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Aim. Analysis of physiological and biochemical characteristics and grain productivity traits of transgenic common wheat plants (Triticum aestivum L.) with a double-stranded RNA suppressor of the proline dehydrogenase gene (pdh) compared to non-transgenic genotypes under conditions of soil drought. Methods. Biochemical assays: spectrophotometric measurements of antioxidant enzymes (SOD, APX) activity, proline dehydrogenase activity and free L-proline content; biotechnological assays: Agrobacterium-mediated transformation in planta; physiological: morphometric traits and elements of grain productivity; mathematical statistics. Results. The presence of a double-stranded RNA suppressor of the gene pdh in transgenic plants leads not only to a decrease in enzyme activity (on average 2 times compared to the nontransgenic plants), but also to an increase in the content of free L-proline both under optimal conditions and under soil drought (2.6–4.1 times). Under soil moisture defi ciency, transgenic plants with reduced pdh gene activity in terms of yield structure signifi cantly exceeded the corresponding values of grain productivity elements for the non-transformed ones. In terms of the grain weight from the main stem, the biotechnological plants under soil moisture defi ciency exceeded the control plants 1.5–1.6 times, while the number of grains did not differ signifi cantly. The grain productivity of the whole plant in the transformed lines under conditions of soil moisture defi ciency was somewhat inferior to those in the nontransformed plants grown under optimal conditions. Soil drought caused a signifi cant increase in SOD and APX activity (by 40 and 11 %, respectively) in plants of the original variety. On the contrary, the activity of both antioxidant enzymes under drought conditions in transgenic plants decreased: SOD – down to 73–76 %, APX – down to 82–86 %, compared with the variant of 70 % of fi eld capacity. Conclusions. The analysis of physiological and biochemical characteristics, as well as economic and grain productivity elements of transgenic common wheat plants with a double-stranded RNA suppressor of the proline dehydrogenase gene showed their increased tolerance to soil drought, compared with non-transgenic genotypes, which may be associated with higher proline accumulation and an increase in the antioxidant enzymes activity. Under soil moisture defi ciency, transgenic wheat plants with reduced pdh gene activity signifi cantly exceeded the corresponding values of grain productivity elements for non-transformed plants. The analysis of the antioxidant enzymes activity in the chloroplasts of transgenic plants showed that under physiological conditions, the antioxidant system works more actively in comparison with non-transgenic genotypes, which may be a prerequisite for increasing the tolerance of these plants to the infl uence of stressors of various origin. It is likely that the positive relationship between the level of free L-proline and the resistance of transgenic wheat plants to osmotic stress is associated either with the effect of L-proline on the expression of other genes of the stress-strain response of plants, or with the positive effect of the increased content of this amino acid on resistance at the early stages of stress development. It has been suggested that an increase in the antioxidant enzymes activity in biotechnological plants can be caused by the expression of heterologous genes.

Drought is a major abiotic factor adversely affecting wheat productivity. Water deficit reduces significantly photosynthesis and hence the remobilization of stored assimilate reserves from the stem becomes important sources for grain filling. We assessed the ability of different stem internodes and leaf sheaths to deposit and remobilize reserve assimilates as well as their role in grain yield formation in 6 winter wheat varieties under drought conditions during the period of grain filling. The dry weight and content of water-soluble carbohydrates in the dry matter of stem internodes and leaf sheaths of the main shoot was determined at anthesis, the beginning of milk ripeness and full grain ripeness. The total amount of water-soluble carbohydrates in stem segments was calculated as the product of their specific content in the dry matter of the stem segment and its mass. The amount of remobilized dry matter and water-soluble carbohydrates for each segment was estimated as the difference between the appropriate values at anthesis or milk ripeness and full ripeness. The maximum accumulation of water-soluble carbohydrates in the stem was reached at early milk ripeness. The most productive varieties Kyivska 17 and Horodnytsia had the largest amount of remobilized water-soluble carbohydrates in all internodes. Depositing capacity of the second and third (counting from the top) internodes was higher compared to others and has a significant effect on the grain productivity of wheat varieties studied. Despite significant variability and strong genotype x year interaction of the relationships between depositing capacity traits of different stem segments and grain productivity, mainly tight correlations were found for dry matter and total water-soluble carbohydrates accumulation and remobilization in second and third internodes with yield and grain weight per spike. The obtained data suggests that the remobilization of deposited water-soluble carbohydrates is an important factor contributing to the filling of winter wheat grain in arid conditions and more detailed studies of relationships of depositing capacity of individual stem segments with yield can be useful for development of breeding tools for further genetic yield improvement.

Обобщены результаты исследований, проведенных в отделе физиологии и экологии фотосинтеза ИФРГ НАН Украины, в глобальном контексте изучения роли фотосинтеза в продукционном процессе растений. Проанализированы перспективы и стратегии активизации фотосинтетических процессов на разных уровнях организации-от молекулярного до ценотического-с целью повышения продуктивности сельскохозяйственных растений, в особенности озимой пшеницы. Подчеркнута важность примененного системного подхода для поиска лимитирующих факторов фотосинтеза и продукционного процесса растений.

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