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.

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.