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Abstract
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Plant proteinase inhibitors are among the promising biopesticides which are induced in plants tissues
against the several Lepidoptera pests to inhibit digestive proteases. In this study, protein extracts of
two nonhost plant seeds, Amaranthus retroflexus Linnaeus (Amaranthaceae) and Cuminum cyminum
Linnaeus (Apiaceae), were examined on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). The
results obtained by using azocasein as a substrate showed that inhibitory activity of general proteases
of the larvae fed on a diet incorporated with both inhibitors was dose dependent. Seed extracts of
A. retroflexus and C. cyminum at the highest concentration showed that inhibition activities of
chymotrypsin-like proteinase and trypsin-like proteinase were between 31–45% and 28–61%, respectively.
Based on polyacrylamide gel electrophoresis, all of the proteinase isoforms, including those of A. retroflexus
seed extracts, disappeared entirely, and only one band was detected in the seed extracts of C. cyminum.
Larval mortality in the larvae fed on A. retroflexus and C. cyminum seed extracts was 56 ± 2.15 and
68 ± 2.23, respectively, but mortality in control (no seed protein extract) was 12 ± 2.34 individuals.
Also, the life table parameters were affected significantly by A. retroflexus and C. cyminum protein seed
extracts. Therefore, A. retroflexus and C. cyminum seed protein extracts showed inhibitory effect on H.
armigera digestive proteinases and adverse effects on survival and fitness of the pest; hence, they could
be introduced as a successful biopesticide in the near future.
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