Kernel weight is a vital trait for selecting high-yielding wheat in breeding programs. We evaluated the thousand-kernel weight (TKW), test weight (TW), grain length (GL), grain width (GW), grain thickness (GT), and grain roundness (GR) of 41 Korean winter wheat cultivars over a period of 4 years. Correlation analyses revealed that TKW was positively correlated with GL (r=0.76***), GW (r=0.85***), and GT (r=0.84***), whereas TW was negatively correlated with GL (r=-0.38*) and GT (r=-0.31*). Allelic variation was analyzed for 13 kernel weight-related genes/loci (TaCwi-A1, TaCWI-4A, TaCWI-5D, TaGW2-6A, TaTGW6-A1, TaTGW-7A, TaGS1a, TaSus1-7A, TaSus1-7B, TaSus2-2B, TaCKX6-D1, TaCKX6a02-D1, and TaSnRk2.3). Significant associations between the allelic variation and kernel traits were identified in TaCWI-4A (TW, GL, and GR), TaCWI-5D (TKW), TaGW2-6A (TKW, GL, GW, and GT), TaSus2-2B (TKW, GL, GW, and GT), and TaGS1a (TW). In contrast, we detected no significant association between the allelic variation of TaCwi-A1, TaTGW6-A1, TaSus1-7A, and TaSus1-7B and variations in kernel traits. Also, TaTGW-7A, TaCKX6-D1, TaCKX6a02-D1, and TaSnRK2.3 were found to be monomorphic. The four loci TaCWI-4A, TaCWI-5D, TaGW2-6A, and TaSus2-2B showed significant phenotypic differences, a totalof 10 different haplotypes (AC1-AC10) were observed at four loci among the Korean wheat cultivars. Cultivars with the AC1 haplotype exhibited significantly higher TKW than those with the AC8 haplotype, which comprises alleles for high TKW at all four loci, indicating that additional loci controlling kernel weight might be present in the high TKW cultivars.

AbstractStem rust is a major wheat disease caused by the fungus Puccinia graminis f. sp. tritici (Pgt). Occurring mainly in warm and humid climates, stem rust has generally been considered less prevalent than leaf rust (P. triticina) and stripe rust (P. striiformis f. sp. tritici). However, a highly virulent stem rust race, Ug99, appeared in Uganda in 1998 and has devastated wheat production throughout Africa and the Middle East. As damage caused by the Ug99 lineage and other newly diverging stem rust races continues to increase, extensive research on wheat breeding and genetics to enhance stem rust resistance has been conducted internationally. Among the 60 stem rust resistance genes reported thus far, 11 (Sr13, Sr21, Sr22, Sr33, Sr35, Sr45, Sr46, Sr50, Sr55, Sr57, and Sr60) have been cloned. New resistance sources have been sought by screening diverse wheat germplasms through international collaborations. Such efforts are urgently required in Korea to address the increasing threat of stem rust epidemics. Furthermore, major Pgt races in the Korean peninsula need to be pathotyped. This information can be used to screen major wheat cultivars, breeding lines, and landraces to identify effective resistance sources. Previously reported stem rust resistance genes should also be introduced and pyramided into the genetic background of Korean wheat breeding populations via available molecular markers. Finally, research capacity in molecular genetics and genomics needs to be strengthened to enable the identification of new stem rust resistance genes and the development of precise molecular markers.

AbstractExtensive research has been conducted in wheat to improve genetic resistance to rust, a major disease that deteriorates wheat yield and quality worldwide. Leaf rust caused by Puccinia triticina is the most prevalent among the three major wheat rust diseases (leaf, stripe, and stem rust) globally and is adapted to a wide range of climates. Approximately 80 genes for leaf rust resistance have been reported, and six (Lr1, Lr10, Lr21, Lr22a, Lr34, and Lr67) have been cloned. Among these cloned genes, Lr34/Yr18/Sr57/Pm38 and Lr67/Yr46/Sr55/Pm46 are of special interest for breeding programs, as they provide pleiotropic resistance to stripe rust, stem rust, and powdery mildew as well as leaf rust. In Korea, knowledge on wheat breeding and genetics for rust resistance is insufficient, as agronomic measures have mainly been used to avoid rust. Therefore, an extensive research program to address the increasing threat of rust epidemics due to climate change is urgently required. Major Korean wheat cultivars, breeding lines, and landraces should be screened for leaf rust resistance. Diverse germplasms also need be introduced through international collaborations to broaden the genetic background for resistance. It is equally important to characterize the distribution of different leaf rust races in Korea and respond to changes in pathogen populations by using effective resistance genes in breeding programs. Research on molecular genetics and genomics needs to be furthered to identify new leaf rust resistance genes and develop efficient molecular markers.

