Assessment of DNA integrity from trap captured boll weevil (Coleoptera: Curculionidae) for use in a new PCR-based diagnostic tool

Authors: Perkin, Lindsey; Oppert, Brenda; Duke, Sara; Suh, Charles

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2021
Publication Date: 4/22/2021
Citation: Perkin, L.C., Oppert, B.S., Duke, S.E., Suh, C.P. 2021. Assessment of DNA integrity from trap captured boll weevil (Coleoptera: Curculionidae) for use in a new PCR-based diagnostic tool. Journal of Economic Entomology. 114(3):1321-1328. https://doi.org/10.1093/jee/toab073.
DOI: https://doi.org/10.1093/jee/toab073

Interpretive Summary: Boll weevil eradication programs rely exclusively on pheromone traps to monitor boll weevil populations and to determine the need for insecticide treatments, but these traps often capture other weevil species that look similar to the boll weevil. Misidentification of weevils could preclude or delay deployment of timely remedial actions or, conversely, lead to unnecessary insecticide applications. Efforts are underway to develop a diagnostic tool that can be used to rapidly and accurately differentiate boll weevils from other weevil species. However, in order for the diagnostic tool to work, both the quantity and quality of DNA extracted from weevils have to be above certain levels. We measured the quantity and quality of DNA from boll weevils and weevil body parts that were held in pheromone traps under field conditions for up to three weeks, which corresponds to the maximum trap servicing interval used by eradication programs in the U.S. We found that the quantity and quality of DNA from whole weevils, heads, abdomens, and legs generally declined through the three-week aging period, but both remained above the levels needed for the diagnostic tool to work. However, we found that rainfall and the subsequent exposure of weevils to moisture greatly accelerated degradation of weevil DNA.

Technical Abstract: The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a major pest of commercial cotton (Gossypium hirsutum) in the Southern U. S. and throughout Central and South America. Efforts are underway to develop a PCR-based diagnostic tool that can be used to rapidly and accurately differentiate boll weevils from other weevil species that are commonly captured in pheromone traps. However, the quantity and integrity of weevil DNA must be above a certain level for the PCR assay to work. Currently, active eradication programs service traps weekly, but post-eradication programs service traps at two- or three-week intervals. Consequently, captured weevils may be dead, dismembered, and exposed to environmental conditions for prolonged periods which may adversely affect the quantity and quality of weevil DNA. We documented the degradation of DNA quantity and integrity in boll weevils and weevil body parts aged in traps over a three-week period under field conditions. The quantity of DNA extracted from whole weevils, heads, abdomens, and legs generally remained sufficient (> 1 ng/'L) through the 21-day period. The integrity (fragment length) declined through time but generally was sufficient (> 700 bp) for use in the assay. PCR amplification of three markers validated that the quality and integrity of DNA extracted from dead weevils and individual weevil body parts aged in traps up to 21 days remained at sufficient levels for the PCR-based assay. However, our data also suggests that rain events may accelerate degradation of weevil DNA.