Study of phosphine resistance in Rhyzopertha dominica infesting wheat

Abstract

newline The lesser grain borer, Rhyzopertha dominica (Fabricius) is a major coleopteran insect pest of stored grain products. Both grubs and adults are internal feeders and damage the grains by converting them into powdery material. This pest attacks mainly wheat, maize, rice, sorghum, pulses, and other stored commodities and causes serious losses to stored grains in tropical and subtropical regions. Fumigation with phosphine is the main control method for R. dominica, however the indiscriminate and continuous use of phosphine has led to the development of resistance in this insect pest. Developing and implementing an effective phosphine resistance management strategy relies on evaluating the susceptibility levels of R. dominica populations. Taking cognizance of this fact the aim of this study was to evaluate the susceptibility levels of R. dominica populations collected from six states viz., Uttar Pradesh, Haryana, Punjab, Rajasthan, Madhya Pradesh and Delhi from bulk grain storage godowns. Toxicological studies were carried out to investigate and understand the susceptibility levels in the different populations towards phosphine. Two discriminating doses, 0.03 mg/l, and 0.25 mg/l were used to screen the populations of R. dominica for resistance to phosphine. The resistance percentage indicated that there were high tolerance levels of the different populations to phosphine. With two discriminating doses, the median lethal concentration of all collected populations was estimated to assess the toxicity of phosphine. In addition, further, molecular screening of phosphine resistance was performed to confirm the resistance, quantify and evaluate the resistant alleles in the collected R. dominica populations.