Photosynthetic and Agronomic Traits of Winter Barley (<i>Hordeum vulgare</i> L.) Varieties

We tested six winter barley (<i>Hordeum vulgare</i> L.) cultivars in a small plot field experiment, measuring photosynthesis and other parameters three times during the growing season. Four genotypes—Andoria, Jakubus, Paradies and Zophia—are new, promising varieties with requirements of intensive technology, high yield potential and very good disease resistance. The two popular Hungarian varieties (KG Apavár and KG Puszta) are relatively old but they have good tolerance to extreme ecological conditions and outstanding resistance and winter hardiness. The aim of our research was to test the new varieties’ performance. Several recent studies found close connections among various photosynthetic parameters in barley, and we confirmed that in our research. There were significant differences between the varieties in the assimilation rate—the highest values were measured at the BBCH 47–49 stage (end of booting), except Jakubus and Zophia, where the highest values were at BBCH 73–75 (milk ripe). The cultivars’ response to irradiation change varied, especially at higher photosynthetic photon flux density (PPFD) levels. In April and May, the plants were in drought stress according to the intercellular CO₂ level and the total conductance to carbon dioxide. The differences between the air and leaf temperature were also low, indicating water stress, but the assimilation rate was relatively high (9.07–14.09 µmol m⁻² s⁻¹).We found a close connection between normalized difference vegetation index (NDVI) values and grain protein content in each of the tested barley cultivars. The correlation was significant, at <i>p</i> = 0.01 level. The protein yield per hectare was determined rather by grain yield than protein content. The relationship between the NDVI values and grain yield was moderate, but NDVI values and protein content are in strong correlation.