Abstract
Plant protease inhibitors) PIs) are one of the plant strategies to maintain favorable growth and survival. Soybean trypsin inhibitor is the most well-known of the plant serine proteinase. The present study aims to detect the inhibitory activity of two concentrations of partially purified trypsin inhibitors from seeds of soybean(Glycine max). Comparing the results of feeding larvae on partially purified soybean inhibitors with control, revealed that the larval weight reduction caused by soybean PI was noticed after seven days of treatment. The highest larval weight reduction was obtained due to treatment with SPI at levels SPI 30% and SPI 60%, and there was no significant difference between the two levels. Feeding larvae on SPI 60% caused higher larval mortality about 20% than the control followed by SPI 30% which caused 16% larval mortality. The pupation in treated larvae was delayed two days by comparing to control. The highest weight reduction in pupal weight was 3.5± 0.3 gm at SPI 60% compared with control. Besides, the pupation rate decreased from 83% at SPI 60% to 80% at SPI 30%. Also, the reduction in adult emergency % was recorded at SPI level 30% by 41% and at SPI level 60% by 16% compared with the control. Results reveal that soybean protease inhibitors inhibit the growth and development of S. littoralis, and may be used in integrated pest control strategies.
Highlights
The major biotic stresses to crops are insect pests, responsible for severing crop reduction despite the extensive use of chemical pesticides
There are no significant differences in the larval weight between untreated larvae, and that treated with SPI 30% through the first seven days post-treatment except at day six which increased significantly
Protease inhibitors have been determined as natural control agents against herbivorous insects and could reduce the digestive proteolytic enzyme activity and larval development in different species of Lepidoptera and Coleoptera (Chen et al 2007; Ramesh Babu et al 2012 and Aghaal et al 2013).Protease inhibitors have an inhibitory or activating function on serine protease in the midgut of insects, destroying coordination among the proteases which disrupt the digestion process of the insect
Summary
The major biotic stresses to crops are insect pests, responsible for severing crop reduction despite the extensive use of chemical pesticides. Insects often append losses of 15 to 50% of the yield of some crops in various parts of the world and provide infection for various pathogens that append even greater damage (Ferry et al 2004). The cotton leafworm is the destructive pest to about 112 host plants from different families in Egypt as well as in Mediterranean and Middle East countries (Kandil et al 2003; El-Sinary et al 2008 and El-Zoghby et al 2011). Previous researchers demonstrated that plants were considered one of the richest sources which could be used as pest control agents. They attended to use plant extracts as toxicants, repellents, synergists, growth regulators, and antifeedant for cotton leafworm (El-Kholy et al 2014)
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