| Barley (Hordeum vulgare L.) is not only the raw materials for malting industry, but also the feeder for animal and food for Tibetan. The production of beer in China has been the largest in the world since 2002. However, plenty of malting barley needs to be imported every year due to less production and poor quality. It is urgent to improve the production and quality for domestic malting barley. The qualities of malting barley are complex and typical quantitative characters controlled by polygene. Both inheritance and environment play important roles on barley quality characters. Significant relationship was found between these quality characters, including promoting and restricting for each other. In this study,185 DH population derived from cross Japanese malting barley Naso Nijo and Chinese malting barley TX9425 were used to analyze the genetic mechanism and relationship between malting qualities. SNP and SSR markers were used to construct the genetic maps and map the QTLs for seed and malting quality. Then function markers closely linked to favorable genes were developed, which provided a foundation for marker assist selection of barley quality. Following were the main results:1). Amylose content (AC) in Naso Nijo was significantly higher than that in TX9424, while amylopectin content (APC), ratio of AC/APC and total starch content (SC) in Naso Nijo all significantly lower than these in TX9425. For the DH population, all the four starch characters had significant differences between DH population. Significant differences were also found between years for the starch characters except for AC. And the effect of AC×year was also significant for SC. The correlation between starch characters was consistent among two years. AC showed positive correlation with SC, but negative correlation with APC and AC/APC. APC showed positive correlation with SC and AC/APC. SC showed negative correlation with AC/APC. The amylose content of 2012 years and 2013 years respectively accord with two linkage complementary major genes model (B-2-7) and two linkage inhibition major genes plus polygenic inheritance model (E-2-9), amylopectin content conform to two linkage dominant epistatic major genes plus additive polygenic inheritance model (E-2-4), the ratio of amylopectin and amylose of 2012 years and 2013 years respectively accord with the two inhibition major gene model (B-1-9) and two overlap major gene model (B-1-8), starch content accord with three major gene plus polygenic inheritance model (G-2). Starch components of barley showed the existences of two or three major model.2). Peak viscosity, trough viscosity, breakdown value, termination viscosity, falling value and pasting time were all significantly higher than these in TX9424, while pasting temperature was significantly lower than that in TX9425. The effects of genotype, year and genotype xyear were significant for all pasting properties. The correlation between pasting properties was consistent among two years. Most pasting properties showed significantly positive correlation with each other except for pasting temperature and pasting time. AC was positive with peak viscosity, breakdown value and termination viscosity but negative with pasting temperature. APC was positive with pasting temperature. SC was positive with pasting temperature but negative with breakdown value and termination viscosity.3). Malting extract, a-amino nitrogen, soluble nitrogen, kolbach index, diastatic power and malting score were significantly higher than these in TX9424, while wort viscosity and total nitrogen were significantly lower than these in TX9424. All malting qualities were significantly different on effects of genotype, year and genotype x year except that wort viscosity and diastatic power were not significantly different on effects of genotype×year. Malting score also showed positive correlation with seeds quality AC, peak viscosity and trough viscosity.4).569 SNP and 58 SSR markers were mapped on genetic maps, which covered the genetic distance of 986.7cM. Then QTLs for barley quality were analyzed using Windows QTL Cartographer V2.5 software in each year. Six QTLs for starch quality were identified in two years and two of them were reproducible. QAC-5H explained 6.84% and 6.91% of phenotype variation in 2012 and 2013 year, and QAPC-3H-2 explained 5.75% and 6.02% of phenotype variation in 2012 and 2013 year. Twenty-two QTLs for starch characters were identified in two years and six of them were reproducible, which were QPV-5H, QTV-7H, QBD-7H-2, QFV-4H, QTTPV-4H and QTTPV-5H. QTTPV-5H explained the largest phenotype variation with R2 of 12.80% and 10.88% in 2012 and 2013 year. Forty-one QTLs for malting quality were identified in two years and twelve of them were reproducible, which were QME-3H-2, QVS-3H, QAN-1H-1, QAN-5H, QTN-3H-2, QSN-1H-1, QSN-1H-2, QSN-5H, QSN-7H-2, QKI-3H, QKI-5H-2 and QDP-3H-1. The QTL QAN-5H, QSN-5H and QKI-5H-2 all explained over 10% of phenotype variation. QKI-5H-2 explained the largest phenotype variation with R2 of 28.73% and 15.46% in 2012 and 2013 year.5). Based on Morex public sequence database, synteny analysis was conducted according to rice chromosomes. There were 81 and 225 genes in rice intervals synteny to QTL QAC-5H and QAPC-3H-2, respectively. Gts-1 gene was considered as the candidate gene for AC and ATPase gene was considered as the candidate gene for APC. There was a SNP at 602bp in Gts-1 between two parents, leading to a Lys substitution with Glu, affecting the β-folding of protein tertiary structure which is closely coupled to its function. And there was a SNP at 467bp in ATPase gene. DH population with Gts-1 gene had significantly higher amylose content in both years.DH population with QTL QAPC-3H had significantly lower amylopectin conten in two years, comparing the average content 40.72% to 36.15% and 39.46% to 35.78%, respectively... |
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