The rice cultivar affects the population growth and physiological enzyme activity of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) reared on rice grains

Abstract

The rice weevil, Sitophilus oryzae, is an important pest of stored rice that causes substantial post-harvest losses. In this study, the population growth and physiological enzyme activity of S. oryzae reared on grains from five rice cultivars, red brown rice (RBR), Daohuaxiangmi (DHXM), Baishuigongmi (BSGM), Yashuixinmi (YSXM), and white glutinous rice (WGR), were studied. The duration of the immature stages of S. oryzae was shortest when reared on RBR (29.74 d) and longest when reared on YSXM (34.34 d). When reared continuously on grains of each cultivar for multiple generations for a period of 5 consecutive months, the average growth rate of the S. oryzae population was the highest in RBR (384.38%), followed by BSGM (98.35%) and WGR (82.02%), whereas in DHXM (−24.38%) and YSXM (−27.12%) a negative population growth was observed. The catalase and superoxide dismutase activities were significantly higher in S. oryzae fed on YSXM than on the other cultivars, whereas peroxidase activity took its highest value for S. oryzae fed on BSGM and lowest when fed on YSXM, WGR or RBR. The activities of three detoxification enzymes were highest in S. oryzae reared on YSXM, while glutathione transferase and carboxylesterase activities were lowest when fed on RBR. Activities of the digestive enzymes α-amylase, cellulase, and lipase were lowest in S. oryzae reared on YSXM and highest when fed on RBR. Pepsin activity was highest in S. oryzae reared on YSXM, with no significant difference to that on RBR. Our results suggest that the significant impact of the rice cultivar on the population growth of S. oryzae may be associated with physiological enzyme activities, which play an important role in the nutrient and detoxification metabolism and growth of insects.