In a major step towards accuracy and completeness for the wheat genome, a
team of scientists from Johns Hopkins present a new assembly that
demonstrates the importance of using long, highly-accurate reads for
resolving extremely complex, repetitive genomes.

The project aimed to overcome a longstanding challenge for wheat research as
common bread wheat has one of the most complex genomes, with 6 copies of
each chromosome, enormous numbers of near-identical sequences scattered
throughout, and an overall size of more than 15 billion bases. Multiple
attempts in the past to assemble the genome have failed.

In 2012, only one-third of the genome was assembled. In 2014, a short-read
assembly managed to capture two-thirds of the genome in a highly fragmented
assembly, while a subsequent short-read-based effort delivered more sequence
but in millions of contigs. According to the authors of the study, this
project is the first assembly that contains essentially the entire length of
the genome, with more than 15.3 billion bases, and its contiguity is more
than ten times better than the partial assemblies published in the past.

The most interesting finding of this study was the delineation of the
ancestral plant's contributions to the bread wheat genome (known as the
wheat D genome). "By aligning this assembly to the draft genome of Aegilops
tauschii, the progenitor of the wheat D genome, we were able to cleanly
separate the D genome component from the A and B genomes of hexaploid wheat,
which is reported here for the first time," the team explains

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