Kernel Hardness Research Articles

Fertilizer Effects on Endosperm Physicochemical Properties and Resistance to Larger Grain Borer, Prostephanus truncatus (Coleoptera: Bostrichidae), in Malawian Local Maize (Zea mays L.) Varieties: Potential for Utilization of Ca and Mg Nutrition

Maize grain hardness influences storage pest resistance, a key characteristic valued by smallholder farmers. The structural changes in the endosperm determine grain hardness and are influenced by agronomic practices. The purpose of this study was to establish whether supply of calcium and magnesium based fertilizers can alter physicochemical properties of local and hybrid maize varieties and reduce the infestation by larger grain borer (Prostephanus truncatus (Coleoptera: Bostrichidae)) during storage. Two local and one hybrid maize varieties commonly grown by smallholder farmers in Malawi were cultivated under three fertilizer treatments (NPK (nitrogen, phosphorous, potassium), NPK plus gypsum, and NPK plus dolomite). After harvest, the grains were classified into flint and dent types, followed by P. truncatus infestation and determination of their physicochemical properties. The addition of gypsum and dolomite fertilizers led to higher levels of amylose, total zein and β-14 zein, traits associated with kernel hardness, compared to the application of NPK fertilizer. Moreover, local maize varieties showed higher resistance to P. truncatus infestation, hardness and biochemical properties associated with hardness (total zein, α-19 and β-14 zein, starch lysophosphatidylcholine, and non-starch free fatty acid) compared to hybrid variety. Our study suggests the potential for utilizing Ca and Mg nutrition in maize to improve kernel hardness, thus adoption of gypsum and dolomite by smallholder farmers may be beneficial against P. truncatus during storage.

Characterization of various wheat types and processing methods using in vitro ruminal batch cultures

This study investigated the effect of kernel hardness, processing method, and their interaction on particle size, dry matter (DM) disappearance (DMD), and fermentation characteristics of wheat grain in batch cultures. The study was a completely randomized design with 3 wheat classifications (soft, medium, hard) × 3 processing methods (grinding, dry- and temper-rolling). Fifty-five wheat samples were characterized for chemical traits and classified for kernel hardness. Samples were either ground through 1-mm screen, dry-rolled or temper-rolled to a constant processing index (PI) of 0.80. In vitro gas production (GP) kinetics, fermentation characteristics and DMD at 6, 24 and 48 h of incubation were measured. Crude protein (CP) (g/kg) was lower and starch (g/kg) was higher for soft than medium and hard wheat. The PSD of rolled wheat was affected (P < 0.01) by a wheat hardness × processing interaction. With dry-rolling, soft wheat had more particles retained on the 2.36-mm sieve and less on the 1.18-mm sieve, while, with temper-rolling, soft wheat had more particles retained on the 3.35-mm sieve and less on the 2.36-mm sieve than those for dry- or temper-rolled medium and hard wheat. Kernel hardness × processing was observed (P < 0.01) for DMD and CPD after 24 h and 48 h of incubation; the DMD and CPD were higher (P < 0.01) with dry- than temper-rolled hard or medium wheat, but no differences in DMD and CPD were observed between dry- and temper-rolled soft wheat. A kernel hardness × processing interaction was also noted for total VFA production and molar proportions of propionate after 24 h of incubation (P < 0.05). Dry-rolled soft wheat had a higher (P = 0.04) total VFA concentration and molar proportion of propionate after 24 h of incubation as compared to dry-rolled hard wheat. Compared to grinding, VFA concentrations and proportion of propionate were all reduced by both dry- and temper rolling with the magnitude of these differences generally being greater for soft as compared to medium and hard wheat. In conclusion, regardless of kernel hardness, PSD of dry- and temper-rolled wheat had a significant impact on DMD. Tempering was more effective at reducing the generation of fine particles than dry-rolling, particularly with hard wheat, a factor that may reduce the risk of digestive disturbances in ruminants fed wheat.

