MADS-box transcription factors are crucial regulators of inflorescence and flower development
in plants. Therefore, the recent interest in this family has received much attention in plant
breeding programs due to their impact on plant development and inflorescence architecture. The
aim of this study was to investigate the role of HvMADS-box genes in lateral spikelet development
in barley (Hordeum vulgare L.). A set of 30 spike-contrasting barley lines were phenotypically and
genotypically investigated under controlled conditions. We detected clear variations in the spike and
spikelet development during the developmental stages among the tested lines. The lateral florets in
the deficiens and semi-deficiens lines were more reduced than in two-rowed cultivars except cv. Kristina.
Interestingly, cv. Kristina, int-h.43 and int-i.39 exhibited the same behavior as def.5, def.6, semi-def.1,
semi-def.8 regarding development and showed reduced lateral florets size. In HOR1555, HOR7191
and HOR7041, the lateral florets continued their development, eventually setting seeds. In contrast,
lateral florets in two-rowed barley stopped differentiating after the awn primordia stage giving
rise to lateral floret sterility. At harvest, the lines tested showed large variation for all central and
lateral spikelet-related traits. Phylogenetic analysis showed that more than half of the 108 MADS-box
genes identified are highly conserved and are expressed in different barley tissues. Re-sequence
analysis of a subset of these genes showed clear polymorphism in either SNPs or in/del. Variation in
HvMADS56 correlated with altered lateral spikelet morphology. This suggests that HvMADS56 plays
an important role in lateral spikelet development in barley