Gamma (γ)-irradiation of plants at low doses can provoke a broad range of growth-stimulating effects. In order to reveal universal target genes that are involved in molecular pathways of radiation hormesis establishment, we studied nine barley cultivars for their tolerance to γ-irradiation of seeds. Four morphological traits were assessed in barley seedlings after γ-irradiation of seeds at 20 Gy. Nine cultivars were sorted according to the sensitivity to irradiation as γ-stimulated, “no morphological effect”, or γ-inhibited. Gene expression of 17 candidate genes was evaluated for the 7 most contrasting cultivars. Changes in expression of barley homologues of PM19L and CML31 were suggested as possible determinants of radiation hormesis effect. The possible role of jasmonate signaling in roots in radiation growth stimulations was revealed. Morphological analysis and gene expression study showed that the genetic background of a cultivar plays an important role in eustress responses to low-dose γ-irradiation of seeds.

The stimulation of growth and development of crops using ionising radiation (radiation hormesis) has been reported by many research groups. However, specific genes contributing to the radiation stimulation of plant growth are largely unknown. In this work, we studied the impact of the low-dose γ-irradiation of barley seeds on the growth dynamics and gene expression of eight barley cultivars in a greenhouse experiment. Our findings confirmed that candidate genes of the radiation growth stimulation, previously established in barley seedlings (PM19L-like, CML31-like, and AOS2-like), are significant in radiation hormesis throughout ontogeny. In γ-stimulated cultivars, the expression of these genes was aligned with the growth dynamics, yield parameters, and physiological conditions of plants. We identified contrasting cultivars for future gene editing and found that the γ-stimulated cultivar possessed some specific abiotic stress-responsive elements in the promotors of candidate genes, possibly revealing a new level of radiation hormesis effect execution. These results can be used in creating new productive barley cultivars, ecological toxicology of radionuclides, and eustress biology studies.

Background. Small doses of radiation stimulate the growth and development of plants including seed germination. ABA plays a key role not only in seed dormancy and germination but also in the regulation of adaptive reactions of plants. The aim of our work was to study the effect of -irradiation of barley seeds in a small doses on the expression of genes encoding ABA biosynthesis enzyme 9-cis-epoxycarotenoid dioxygenase (HvNCED1) and catabolism enzyme ABA 8-hydroxylase (HvABA8OH-1). Materials and Methods. The barley seeds were irradiated at dose range of 450 Gy at a dose rate of 60 Gy/h, the radiation source was 60Co. The study was carried out in the embryos within the first 30 hours after germination. Relative gene expression was investigated using real-time PCR (RT-PCR). Results. It was shown that -irradiation of barley seeds changes the expression of ABA biosynthesis and catabolism genes in all experimental groups. Conclusion. This alterations can lead to a decrease the ABA content under irradiation with stimulating doses and increase the biosynthesis of phytohormone under irradiation with inhibitory dose.

The purpose of the current work was to identify photosynthetic parameters that are predictors of barley drought tolerance, determined at early stages of development, and to verify the results obtained in field conditions. The study was carried out with the barley varieties ‘Leon’, ‘Ratnik’ and ‘Foks 1’, used in mutation breeding to develop drought-resistant genotypes. Drought was modeled by stopping irrigation. Plant resistance was estimated by changes in chlorophyll fluorescence (Fv /Fm, Y(II), NPQ) and morphometric parameters (leaf length, wet and dry weight) compared to the control group with normal water supply. Under stress-free conditions, the variety ‘Leon’ demonstrated a statistically significantly lower efficiency of photosynthesis in terms of Y(II) and Fv /Fm (0.535 ± 0.005 and 0.776 ± 0.004, respectively) in comparison with other varieties (0.577 ± 0.005 and 0.788 ± 0.001 for the variety ‘Foks 1’; 0.574 ± 0.004 and 0.787 ± 0.001 for the variety ‘Ratnik’). When modeling drought, there has been established a decrease in all morphometric indicators for all varieties relative to the control, with the highest degree of inhibition for the variety ‘Ratnik’ (70.16 ± 3.88 %; 8.09 ± 0.73 %; 68.50 ± 4.42 % for leaf length, wet and dry weight, respectively) and with the lowest degree for the variety ‘Leon’ (88.06 ± 7.83 %; 26.51 ± 7.11 %; 79.32 ± 11.17 %, respectively). A decrease in the photosynthesis intensity was manifested in the suppression of Fv /Fm and Y(II) and an increase in NPQ, with the earliest changes in the parameters Y(II) and NPQ in the varieties ‘Foks 1’ and ‘Ratnik’ (on the 4^th and 5^th day, respectively), compared to the variety ‘Leon’ (on the 7^th day). In the field conditions, there has been estimated productivity of the varieties and its dependence on precipitation. A positive correlation between the difference in yield of two varieties ‘Leon’ and ‘Ratnik’, contrasting in their response to drought, and the amount of precipitation during the active vegetation period in 2014–2017 and 2022 (Pearson’s R2 = 0.77, p < 0.05) has been identified. The most sensitive parameters of photosynthesis, which can be used to predict resistance to moisture deficiency, were Y(II) and NPQ.

The growing need to improve agricultural production in changing climatic conditions necessitates the acceleration of development of new stress-resistant varieties. The lines obtained as a result of breeding require rapid and highquality estimation for resistance to various impacts. Due to the high degree of correlation between the activity of a photosynthetic apparatus and a plant, the efficiency of photosynthesis is one of the most indicative parameters of the state of a plant. There has been shown above that chlorophyll fluorescence parameters can be effectively used to screen new barley lines for drought resistance. The purpose of the current work was to test new barley lines for resistance to drought and salt stress under controlled conditions based on the parameters of photosynthesis at the early stages of plant development. The study was conducted on the promising lines ‘11027’ (Zernogradsky 1895), ‘11023’ (Zernogradsky 1898) and a new variety ‘Feniks’ developed by the FSBSI “Agricultural Research Center “Donskoy”. Drought conditions were created by stopping watering the plants from the 14th day until the end of the trial. To simulate salt stress, the 14-day old plants were watered with a 600 mM salt solution every other day. The parameters of photosynthesis and transpiration intensity were recorded daily, starting from the 12-day old seedlings. Morphometric parameters were measured once when the plants were 30 days old. There has been shown that under stress-free conditions, the morphometric parameters and photosynthetic activity of the line ‘11027’ and the variety ‘Feniks’ are higher than similar indicators of the line ‘11023’. The variety ‘Feniks’ turned out to be the most drought-resistant. The line ‘11023’ has demonstrated the greatest salt stress resistance. The line ‘11027’ has demonstrated the lowest resistance to both abiotic effects, showing the earliest changes in photosynthetic indices. There has been noted that chlorophyll fluorescence indices allow obtaining statistically significant differences between the studied lines using a smaller number of individual plants than is required to accumulate morphometric data, which is an important advantage of the method in breeding.