Exploiting natural variation in Brachypodium to understand the control of grain size and shape

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This project aims to exploit natural variation in the Grain size of a wild grass, Brachypodium, to understand the underlying mechanisms. Grain size is an important trait in agriculture, often associated with yield. However, grain size is also crucial in wild populations where plants are often under conflicting selective pressures. For example, large grains might provide progeny with a competitive advantage during seedling establishment but dispersal of large grains can be a limiting factor. Our understanding of the control and consequences of grain size is almost non-existent - with the exception of a few growth-inhibitory genes that have been inactivated during domestication of rice few other factors are known. Although various cell cycle and growth-related genes are expressed in a highly suggestive manner during grain development the precise role of cell cycle related processes remains unclear. A small wild grass, Brachypodium distachyon, has recently emerged as a new experimental model providing an opportunity to genetically dissect how grain size is controlled. Brachypodium has a grain similar to those of wheat and barley and its short life cycle and ease of cultivation under laboratory conditions and a fully sequenced genome make it a really attractive genetic model system. Even before the entire genome was available, Brachypodium proved its worth in helping to clone the Ph1 locus from wheat and the Ppd-H1 locus from Barley. We have found a remarkable degree of natural variation exists for numerous important characteristics including plant size, grain morphology, hairiness, grain shattering, growth habit and leaf size. We are focused on grain-associated characteristics and using segregating F3 populations derived from crosses between different accessions we will analyse the segregating heritable variation for grain size.

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