Contents of Antioxidant Compounds in Turkish Oats: Simple Phenolics and Avenanthramide Concentrations

Antioxidant products such as simple phenolic compounds and avenanthramides in oat (Avena sativa L.) may have health‐promoting effects on humans. Therefore, it is very important to determine simple phenolics and avenanthramide concentrations of different genotypes of oats from different regions of the world. The aim of this research was to determine the concentrations of simple phenolics and avenanthramides of Turkish oat genotypes. According to the results, Turkish oat genotypes were significantly different for three major avenanthramides (Bc, Bp, and Bf) and the simple phenolic, ferulic acid (FA), while not significantly different for p‐coumaric acid (PCA). Ferulic acid concentrations of Turkish oat genotypes were higher than a standard U.S. cultivar, Belle. However, the major avenanthramide concentrations of Turkish oat genotypes were significantly lower than Belle.     

Oat Tocols: Saponification vs. Direct Extraction and Analysis in High‐Oil Genotypes

Tocols are natural antioxidants that occur in grains that may benefit human and animal health. Therefore, it is important to accurately measure their concentrations in foods and feeds and to determine how genetics and growing environment can influence their levels. The first objective was to evaluate saponification versus direct extraction for the analysis of tocols in oat (Avena sativa L.). The second was to determine the effects of growing environment, hulled versus hulless phenotype, and genetic background on tocol concentration, and to see whether tocol and lipid concentrations were associated. For the first objective, oat grain samples from two locations were either extracted by saponification or directly with methanol, and extracts were analyzed by HPLC. The saponification method increased yield by ≈25% and was less time‐consuming, so it was adopted for the second objective. For the second objective, oat genotypes were developed by crossing high‐oil parents from Iowa State University with hulled and hulless cultivars adapted to arid Western environments. These were grown at Aberdeen and Tetonia, ID, and the tocols and lipid concentrations were analyzed at Madison, WI. There were significant effects of growing environment, genotype, and the presence or absence of hulls on tocol concentrations. Tocol and lipid concentrations were not correlated. Progeny of crosses involving the genotype IA91098‐2 had tocol concentrations that exceeded both parents.     

Nitrogen and fungicide effects on winter wheat produced in the Louisiana Gulf Coast region

Management decisions affecting wheat (Triticum aestivum L.) yield include nitrogen (N) fertility rate, cultivar selection, and fungicide application. Since these cultural practices may interact with each other and the environment, often times affecting grain yield, test weight, and disease development, they need to be better defined for wheat production in for the Gulf Coast region. Field experiments were conducted to evaluate the effect of N rate, fungicide, and cultivar on grain yield, test weight, and disease development. Three N rates (67, 101, and 134 kg#lbha^‐1), two fungicide treatments (no‐fungicide control and fungicide), and four high‐yielding wheat cultivars with different levels of resistance to leaf rust (Puccinia recondite Rob. ex f. sp. tritici) were evaluated in 12 Louisiana field environments. Environment and interaction between environment and N rate, fungicide, and cultivar were significant for grain yield, leaf rust ratings, and test weight. Grain yield response to N rate was linear in five environments and quadratic in five environments. Although there was little evidence of a N x fungicide interaction for grain yield, increasing N rates increased leaf rust severity. Grain yields were increased by fungicide application in only four of twelve environments with a significant cultivar x fungicide interaction for grain yield. Grain yield increase from foliar fungicides was related to leaf rust severity and resistance of cultivars to leaf rust. Test weight was increased due to N in three environments and decreased in two environments. Test weight increased with fungicide application and varied among cultivars. The findings indicate that 101 kg N ha is probably adequate for maximum yield in most years. Although the higher N rates may increase yield in some years, disease pressure and the need for fungicides may also be increased.     

