IMPROVING FLY QUALITY IN THE FIELD FOR MEDFLY SIT PROGRAMS: MATING VIGOR AND SURVIVAL ABILITY

Authors: McInnis, Donald; SHELLY, TODD - APHIS; Komatsu, Jason

Submitted to: Genetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2001
Publication Date: 2/28/2002
Citation: Mcinnis, D.O., Shelly, T.E., Komatsu, J. 2002. Improving fly quality in the field for medfly sit programs: mating vigor and survival ability. Genetica. 116:117-124.

Interpretive Summary: The success of the sterile insect technique (SIT) depends critically upon mating between released males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts- mating enhancement and survival improvement. In the former, two methods have been investigated- selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control lab flies. Regarding mating selection, standard lab-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, and then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, ginger root oil was exposed to laboratory-reared males for several hours one day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, i.e. from ca. 0.5 to ca. 1.5 times wild male success, respectively. Irradiation reduced this increase only slightly to ca. 2.5 times wild male mating fitness. Adding the ginger oil exposure to the selected, hybrid strain raised the fitness of the lab males to ca. 9 times wild male fitness, in a synergistic manner. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. two times better than lab control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.

Technical Abstract: The sterile insect technique, or SIT, requires that mass-reared flies be successful in surviving and dispersing adequately in the field. Due to the effects of many artificial treatments on the mass-reared flies, including man-made diets, irradiation to sterilize the flies and considerable handling during the entire process, the final quality of the flies can be severely compromised. As a result, we have been attempting to improve fly quality in 2 critical areas- mating ability and survival ability in the field. To date, we have made progress in both areas. With regard to mating ability, we looked at 2 main approaches- use of genetic selection and use of aromatherapy. We obtained beneficial results in both. By selecting male flies that successfully mated with wild females, repeatedly over 5 cycles of selection, we obtained flies that mated up to 3 times better than unselected controls. With the aid of ginger root oil as aromatherapy, we obtained a surprising ca. 5-fold increase in mating ability vs. controls. With both the genetic and aromatherapy treatments combined, we obtained a ca. 9-fold increase in mating ability. With respect to field survival, we obtained a ca. 2-fold increase in survival of males in field cages compared to controls, but only if both food and water were provided inside the field cage. So far, in the case where no food or water was provided, there was no response to the selection process.