Response of spring barley varieties to high temperatures after anthesis

Intact plants grown in vegetation pots at a sufficiently high water supply and transferred on the eleventh day since heading from a growth room to a KLT 20.000 climatized chamber were exposed for ten days to high temperatures 35/30 degrees C (day/night) at a low relative humidity of air (35 per cent). Check plants were grown in a growth room without any temperature control. The heat stress had the greatest influence on kernel weight; the average value of the test set made (60,69 per cent) of the check, the range of these values for different varieties being 75.49 to 31.81 per cent. The relative kernel weights was decreasing in the test varieties as follows: L 25/21 (75.49 per cent), Alexis, Zenit, KM-S-2, KM-1742, KM-743, Candice, L 2401/77, BR-3011, HE-3631, ST-146, KM-927, Corina, HE-4098, Helios, Mette, Grand Prix, AYR, Nafy and KM-939(31.81 per cent). Grain production per spike decreased to 62.29 per cent of the check, this value ranging from 83.60 to 24.32 per cent in different varieties. The grain number per spike reached 100.45 per cent of the check, with the range of the varieties from 116.23 to 73.41 per cent. The morphological characteristics of stem, spikes and leaves in different varieties influenced the traits of spike productivity in plants exposed to high temperatures. The spike length was in a positive correlation with the kernel weight, the length of the first subcrown internode correlated positively with grain number per spike and the blade area of the upper leaf with grain number per spike and with grain production per spike. The characteristics of variety responses to heat stress after anthesis, like the relative kernel weight and relative grain production per spike, can be used for the selection of suitable genetic resources in plant breeding, and for determining the adequate conditions of growing the different varieties.