Development of a genetic sexing strain in Bactrocera carambolae (Diptera: Tephritidae) by introgression of sex sorting components from B. dorsalis, Salaya1 strain

Abstract

BackgroundThe carambola fruit fly, Bactrocera carambolae Drew & Hancock is a high profile key pest that is widely distributed in the southwestern ASEAN region. In addition, it has trans-continentally invaded Suriname, where it has been expanding east and southward since 1975. This fruit fly belongs to Bactrocera dorsalis species complex. The development and application of a genetic sexing strain (Salaya1) of B. dorsalis sensu stricto (s.s.) (Hendel) for the sterile insect technique (SIT) has improved the fruit fly control. However, matings between B. dorsalis s.s. and B. carambolae are incompatible, which hinder the application of the Salaya1 strain to control the carambola fruit fly. To solve this problem, we introduced genetic sexing components from the Salaya1 strain into the B. carambolae genome by interspecific hybridization.ResultsMorphological characteristics, mating competitiveness, male pheromone profiles, and genetic relationships revealed consistencies that helped to distinguish Salaya1 and B. carambolae strains. A Y-autosome translocation linking the dominant wild-type allele of white pupae gene and a free autosome carrying a recessive white pupae homologue from the Salaya1 strain were introgressed into the gene pool of B. carambolae. A panel of Y-pseudo-linked microsatellite loci of the Salaya1 strain served as markers for the introgression experiments. This resulted in a newly derived genetic sexing strain called Salaya5, with morphological characteristics corresponding to B. carambolae. The rectal gland pheromone profile of Salaya5 males also contained a distinctive component of B. carambolae. Microsatellite DNA analyses confirmed the close genetic relationships between the Salaya5 strain and wild B. carambolae populations. Further experiments showed that the sterile males of Salaya5 can compete with wild males for mating with wild females in field cage conditions.ConclusionsIntrogression of sex sorting components from the Salaya1 strain to a closely related B. carambolae strain generated a new genetic sexing strain, Salaya5. Morphology-based taxonomic characteristics, distinctive pheromone components, microsatellite DNA markers, genetic relationships, and mating competitiveness provided parental baseline data and validation tools for the new strain. The Salaya5 strain shows a close similarity with those features in the wild B. carambolae strain. In addition, mating competitiveness tests suggested that Salaya5 has a potential to be used in B. carambolae SIT programs based on male-only releases.

Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data

“…To record the genetic relationship between the genetic sexing Salaya5 strain (Isasawin et al 2014) and wild populations, a sample of the Salaya5 colony (SY5) was included. The Salaya5 strain was created by hybridization and introgression of the genetic sexing Bactrocera dorsalis strain, named Salaya1 (Isasawin et al 2012), and Bactrocera carambolae from Jakarta, Indonesia.…”

“…The Salaya5 strain was created by hybridization and introgression of the genetic sexing Bactrocera dorsalis strain, named Salaya1 (Isasawin et al 2012), and Bactrocera carambolae from Jakarta, Indonesia. This strain has a genetic background close to Bactrocera carambolae (99.9%) and a part of the Y-pseudo linked autosome carrying a dominant allele of white pupae alleles of Salaya1 strain (Isasawin et al 2014). The strain was confirmed to be Bactrocera carambolae described by Isasawin et al (2014).…”

“…Furthermore, differences of mating times (McInnis et al 1999, Schutze et al 2013) and behavior (Schutze et al 2013) account for reducing mating success. Nevertheless, inadequate reproductive isolation through hybridization was sometimes observed; viable F 1 and further generations were produced under semi-natural conditions (Isasawin et al 2014). Intermixing of pheromone components was consistently observed in semi-natural (Isasawin et al 2014) and natural conditions (Wee and Tan 2005b).…”

“…Nevertheless, inadequate reproductive isolation through hybridization was sometimes observed; viable F 1 and further generations were produced under semi-natural conditions (Isasawin et al 2014). Intermixing of pheromone components was consistently observed in semi-natural (Isasawin et al 2014) and natural conditions (Wee and Tan 2005b). Slightly different genomes between the two species were observed in samples from inbreeding experiments using cytogenetic analysis (Augustinos et al 2014).…”

“…For GSSs, male individuals can be sex-sorted before irradiation and release steps. An available GSS for Bactrocera carambolae has been successfully developed and evaluated, named Salaya5 (Isasawin et al 2014). This strain was proven to competitively mate with two wild populations from Jakarta and North Sumatra, Indonesia, in field cage conditions.…”