Effect of chemical systemic acquired resistance elicitors on avenanthramide biosynthesis in oat (Avena sativa)

Oats produce a group of phenolic antioxidants termed avenanthramides. These metabolites are, among food crops, unique to oats and have shown, in experimental systems, certain desirable nutritional characteristics such as inhibiting atherosclerotic plaque formation and reducing inflammation. Avenanthramides occur in both the leaves and grain of oat. In the leaves they are expressed as phytoalexins in response to crown rust (Puccina coronata) infection. The experiments reported here demonstrate that avenanthramide levels in vegetative tissue can be enhanced by treatment with benzothiadiazole (BTH), an agrochemical formulated to elicit systemic acquired resistance (SAR). The response to BTH was dramatically stronger than those produced with salicylic acid treatment. The roots of BTH treated plants also showed a smaller but distinct increase in avenanthramides. The dynamics of the root avenanthramide increase was substantially slower than that observed in the leaves, suggesting that avenanthramides might be transported from the leaves.     

Genetic variation in nitrogen‐use efficiency of tef

Tef (Eragrostis tef (Zucc.) Trotter) is the ancient and most important cereal food crop of Ethiopia. A set of 20 tef genotypes was investigated in field experiments at three environments in Ethiopia to estimate genetic variation in nitrogen (N)‐use efficiency and in characters related to N accumulation as well as their relationships to grain yield. In each environment, genotypes representing both widely grown landraces and recently released cultivars were grown under three N‐fertilizer rates (0, 4, and 8 g m^–2 N). In grain yield, modern cultivars were superior to landraces, whereas in other characters, differences were less clear. The variation in grain yield was significantly related to the variation in total grain N and total plant N. Grain yield weakly correlated with N‐utilization efficiency and N harvest index. Broad sense heritability was higher for grain yield, total grain N, total plant N, and N harvest index than for N‐use, N‐uptake, and N‐utilization efficiencies. The contribution of uptake efficiency to the variation in N‐use efficiency decreased from 75% to 55% and that of utilization efficiency increased from 22% to 43% at the 4 to 8 g m^–2 N‐supply rate change. This study clearly suggests that tef N‐use efficiency would be increased by selecting genotypes with greater uptake efficiency at low N‐supply levels.     

Effects of Impact Dehuller Rotor Speed on Dehulling Characteristics of Diverse Oat Genotypes Grown in Different Environments

Commercial processing of oats for human consumption generally requires impact dehulling to isolate groats from the hull. Impact dehulling involves feeding oat grain into the center of a spinning rotor that expels the grain against the walls of the dehuller. The force of the impact breaks the hull from the groat. We have tested the effect of rotor speed on dehulling efficiency, groat breakage, and unbroken groat yield on 18 oat genotypes from replicated plots in six different environments. Dehulling efficiency and groat breakage increased with rotor speed with all genotypes and environments, but there were significant genotypic and environmental effects as well. In general, genotypes with higher test weight and kernel density dehulled more efficiently at slower rotor speeds. Oat genotypes with higher oil and protein concentrations in their groats tended to break less during dehulling. Oats from hotter, drier environments suffered greater groat breakage. Maximal unbroken groat yield represented a balance between dehulling efficiency and groat breakage, but groat proportion and dehulling efficiency appeared to be the most important factors contributing to groat yield.     

Oat Grain Density Measurement by Sand Displacement and Analysis of Physical Components of Test Weight

Test weight or bulk density of oats (Avena sativa L.) has a major influence on the monetary value of oat grain. We hypothesize that test weight can be attributed to grain density and packing efficiency. We have measured oat grain volume and density by a sand‐displacement method and derived the packing factor for six oat cultivars grown in three environments. Volumes of individual grains were 31–38 mm³ and were highly correlated with grain mass. Grain densities were 0.96–1.03 g/cm³. Packing efficiency, defined as the space proportion occupied by the grains, was 53–55%. Regression analysis suggested that 78% of the variation in test weight could be attributed to grain density. Size fractionation of grain by sieving and analysis by digital image analysis indicated that smaller grains within an oat sample packed more efficiently than larger grains and larger grains in a sample were less dense than the smaller grains. Analysis of oat grain components indicated groat densities were ≈1.29 g/cm³ and hull densities were ≈0.69 g/cm³. The difference in densities between groat and hull provide a physical basis for the recognized relationship between groat percentage and test weight.     

