kilimandscharicum</i> leaves, average body weight decreased and mortality of the larvae increased. Larvae fed on artificial diet supplemented with <i>O. kilimandscharicum</i> leaf extract, camphor, limonene and β-caryophyllene showed growth retardation, increased mortality rates and pupal deformities. Digestive enzymes of <i>H. armigera -</i> namely, amylase, protease and lipase- showed variable patterns after feeding on <i>O. kilimandscharicum,</i> which implies striving of the larvae to attain required nutrition for growth, development and metamorphosis. Evidently, selected metabolites from <i>O. kilimandscharicum</i> possess significant insecticidal activity.</p></div

Two way analysis of variance for growth inhibition and percentage mortality of <i>H. armigera</i> upon exposure to <i>O. kilimandscharicum</i> leaf extract and selected metabolites on various days.

<p>DF = Degrees of freedom, SS = Sum of squares, MS = Mean square, n = numerator, d = denominator, p = probability of significance, α = 0.05.</p

Digestive enzymes of <i>H. armigera</i> larvae fed on <i>O. kilimandscharicum</i> leaves.

<p>Changes in the levels of <b>A.</b> protease <b>B.</b> amylase <b>C.</b> lipase activity of <i>H. armigera</i> second-instar larvae fed on <i>O. kilimandscharicum</i> plants at 12 h, 24 h, day 3 and day 6. One way ANOVA followed by Tukey's multiple comparisons test suggested significant difference between the data at. <i>p</i><0.001 (indicated as ‘***’), <i>p</i><0.01 (indicated as ‘**’), <i>p</i><0.05 (indicated as ‘*’). Results are an average of three independent experiments conducted in duplicate. Error bars represent Mean ± SD.</p

Metabolic changes in stems and roots of <i>O. kilimandscharicum</i> following <i>H. armigera</i> infestation.

<p>Heat map representing relative expression of a sub-set of volatiles elicited in <b>A.</b> stems and <b>B.</b> roots during <i>O. kilimandscharicum</i>- <i>H. armigera</i> interaction at 12 h, 24 h, and on days 3 (D3) and 6 (D6) as compared to control (C) plants.</p

Two way analysis of variance for macromolecular content of <i>O. kilimandscharicum</i> leaves, stem and root on various days of <i>H. armigera</i> infestation.

<p>DF = Degrees of freedom, SS = Sum of squares, MS = Mean square, n = numerator, d = denominator, p = probability of significance, α = 0.05.</p