Classifying Wheat Genotypes using Machine Learning Models for Single Kernel Characterization System Measurements

The properties related to market value, milling, classification, storage, and transportation of bread wheat are determined by using some important physical quality characteristics such as weight, shape, dimensions, and hardness of wheat kernels. It is possible to measure all these features using single kernel characterization system (SKCS). Classification of wheat genotypes using computer-based algorithms is crucial to determine the most accurate physical quality classification for breeding studies. In this paper, four commercial wheat cultivars (Altay-2000, Bezostaja-1, Harmankaya-99, and Kate A-1) and six doubled haploid (DH) wheat genotypes are studied to classify wheat cultivars and DH wheat genotypes separately. In the classification stage, feature vectors constructed from measured characters namely, kernel weight, diameter, hardness, and moisture are applied to well-known classifiers such as Common Vector Approach (CVA), Support Vector Machines (SVM) and K-Nearest Neighbor (KNN). Satisfactory results especially for the training set are obtained from the experimental studies. Classification results are compared with single linkage hierarchical cluster (SLHC) analysis, which is the most widely used in breeding studies. Recognition of clustered genotypes in all three classification methods and dendrograms present similar results. The SVM model is found to be outperformed over other methods for studied characters and could therefore effectively be utilized for characterizing, classifying and/or identifying the wheat genotypes.

Efficient Production of Dried Whole Peanut Fruits Based on Infrared Assisted Spouted Bed Drying.

The present study is designed to evaluate the effect of infrared assisted spouted bed drying (IR-SBD) on the product quality and energy consumption of whole peanut fruits (including peanut kernels and shells). The dehydration of whole peanuts by means of hot-air drying (HD) and infrared drying (ID) were used as the control groups, and the drying characteristics, energy consumption, microstructure, porosity, hardness and fatty acid content were compared. The results showed that, compared to HD and ID, IR-SBD could reduce the drying time by 40% and 33%, respectively, and reduced energy consumption by 66% and 32%, respectively. During the drying process, the structures of both the peanut shells and peanut kernels underwent significant deformation; specifically, the porosity gradually increased gradually. The maximum porosity value was obtained by the samples dried by means of IR-SBD. Under the three drying conditions, the hardness of the peanut shells first decreased and then increased, while the hardness of the peanut kernels showed a trend of first increasing, then decreasing and finally increasing. Compared to the fresh whole peanuts, the IR-SBD dried samples exhibited a 4.07% decrease in fatty acid. This study shows that IR-SBD is a suitable application for the dehydration process of whole peanuts for the purposes of achieving high-efficiency and -quality production in the industrial sector.

Registration of ten soft red winter waxy wheat germplasm lines

AbstractWaxy wheat carries null alleles at the three Wx loci encoding the granule‐bound starch synthase I and produces endosperm starch composed of mostly amylopectin with less than 5% amylose. The USDA‐ARS developed and released 10 soft red winter (SRW) waxy wheat germplasm lines, SWQL‐K‐ABD‐1, SWQL‐K‐ABD‐2, SWQL‐K‐ABD‐3, SWQL‐K‐ABD‐4, SWQL‐K‐ABD‐5, SWQL‐W‐ABD‐1, SWQL‐W‐ABD‐2, SWQL‐W‐ABD‐3, SWQL‐W‐ABD‐4, SWQL‐W‐ABD‐5 (Reg. no. GP‐1061 to Reg. no. GP‐1070, PI 698615 to PI 698624), by the introgression of the null alleles at the Wx loci from a soft spring waxy wheat germplasm to two SRW wheat cultivars adapted to the eastern region of the United States. Ten waxy wheat germplasm lines were selected from BC4 or BC5 derivatives of the SRW wheat cultivars ‘Kristy’ and ‘Wilson’ (99ID490/5*Kristy and 99ID490/6*Wilson). The kernel hardness and starch amylose content of 10 SRW waxy wheat germplasm lines ranged from 34.1 to 63.1 and 2.5–7.2%, respectively, while those of wild types and SRW wheat parents carrying the functional alleles at the three Wx loci ranged from 33.9 to 60.4 and 26.8–27.0%, respectively. The starch of the waxy wheat germplasm lines exhibited a lower pasting temperature, higher peak viscosity, and lower setback value than the corresponding wild‐type wheat starch. These waxy wheat germplasm lines would be useful for the development of SRW wheat cultivars carrying different null alleles at the Wx loci that are adapted to the eastern region of the United States.

Performance Analysis and Quality Evaluation of Wheat Storage in Horizontal Silo Bags.

