BIOINSECTICIDAL ACTIVITY OFMurraya koenigii MIRACULIN-LIKEPROTEIN AGAINST Helicoverpaarmigera AND Spodoptera litura

摘要

Miraculin-like proteins, belonging to the Kunitz superfamily, are naturalplant defense agents against pests and predators, and therefore arepotential biopesticides for incorporation into pest-resistant crops. Here, amiraculin-like protein from Murraya koenigii was assessed for its in vitroand in vivo effects against two polyphagous lepidopteran insect pests,Helicoverpa armigera and Spodoptera litura. M. koenigii miraculin-likeprotein (MKMLP) inhibited the trypsin-like activity and total proteaseactivity of H. armigera gut proteinases (HGP) by 78.5 and 40%,respectively, and S.litura gut proteinases (SGP) by 81 and 48%,respectively. The inhibitor was stable and actively inhibited the proteolysisof both HGP and SGP enzymes for up to 72 h. Incorporation ofMKMLP into artificial diet adversely affected the growth anddevelopment of pests in a dose-dependent manner. After 10 days offeeding on diets containing 200 mM MKMLP, larval weight was reduced to 69 and 44.8% and larval mortality was increased to 40 and43.3% for H. armigera and S litura, respectively. The LC50 of MKMLPwas 0.34 and 0.22% of the diet for H.armigera and S. litura,respectively. These results demonstrate the efficacy of MKMLP as apotential plant defense agent against H. armigera and S. litura.