Growth and development of melon fruit fly larvae under the influence of soybean trypsin inhibitors

Abstract

Protease inhibitors (PIs) retard growth and development and cause mortality in a range of insect pests belonging to various orders. Some transgenic plants expressing PI genes have also been effective against insect pest attack. The effects of two purified soybean PIs, i.e. trypsin inhibitor (Kunitz type; SBTI) and trypsin-chymotrypsin inhibitor (Bowman-Birk type; SBBI), were investigated on first and third instar larvae of the melon fruit fly Bactrocera Cucurbitae (Coquillett) in laboratory feeding bioassays. The larval period of both the first and third instar larvae was prolonged when the larvae were treated with various concentrations of SBTI and SBBI. The total development period prolonged significantly in both the instars of larvae treated with SBTI, but in SBBI-treated larvae, the development period was delayed significantly only in the third instar larvae. A decrease in percentage pupation and adult emergence was observed in the first and third instar larvae treated with different concentrations of both SBTI and SBBI. The present studies showed that SBTI and SBBI have a potential in inhibiting the growth and development of melon fruit fly, but further detailed and molecular level studies are required before their use in transgenics.