Wheat still suffers from the problem of traditional storage methods, limited storage capacity, and a high percentage of losses in terms of quantity and quality. Hermetic silo bags are economical and alternative technique to the traditional storage methods. Ten horizontal plastic silos with the capacity of 200 tons/silo were tested and evaluated for eight months of wheat storage. The evaluations included grain bulk temperature, CO2 concentration, fungal and microbial count, insect count, grain moisture content, 1000-grain weight, falling number, and protein content. The results showed that the stored wheat quality was maintained without any significant difference during the storage period in terms of 1000-grain weight, grain moisture content, and falling number, while there were slight changes in protein content and kernel hardness with a decrease of 5.5% and 4.6% at the end of the storage period. There were no statistically significant differences at the sampling location along the length of the storage silos, which confirms the homogeneity of the internal conditions of the examined silo. The grain bulk temperature inside the silos was always lower than the surrounding ambient air temperature. The higher concentration of carbon dioxide inside the silos during the storage period led to a decrease in fungal and microbial count and the presence of dead insects at the end of the storage period.

Physical and hydration properties of specialty floury and sweet maize kernels subjected to pan and microwave toasting

The three main underutilized maize types from the Andean region have specialty floury and sweet kernels to make entire ready-to-eat maize by toasting in a pan until a golden brown surface color. The study aims to characterize these maize kernels before and after pan and microwave toasting. The initial moisture content for the raw kernel condition was the same (14.06 ± 0.13 g/100 g) to ensure data reliability by maize types and toasting conditions. The toasting conditions generated kernel expansions studied through the geometric, gravimetric, surface color, instrumental texture, milling average particle size, and hydration properties. Innate to maize types, the color properties (L*, a*, b*, C*, h*, and ΔE*) demonstrated that the toasted kernels developed a comparable range of surface color by the effect of pan and microwave toasting conditions (P ≥ 0.05). Large kernel sizes, low kernel hardness, and small average particle size ascribed to the endosperm softness were the main properties that characterize floury maize. High color differences, high water-soluble index, low density, high kernel hardness, and large average particle size confirmed the sugary-vitreous fraction in sweet maize. Microwave toasting produced lower remaining moisture content and kernel density, larger kernel size associated with the internal porosity created during toasting, higher water absorption capacity, and swelling power than pan toasting.

Corn kernel hardness, drying temperature and amylase supplementation affect live performance and nutrient utilization of broilers

Drying temperature (DT) of corn can influence its nutritional quality, but whether this is influenced by endosperm hardness is not clear. Two parallel experiments were conducted to investigate the effects of 2 yellow dent corn hybrids with average and hard kernel hardness, dried at 3 temperatures (35, 80, and 120°C), and 2 supplementation levels of an exogenous amylase (0, 133 g/ton of feed) on live performance, starch and protein digestibility, and energy utilization of Ross 708 male broilers. Twelve dietary treatments consisting of a 2 × 3 × 2 factorial arrangement were evaluated using 3-way ANOVA in a randomized complete block design. In Experiment 1, a total of 1,920 male-chicks were randomly allocated to 96 floor pens, whereas 480 day-old chicks were distributed among 96 cages for Experiment 2. At 40 d, interaction effects (P < 0.05) were detected on BWG, FCR, and flock uniformity. Supplementation with exogenous amylase resulted in heavier broilers, better FCR and flock uniformity, only in the diets based on corn dried at 35°C. Additionally, interaction effects were observed on FCR due to kernel hardness and DT (P < 0.01), kernel hardness and amylase supplementation (P < 0.001), and DT and amylase supplementation (P < 0.05). Exogenous amylase addition to the diets based on corn with an average hardness improved FCR up to 2 points (1.49 vs. 1.51 g:g) whereas there was no effect of amylase on FCR of broilers fed diets based on corn with hard endosperm. Total tract retention of starch was increased (P < 0.05) in broilers fed diets based on corn with average kernel hardness compared to hard kernel. Corn dried at 80 and 120°C had up to 1.21% points less starch total tract retention than the one dried at 35°C. Supplementing alpha-amylase resulted in beneficial effects for broiler live performance, energy utilization, and starch total tract digestibility results. Treatment effects on starch characteristics were explored. Corn endosperm hardness, DT and exogenous amylase can influence the live performance of broilers. However, these factors are not independent and so must be manipulated strategically to improve broiler performance.

