Early Antioxidative Response to Desiccant-Stimulated Drought Stress in Field-Grown Traditional Wheat Varieties.

Extended drought affects the production and quality of wheat (Triticum aestivum L.), one of the world's most important food crops. Breeding for increased drought resistance is becoming increasingly important due to the rising demand for food production. Four old traditional Croatian wheat cultivars were used in the present study to examine the early antioxidant response of flag leaves to desiccant-stimulated drought stress and to identify drought-tolerant cultivars accordingly. The results indicate that the enzymatic antioxidant system plays the most significant role in the early response of adult wheat plants to drought stress and the removal of excessive H2O2, particularly GPOD and APX. Nada and Dubrava cultivars revealed the strongest activation of the enzymatic defense mechanism, which prevented H2O2 accumulation and lipid peroxidation. Additionally, the Nada cultivar also showed increased synthesis of proline and specific phenolic compounds, which both contribute to the increased stress tolerance. Among the cultivars investigated, cultivar Nada has the broadest genetic base, which may explain why it possesses the ability to activate both enzymatic and non-enzymatic defense mechanisms in an early response to drought stress. This suggests that old traditional wheat cultivars with broad genetic bases can be a valuable source of drought tolerance, which is especially important given the current climate change.

Phenolic Acid Profiles and Antioxidant Activity of Major Cereal Crops.

Phenolic acids (PAs) are a dominant group of phenolic compounds in cereals, existing mostly bound to compounds of cell wall. In this study, a total of 25 cereal grain samples, including wheat, winter and spring barley, corn, and popcorn, were evaluated for bound PAs and antioxidant activity in a two-year field trial. The PA contents, determined by HPLC, were significantly affected by cereal type. The mean total PA content was highest in popcorn and corn (3298 and 2213 µg/gdm, respectively), followed by winter and spring barley (991 and 908 µg/gdm, respectively) and wheat (604 µg/gdm). Ferulic acid was the most abundant, accounting from 62% to 83% of total PAs (in popcorn and winter and spring barley, respectively). Across cereals, p-coumaric (35-259 µg/gdm) and p-hidroxybenzoic (45-79 µg/gdm) were also dominant, while in corn and popcorn o-coumaric (71 and 89 µg/gdm, respectively) also occurred in higher content. The mean total phenol content ranged from 853 µg GAE/gdm (wheat) to 1403 µg GAE/gdm (winter barley) with DPPH scavenging activity from 14% to 67%, respectively. A significant influence of crop years on the ferulic acid and total PA content was found, while the variability of other PAs was dependent on the cereal type. The results indicated a high health benefit potential of selected cereals.

Distribution of ß-Glucan, Phenolic Acids, and Proteins as Functional Phytonutrients of Hull-Less Barley Grain.

Two hull-less barley varieties were roller-milled, and breaks (B) and reduction flours (C), shorts, and bran were collected. Shorts, which mainly originate from endosperm cells with a smaller amount of the outer layers, had the largest yield (48.87-51.54%). Ash (0.82-3.10%) and protein (9.95-14.8%) increased from flours toward shorts and bran, while starch decreased (82.31-48.69%). In contrast to clear distribution differences in protein content (bran > shorts > C > B), albumins/globulins content was lowest in bran (0.78-0.90 g/100 gdw), and their distribution between fractions was uneven and genotype dependent. Distribution of hordeins (6.69-10.49 g/100 gdw) was more distinct and generally decreased in order from bran > B > shorts > C. The proportion of nutritionally poor C-hordeins in total hordeins varied from 28.33% to 30.24%, without significant differences between fractions. The ß-glucan content varied from 0.80% to 7.49% with decreasing content in the order bran, shorts > C > B. Shorts and bran could be classified as moderate and high ß-glucan flour (5.70-7.22%). The total phenolic and antioxidant activities ranged from 0.91 to 2.21 mg GAE/gdw and 28.81-72.06%, respectively. Ferulic and sinapic acids determined by high-performance liquid chromatography (HPLC) were major contributors to the antioxidant activity (45.16-1026.91 ug/gdw and 18.93-206.52 ug/gdw), respectively. The yield and high content of phytonutrients make hull-less barley shorts suitable for the production of health-promoting food and food supplements.

Screening of Various Metabolites in Six Barley Varieties Grown under Natural Climatic Conditions (2016-2018).

Climatic changes influence considerably the distribution and occurrence of different secondary metabolites in cereals. The aim of this investigation was to assess the changes in metabolite prevalence observed in six different winter barley varieties over a statistically significant period of three years by linking agro-climatic conditions with metabolite concentrations in chosen samples. The results showed that temperatures and precipitation levels varied during the observed timeframe and that the multi-toxin concentrations followed the trend of changing climatic conditions depending on the variety. All quantified (fungal) metabolites showed significant variations throughout the years and, for some (tryptophol and the cyclic dipeptides cyclo(L-Pro-L-Tyr) and cyclo(L-Pro-L-Val)), an unexpected, but clear connection can be made with temperature changes and precipitation levels during the growing season.

Lignin synthesis and accumulation in barley cultivars differing in their resistance to lodging.

Since lignin greatly affects stem strength, which is an important agronomical trait, understanding the relationship between lodging resistance and lignin synthesis is important in barley breeding and selection processes. The aim of the study was to reveal the connection between physiological aspects of lignin synthesis and genetic background of barley cultivars with different lodging phenotype. Three barley cultivars Astor, Scarlett and Jaran were compared by measuring lignin, cellulose and total soluble phenolics content, phenylalanine ammonia-lyase activity (PAL) and expression of cinnamoyl-CoA reductase (CCR) and cinnamyl-alcohol dehydrogenase (CAD) in three lower internodes at flowering and grain filling stage. To assess their genetic background simple sequence repeats (SSR) markers, connected to lodging resistance and plant height, were analyzed. Compared to lodging susceptible cultivars Scarlett and Jaran, a lodging resistant cultivar Astor revealed different dynamics of lignin synthesis and deposition, showing higher PAL activity and total soluble phenolics content as well as higher expression of CCR and CAD genes in the second internode at grain filling stage. Analysis of SSR markers associated with quantitative trait loci (QTL) for lodging resistance revealed that Astor discriminates from Scarlett and Jaran by marker Bmag337 connected with elongation of the second internode. Lignification process is under a strong influence of genotype and environmental factors which determine lignin synthesis dynamics and deposition of lignin in the cell walls of barley.