Effect of plant seeds protein extract on the Sunn pest, Eurygaste integriceps Puton, growth and development and its gut serine protease activity

Abstract

The sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is a major pest of wheat and barley in wide areas of the world that cause 100% crop loss when no control measures are taken. The aim of this study was to investigate the effect of the seed proteinous extract of different plant species including Chickpea Cicer arietinum (Fabaceae), bean Phaseolus vulgaris var. naz (Fabaceae), triticale Triticosecale wittmack (Poaceae), Celosia argentea (Amaranthaceae) in artificial diet against the Sunn pest growth and development as well as gut serine proteinase such as trypsin and chymotrypsin activities. The obtained results showed that protease inhibitors present in the seed extract affected nymphal development, adult weight and survivability to some extent. Mean developmental time of third and fourth instar nymphs were not significantly affected by the presence of seed extracts. However, developmental time of the fifth instar nymph was affected by seeds proteinous extracts. Bean proteinous extract increased developmental time significantly by almost two days followed by Chickpea that increased developmental time by one day (P < 0.01). Amaranthus seed proteinous extract caused slight increase in development time. Triticale extract did not affect nymph growth and development and there were no significant differences between developmental time of triticale extract and control. Azocaseinolytic activity of gut extract of E. integriceps was affected greatly by seed proteinous extracts. There were significant differences in general protease activity between control and all treatments. General protease activity dropped significantly low when treated with bean and cowpea extracts (P< 0.01). Almost the same trend was observed when trypsin and chymotrypsin activities were measured using BApNA and SAAPFpNA as substrates, respectively. It is concluded that seed extracts from non host plants of the Sunn pest caused significant reduction of general and specific protease activity in vitro.

Key words: Sunn pest, growth, development, seed extracts, protease activity.