Effect of soil cadmium concentration on three Chilean durum wheat cultivars in four environments

Durum wheat (Triticum turgidum L. var durum) is a species that accumulates cadmium (Cd). Durum wheat cultivars differ in their absorption ability of Cd; therefore, identifying and selecting genetic material with low Cd accumulation reduces human exposure to this toxic element. In the present study, Cd concentration was evaluated in three Chilean durum wheat cultivars (Llareta-INIA, Corcolén-INIA, and Lleuque-INIA) grown in four Chilean locations with varying concentrations of Cd in soils. The objective of this study was to evaluate the response of these durum wheat cultivars to different doses of cadmium in terms of grain yield; Cd concentration in different plant tissues (grain, straw, roots); soil Cd concentration was also evaluated. Results show that grain yield was not affected by soil Cd; differences in Cd concentration in plant tissues were generally associated with location, cultivar, and soil Cd concentration. Grain Cd concentration in all three cultivars was classified in the low accumulation category for this metal; ‘Lleuque-INIA’ noted as having a very low accumulation.     

Genotypic and Environmental Effects on Oat Milling Characteristics and Groat Hardness

The production of oat bran involves the dehulling of oats, inactivation of their enzymes, and the subsequent grinding and sieving of the clean groats to isolate the larger bran particles. The bran yield from the oat groats may be related to their hardness, as it is in wheat. Groat breakage, which occurs during the dehulling process, reduces milling yield and may also be related to groat hardness. This study sought to investigate genotypic and environmental effects on oat dry milling and oat dehulling characteristics, and attempted to define properties associated with oat groat hardness. Significant genotypic differences in bran yield were largely attributed to groat composition, where higher β‐glucan and oil concentrations in the groat were associated with higher bran yields. Bran composition was largely dependent on a combination of the bran yield and the groat composition. Although groat breakage was correlated with bran yield and with groat β‐glucan concentration, environmental factors appeared to be more influential. Locations that had suffered severe crown rust infestations exhibited higher rates of groat breakage during dehulling. Bran yield was not as strongly affected at the locations infested with crown rust, indicating that bran yield and groat breakage are manifestations of different types of groat hardness and are only partially related.     

The Impact of Oat Quality on White Salted Noodles Containing Oat Flour

This research compared the physicochemical properties of six milling oat cultivars from Western Australia over two growing seasons (2011 and 2012). Variations among the cultivars in physicochemical properties, particularly β‐glucan content, were assessed to determine their suitability for incorporation into white salted noodles at a level of 30% of the flour component. The average across six oat cultivars grown in 2012 was significantly higher (P < 0.05) for protein content, lipid content, and volume of smaller sized particles (<100 µm) and significantly lower for ash content, starch damage, and volume of larger particles (>100 µm) in comparison with the average across the same oat cultivars grown in 2011. The year of cultivation by cultivar interaction was significant (P < 0.05) for ash content, protein content, β‐glucan content, starch damage, and particle size. Oat cultivar Mitika had the highest peak viscosity for 100% oat flour (whole groat) and 30% oat–wheat (OW) flour blend, which may be owing to lower amylose percentage, high protein content, and greater volume of smaller particles. The effect of growing season had greater impact on OW noodle firmness than the genetic effect of cultivars. The eating and cooking quality attributes of OW noodles, such as color, color stability, firmness, and cooking solid loss were superior for those incorporated with 2012 oat flour (whole groat) compared with 2011 oat flour. Among the six oat cultivars, Williams produced noodles with poor cooking and eating quality, and Mitika was easier to handle during processing and produced noodles with superior brightness and color stability in comparison with other oat cultivars evaluated.     

