Abstract
BackgroundA genetic sexing strain (GSS) is an essential component for pest control using the sterile insect technique (SIT). A GSS is developed using a combination of Y-autosome translocation and a selectable marker such as pupal color, resulting in heterozygous males and homozygous females that possess wild-type brown pupae (wp+) and mutant white pupae (wp) alleles, respectively. The genetic sexing Salaya1 strain developed for Bactrocera dorsalis was evaluated using a clean stream and scaled-up for subsequent production lines (e.g., initiation, injection, and release). Colony management under small- and large-scale conditions for long-term rearing may affect the sexing system, genetic background, and fitness performance of the strain. Routine monitoring was applied to study genetic stability, genetic variation, and male mating competitiveness.ResultsThe percentage of recombinants was significantly different between males (wp) and females (wp+), ranging between 0.21–0.43% and 0.01–0.04%, respectively. Using 106 bands from six ISSR markers, the genetic backgrounds of two generations (F40 and F108) of the clean stream were found to be almost identical (0.960), and between those two generations and the wild population, the similarities were 0.840 and 0.800, respectively. In addition, the sterile males performed well in competitive mating with fertile females (Relative Sterility Index = 0.67 ± 0.13). The rates of fliers calculated from both clean and release streams were higher than 0.95. Regarding the fitness of the Salaya1 strain, the fertility and pupal recovery were similar in all production lines. The sex ratio (Male/Female) distortion was also recorded.ConclusionsThe Salaya1 strain reared at the mass-rearing facility retained its genetic stability, genetic variation, behavior (e.g., competitive mating and flight ability), and traits related to fitness for at least 10 consecutive generations. The filter rearing system is effective at minimising the selection pressure while maintaining the genetic background and fitness performances of the clean stream. These characteristics were stable throughout the production lines. In addition, the production efficiency is comparable among the different production lines and other similar types of GSSs.
Highlights
A genetic sexing strain (GSS) is an essential component for pest control using the sterile insect technique (SIT)
Recombination occurring in the different streams was characterised as the accumulation of females emerging from brown pupae (WT females) and males emerging from white pupae under semi-mass rearing conditions over 10 consecutive generations (Table 1 and Additional file 1: Table S1)
Genetic variation Genetic variation was evaluated in two generations (F40 and F108) of the clean stream and the wild population, using six inter simple sequence repeat (ISSR) markers
Summary
A genetic sexing strain (GSS) is an essential component for pest control using the sterile insect technique (SIT). The genetic sexing Salaya strain developed for Bactrocera dorsalis was evaluated using a clean stream and scaled-up for subsequent production lines (e.g., initiation, injection, and release). Colony management under small- and large-scale conditions for long-term rearing may affect the sexing system, genetic background, and fitness performance of the strain. Using 106 bands from six ISSR markers, the genetic backgrounds of two generations (F40 and F108) of the clean stream were found to be almost identical (0.960), and between those two generations and the wild population, the similarities were 0.840 and 0.800, respectively. The sterile insects are systematically released to compete against the wild male population. The elimination of females lowers the cost of mass rearing and field release
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