Higher accumulation of proteinase inhibitors in flowers than leaves and fruits as a possible basis for differential feeding preference of Helicoverpa armigera on tomato (Lycopersicon esculentum Mill, Cv. Dhanashree)

Tomato (Lycopersicon esculentum, Mill; cultivar- Dhanashree) proteinase inhibitors (PIs) were tested for the potential inhibitory activity against Helicoverpa armigera gut proteases (HGP) by in vitro and in vivo studies. Analysis of TI and HGPI distribution among various plant parts of tomato showed that flowers accumulated about 300 and 1000 times higher TI while 700 and 400 times higher HGPI levels of inhibitors as compared to those in leaves and fruits, respectively. This can be attributed to the differential feeding preference of H. armigera on tomato. Tomato PIs inhibited about 50-80% HGP activity of H. armigera larvae feeding on various host plants including tomato, of larvae exposed to non-host plant PIs and of various larval instars. In addition, they were found to be highly stable to insect proteinases and exhibited similar isoform pattern against bovine trypsin, bovine chymotrypsin and HGP, when visualized by X-ray film contact print technique after native PAGE.