Analysis of bread wheat genome will aid higher yields

An international team of scientists has completed the first comprehensive analysis of the bread wheat genome. Due to the complexity of the plant’s genome, the analysis was technically challenging, but the payoff is potentially huge as it will help develop new strategies for breeding and improving wheat crops.

Bread wheat (Triticum aestivum) is one of the ‘big three’ globally important crops, accounting for 20% of the calories people consume. 35% of the world’s population depend on this staple crop for survival.

The bread wheat genome has around 17,000,000,000 paired DNA bases, or nucleotides - around five times the amount of DNA in the human genome. It has a total of 42 chromosomes; human DNA has 46 chromosomes.

To sequence the large, complex genome, the research team used ‘next-generation’ sequencing techniques in which the DNA is broken up randomly into numerous small segments and assembled into longer sequence reads by identifying the overlapping ends. The sequence ‘reads’ generated for bread wheat were then compared to those from the known sequences of a diverse range of grasses, including rice and barley.

“We wanted to know whether we could use next-gen sequencing on large complex genomes in what was almost a worst-case scenario for challenging the technology, and we wanted to do it using an agriculturally important crop,” said Professor W Richard McCombie, part of Cold Spring Harbor Laboratory (CSHL), who was part of the collaborative international effort.

The research shows that the bread wheat genome has undergone rapid and significant changes, including loss of gene family members during the time it was being domesticated. At this time, bread wheat moved from having two sets of chromosomes to having six copies of each of its seven chromosomes. This chromosomal multiplication is desirable, as selecting for them is a way to overcome the sterility that occurs when breeding hybrid crops.

“While we and our collaborators continue to work to enhance the resolution of our knowledge of the wheat genome, these results should have a significant impact on breeding efforts and further research studies of the wheat genomes and those of its wild relatives,” said McCombie.

The research, ‘Analysis of the bread wheat genome using whole genome shotgun sequencing’, was published online in the journal Nature. To read the full report, click here.