Genetics of Tillering in Barley.

The activity of the shoot apical and axillary meristems largely determines above ground plant architecture.  In barley (Hordeum vulgare L.), tillers develop in the leaf axil from axillary meristems.  The number of vigorous tillers with spikes determines the overall grain yield.  The objectives of this work are to understand the genetics of tillering in barley.  We have collected and characterized four mutants that exhibit fewer tillers than wildtype including: uniculm2 (cul2), uniculm4 (cul4), low number of tillers (lnt) and absent lower laterals (als).  We used histological approaches to examine the morphology of axillary meristems in the mutants.  RNA profiling was used to identify candidate genes for the mutants and physiological processes that are unique to the mutants.  Double mutants of cul2, cul4, als and lnt with a set of high tillering mutants show a low tillering phenotype, indicating that the low tillering mutants are epistatic to the high tillering mutants.  Finally, we identified and characterized a suppressor of uniculm2 (suc2) mutant that in combination with cul2 exhibits tillering.  Based on these results, models for tillering in barley will be presented.