Theoretical and Empirical Relationships Between Oat Test Weight and Groat Proportion

Test weight and groat proportion are two very important quality characteristics of oat grain. In this study, we pose the hypothesis that these two characteristics are related through characteristics of grain density. Test weight is defined as the product of kernel density and packing proportion. Groat proportion, in theory, is the ratio of the groat mass to the kernel mass. We present two theoretical constructions expressing test weight in terms of groat proportion, packing proportion and kernel density components. To test these, we have applied measurements of test weight, groat proportion, kernel density components, and packing proportion of 18 oat cultivars grown at six environments. Whereas the groat proportion alone accounted for only 34% of the variation in test weight, our theoretical constructions that included groat proportion could account for ≤82% of variation in test weight. Also, we present previously undescribed variation in oat kernel density components across genotypes and environments. Although the kernel density alone could account for most of the variation in test weight across genotypes, packing proportion appeared to be more important in describing variation in test weight of a genotype across different environments. We observed significant variation in both groat and hull density which, together with groat proportion, described most of the variation in kernel density.     

Genetic Differences in Resistance to Iron Deficiency Chlorosis in Peanut

Iron (Fe) deficiency has been a widespread problem in peanut (Arachis hypogaea L.) grown on calcareous soils of northern China and has resulted in significant yield losses. Field observations showed considerable variability in visual chlorosis symptoms among peanut cultivars in the same soil. The objective of this study was to confirm the genetic differences in resistance to Fe-deficiency chlorosis in peanut and to identify feasible indicators for screening Fe-efficient genotypes. Resistance to Fe chlorosis of sixteen peanut cultivars grown on calcareous soil was evaluated in the field and physiological responses to Fe-deficiency stress were studied in nutrient solution. There were significant differences in resistance to Fe-deficiency chlorosis among the sixteen peanut cultivars tested, which was identified with SPAD readings, active Fe concentrations in young leaves in the early growth stages, and the pod yield. For Fe-resistant peanut cultivars, Fe-reduction capacity and quality of releasing hydrogen ions from roots increased under Fe-deficiency stress. Highly correlated relationships were observed between the summation of root Fe reduction and field chlorosis scores for sixteen cultivars (r² = 0.79). It was concluded that Fe-reduction capacity was a better physiological indicator for screening Fe-efficient peanut genotypes of the mechanisms measured.     

Flavonoids of zoysiagrass (Zoysia spp.) cultivars varying in fall armyworm (Spodoptera frugiperda) resistance

Flavonoid profiles of 12 zoysiagrass (Zoysia spp.) cultivars sampled six times in 1998 were correlated to fall armyworm (Spodoptera frugiperda J. E. Smith) larval weights and survival on replicated field-grown plant material and analyzed to determine genetic and seasonal variations of flavonoids among zoysiagrass cultivars. From multiple regression analyses and correlations, flavonoid peak 10 (luteolin-glucoside) had the greatest positive association with average fall armyworm weight; however, resistance appeared to be correlated with a number of other flavonoids. The flavonoid profiles of cultivars subjected to clustering procedures showed consistent genetic variability for five of six samplings and was used to genotype 23 cultivars. The dendrogram supported the results of the FASTCLUS procedure in clustering certain genotypes such as fall armyworm-resistant Cavalier and Zeon together, as well as J-36 and Meyer. Flavonoid evaluations measure genetic relatedness among cultivars and could be used for selective breeding of resistance to fall armyworm.     

Tentative Avenanthramide‐Modifying Enzyme in Oats

A decrease of the concentration of the synthetic avenanthramide N‐(4′‐hydroxy‐(E)‐cinnamoyl)‐5‐hydroxyanthranilic acid in a buffered slurry of milled oat groats (Avena sativa L.) was temperature and pH‐dependent, with a maximum rate at 30°C and pH 9. The reaction was inhibited in the presence of 2‐mercaptoethanol, acetic acid and at high temperature; suggestive of enzymatically catalyzed nature. Among eight different synthetic avenanthramides tested, the tentative enzyme had highest affinity for avenanthramides comprising caffeic and p‐coumaric acids and lowest for those comprising sinapic and ferulic acids. The activity was found in samples from several oat cultivars and was equally pronounced in both bran and endosperm flour of oats. Steeping of oat grains did not influence the reaction.     

