design: ONT regular DNA and ONT ultra-long DNA were extracted using the Grandomics Genomic DNA Kit and BAC-long DNA Kit respectively following the manufacturers guidelines. Quality and quantity of total DNA were evaluated using a NanoDrop One UVVis spectrophotometer (ThermoFisher Scientific, Waltham, MA) and Qubit 3.0 Fluorometer (Invitrogen life Technologies, Carlsbad, CA), respectively. The Blue Pippin system (Sage Science, Beverly, MA) was used to retrieve large DNA fragments by gel cutting.For the ultra-long Nanopore library, approximately 810 g of genomic DNA was selected (>50kb) with the SageHLS HMW library system (Sage Science), and then processed using the Ligation sequencing 1D Kit (Catalog No.SQK-LSK109, Oxford Nanopore Technologies, Oxford, UK) according to the manufacturers instructions. DNA libraries (approximately 400 ng) were constructed and sequenced on the PromethION (Oxford Nanopore Technologies) at the Genome Center of Grandomics (Wuhan, China).