Credit: BrachyTAG programme (John Innes Centre, Norwich, UK)

Grasses are, in human terms, perhaps the most economically important of all plant families. And of the twelve grass subfamilies, the Ehrhartoideae, Panicoideae and Pooideae include many of the species with the greatest potential to address humankind's need for food, feed and fuel. Genome sequences are currently available for crop members of the Ehrhartoideae (rice) and Panicoideae (sorghum and maize). Now, writing in Nature, an international consortium reports the genomic sequence of the wild grass Brachypodium distachyon—a first for a member of the Pooideae1.

Many crops have unintentionally been bred to a high level of ploidy after centuries of domestication. This makes genome sequencing and genetic analysis particularly challenging for species such as bread wheat (17,000 Mb). Although it is of no intrinsic commercial importance, B. distachyon has emerged as a valuable model for understanding other grasses, in large part because of its far more streamlined genome (272 Mb). When compared with wheat (right), the much smaller stature of mature B. distachyon (center) compares favorably with that of the better-known model plant, Arabidopsis thaliana (left). This makes it easier to cultivate large numbers of lines in a relatively small space. And like A. thaliana, its rapid life cycle and amenability to genetic manipulation further enhance its experimental tractability relative to most crops.

The new genome sequence enables cross-species comparison of the genomes of the three major subfamilies of grasses, generating results that should prove useful for analyzing members of the Pooideae with larger genomes, such as wheat, oats, barley, rye and several forage grasses. And coupled with a wealth of mutant strains, detailed genetic maps, and resources for marker-assisted breeding, the B. distachyon genome sequence promises to provide valuable insights into how grasses from other subfamilies, such as the bioenergy species switchgrass and Miscanthus, might be improved to enhance their potential for sustainable fuel production.

Genes in B. distachyon bear a closer resemblance to their counterparts in rice and sorghum than to the relevant genes in their more distant relative A. thaliana, suggesting that B. distachyon has a valuable part to play in accelerating progress in grass functional genomics.