Determination of hardness for maize kernels based on hyperspectral imaging

In order to realize rapid and non-destructive detection of hardness for maize kernels, a method for quantitative hardness measurement was proposed based on hyperspectral imaging technology. Firstly, the regression model of hardness and moisture content was established. Then, based on reflectance hyperspectral imaging at wavelengths within 399.75–1005.80 nm, the prediction model of the moisture content was studied by the partial least squares regression (PLSR) based on the characteristic wavelengths, which was selected through successive projection algorithm (SPA). Finally, the hardness prediction model was validated by combing the prediction model of moisture content with the regression model of hardness. The coefficient of determination (R2), the root mean square error (RMSE) the ratio of performance-to-deviation (RPD) and the ratio of error range (RER) of hardness prediction were 0.912, 17.76 MPa, 3.41 and 14, respectively. Therefore, this study provided a method for rapid and non-destructive detection of hardness of maize kernels.

Changes in the physical, chemical, and sensory properties from three native corn landraces from Chiapas using two nixtamalization times

The objective of this study was to investigate the variation in physical, chemical, and sensory properties of tortillas when using two nixtamalization cooking times for three native corn landraces with different kernel hardness levels. When Olotón and Comiteco races are cooked with lime for 60 min, tortillas were softer and rolled better. In contrast, when Tuxpeño was nixtamalized for 30 min tortillas were less prone to breaking. Starch gelatinization is the main factor responsible for textural changes, although retrogradation may also be involved. Structural composition of grains affects thermal and rheological properties and, consequently, the texture of tortillas. Textural properties (tension, rollability, and elasticity) of tortillas are affected by the type of endosperm (hard and soft), whereas kernel hardness correlated only with tortilla tension. Chemical composition correlated well with kernel shape, starch thermal (enthalpy) and rheological properties. Protein affected tortilla elasticity, firmness, and smoothness. Fat and carbohydrate were negatively correlated with nixtamal aroma but protein was positively correlated. Crude fiber correlated negatively with tortilla smoothness, and corn-aroma. Even though the perception of aroma, flavor, smoothness was related to corn landrace, cooking time also exerted an effect. A longer nixtamalization cooking time usually reduces the intensity of tortilla sensory properties like corn and nixtamal aromas.

Combined selection of Gpc-B1 and Glu-B1 locus encoding the Bx7OE subunit for improving end-use quality of hard white wheat

Wheat in Canada is classified into nine different market classes based on attributes that impact end-use functionality. The Canada Western Hard White Spring (CWHWS) class was created in 2001 to diversify wheat production. The quality requirements of the CWHWS class demand strong gluten properties but lower grain protein (GP) content levels compared to the premium CWRS class. Generally, GP and grain yield are negatively correlated, so a reduction in GP would allow CWHWS cultivars to express greater yield potential. However, lowering GP can result in weaker gluten strength. This study investigated the combined use of Gpc-B1 and Bx7OE to increase GP while maintaining the dough strength in hard white wheat lines. Additionally, the effects of these introgressions on agronomic traits (grain yield, days to heading, days to maturity, plant height, test weight, and thousand kernel weight) were evaluated. Seven populations (each comprising 40 RILs, all varying for presence of Bx7OE, and five populations carrying all possible combinations of Gpc-B1 and Bx7OE) were developed using marker-assisted selection and elite cultivars or advanced breeding lines as parents and tested in three field environments in Saskatchewan, Canada. End-use quality was measured on grain (protein content, kernel hardness), and flour (protein, ash, protein loss, color, and farinograph). Results from our study showed a 0.8–1.1% increase in GP content relative to CWHWS cultivars (used as checks in the study) and dough strength properties similar to CWRS cultivar ‘CDC Teal’ (representing uppermost limit of dough strength in CWRS class at the time). Except for a slight increase in plant height (still comparable to elite cultivars), no deleterious effects on agronomic or other quality traits were observed. We conclude that combined selection of Gpc-B1 DIC with Bx7OE is effective in developing CWHWS lines with a desirable end-use quality.

