The objective of this study was to investigate the genetic diversity of barley accessions. Additionally, association trait analysis was conducted for grain yield under salinity, heading date and plant height. For this purpose, 48 barley genotypes were analyzed with 22 microsatellite simple sequence repeat (SSR) markers. Four of the 22 markers (Bmac316, scssr03907, HVM67 and Bmag770) were able to differentiate all barley genotypes. Cluster and principal coordinate analysis allowed a clear grouping between countries from the same region. The genotypes used in this study have been evaluated for agronomic performance in different environments. Conducting association analysis for grain yield under salinity conditions using TASSEL software revealed a close association of the marker Bmag749 (2H, bin 13) in two different environments with common significant alleles (175, 177), whereas the HVHOTR1 marker (2H, bin 3) was only significant in Sakhar_Egypt with alleles size being 158 and 161. Heading date also showed an association with scssr03907 through the common significant specific allele 111 and EBmac0415 markers in three different agro climatic locations, whereas HVCMA, scssr00103 and HVM67 were linked to heading date in the Egyptian environment only. The plant height association analysis revealed significant markers Bmag770 via the significant allele 152 and scssr09398.

Highlight 19 We show that Ppd-H1 integrates photoperiod and drought stress signals via 20 FLOWERING LOCUS T 1 (FT1) and the downstream MADS-box genes BM3 and BM8 21 to modulate reproductive development, and shoot and spike morphology in barley. 22Abstract 23 Drought impairs growth and spike development and is therefore a major cause of yield 24 losses in the temperate cereals barley and wheat. Here, we show that the photoperiod 25 response gene PHOTOPERIOD-H1 (Ppd-H1) interacts with drought stress signals to 26 modulate spike development. We tested the effects of a continuous mild and a transient 27 severe drought stress on developmental timing and spike development in spring barley 28 cultivars with a natural mutation in ppd-H1 and derived introgression lines carrying the 29 wild-type Ppd-H1 allele from wild barley. Mild drought reduced the spikelet number and 30 delayed floral development in spring cultivars but not the introgression lines with a wild-31 type Ppd-H1 allele. Similarly, drought-triggered reductions in plant height, tiller and 32 spike number were more pronounced in the parental lines compared to the 33 introgression lines. Transient severe stress halted growth and floral development, upon 34 rewatering introgression lines, but not the spring cultivars, accelerated development so 35 that control and stressed plants flowered almost simultaneously. These genetic 36 differences in development were correlated with a differential downregulation of the 37 flowering promotors FLOWERING LOCUS T1 and the BARLEY MADS-box genes 38 BM3 and BM8. Our findings, therefore, demonstrate that Ppd-H1 affects 39 developmental plasticity in response to drought in barley. 40 41

21 FLOWERING LOCUS T-like genes (FT-like) control the photoperiodic regulation of flowering 22 in many angiosperm plants. The family of FT-like genes is characterised by extensive gene 23 duplication and subsequent diversification of FT functions which occurred independently in 24 modern angiosperm lineages. In barley, there are 12 known FT-like genes (HvFT) but the 25 function of most of them remains uncharacterised. This study aimed to characterise the role of 26 HvFT4 in flowering time control and development in barley. The overexpression of HvFT4 in 27 the spring cultivar Golden Promise delayed flowering time under long-day conditions. 28 Microscopic dissection of the shoot apical meristem (SAM) revealed that overexpression of 29 HvFT4 specifically delayed spikelet initiation and reduced the number of spikelet primordia 30 and grains per spike. Furthermore, ectopic overexpression of HvFT4 was associated with floret 31 abortion and with the downregulation of the barley MADS-box genes VRN-H1, HvBM3 and 32 HvBM8 which promote floral development. This suggests that HvFT4 functions as a repressor 33 of reproductive development in barley. Unraveling the genetic basis of FT-like genes can 34 contribute to the identification of novel breeding targets to modify reproductive development 35 and thereby spike morphology and grain yield. 36