Evaluation of wheat (Triticum aestivum L.) phenolic acids during grain development and their contribution to Fusarium resistance

The phenolic acid profiles of six cultivars of wheat with known tolerance to Fusarium head blight were evaluated during plant development from anthesis through maturity. Analysis by HPLC of grain at anthesis revealed that p-coumaric and ferulic acid were the two principal phenolic compounds present. The effect of these two phenolic acids on Fusarium species was evaluated in vitro. Both phenolic acids demonstrated significant reductions (p < 0.05) of Fusarium species growth at all concentrations tested. Ferulic acid is the primary phenolic acid in grain at all stages of development, and its concentration increased steadily during grain development prior to a 50% decrease during grain ripening. The accumulation of ferulic acid synthesis from anthesis until approximately 20 days after anthesis appears related with cultivar resistance to Fusarium. Concentrations of ferulic acid in the grain were similar at maturity, implying that the end-use quality would be similar for both resistant and susceptible cultivars.     

Landraces of cowpea, <Emphasis Type="Italic">Vigna</Emphasis><Emphasis Type="Italic">unguiculata</Emphasis> (L.) Walp., as potential sources of genes for unique characters in breeding

Cowpea landraces belonging to Vigna unguiculata (L.) Walp. subsp. unguiculata cv.-gr. unguiculata and cv.-gr. sesquipedalis collected from part of the Deccan Plateau and West Coast of India were evaluated to (i) identify the diverse source(s) of variation for improved characters like pods/peduncle and seed index (ii) study the response of landraces for adaptation to drought and heat stress and (iii) understand the breeding value of a landrace in the genetic improvement of a popular cowpea cultivar. Landraces were evaluated for various morphological characters, pods/peduncle, seed index and other economically important agronomic traits, rust resistance and drought and heat tolerance in different years and environments. Landraces were found as an important source of genetic variability for pods/plant, pods/peduncle, better pod filling ability (seed index), grain yield/plant as well as drought and heat tolerance and rust resistance. Hybridization between C 152 (cv.) and DWDCC 016 (landrace) resulted in release of new variation not present in the two parents. Thus the landrace, DWDCC 016, can be utilized to improve cultivated varieties by transferring to them the economically valuable traits like pods/peduncle and seed index thereby enhancing realisation of sink potential and ultimately grain yield in a sustainable way.     

Oat Grain/Groat Size Ratios: A Physical Basis for Test Weight

Market value of oat grain is largely determined by test weight or bulk density, yet little is known of the physical basis for test weight in oats. We have hypothesized that a larger sized groat relative to the oat grain (the kernel with the hull) would generate higher test weight oats because the groat is the densest structure in the oat grain. We tested this by measuring oat grain size and oat groat size by digital image analysis for 10 genotypes grown in 10 environments. We also measured other physical characteristics of the oats grains and groats including mean grain and groat mass, test weight, and groat percentage. We found that the groat/ grain size ratio was highly correlated with test weight. Because the oat grain image area was nearly twice that of the groat, we suggest that there are significant amounts of empty space within the oat hull, which detracts from test weight. We also found that oat groat size distributions, like oat grains, fit bimodal distributions better than normal distributions.     

Timing and level of nitrogen supply affect nitrogen distribution and recovery in two contrasting oat genotypes

Human diets containing oat (Avena sativa L.) grain offer health benefits resulting in an emerging interest in oat improvement. Information on nitrogen (N) uptake, distribution, and use efficiency (NUE) in oat is limited. A greenhouse study using a ¹⁵N‐labeling technique was conducted to determine the responses of two contrasting oat genotypes to timing and level of N deficiency. Hulled oat cv. Prescott and hulless cv. AC Gehl were grown in soil‐mix pot culture with five N treatments applied through modified Hoagland solutions. Differences in ¹⁵N accumulation, ¹⁵N distribution, plant N originating from the labeled source, and NUE between the contrasting cultivars, were examined for each N strategy. Level of N deficiency and timing of N supply of ¹⁵NH₄¹⁵NO₃ greatly affected ¹⁵N distribution, the origins of plant N, and the amount of ¹⁵N recovered in the plant. When N was supplied from seedling emergence to maturity (T₁), AC Gehl accumulated 61% more ¹⁵N in the shoots, but 46% less ¹⁵N in the grain than Prescott (0.43 vs. 0.80 mg plant^–1), indicating that AC Gehl was less effective in producing grain yield than Prescott as AC Gehl produced greater total dry matter (DM). Withholding N supply until flag‐leaf stage (FL) increased ¹⁵N in the grain of both cultivars by 29.6%, resulting in the highest NUE. In most cases, there were larger portions of plant N derived from the labeled source for AC Gehl than for Prescott. Our results suggest that greater NUE in the newly released AC Gehl was associated with N accumulation in the vegetative tissues. It is concluded that genotype improvement of hulless oat should be focused on enhancing N‐translocation efficiency.     