Stripe rust (or yellow rust) caused by Puccinia striiformis f. sp. tritici is the major wheat disease responsible for deteriorating global wheat yield and quality. Although stripe rust appears to be prevalent mainly in temperate areas, new races adapting to high temperature have recently appeared in warmer areas, such as Australia, the Middle East, and Africa, increasing the threat to global food security. Among the approximately 80 reported genes for stripe rust resistance, six (Yr5, Yr7, Yr15, Yr18, Yr36, Yr46) have been cloned. Stripe rust resistance genes are generally classified into race-specific (or all-stage) and non-race-specific (or high temperature adult plant) resistance genes. While resistance conferred by most race-specific genes are overcome by the appearance of new pathogen races within few years, non-race-specific genes, such as Yr18, Yr36, and Yr46, provide more durable resistance and are often stable for several decades. Yr18/Lr34/Sr57/Pm38 and Yr46/Lr67/Sr55/Pm46 are especially useful in breeding as they confer resistance to leaf rust, stem rust, and powdery mildew as well as stripe rust. Unlike the extensive global research efforts, few studies have been conducted in Korea regarding breeding and genetics for stripe rust resistance. To prevent damage by stripe rust in advance, it is important to monitor the changes in major pathogen races in Korea, evaluate major wheat breeding lines and landraces for stripe rust resistance by establishing an efficient screening system, and introduce new germplasm with various resistance genes. Reinforcing wheat molecular genetics and genomics capacity is also important to enable identification of new stripe rust resistance genes and efficient transfer of the novel genes into elite wheat cultivars using molecular markers.

An advanced F₈ population was derived from a cross between the hard wheat cultivar “Keumkang” carrying Pinb-D1b and the soft wheat cultivar “Olgeuru” carrying Pinb-D1a. A breeding line named “Hetero”, which exhibited the heterozygous-like Pinb-D1a/Pinb-D1b genotype, was selected by sequence analysis and KASP (Kompetitive Allele Specific PCR) assay. Physicochemical and processing characteristics of flour were tested in the Hetero line and compared with the two parental cultivars for two years. Hetero display a Glu-1 composition similar to Keumkang and a Glu-3 composition intermediate between Keumkang and Olgeuru. Contrary to the expectation that Hetero carrying the Pinb-D1a/Pinb-D1b genotype would exhibit an intermediate phenotype between the two parents, its overall flour physicochemical characteristics were more similar to Keumkang than to Olgeuru. The flour yield of Hetero (71.6%) was lower than that of Keumkang (74.5%). However, the flour particle size (73.3 μm) and damaged starch content (4.6%) of Hetero were similar to those of Keumkang (71.9 μm and 4.5%). The protein content (16.5%) and sodium dodecyl sulfate-sedimentation volume (72.8 mL) of Hetero were higher than those of Keumkang (14.0% and 57.5 mL) and Olgeuru (11.4% and 45.5 mL). The mixograph water absorption (68.7%) and mixing tolerance (17.7 mm) values of Hetero were higher than those of Keumkang (65.6% and 15.9 mm) with the same mixing time of 3.9 min. The bread loaf volume of Hetero was lower than that of Keumkang (866.7 vs. 894.7 mL). The cooked noodles hardness of Hetero was higher than that of Keumkang (5.9 vs. 4.7 N).

The
objective
of this study was to identify quantitative trait loci (QTL) of spike length by association analysis with 94 doubled haploid wheat lines derived from Keumkang and Olgeuru. Days to heading date, culm length, spike length, and kernels per spike were evaluated in 2017 and 2018 in upland conditions. Culm length and spike length were biased short culm length and spike length (skewness=0.2 and 1.5, respectively). Kernel number per spike was biased low kernel number per spike (skewness=0.8). A genetic map was constructed with 170 microsatellite marker loci. One QTL was detected for spike length. The QTL on chromosome 4A, qSL-1 was detected by Xwmc283 and Xbarc327 explained 44.3% of the phenotypic variation. The QTL was applied to validate the relationship between genotypes of QTL and 29 Korean wheat cultivars grown for nine years under upland conditions. Korean wheat cultivars were classified into 5 types based on the combination of the two SSR markers. In Korean wheat cultivars, genotype b at Xbarc327, which was homozygous to Keumkang, had a shorter spike length (7.48 cm) than genotype c, which was different from the genotypes of Keumkang and Olgeuru, (8.45 cm). The two Korean wheat cultivars with genotypes ac at Xwmc283 and Xbarc327 had longer spike length (8.45 cm) than genotypes ba and bb (<7.42 cm).

