Effects of bean and wheat α‐amylase inhibitors on α‐amylase activity and growth of stored product insect pests*

Abstract

Insect α‐amylase inhibiting and/or growth inhibiting activities of proteinaceous inhibitors from red kidney bean (Phaseolus vulgaris) and hard red winter wheat (Triticum aestivum) were examined. The bean inhibitor was most effective in vitro against α‐amylases from the red flour beetle (Tribolium castaneum) and the confused flour beetle (T. confusum), followed by those from the rice weevil (Sitophilus oryzae) and yellow mealworm (Tenebrio molitor). The insect enzymes were from two‐ to 50‐fold more susceptible than human salivary α‐amylase. When the inhibitors were added at a 1% level to a wheat flour plus germ diet, the growth of red flour beetle larvae was slowed relative to that of the control group of larvae, with the bean inhibitor being more effective than the wheat inhibitor. Development of both the red flour beetle and flat grain beetle (Cryptolestes pusillus) was delayed by 1% bean inhibitor, but development of the sawtoothed grain beetle (Oryzaephilus surinamensis) and lesser grain borer (Rhyzopertha dominica) was not affected by either the bean or wheat inhibitor at the 1% level. Rice weevil adults fed a diet containing 1% bean or wheat inhibitor exhibited more mortality than weevils fed the control diet. When the wheat amylase inhibitor was combined with a cysteine protease inhibitor, E‐64, and fed to red flour beetle larvae, a reduction in the growth rate and an increase in the time required for adult eclosion occurred relative to larvae fed either of the inhibitors separately. The bean inhibitor was just as effective alone as when it was combined with the protease inhibitor. These results demonstrate that plant inhibitors of insect digestive enzymes act as growth inhibitors of insects and possibly as plant defense proteins, and open the way to the use of the genes of these inhibitors for genetically improving the resistance of cereals to storage pests.

Pectin digestion in herbivorous beetles: Impact of pseudoenzymes exceeds that of their active counterparts

“…In plants, starch is the main storage polysaccharide and the major source of carbohydrate-based energy in herbivorous insects. Fitness costs, such as developmental delay resulting from altered starch digestion in insects either through the ingestion of plant α-amylase inhibitors or the knockdown of amylase genes, illustrate the importance of carbohydrate accessibility [49][50][51]. There is another potential carbohydrate source that is omnipresent in a herbivore´s diet but often overlooked: the plant cell wall (PCW).…”

In vitro and in vivo inhibition of α-amylases of stored-product mite Acarus siro

“…Gatehouse et al 1986;Pueyo et al 1995;Chrispeels et al 1998;Gatehouse and Gatehouse 1998;Hou and Fields 2003), however, little information is currently available about their effect on physiology and population dynamics of the stored-product mites.…”

The effect of wheat α‐amylase inhibitors incorporated into wheat‐based artificial diets on development of Sitophilus granarius L., Tribolium confusum Duv., and Ephestia kuehniella Zell

“…The insect resistance mechanisms of cereal grains are complex and depend on physico‐chemical and biochemical properties of the grain and on the subsequent biochemical and physical adaptation of post‐harvest insects to these properties (B AKER , 1986; W ARCHALEWSKI et al., 1989; D OBIE , 1991; W ARCHALEWSKI and N AWROT , 1993; W ARCHALEWSKI et al., 1993). Stored seeds may have high resistance to insect pests because of the lack of vital nutrients or the presence of compounds that adversely affect insect development (T AYLOR and M EDICI , 1966; M EDICI and T AYLOR , 1966; Y ETTER et al., 1979; N AWROT et al., 1985; G ATEHOUSE et al., 1986; D OBIE , 1991; B AKER et al., 1991; H UESING et al., 1991; W ARCHALEWSKI and N AWROT , 1993; P UEYO et al., 1995; Z HANG et al, 1997; P IASECKA ‐K WIATKOWSKA , 1999; P IASECKA ‐K WIATKOWSKA and W ARCHALEWSKI , 2000a, b). In general, insects tend to develop more slowly on resistant grain varieties.…”