From immobilization to recovery: Towards the development of a rapid diagnostic indicator for phosphine resistance

Authors: ATHANASSIOU, CHRISTOS - UNIVERSITY OF THESSALY; KAVALLIERATOS, NICKOLAS - AGRICULTURAL UNIVERSITY OF ATHENS; Brabec, Daniel - Dan; Oppert, Brenda; GUEDES, RAUL N. - UNIVERSIDADE FEDERAL DE VICOSA; Campbell, James - Jim

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2018
Publication Date: 11/23/2018
Citation: Athanassiou, C.G., Kavallieratos, N.G., Brabec, D.L., Oppert, B.S., Guedes, R.C., Campbell, J.F. 2019. From immobilization to recovery: Towards the development of a rapid diagnostic indicator for phosphine resistance. Journal of Stored Products Research. 80:28-33. https://doi.org/10.1016/j.jspr.2018.10.004.
DOI: https://doi.org/10.1016/j.jspr.2018.10.004

Interpretive Summary: Phosphine is a gas used as a fumigant for the control of insect pests in grain and other materials, but resistance to phosphine has been increasing worldwide. Determining levels of resistance prior to treatment is important in order to determine the phosphine concentration or exposure time that will be effective or if alternative treatments are needed. There are several protocols to detect phosphine resistance, but many are labor, equipment, and time intensive procedures. A new quick diagnostic test was used to characterize how quickly two strains of the red flour beetle, one susceptible and one resistant to phosphine, respond to different concentrations of phosphine. At 1000 ppm phosphine, the majority of the adults from the susceptible strain was quickly immobilized after 15 min, but the majority of the adults from the resistant strain was still active after exposure up to 90 min. At greater phosphine concentration, 3000 ppm, a larger percentage of immobilization occurred with the susceptible strain and the majority of the adults of the resistant strain were immobilized after 90 min. When beetles were removed from exposure to phosphine, the vast majority of the adults of the susceptible strain never recovered and died. In contrast, for the resistant strain, most adults recovered to normal activity after being removed from both the 1000 and 3000 ppm phosphine treatment. The initial immobilization of active beetles during exposure to phosphine and the recovery after exposure both appear to be useful rapid methods to detect phosphine resistance and will be helpful in field evaluations. This method will also be useful for genetic selection and functional genomics research, since the same individual beetles identified as resistant can be used in subsequent procedures.

Technical Abstract: The aim of this work was to evaluate the immobilization and narcosis patterns after exposure to phosphine, of the adults of two strains of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), from which one strain was susceptible and one resistant to phosphine. Exposure bioassays were carried out at two concentrations, 1000 and 3000 ppm, while adults were observed every 15 minutes (min), for a total period of 90 min. During this observation interval, the adults were classified as active (able to walk normally), under narcosis (not able to walk), or immobilized (no visible movement). Then, all adults were placed in phosphine-free environment and they were classified again as active, under narcosis and immobilized. At 1000 ppm, the majority of the adults from the susceptible strain was quickly immobilized after 15 min, while, in contrast, the majority of the adults from the resistant strain was still active after the termination of the 90 min interval. At 3000 ppm, the percentage of immobilization of adults of the susceptible strain was increased at the 15-min observation period, while the majority of the adults of the resistant strain was immobilized after 90 min. Regarding the post-exposure period, the vast majority of the adults of the susceptible strain were dead. In contrast, for the resistant strain, most adults recovered, regardless of their condition during exposure. The results of this study can be utilized further in designing a quick diagnostic bioassay for the evaluation of resistance to phosphine in stored product insects.