design: DNA digestion with PstI and SphI enzymes, ligation with site-specific adapters and amplification of adaptor-ligated fragments. The PstI-compatible adaptor incorporated Illumina flow-cell attachment sequence, sequencing primer sequence and a varying length barcode region for multiplexing. The reverse SphI-specific adaptor incorporated a second Illumina flow-cell attachment sequence to facilitate bridge amplification. Only fragments containing both PstI and SphI cut sites were amplified with 30 rounds of PCR. Sequencing for 100 cycles.