The performance and physiological responses of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) to different sorghum cultivars

Utilizing pest-resistant cultivars is a highly effective and environmentally-friendly approach for managing crop infestations by pests. In the present study, the differences in the resistance of eight cultivars of Sorghum bicolor (L.) Moench (Kimia, Payam, Pegah, Sepideh, Spidfid, KGS₂₃, KFS₂, and KFS₁₈) against Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), a polyphagous pest of stored products, were evaluated based on demographic parameters, nutritional indices, and digestive enzymatic activities within the pest. The results revealed that the development time of R. dominica was the shortest when reared on Kimia, Spidfid, and KFS2, while the longest was recorded in those fed on Payam and Pegah. The fecundity of R. dominica was the lowest on Pegah. Furthermore, Kimia and Sepideh showed the highest intrinsic rate of increase (r) and finite rate of increase (λ), whereas the lowest values for these parameters were observed on Pegah and KGS₂₃. The highest relative growth rate (RGR) of R. dominica was achieved on Sepideh, whereas the lowest RGR was observed on KGS₂₃. The highest level of digestive proteolytic activity in R. dominica was observed on Sepideh, whereas the lowest level was found on KGS₂₃. The amylolytic activity in R. dominica was the highest on Sepideh, and the lowest on Pegah and KGS₂₃. The findings showed significant negative correlations between fecundity, intrinsic rate of increase, and amylolytic activity of the pest with the total phenolic content of the studied sorghum cultivars. Furthermore, the results obtained from cluster analysis revealed that Sepideh, Kimia, and KFS₂ were the susceptible cultivars for population growth of R. dominica, while Payam, Pegah, and KGS₂₃ were the partially resistant hosts for this pest. The pest-resistant sorghum cultivars identified in this study can potentially be utilized in combination with other pest control strategies for sustainable management of R. dominica, which may help reduce the excessive use of chemical insecticides.