2.2 Growth and phenotyping.
We conducted the net house experiments in the Agricultural Research Organization - Volcani (ARO) Center (Bet Dagan, Israel) following similar sowing and transplanting as described previously for water limitation experiments by (Merchuk-Ovnat et al., 2018) . Due to the sensitivity of wild barley to day-length conditions, we preferred to achieve mild higher temperature conditions by warming the nethouse rather than late sowing conducted for example for tomato (Bineauet al., 2021). The thermal differences between ambient and high temperatures (AT and HT) is depicted in Figure S1 , with a mean increase of 3.9 °C and 2.8 °C during day and night time and maximum delta of mean 7.5 °C between AT to HT.
The RH lines were grown during winter of 2019-2020 in a completely randomized block design. We began phenotyping by measuring Tiller height (TH) that is the length of the longest tiller from ground level to the beginning of the last fully expended leaf in the tiller. Tiller number (TN) is the number of tillers per plant and it was determined about one month after transplanting the plants. TH and TN ware measured once (_1) or twice (_2) with 14 days apart. We calculated TH rate by subtracting TH_2 with TH_1 and dividing with the number of days between these two measurements. We determined the number of days to flowering (DTF) based on the date when the first awns appear in the main tiller. During grain filling, we measured five spikes per plant for spike length (SL) and later to obtain SL coefficient of variation (SLCV). In addition, during grain filling we measured plant height (PH) from ground to the start of the tallest spike. We then cached the five and whole spikes of each plant in separate paper and nylon bags, respectively. Plants were left to dry for several weeks after irrigation was terminated. We harvested dry plants by cutting at soil level and placing them in the nylon bags. Weight of the nylon bag with the plant is the total dry matter (TDM). We collected dispersal units from bag and weighted them. We calculated average spike dry weight (ASDW) based on weighing the five spikes that we cached in the paper bag. We then summed the weight of spikes (dispersal units) in the plastic and paper bags to obtain spikes dry weight (SpDW). Vegetative dry weight (VDW) is the reduction of SpDW from TDM.
We measured circadian clock amplitude and period in high-throughput SensyPAM (SensyTIV, Aviel, Israel) custom-designed to allow Fluorescence measurements under optimal or high temperatures of 22ºC (OT) or 32ºC (HT) as previously described (Bdolach et al. , 2019).