DFG HEISENBERG-Research Group Plant Architecture
Head: PD Dr. sc. nat. Thorsten Schnurbusch
Developmental and Molecular Genetics of Cereal Spikes
The research program primarily centers on spike and spikelet development in wheat and barley.
Inflorescence Architecture of Cereal Spikes
Our understanding of the molecular genetics of spike or spikelet development is very limited in small grain cereals. Functional knowledge of genes, which regulate key developmental traits such as inflorescence branching, spikelet initiation or abortion, rachis internode length, or total number of rachis internodes is almost completely lacking in most of our cereal crops. We are utilizing natural spike variants from wheat and induced spike mutants from barley to clarify the genetic make-up of genes underlying developmental phenotypes for reduced and increased grain number per spike.
Spikelet and Floret Development
Among the Triticeae, barley (Hordeum vulgare L.) shows a distinct spikelet formation with three single-flowered spikelets per rachis node. Based upon the size and fertility of the two lateral spikelets barley can be classified into five row-types (Mansfeld 1950): (1) convar. deficiens, (2) convar. distichon, (3) convar. intermedium, (4) convar. labile, and (5) convar. hexastichon. Three mutant barley loci—vrs2, vrs3, and vrs4—individually determine the conversion from two- (distichon) to six-rowed (hexastichon) barleys but, however, were exclusively found after mutagenesis. The molecular isolation of genes being involved in lateral spikelet fertility may provide an important contribution to further insights into the developmental genetic processes underlying floret formation in barley and other grasses.
Genetic and Molecular Determinants of Spikelet/Floret Survival in Cereal Crops
One promising avenue for improving grain yield of cereal crops, including wheat and barley, involves reducing spikelet/floret mortality. Spikelets, the grain-bearing units of cereal spikes, usually form in excess and subsequently abort during development; increased spikelet/floret survival is linked to increased numbers of grains per spike. Therefore, reducing spikelet/floret mortality is an intriguing appraoch to improve grain yield.
In barley, the number of spikelets per spike at around awn primordium stage represents the maximum yield potential per spike. Afterwards, significant spikelet mortality results in fewer grains sper spike. Our previous results indicated that spikelet/floret survival in barley is highly genetically controlled (Alqudah and Schnurbusch 2014, Functional Plant Biology). However, the underlying genetic and molecular determinants of spikelet survival remain to be discovered. Thus, obtained results during the LUSH SPIKE (ERC CoG) project will advance our understanding of how to improve yields of cereal crops.
Pre-Flowering Development in Cereals
We are interested in the molecular-genetic elucidation of early spike development in small grain cereals. To this end, we are investigating the pre-flowering development of barley and wheat which usually can be divided into three major phases: the leaf initiation (LI) phase, the spikelet initiation (SI) phase, and the spike growth (SG) phase. The duration of each phase can vary depending on environmental conditions (temperature and photoperiod) and contributes independently towards final time to flowering and subsequently yield.
Barley plant life cycle
SREENIVASULU, N. and TH. SCHNURBUSCH (2012) A genetic playground for enhancing grain number in cereals. Trends Plant Science 17: 91-101