Variation among sorghum genotypes for reduction in popping caused by threshing-induced kernel damage

ABSTRACT Interest has increased in pop sorghum (Sorghum bicolor (L.) Moench) as an alternative to popcorn as an ingredient in snack foods and as a confectionary snack per se. However, studies on the effect of sorghum genotype, agronomic production and grain processing on popping quality are limited and this has hindered the development of sorghum hybrids specifically for popping. This study assessed the effects of sorghum genotypes, threshing methods, environments and their interactions on sorghum popping quality. Grain from six sorghum genotypes previously documented to have good popping quality was produced in two Texas environments and was threshed using five methods which were expected to cause varying levels of kernel damage. Popping quality, measured as popping efficiency, expansion ratio and flake size was influenced primarily by threshing method, sorghum genotype and to a lesser extent by environment and the genotype × threshing method interaction. The results herein indicate that threshing methods can significantly reduce popping quality and that sorghum genotypes differ in their inclination to threshing-induced kernel damage. Based on these results, popping quality in sorghum is optimized by selecting genotypes for high popping quality and threshing the grain using a method that inflicts minimal damage to the kernel. Abbreviations: ER, Expansion Ration; FS, Flake Size; KHI, Kernel Hardness Index; PE, Popping Efficiency; TKW, Thousand Kernel Weight; UPK, Un-popped Kernels

Novel Loci for Kernel Hardness Appeared as a Response to Heat and Combined Heat-Drought Conditions in Wheat Harboring Aegilops tauschii Diversity

Kernel hardness influences the milling and baking quality of wheat. Stress environments such as heat and combined heat-drought can produce harder kernels, thereby affecting the overall wheat quality. Beside puroindoline genes that are known to determine hardness, other QTLs contribute to the hardness. These QTLs, especially under stress conditions, need extensive research. Moreover, understanding the modification or stabilization of hardness under stress condition and the relationship with stress tolerance will facilitate the selection of superior lines that maintain both high yield and quality even under the stress environment. Therefore, in the current work, we aimed to identify the genetic loci and marker trait associations (MTAs) that contributes for hardness under optimum conditions in Japan, and heat and combined heat-drought (HD) conditions in Sudan. We used a panel of multiple synthetic derivatives (MSD) having diverse Aegilops tauschii genome segments and investigated the association between hardness stabilization and stress tolerance. Under stress conditions, we observed that less reduction of kernel weight is associated with either low change or stable kernel hardness. We identified 47 markers associated with hardness under all conditions; the D genome was the main contributor. For the first time, we found a significant association with hardness under stress conditions on chromosome 4D. We dissected several candidate genes associated with the change of hardness under stress conditions. Our results will improve the understanding of the genetic factors that affect wheat hardness stability.

The study of collection durum winter wheat samples according to grain quality in the Rostov region

The success of any agricultural crop breeding, including winter durum wheat primarily depends on the initial material at the breeder’s disposal, its value, and the degree of study. The purpose of the current study was to evaluate collection samples of winter durum wheat according to quality indicators and to select the best ones for use in breeding programs. In the Rostov region there were studied 159 winter durum wheat samples of different ecological and geographical origin according to grain quality (protein percentage, gluten content, amount of carotenoid pigments, kernel hardness, nature weight). The winter durum wheat samples had a high protein percentage and belonged to the 1-st quality class. According to gluten content in grain there were identified 17 (10.7%) samples. The following samples had the maximum values of trait ‘SDS-sedimentation’: ‘588/15’ (Russia) with 50 ml; ‘SAHINBEY’ (Turkey), ‘SARI BUGDAY 2’ (Turkey), ‘543/15’ (Russia) with 49 ml; ‘ANKARA 98’ (Turkey) with 48 ml. The following 43 winter durum wheat samples (more than 85%) had large kernel hardness in the trial: ‘663/17’, ‘1121/12’, ‘Novinka 4’, ‘Alena’ (Russia), ‘C1252’ (Turkey), ‘SN TURK MI 82-83 90 / GUTROS-2’, ‘DF 28.82.84 / DAB-18’, ‘P 1290493 // HUI // AV79’ (Mexico), ‘K-61869’ (Moldova). Over the years of study, a large amount of carotenoid pigments was identified in the following samples: ‘Novinka 4’ with 705 μg /%, ‘535/17’ with 689 μg /%, ‘543/15’ with 664 μg /% (Russia), ‘OSU-3880001 / 4AOS / SNIP / 3 / MEDIUM / KIF // SAPI’ with 704 μg /% (Mexico), ‘Winter Gold’ with 697 μg /% (Germany). According to the complex of qualitative indicators, there were identified 5 winter durum wheat samples, which are recommended to be included in the breeding programs of the Rostov region.