Genotype and Environment Variation for Arabinoxylans in Hard Winter and Spring Wheats of the U.S. Pacific Northwest

The development of high‐quality wheat (Triticum aestivum L.) cultivars depends on a thorough understanding of the constituents of grain and their variation due to genetics and environment. Arabinoxylans (pentosans) are key constituents of wheat grain and have broad and far‐reaching influences on milling and baking quality. However, variation in arabinoxylans due to genotype and environment are not fully understood. In this study, 25 hard winter and 25 hard spring wheat commercial cultivars and advanced breeding lines developed from eight public and private breeding programs in the U.S. Pacific Northwest were analyzed for water‐extractable and total arabinoxylan contents (WE‐AX and total AX), and the proportion of total AX that was water‐extractable. Winter and spring genotypes were grown in three environments each. The results indicated that there were significant differences among both sets of hard wheat genotypes for WE‐AX, total AX, and proportion of total AX that was WE‐AX. The WE‐AX and total AX mean content ranges for the winter cultivars were 0.390–0.808 and 3.09–4.04%, respectively; and for the spring cultivars 0.476–0.919 and 3.94–4.70%, respectively. WE‐AX as a percentage of total AX was similar between the two genotype sets, 11.7–23.0%. Arabinoxylan fractions were generally not correlated with grain protein, test weight, and kernel hardness. The two highest correlations for winter wheats were between protein and total AX (r = –0.40) and test weight and percentage of total AX that were water‐extractable (r = 0.37) for winter wheats. Among spring wheats, single‐kernel characterization system hardness was negatively correlated with WE‐AX and proportion of total AX that was WE‐AX (r = –0.46 and –0.51, respectively). Although often significant, arabinoxylan fractions were usually not highly intercorrelated, indicating some independence of traits. Notable genotypes, being especially high or low for one or more arabinoxylan fraction and, thus, candidates for further genetic study and cross‐breeding, included Juniper, Eddy, and ORN980995 winter wheats, and Hollis, Alta Blanca, and WQL9HDALP spring wheats. Although the results indicate that arabinoxylan fractions of wheat grain can be highly influenced by environment, there is clear support for the existence of genetic differences, especially for WE‐AX and the proportion of total AX that is water‐extractable. As such, the manipulation of arabinoxylan content of wheat grain seems to be a reasonable breeding objective.     

Genotypic variation in partitioning of phosphorus in relation to nitrogen and dry matter during wheat grain development

Phosphorus has many similarities to N for plant nutrition, but little is known regarding P partitioning among genotypes and factors that affect it. Experiments were conducted to measure variation in partitioning of P and its relationship to N, dry matter, and yield components of wheat (Triticum aestivum L.). Sixteen cultivars grown under field conditions were sampled at anthesis for P, N, and dry matter and at maturity for the same constituents and for yield components. Relationships among the traits were determined by Spearman rank correlation coefficients. Accumulation of P and dry matter during grain development and grain HI, NHI, and PHI differed significantly among genotypes. Post‐anthesis P, N, and dry matter accumulation correlated positively as did HI, NHI, and PHI, but accumulation of the constituents was not related to their His. The positive associations were attributed to requirement of P and N for growth and their accumulation as reserve compounds in grain. Genotypic variation in PHI may be as useful as variation in HI and NHI for wheat improvement.