Cereal Inflorescence Development

Rice, wheat, maize and barley dominate world agriculture and are vital for world food security. They are related grasses, but are quite distinct in the number and organisation of the flowers they make, something that we call inflorescence architecture. Likewise, the cultivated varieties domesticated by human selection over 1000s of years differ markedly from the wild ancestors from which they derive. Understanding how cereals control the number of flowers they make is important as this ultimately determines yield potential. Despite this, we know very little about the genes involved in this process. The model plant, Arabidopsis, is of limited help to us in this area because cereal flowers are borne on cereal-specific structures called spikelets.

As the major cereals differ so markedly in inflorescence architecture, they each represent different starting points in the analysis of inflorescence development. We think that analysing this process only in maize, for example, cannot fully explain development of the rice panicle, although some fundamental features will be shared. We have therefore started to analyse inflorescence development in barley. We have identified mutants defective in inflorescence development and taken a molecular genetic approach to map the chromosomal location of the disrupted genes.

We have two different set of genetic resources:

First, we have identified inflorescence mutants in a publicly available collection of barley mutants. In an amazing contribution to the barley community, Prof Jerry Franckowiak collected morphological mutants of barley and over the course of his career in North Dakota crossed them repeatedly to the same background, cv Bowman. Jerry held a sabbatical here in Dundee in 2006 and together we went through his mutant collection grown out here in Dundee and identified around 70 mutants defective in inflorescence development.

Second, we have isolated mutants here in Dundee from forward screening of a barley TILLING population at SCRI. We identified sterile mutants defective in inflorescence development that are not found in the publicly available collection. Working with heterozygous material we have generated mapping populations for these mutants.

We are currently focused on one particular mutant that we call multilemma. This mutant makes the lemma and awn repeatedly, but fails to make floral organs. Therefore this mutation disrupts a gene essential to barley inflorescence development.