Variation in avenanthramide content in spring oat over multiple environments

Implementing multi-trait genomic selection to improve grain milling quality in oats (Avena sativa L.)

Oats (Avena sativa L.) provide unique nutritional benefits and contribute to sustainable agricultural systems. Breeding high-value oat varieties that meet milling industry standards is crucial for satisfying the demand for oat-based food products. Test weight, thins, and groat percentage are primary traits that define oat milling quality and the final price of food-grade oats. Conventional selection for milling quality is costly and burdensome. Multi-trait genomic selection (MTGS) combines information from genome-wide markers and secondary traits genetically correlated with primary traits to predict breeding values of primary traits on candidate breeding lines. MTGS can improve prediction accuracy and significantly accelerate the rate of genetic gain. In this study, we evaluated different MTGS models that used morphometric grain traits to improve prediction accuracy for primary grain quality traits within the constraints of a breeding program. We evaluated 558 breeding lines from the University of Illinois Oat Breeding Program across 2 years for primary milling traits, test weight, thins, and groat percentage, and secondary grain morphometric traits derived from kernel and groat images. Kernel morphometric traits were genetically correlated with test weight and thins percentage but were uncorrelated with groat percentage. For test weight and thins percentage, the MTGS model that included the kernel morphometric traits in both training and candidate sets outperformed single-trait models by 52% and 59%, respectively. In contrast, MTGS models for groat percentage were not significantly better than the single-trait model. We found that incorporating kernel morphometric traits can improve the genomic selection for test weight and thins percentage.

Nutritional and Phytochemical Composition and Associated Health Benefits of Oat (Avena sativa) Grains and Oat-Based Fermented Food Products

Oats (Avena sativa L.) are a popular functional cereal grain due to their numerous health benefits. This review article summarized the information on the chemical composition and phytonutrients of oats grown in different countries. It also reviewed recently developed fermented oat products to highlight their potential for human health. Oats have an interesting nutritional profile that includes high-quality protein, unsaturated fats, soluble fiber, polyphenolic compounds, and micronutrients. Oat grain has a unique protein composition, with globulins serving as the primary storage protein, in contrast to other cereals, where prolamins are the main storage proteins. Oats have the highest fat content of any cereal, with low saturated fatty acids and high essential unsaturated fatty acid content, which can help reduce the risk of cardiovascular diseases. Oats are a good source of soluble dietary fiber, particularly β-glucan, which has outstanding functional properties and is extremely important in human nutrition. β-Glucan has been shown to lower blood cholesterol and glucose absorption in the intestine, thereby preventing diseases such as cardiovascular injury, dyslipidemia, hypertension, inflammatory state, and type 2 diabetes. Oats also contain high concentration of antioxidant compounds. Avenanthramides, which are unique to oats, are powerful antioxidants with high antioxidative activity in humans. Recognizing the nutritional benefits of oats, oat-based fermented food products are gaining popularity as functional foods with high probiotic potential.

Genotypic and environmental variations in phenolic acid and avenanthramide content of Canadian oat (Avena sativa)

Phenolic compounds (PC) in oat may possess health promoting properties. This study evaluated the effect of genotype, environment, and their interaction on the phenolic acid and avenanthramide (AVN) concentration in Canadian oat. Six cultivars were grown at eight locations across Canada in a randomised complete block design with three field replicates. Free PCs were extracted from oat groat flour and analysed using a UPLC-PDA system. The cumulative concentration of free PCs and AVN ranged from 58 to 350 and 9 to 244 µg/g, respectively. The effect of environment was significant (p < 0.0001) for the concentration of all PCs. Cultivar differences significantly influenced the concentration of all PCs but AVNs A and B. The growing location explained > 68% of the variation in the concentration of AVN. Thus understanding the genotypic and environmental triggers of individual PCs may help agronomists and breeders strategize in selecting and growing oat cultivars of interest.

Selection for seed size has uneven effects on specialized metabolite abundance in oat (Avena sativa L.)

