Differences in iron accumulation in the grain between and within Aegilops and Triticum species

Plants are the most important source of Fe for humans and animals; therefore, its accumulation in edible plant parts is of great importance. Since plant species, ecotypes, genotypes, lines, and varieties may differ in their ability to accumulate mineral elements, the aim of this study was to i) examine the accumulation of Fe in the grain of Aegilops and Triticum species with different genomes (AA, BB, BBAA, BBAADD), ii) study the relationship between the level of ploidy and grain Fe accumulation, and iii) analyze correlations between grain size and Fe concentration. Twenty different genotypes were included in three-year field experiments. The examined species and genotypes differed significantly with respect to grain Fe concentration, which was the highest in diploid Aegilops speltoides (BB genome). Tetraploid and modern cultivated hexaploid varieties displayed substantial variation in Fe concentration in the whole grain. Genotypes also differed significantly in thousand grain weight (TGW), which was the smallest in Aegilops speltoides. A significant negative correlation was found between grain Fe concentration and TGW, and a positive correlation between TGW and Fe content in individual grains. The higher accumulation of Fe in individual grains of tetraploid and hexaploid wheat vs. diploid ancestors suggests that the increase in ploidy led to an increase in the capacity of grains to serve as a sink for that Fe. The results indicate that genetic diversity in the wheat genome is sufficient to allow a significant increase in Fe concentration in the wheat grain.

Concentrations of Phenolic Acids, Flavonoids and Carotenoids and the Antioxidant Activity of the Grain, Flour and Bran of Triticum polonicum as Compared with Three Cultivated Wheat Species

The experiment was performed on 66 breeding lines of Triticum polonicum, four T. durum cultivars, four T. aestivum cultivars, and one T. turanicum cultivar (Kamut® wheat). Wheat grain, bran, and flour were analyzed to determine the concentrations of carotenoids, free and bound phenolic acids, and flavonoids, as well as antioxidant activity in the ABTS+ assay. The total concentrations of lutein, zeaxanthin, and β-carotene in grain and milling fractions were determined at 3.17, 2.49, and 3.16 mg kg−1 in T. polonicum (in grain, flour, and bran, respectively), and at 4.84, 3.56, and 4.30 mg kg−1 in T. durum, respectively. Polish wheat grain was characterized by high concentrations of p-coumaric acid and syringic acid (9.4 and 41.0 mg kg−1, respectively) and a low content of 4-hydroxybenzoic acid (65.2 mg kg−1). Kamut® wheat (T. turanicum) which is closely related to T. polonicum was particularly abundant in 4-hydroxybenzoic, chlorogenic, ferulic, gallic, and t-cinnamic acids. The studied Triticum species did not differ considerably in the concentrations of the eight analyzed flavonoids, and significant differences were noted only in rutin levels. The grain and milling fractions of Kamut® wheat were characterized by very high concentrations of quercetin, naringenin, and vitexin, but significant differences were observed only in vitexin content. Quercetin concentration in Kamut® wheat grain (104.8 mg kg−1) was more than five times higher than in bread wheat (19.6 mg kg−1) and more than twice higher than in Polish wheat (44.1 mg kg−1). Antioxidant activity was highest in bran, followed by grain and flour (4684, 1591, and 813 μM TE g−1, respectively). The grain and flour of the analyzed Triticum species did not differ significantly in terms of antioxidant activity.

The unique disarticulation layer formed in the rachis of Aegilops longissima probably results from the spatial co-expression of Btr1 and Btr2

Background and Aims The brittle rachis trait is a feature of many wild grasses, particularly within the tribe Triticeae. Wild Hordeum and Triticum species form a disarticulation layer above the rachis node, resulting in the production of wedge-type dispersal units. In Aegilops longissima, only one or two of the nodes in the central portion of its rachis are brittle. In Triticeae species, the formation of a disarticulation layer above the rachis node requires the co-transcription of the two dominant and complementary genes Btr1 and Btr2. This study aims to establish whether homologues of Btr1 and/or Btr2 underlie the unusual brittle rachis phenotype observed in Ae. longissima. Methods Scanning electron microscopy was used to examine the disarticulation surfaces. Quantitative RT-PCR and RNA in situ hybridization experiments were used to identify gene expression in the immature inflorescence. Key Results Analysis based on scanning electron microscopy was able to demonstrate that the disarticulation surfaces formed in the Ae. longissima rachis are morphologically indistinguishable from those formed in the rachises of wild Hordeum and Triticum species. RNA in situ hybridization showed that in the immature Ae. longissima inflorescence, the intensity of Btr1 transcription varied from high at the rachis base to low at its apex, while that of Btr2 was limited to the nodes in the central to distal portion of the rachis. Conclusions The disarticulation pattern shown by Ae. longissima results from the limitation of Btr1 and Btr2 co-expression to nodes lying in the centre of the rachis.