Association analysis was conducted to identify quantitative trait locus (QTL) of yield potential traits, days to heading date, culm length, spike length and kernels per spike in the genetic mapping population (94 F₁₀ recombinant inbred line) produced from a cross between two Korean wheat cultivars, Taejoong which has a large kernel number line, a longer spike length, and a higher kernel number per spike and Keumkang. Yield potential traits, days to heading date, culm length, spike length and kernels per spike were evaluated in 2017 and 2018 under upland conditions. Days to heading date were biased toward late heading date (skewness=-0.3), and spike length was biased toward short spike length (skewness=0.7). A genetic map was constructed with 57 microsatellite marker loci and two QTLs were detected for spike length. The first QTL on chromosome 2A, qSL-1 was detected by Xcfd5 and Xpsp3050 and explained 20.7% of phenotypic variation. The second QTL on chromosome 5B, qSL-2 was detected by Xwmc656 and Xwmc415 and explained 40.8% of phenotypic variation. These QTLs were applied to validate the relationships between genotypes of QTLs and 29 Korean wheat cultivars cultivated for nine years, from 2010 to 2018. The Korean wheat cultivars were classified into 6 types according to the genotypes of Xcfd5-Xpsp3050 and Xwmc656-Xwmc415. The same genotypes as Keumkang showed a higher frequency and shorter spike length than that of Taejoong in Korean wheat cultivars.

Starch properties of 32 Korean barley cultivars (Hordeum vulgare L.) were evaluated to improve the Korean barley breeding program. The average amylose content of non-waxy barley cultivars was approximately 3.5 times higher than that of waxy barley cultivars. Furthermore, non-waxy barley cultivars showed lower damaged starch content, water retention capacity, swelling volume, swelling power, and peak viscosity than waxy barley cultivars, while they showed bigger average starch granule size and higher final viscosity. Among Korean barley cultivars, the amylose content showed a positive correlation with damaged starch content, water retention capacity, swelling volume and power, and peak viscosity, while showing a negative correlation with pasting temperature and final viscosity. Among non-waxy barley cultivars, the amylose content showed a positive correlation with damaged starch content, but correlation with swelling power, peak viscosity, pasting temperature, and final viscosity was negative. Among waxy barley cultivars, the amylose content showed negative correlation with peak viscosity. There were positive correlations between swelling volume and peak viscosity among Korean barley and waxy barley cultivars. Also, there were positive correlations between swelling power and peak viscosity among Korean barley and non-waxy barley cultivars. Principal Components Analysis revealed that amylose content and peak viscosity are the main factors affecting starch properties of Korean non-waxy barley cultivars, and Korean non-waxy barley cultivars can be classified into two groups with these two factors. Water retention capacity and peak viscosity are the main factors affecting starch properties of waxy barley cultivars and classify them into two groups. The starch properties of Korean barley cultivars demonstrated in this study are useful to improve end-use quality for processed foods using barley. In addition, the continuous qualitative evaluation of barley is very important for the Korean barley breeding program.

The flour physiochemical properties and end-use quality of wheat were evaluated to identify the effect of high temperature (HT) during grain maturation. HT caused a decrease in the width and thickness of grains. However, HT did not affect the grain weight, volume, length, test weight and 1,000-kernel weight in Korean wheat cultivars. Although HT marginally affected the general flour physiochemical properties and gluten composition, the effects were not significant. Based on the results of the evaluation of end-use quality, the effect of HT on the end-use quality was not significant. Nevertheless, the allelic composition was related to the quantity and quality of grain under HT conditions. In Korean wheat cultivars containing Glu-D1d and -D1f alleles, the 1,000-kernel weight was decreased by HT. In addition, Glu-D1f was more sensitive to HT than was Glu-D1d. The proportion of the y-type high-molecular-weight glutenin subunits (HMW-GSs) was decreased by HT in Korean wheat cultivars containing the Glu-A1ab allele, and was increased in cultivars containing the Glu-B3d allele. Furthermore, the proportions of gliadin and low-molecular-weight glutenin subunits (LMW-GSs) were decreased by HT in Korean wheat cultivars containing Glu-A1ab or Glu-B3ahi alleles.

Hexaploid wheat (common wheat/bread wheat) is one of the most important cereal crops in the world and a model for research of an allopolyploid plant with a large, highly repetitive genome. In the heritability of agronomic traits, variation in gene presence/absence plays an important role. However, there have been relatively few studies on the variation in gene presence/absence in crop species, including common wheat. Recently, a reference genome sequence of common wheat has been fully annotated and published. In addition, advanced next-generation sequencing (NGS) technology provides high quality genome sequences with continually decreasing NGS prices, thereby dawning full-scale wheat functional genomic studies in other crops as well as common wheat, in spite of their large and complex genomes. In this review, we provide information about the available tools and methodologies for wheat functional genomics research supported by NGS technology. The use of the NGS and functional genomics technology is expected to be a powerful strategy to select elite lines for a number of germplasms.