Plant breeding strategies to optimize metabolite profiles are necessary to develop health-promoting food crops. In oats (Avena sativa L.), seed metabolites are of interest for their antioxidant properties, yet have not been a direct target of selection in breeding. In a diverse oat germplasm panel spanning a century of breeding, we investigated the degree of variation of these specialized metabolites and how it has been molded by selection for other traits, like yield components. We also ask if these patterns of variation persist in modern breeding pools. Integrating genomic, transcriptomic, metabolomic, and phenotypic analyses for three types of seed specialized metabolites—avenanthramides, avenacins, and avenacosides—we found reduced heritable genetic variation in modern germplasm compared with diverse germplasm, in part due to increased seed size associated with more intensive breeding. Specifically, we found that abundance of avenanthramides increases with seed size, but additional variation is attributable to expression of biosynthetic enzymes. In contrast, avenacoside abundance decreases with seed size and plant breeding intensity. In addition, these different specialized metabolites do not share large-effect loci. Overall, we show that increased seed size associated with intensive plant breeding has uneven effects on the oat seed metabolome, but variation also exists independently of seed size to use in plant breeding. This work broadly contributes to our understanding of how plant breeding has influenced plant traits and tradeoffs between traits (like growth and defense) and the genetic bases of these shifts.

Simplified Analysis and Expanded Profiles of Avenanthramides in Oat Grains

Uniquely, oats contain avenanthramides (AVAs), a group of phenolic alkaloids, exhibiting many health benefits. AVA analysis involves extraction with alcohol-based solvents and HPLC separation with UV and/or mass spectrometer detectors. There are many reported methods to extract AVAs. Almost all entail multiple extractions. The whole procedure is time- and labor-intensive. Furthermore, most quantifications are limited to three common AVAs (2f, 2p, 2c). The present study compared three extraction methods (all at 50 °C) for their effects on AVA concentrations and composition (% relative to total AVA) of oat grains. These included triplicate extractions with 80% ethanol containing 10 mM phosphate buffer (pH 2.0) (A), triplicate extractions with 80% ethanol (B), and a single extraction with 80% ethanol (C), while keeping solid/total solvent ratio at 1/60 (g/mL) and total extraction time of 60 min. Results showed that 80% buffered ethanol gave significantly lower AVA contents than 80% ethanol, while single and triplicate extractions with 80% ethanol produced the same extractability. However, the extraction method had no effect on AVA composition. Using 0.25 g sample size instead of 0.5 g saved extractants by half, without affecting AVA measurements. Consequently, a simplified method of extraction was developed, featuring Method C. The present study also expanded profiling individual AVAs beyond AVA 2c, 2p and 2f. Other AVAs identified and semi-quantified included 5p, 4p, 3f/4f, and 2pd. The simplified analysis was validated by measuring 16 selected oat grain samples. Some of these grains had relatively high contents of 4p, 3f/4f and 2pd, which have been considered minor AVAs previously.

Avenanthramides: Unique Bioactive Substances of Oat Grain in the Context of Cultivar, Cropping System, Weather Conditions and Other Grain Parameters

Our study was focused on the evaluation of the content of a wider spectrum of eight avenanthramides (AVNs) as unique components of oat grain under the effects of four selected factors (cultivar, locality, cropping system, and year). The weather effects on changes in the AVN content and their relationship to other important parameters of oat grain were further evaluated in more detail. A sensitive UHPLC system coupled with a QExactive Orbitrap mass spectrometer was used for AVN quantification. AVNs confirmed a high variability (RDS = 72.7–113.5%), which was dominantly influenced by the locality and year factors. While most AVN types confirmed mutually high correlations (r = 0.7–0.9), their correlations with the other 10 grain parameters were lower (r ≤ 0.48). Their significant correlations (0.27–0.46) with β-D-glucan could be used in perspective in breeding programs for the synergetic increase of both parameters. PCA analysis and Spearman correlations based on individual cultivars confirmed a significant effect of June and July precipitation on the increase of Σ AVNs. However, the results also indicated that higher precipitation can generate favorable conditions for related factors, such as preharvest sprouting evoking a direct increase of AVNs synthesis in oat grain.

Distributions of nutrients and avenanthramides within oat grain and effects on pearled kernel composition

Hulled Reins and hulless Lamont oats were dehulled and/or sequentially abraded to produce ten pearling fines and corresponding pearled kernels. Contents of nutrients (protein, oil, starch, beta-glucan, ash and other carbohydrates) and avenanthramides (AVA) 2p, 2c, 2f, and 5p in processing fractions and starting grains were measured. Results show that distribution patterns of nutrients varied with individual nutrients, but those of AVAs varied with variety and individual AVAs. In both varieties, from the surface to inner endosperms, protein and oil increased then decreased; ash and other carbohydrates decreased; starch increased; and beta-glucan unchanged except for the surface area. In Lamont oat, the four AVAs decreased, but in Reins oat, AVA 2p decreased while 2c, 2f and 5p increased, then decreased. Compared to whole grain, pearled oats not only contained lower AVAs, protein, oil, ash, and other carbohydrates and higher beta-glucan and starch but also had a different AVA composition.