Characteristics of two hybrid male sterile lines. (A–C) Confirmation of introgression boundaries by NGS for ZZY10307 (A) and ZZY10330 (C), each carrying an introgression derived from C. briggsae X Chromosome in an otherwise C. nigoni background. Read coverage (y-axis) is shown across C. briggsae X Chromosome coordinates (x-axis). Genotyping results by single-worm PCR are shown in the middle (B), with PCR positive and negative corresponding to the presence and absence of C. briggsae–specific amplification, respectively. (D) Schematic diagram showing steps of generating two hybrid sterile lines. (E–J) Sperm morphology and activation in C. nigoni (JU1421) or hybrid males. (E–G) DIC micrographs showing sperm morphologies for JU1421, ZZY10307, and ZZY10330, respectively. (H–J) DIC micrographs showing sperm activations for JU1421, ZZY10307, and ZZY10330, respectively. Residual bodies and sign of activation in hybrids are indicated with an arrowhead and arrow, respectively. (SM) Sperm media.
