Effects of α -amylase Inhibitor on Mungbean Weevil, Callosobruchus maculatus, in vivo and in vitro and on Barley Malt α-amylase in vitro

Abstract

Effects of protein part of α-amylase inhibitor crude extracts from mungbean seeds of the recommended varieties, KPS1 and CN36, and mutant lines, M5-16 and M5-29 were evaluated on the mortality of the larval and adult stages of mungbean weevil, Callosobruchus maculatus. KPS1 seeds were used as the medium soaked with different extract concentrations of all mungbean varieties/lines and distilled water (the control). Each, with three replicates, was fed to one pair of C. maculatus and percent mortality of each stage was recorded. Of all different protein α-amylase inhibitor extracts at each concentration, significant difference was not found in larval mortality percentage between the extract-treated seeds and distilled water-treated seeds. Only seeds treated with 0.2% w/w protein extracts from CN36 and KPS1 seeds significantly differed in percent adult mortality from those of the control, respectively. At 0.4, 0.6 and 1% w/w protein, each extract was significantly different from the control in adult mortality percentage. Each extract of various concentrations, except for KPS1 and M5-29 extracts gave significantly different larval mortality percentages at 0.4 and 0.6 and 1% w/w protein, respectively. There were significant differences in adult mortality percentage of every extract at each concentration from that of the control. An effect of α-amylase inhibitor on α-amylase activity in vitro was also studied. One hundred percent inhibition of protein part to α-amylase activity of C. maculatus was found in all variety/line mungbean seeds. Similar study was also conducted against α -amylase extracted from barley. The effects were less than those of α-amylase of the weevil.