Awn primordium to tipping is the most decisive developmental phase for spikelet survival in barley

In small-grain cereals, grain yield is closely associated with grain number. Improved spikelet survival is an important trait for increasing grain yield. We investigated spikelet number, spikelet survival and yield-related traits under greenhouse conditions, and pot- and soil-grown field conditions. Thirty-two spring barley (Hordeum vulgare L.) accessions (14 two- and 18 six-rowed accessions) were manually dissected to determine spikelet/floret number on the main culm spike (SNS) at awn primordium (AP), tipping (TIP), heading and anther extrusion. We observed a significant difference between two- and six-rowed barley for SNS and spikelet survival at all stages and growing conditions. Both traits were highly genetically controlled, with repeatability and broad-sense heritability values of 0.74-0.93. The rate of spikelet survival from AP to harvest was higher in two- (~70%) than in six-rowed (~58%) barley. Spikelet abortion, starting immediately after AP, was negatively affected by increased SNS and the thermal time required to reach the AP stage. The largest proportion of spikelet reduction happened during the AP-TIP phase, which was the most critical period for spikelet survival. The duration between AP and the end of stem elongation correlated better with spikelet survival and yield-related characters than the estimated duration of stem elongation using leaf height measurements. Our observations indicate that the main spike plays an important role in single-plant grain yield. Extending the length of the critical AP-TIP phase is promising for improving yield through increased spikelet development and survival. The results also demonstrate that greenhouse conditions are appropriate for studying traits such as phase duration and spikelet survival in barley.