Wheat has resisted crop geneticists’ best sequencing efforts for years; its genome is more than 15 billion DNA bases long, harbours 6 copies of each chromosome and contains many hard-to-sequence repetitive stretches. Despite these challenges, researchers have now assembled a near-complete sequence for bread wheat (Triticum aestivum).
An international consortium assembled an abbreviated genome sequence, full of gaps, in 2014. To improve on that, a team led by Steven Salzberg at Johns Hopkins University School of Medicine in Baltimore, Maryland, tackled the genome using a pair of sequencing technologies. One generates highly accurate short stretches of DNA; the second results in long DNA pieces that can span highly repetitive DNA sequences. Stitching these ‘reads’ together resulted in nearly continuous chromosome sequences that encompassed 15.3 billion of the wheat genome’s bases.