Characterising corn grain using infrared imaging and spectroscopic techniques: a review

Corn is the largest cultivated grain crop in the world and the need to characterize corn grains based on various quality parameters is becoming essential as the demand for corn is increasing continuously in various end product applications. The conventional methods like visual inspection and analytical techniques involves sample destruction and are either subjective or time-consuming resulting in a growing requirement for the development of non-destructive techniques for a rapid and accurate determination of corn grain constituents and contaminants. This paper reviews the potential of infrared (IR) based imaging and spectroscopic techniques to determine quality parameters of corn grains, and their opportunities to incorporate in the supply chain of corn-based agro-industries. The variety and hardness of corn grains could be efficiently identified through the near infrared (NIR) hyperspectral imaging with accuracies ranging from 80 to 95% and 60 to 85%, respectively. IR imaging techniques determined the oil content of corn grains with standard error ranging between 0.7 and 1.3%. The detection of fungal infestations and mycotoxins in corn grains were widely studied using NIR, short-wave infrared (SWIR) and fluorescence hyperspectral imaging techniques with accuracies ranging from 75 to 98% and 70 to 97%, respectively. These techniques showed a better accuracy for infestations and variety classification (85–90%) and kernel hardness (60–65%) when used in the reflectance operational mode and proved effective for both single and bulk kernel analysis.

Comparative Study on Kernel Quality and Chemical Composition of Ancient and Modern Wheat Species: Einkorn, Emmer, Spelt and Hard Red Spring Wheat.

Hulled wheat species are often used as whole grains in processing, and have been attracting attention in the last 20 years in the food industry. Whole wheat flour of hulled wheat can be used in the food industry for value addition. This study was conducted to evaluate the kernel quality and chemical composition of the whole grain flour of hulled wheats as a preliminary approach to use these species for value addition. The experimental design was separate, randomized complete block designs for einkorn, emmer, and spelt, with four field replicates. According to the results, significant differences (p < 0.05) were observed in kernel quality traits, such as test weight, 1000 kernel weight, and kernel hardness, compared to hard red spring wheat. The results of the chemical composition revealed that hulled wheats were characterized by significantly lower (p < 0.05) protein and higher (p < 0.05) crude fat contents compared to whole wheat flour of hard red spring wheat. Among hulled wheats, total dietary fiber content was highest in emmer, followed by einkorn and spelt. In conclusion, the whole wheat flour of einkorn, emmer, and spelt used in this study differ from hard red spring wheat in their kernel quality and chemical composition.

The effects of drought after anthesis on the grain quality of bread wheat depend on drought severity and drought resistance of the variety

The quality responses of two resistant (Mufitbey, Gun 91), two moderately resistant (Sonmez 2001, Gerek 79), two moderately sensitive (Cetinel 2000, Bereket), and two sensitive (Kirik, Bezostaja 1) bread wheat varieties to drought after anthesis were investigated in field experiments conducted in irrigated and drought conditions during the 2011–2012 and 2012–2013 seasons in Erzurum, Turkey. In drought conditions, for the 2011–2012 and 2012–2013 seasons, the highest grain yield was obtained from the Mufitbey variety, the highest protein content from Kirik and Mufitbey, the highest wet gluten content from Kirik and Gun 91, and the highest sedimentation volume from Mufitbey and Bereket, respectively. Drought stress decreased the grain yield, 1000-kernel weight, test weight, and kernel hardness but increased grain ash content in both years, compared with irrigated conditions. Protein content, wet gluten content, and sedimentation volume were increased by drought stress in 2011–2012, but decreased in 2012–2013. The environmental factors had a greater effect on the variations of quality traits than genetic factors. The influence of drought after anthesis on quality traits was primarily dependent on stress severity. The results suggest that moderate drought stress enhances the grain quality traits of wheat, but severe drought stress reduces its quality. The quality response of a wheat variety to drought stress is related to its drought resistance, and drought-resistant varieties can maintain quality characteristics under moderate stress conditions.

