Barriers of Hexaploid Genomes and Limitations in Crop Drought-Resistance R&D Bread wheat (Triticum aestivum L.) is a highly complex allohexaploid (2n = 6x = 42) composed of three subgenomes (A, B, and D), with more than ~85 % of its genome occupied by repetitive sequences (transposable elements). Because of this extreme genomic complexity, conventional short-read sequencing or mapping to the standard reference genome (Chinese Spring) was virtually unfeasible for fully identifying the structural variations (SVs) unique to drought-resistant cultivars. As climate-driven global food-security threats intensify, deciphering the hidden genomic domains that confer drought-resistance has become a top priority in agricultural genomics.

JIN50 De Novo Genome Assembly: Ultra-Precise Physical Map Constructed with Long-Read Technology The research team combined ultra-long PacBio HiFi sequencing with three-dimensional genome capture (Hi-C) to generate a chromosome-level de novo assembly of the drought-resistant wheat genotype JIN50. Released in Nature Genetics on 19 May 2026, comparative analysis of this genome atlas against other wheat germplasm revealed thousands of large-scale insertions/deletions (INDELs), inversions, and translocations that were completely absent from the standard reference, effectively isolating these SVs with high precision.

Copy Number Variation of the DREB Transcription-Factor Cluster and Drought-Defense Dynamics A central molecular breakthrough of this study is the identification of copy number variation (CNV) within the DREB (Dehydration-Responsive Element-Binding) transcription-factor family, a master regulator of drought-stress responses. Unlike drought-susceptible cultivars, the JIN50 genome harbors tandem duplications of DREB gene copies, resulting in a significant increase in copy number. This CNV architecture triggers an immediate, downstream activation of stomatal-closure regulation and osmoprotectant-protein synthesis pathways upon onset of water deficit, constituting an evolutionary adaptation that preserves metabolic function while minimizing water loss.

Why it Matters: Polyploid Genomics Marker Development and Temporal Compression of Molecular Breeding The impact of this megagenome dataset on agricultural biotech and climate-resilience strategies lies in its ability to accelerate marker-assisted selection (MAS) simulations for complex hexaploid crops. By integrating the DREB CNV and key structural-variation markers from JIN50 into AI-driven genomic-value prediction models, breeders can design drought-resistant elite varieties within a few generations, bypassing the decades-long conventional crossing cycles. This constitutes a powerful biological safeguard for food-supply chain security.