It’s a good day for cereal genomes. Nature offers both bread wheat and barley, and they’re both open access. That’s great; you can read them yourself and draw your own conclusions. Nature’s commentary on the matter, however, will set you back $18, which seems fair enough. The crucial points are:
- The wheat genome is huge — three sets of chromosomes derived from three different ancestors — and complex. So this isn’t actually a complete sequence.
- It is, however, a great scaffold on which to build a more detailed sequence, using additional techniques.
- The sequence has already revealed that members of some gene families have been lost since the ancestral hybridisation, while others, notably those involved in specific areas of plant metabolism and growth, have expanded.
- The best wheat yields can exceed 12 tonnes per hectare; the global average is more like 2 t/ha, and that is likely to be undermined by climate change. Will the genome help breeding efforts? Some people clearly hope so.
Barley was a relatively simple challenge, just one set of chromosomes, and smallish ones at that. And barley is already much more tolerant of physical stresses than many other cereals. So rather than looking to the genome for help in breeding better barley (though that is surely on the cards) researchers ask how barley’s genes help it to be so tolerant, and then use the answers to improve other cereals.
Strictly speaking, the barley example (which I know about) is a genome assembly not a full genome sequence – there are still gaps to fill. An interesting point is that sequences that look very close together in genetic maps can actually be a long way apart physically on chromosomes. This is a challenge for breeding, but also means that new methods to ‘break up’ these regions could be very useful in increasing our knowledge and for breeding…