Genetic analysis of end‐use quality traits in wheat

AbstractWheat (Triticum aestivum L.) is a major cereal food crop in the world. End‐use quality improvement is a major objective in wheat breeding programs. ‘Tiger’ is a hard white winter wheat cultivar with excellent bread baking qualities. The objective of this study was to identify the genetic loci underlying the quality traits in Tiger. A doubled‐haploid (DH) population derived from a cross between Tiger and ‘Danby’ was grown in two environments. A total of 17 quality traits together with grain yield (GY) and stripe rust (Puccinia striiformis f. sp. Tritici) were evaluated. The population was genotyped using single nucleotide polymorphism (SNP) markers generated through genotyping‐by‐sequencing (GBS). A linkage map was constructed with 1,507 GBS‐SNP markers that distributed over all 21 chromosomes. Most traits in this study showed normal or approximately normal distributions. Composite interval mapping analysis revealed a total of 72 quantitative trait loci (QTL), 67 for quality traits that were dispersed on all chromosomes except 3D, 5D, 6A, and 7A. Among the 67 QTL, some were novel QTL that have not been reported previously. Although many QTL were only significant in one environment, six genomic regions on chromosomes 1B, 1D, 2D, 5BL, 6B, and 6DL harbored major QTL for several important quality traits including kernel hardness (KH), grain and flour protein content (GPC, FPC), flour yield (FY), mix time (MT), mixing tolerance (MTOL), loaf volume (LV), and loaf volume regression (LVReg). At these major loci, Danby contributed favorable alleles for KH, GPC and FPC, while Tiger contributed favorable alleles for the other traits. The findings in this study will be useful for the genetic improvement of bread‐making quality in wheat.

Porosity and hardness of long-grain Brown rice kernels in relation to their chemical compositions

Rice kernel hardness is an important characteristic to the rice industry because of the greater economic value of whole kernels over brokens. Rice hardness may be weakened by increased porosity, i.e., void spaces formed from loose interaction between chemical components like starch, proteins and lipids. The objective of this study was to elucidate the impacts of rice proteins and lipids on porosity and hardness via heat treatment and solvent extraction. Brown rice kernels of similar thickness from four cultivars with varying protein and lipid contents were subjected to protein denaturation by heat treatment and/or lipid removal by hexane extraction and then characterized for protein solubility, residual lipids, porosity and breaking force. The results show that although porosity is generally negatively correlated with kernel hardness, porosity was primarily influenced by the quantity of proteins and lipids, whereas kernel hardness was primarily affected by their compositions. The continuity of the protein-starch matrix was the dominant factor that governed kernel hardness. This matrix is proposed to be strengthened by an increase in glutelin content and a decrease in non-polar lipids. This study demonstrates the importance of chemical composition on kernel hardness and elucidates the relationship between porosity and breaking force in rice kernels.

Carotenoid profiles in maize genotypes with contrasting kernel hardness

Kernel hardness is commonly related to total maize (Zea mays L.) carotenoid concentration. Based on the specific interactions between carotenoids and hardness related zeins, we tested the hypothesis that hardness is associated with the ability to store different carotenoids. Carotenoid profiles and flour color were measured in 13 flint and 5 dent temperate commercial hybrids, with known differential hardness and dry milling quality. They were grown in two environments during one season in Argentina. Significant genotype and environmental differences (p < 0.05) were found in all analyzed kernel hardness traits and total carotenoid concentration (11.85–28.68 mg kg−1). Kernel type (flint, dent) showed significant differences in the concentration and proportion of specific carotenoids. Flint genotypes had higher β-branch carotenoids (zeaxanthin, β-cryptoxanthin, and β-carotene), while dented hybrids had higher α-branch carotenoids (lutein, α-cryptoxanthin, and α-carotene). On average flint kernels had twice as much provitamin A concentration than dent ones. This had a direct impact on kernel flour color, flints yielded more saturated orange-colored flours and dents light-yellow colored flours. Our results support the concept that kernel hardness is an important driver for carotenoid profiles in yellow and orange temperate maize genotypes.