Physiological, Biochemical and Molecular Response of Different Winter Wheat Varieties under Drought Stress at Germination and Seedling Growth Stage.

Due to climate change in recent years, there has been an increasing water deficit during the winter wheat sowing period. This study evaluated six Croatian winter wheat varieties' physiological, biochemical, and molecular responses under two drought stress levels at the germination/seedling growth stage. Lipid peroxidation was mainly induced under both drought stress treatments, while the antioxidative response was variety-specific. The most significant role in the antioxidative response had glutathione along with the ascorbate-glutathione pathway. Under drought stress, wheat seedlings responded in proline accumulation that was correlated with the P5CS gene expression. Expression of genes encoding dehydrins (DHN5, WZY2) was highly induced under the drought stress in all varieties, while genes encoding transcription factors were differentially regulated. Expression of DREB1 was upregulated under severe drought stress in most varieties, while the expression of WRKY2 was downregulated or revealed control levels. Different mechanisms were shown to contribute to the drought tolerance in different varieties, which was mainly associated with osmotic adjustment and dehydrins expression. Identifying different mechanisms in drought stress response would advance our understanding of the complex strategies contributing to wheat tolerance to drought in the early growth stage and could contribute to variety selection useful for developing new drought-tolerant varieties.

Oxidative Status and Antioxidative Response to Fusarium Attack and Different Nitrogen Levels in Winter Wheat Varieties.

Abiotic and biotic stresses, such as mineral nutrition deficiency (especially nitrogen) and Fusarium attack, pose a global threat with devastating impact on wheat yield and quality losses worldwide. This preliminary study aimed to determine the effect of Fusarium inoculation and two different nitrogen levels on oxidative status and antioxidative response in nine wheat varieties. Level of lipid peroxidation, activities of antioxidant enzymes (catalase, ascorbate peroxidase, glutathione reductase), phenolics, and chloroplast pigments content were measured. In general, wheat variety, nitrogen, and Fusarium treatment had an impact on all tested parameters. The most significant effect had a low nitrogen level itself, which mostly decreased activities of all antioxidant enzymes and reduced the chloroplast pigment content. At low nitrogen level, Fusarium treatment increased activities of some antioxidative enzymes, while in a condition of high nitrogen levels, antioxidative enzyme activities were mostly decreased due to Fusarium treatment. The obtained results provided a better understanding on wheat defense mechanisms against F. culmorum, under different nitrogen treatments and can serve as an additional tool in assessing wheat tolerance to various environmental stress conditions.