Extending the phase of stem elongation (SE) has been proposed as a tool to further improve yield potential in small-grain cereals. The genetic control of pre-heading phases may also contribute to a better understanding of phenological traits conferring adaptability. Given that an optimized total time to heading is one of the most important traits in a breeding program, a prerequisite for lengthening SE would be that this and the previous phase (leaf and spikelet initiation, LS) should be under different genetic control. We studied the genetic control of these two pre-heading sub-phases (from sowing to the onset of stem elongation, LS, and from then to heading, SE) in terms of Quantitative Trait Loci (QTL) in a barley double-haploid population derived from the cross Henni × Meltan, both two-rowed spring North European barley cultivars. DH lines (118) and their parents were studied in four field trials in North-Eastern Spain. Genetic control of a number of traits related to leaf appearance and tillering dynamics, which could be important for an early crop canopy structure, were also studied. LS and SE are, at least partially, under a different genetic control in the Henni × Meltan population, mainly due to a QTL on chromosome 2HS. The QTLs responsible for a different control of LS and SE did not seem to correspond with any major gene reported in the literature. Moreover shortening LS, so as to lengthen SE without modifying heading date, would not necessarily imply a negative drawback on traits that could be important for early vigour, such as phyllochron and the onset of tillering.

GB held a pre-doctoral FPU scholarship from the Spanish Ministry of Science and Innovation. This study was partially funded by the European Union – INCO - MED program (ICA3-CT2002-10026) Mapping Adaptation of Barley to Drought Environments (MABDE) and by the Spanish Ministry of Science and Innovation competitive grants AGL2006-07814, AGL2007-63625 and AGL2008-05541. The Centre UdL-IRTA forms part of the Centre CONSOLIDER on Agrigenomics.