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Proline is one of the organic osmolytes that accumulates in plants in response to stressful environmental conditions. The aim of this study was to determine the concentration of proline in the grain filling phase in ten winter wheat cultivars under conditions of prolonged periods of air temperatures above 30°C and to assess the variability of wheat variety responses. The correlation between proline accumulation and photosynthetic pigments, accumulated starch and yield was also determined. In the experimental field, flag leaves were sampled for each variety in the grain filling phase. Statistical data analysis and parameter correlation were performed using the SPSS program. The results showed that there is a statistically significant difference between proline values in moderate and high air temperature conditions when proline accumulation occurs. The significant correlation of accumulated starch content and yield with proline concentration showed that in addition to higher proline values under heat stress, wheat varieties Apac, Talas and Futura also have higher yield and starch content. A correlation was also found between proline concentration and photosynthetic pigment contents, where the Apac wheat variety showed the best adaptive response to the investigated traits and was characterized by a smaller reduction in photosynthetic pigment content under heat stress. The interrelation of proline with the photosynthetic pigment content and wheat quality parameters may be important in breeding technologies aimed at improving wheat stress tolerance.

Growth and development of cereals is affected by abiotic factors, particularly by high temperature. An important factor in plant adaptation to abiotic stress can be the proline accumulation. Proline is an amino acid involved in a series of metabolic processes and is important as a protein stabilizer, osmolyte and antioxidant. The aim of this experiment was to determine the effect of high temperature on the proline content and yield elements in different cereal varieties during two vegetative seasons. For the investigation, plant material of 8 genetically divergent winter wheat varieties, 1 variety of triticale and 1 oat variety were used. Samples were collected in days with moderate midday air temperatures of 24-26°C in the milk stage and after a few days in the same phenological stage, in conditions of high midday air temperatures of 34-36°C. Proline accumulation was determined spectrophotometrically. Statistical analyses of data were done in the SPSS program. The results during the first experimental year showed that under moderate air temperature conditions proline content was 0.661 μmol g-1 fresh plant, and in the second experimental year 0.777 μmol g-1 fresh plant. Under conditions of heat stress during the first year, the content of proline increased to 2.169 μmol g-1 fresh plant, and in the second experimental year the average content was 2.510 μmol g-1 fresh plant, which confirms the increase of proline accumulations under heat stress. Compared with other cereal varieties, wheat varieties Zvezdana, Pobeda, Simonida and Avenu were characterized by higher contents of proline in conditions of heat stress in both vegetative seasons. Statistical analysis and correlation of the results of proline accumulation and yield elements showed that more resistant varieties to heat stress conditions have higher yields.

Barley and oat have been promoted for years as good sources of dietary fiber, especially β -glucan. Studies have shown a positive effect of bar­ley and oat β -glucan on human health and as a result, there has been an inc­reasing demand for β -glucans in the past decade. Thus, the variability of the β -glucan content was investigated in the grain of 10 barley and 10 oat varieties. The β -glucan contents were determined by the ICC Standard Method No 168. The content of β -glucan in the analyzed barley varieties were within the range 3.52–7.81 % and in analyzed oat varieties, the content of β -glucan were within the range of 3.15–7.28 %. Among analyzed barley varieties, Novosadski 314 contained the highest content of β -glucan (7.81 %), while Tomba had the high­est content of β -glucan (7.28%) in the analyzed oat varieties. Based on the results, it could be concluded that there is genetic diversity of oat and barley varieties with respect to their β -glucan content. This fact enables varieties with a high a nutritional capacity to be selected.