Gene identification and functional analysis of high tillering mutants in barley

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Cereal crop yield is influenced by the number of tillers (side shoots) and the number of seeds per spike. Both traits have been modified during domestication of barley and wheat. The wild forms are characterized by high and asynchronous tillering while the cultivated forms show low synchronous tillering. Domestication related changes of the spike included the failure of the spike to disarticulate and (ii) altered spikelet fertility. Tiller number and seed number per spike are often negatively correlated which complicates the improvement of overall yield. Consequently, a fundamental understanding of the molecular mechanisms that affect both inflorescence and shoot architecture is important to improve yield. The overall objective of this project is to identify and characterize the genes that affect both tiller and seed number in barley, an emerging model system for small grain cereals. We will use the high tillering mutants granum-a (gra-a) and intermedium-m (int-m) to investigate the genetic and molecular correlations of shoot and inflorescence architecture. There are three main objectives; (1) identification of the causal genes underlying gra-a and int-m; (2) functional characterization of the gra-a and int-m mutant loci by microscopic phenotyping and whole transcriptome analysis of developing shoot apical meristems (SAM) and axillary meristems (AM, tillers); (3) analysis of natural variation of the candidate genes for gra-a and int-m in a diverse set of wild and cultivated barley genotypes. Overall, the proposed project will reveal novel genetic and molecular components controlling shoot and spike architecture and thus provides novel insights into the molecular basis underlying the trade-off between seed and tiller number.