Molecular markers of doubled-haploid (DH) and long spike Korean wheat cultivar populations were evaluated to improve the yield potential of Korean wheat breeding programs by improving the tiller numbers. In Korean wheat cultivars, the tiller number was affected more by vernalization (Vrn) and photoperiod (Ppd) than by tiller inhibition gene (tin) and fertile tiller inhibition gene (ftin). Also, it was negatively correlated with the yield. In DH lines, the tiller number was significantly affected by neither the tiller inhibition genes nor Vrn and Ppd. Additionally, it was not significantly correlated with the yield. However, the adaptability of both SSR markers, Xgpw2206 and Xgwm247, was higher in the DH lines than in the other populations. In the long spike population, the tiller number differed according to the Ppd-D1 allele, affecting the yield. In this study, genes and molecular markers related to the tiller number, as described in previous studies, might be difficult to use to evaluate the tiller number and yield of the Korean wheat population. Hence, continuous study is necessary to develop molecular markers suitable for improving the tiller number and yield of Korean wheat cultivars.

Yellow alkaline noodles were prepared with various Korean wheat cultivars including different protein and amylose contents and made from two types of noodle machines. Korean food companies and restaurants generally used noodle machine made in Korea, whereas research institutes mainly practiced with noodle machine made in Japan. Noodle dough sheet from Korean machine showed 5% higher water absorption and 30 min shorter resting period than the noodle dough from Japanese machine because of the difference of size and weight of roller in two types of the machines. In 15 Korean wheat cultivars, thickness of noodle dough sheet was positively correlated with protein content and mixograph water absorption regardless of both types of the machines. Cooked noodles from Korean machine showed higher hardness and lower springiness than noodles from Japanese noodle machine, but difference in cohesiveness of cooked noodles was not found between two different noodle machines. In the three Korean wheat cultivars with different protein content, thickness of noodle dough sheet was also positively correlated with protein content, SDS sedimentation volume and mixing time of mixograph in both types of the machines. The more protein content increased, the more hardness of cooked noodles increased regardless of both types of the machines. However, springiness and cohesiveness of cooked noodles were not significantly correlated with protein content. In waxy and partial waxy wheat cultivars, lightness of noodle dough sheet from Korean noodle machine positively correlated with amylose content. Amylose content and setback in pasting properties were positively correlated with hardness, springiness, and cohesiveness of cooked noodles while both damaged starch and breakdown were negatively correlated with those.

Mixolab is suitable to evaluate mixograph and farinograph for testing dough rheology and amylopgraph for properties of starch pasting with a view to analyze protein and starch quality at the same time. Mixolab analysis revealed that water absorption and dough development time of Korean wheat cultivars were similar to it of soft wheats and flour while dough stability and protein weakening of Korean wheat cultivars were similar to it of hard wheat and strong flour. Also, starch properties of Korean wheat cultivars showed similar properties of hard wheats. There was a significantly positive correlation between mixolab and mixograph in the water absorption of dough, whereas no correlation was observed between them in dough development time and stability. Furthermore, maximum viscosity of starch and breakdown in amylopgraph were correlated to stabilities of pasting and cooking and setback in mixolab. Resultantly, in mixolab, properties of dough and protein highly and positively correlated to loaf volume, hardness of noodles, and size of cookies i.e. diameter. Moreover, positive correlation was identified between viscoelasticity of noodles and properties of protein, pasting, and setback in mixolab.

This study was executed to establish a basis of evaluation of starch properties of Korean wheat cultivars e.g. damaged starch, swelling, and pasting properties for Korean wheat breeding program. Damaged starch is critical evaluation factor for flour milling related industry because it influences water absorption and color of dough for processing quality and preference of end-use products. The present results revealed that there was significantly high positive correlation between the results of damaged starch analysis by amperometric (SD-matic) and enzymatic (Megazyme assay) methods. Evaluation of damaged starch must be considered as one factor to evaluate properties of starch due to its accuracy and a stable efficiency for the wheat breeding program. Properties of swelling and pasting of dough were important for cooking time and texture. Nevertheless, it was impossible to evaluate starch extracted from flour in the wheat breeding program i.e. small amount of flour or small number of spikes Comparison of results of evaluation of properties of swelling and pasting with starch or flour, the evaluation using flour positively correlated with the other evaluation using starch. In addition, swelling evaluation must be considered to apply for the wheat breeding program because the result of evaluation of swelling property, which possible to evaluate with low efficiency, and the quantity of a sample is highly under positive correlation with paste peak viscosity. In the future, studies using NIR (Near Infrared) analysis must be necessary to evaluate starch properties with grains in early generation lines for improvement of wheat breeding program.