QTL analysis of agronomic traits in barley based on the doubled haploid progeny of two elite North American varieties representing different germplasm groups

A better understanding of the genetics of complex traits, such as yield, may be achieved by using molecular tools. This study was conducted to estimate the number, genome location, effect and allele phase of QTLs determining agronomic traits in the two North American malting barley (Hordeum vulgare L.) quality variety standards. Using a doubled haploid population of 140 lines from the cross of two-rowed Harrington×six-rowed Morex, agronomic phenotypic data sets from nine environments, and a 107-marker linkage map, we performed QTL analyses using simple interval mapping and simplified composite interval mapping procedures. Thirty-five QTLs were associated, either across environments or in individual environments, with five grain and agronomic traits (yield, kernel plumpness, test weight, heading date, and plant height). Significant QTL×environment interaction was detected for all traits. These interactions resulted from both changes in the magnitude of response and changes in the sign of the allelic effect. QTLs for multiple traits were coincident. The vrs1 locus on chromosome 2 (2H), which determines inflorescence row type, was coincident with the largest-effect QTL determining four traits (yield, kernel plumpness, test weight, and plant height). QTL analyses were also conducted separately for each sub-population (six-rowed and two-rowed). Seven new QTLs were detected in the sub-populations. Positive transgressive segregants were found for all traits, but they were more prevalent in the six-rowed sub-population.QTL analysis should be useful for identifying candidate genes and introgressing favorable alleles between germplasm groups. Received: 18 August 2000 / Accepted: 15 December 2000     

QTL analysis of malting quality in barley based on the doubled-haploid progeny of two elite North American varieties representing different germplasm groups

Characterization of the determinants of economically important phenotypes showing complex inheritance should lead to the more effective use of genetic resources. This study was conducted to determine the number, genome location and effects of QTLs determining malting quality in the two North American barley quality standards. Using a doubled-haploid population of 140 lines from the cross of Harrington×Morex, malting quality phenotype data sets from eight environments, and a 107-marker linkage map, QTL analyses were performed using simple interval mapping and simplified composite interval mapping procedures. Seventeen QTLs were associated with seven grain and malting quality traits (percentage of plump kernels, test weight, grain protein percentage, soluble/total protein ratio, α-amylase activity, diastatic power and malt-extract percentage). QTLs for multiple traits were coincident. The loci controlling inflorescence type [vrs1 on chromosome 2(2H) and int-c on chromosome 4(4H)] were coincident with QTLs affecting all traits except malt-extract percentage. The largest effect QTLs, for the percentage of plump kernels, test weight protein percentage, S/T ratio and diastatic power, were coincident with the vrs1 locus. QTL analyses were conducted separately for each sub-population (six-rowed and two-rowed). Eleven new QTLs were detected in the subpopulations. There were significant interactions between the vrs1 and int-c loci for grain-protein percentage and S/T protein ratio. Results suggest that this mating of two different germplasm groups caused a disruption of the balance of traits. Information on the number, position and effects of QTLs determining components of malting quality may be useful for maintaining specific allele configurations that determine target quality profiles. Received: 28 May 1999 / Accepted: 9 November 1999     

Genetic investigation of contributions of embryo and endosperm genes to malt Kolbach index, alpha-amylase activity and wort nitrogen content in barley

 A genetic model is proposed for the analysis of embryo and endosperm effects as well as GE interaction effects. An investigation of three malting quality traits in grains of seven parents and their F₂s was undertaken in a half-diallel cross of barley (Hordeum distichum L.) over 2 years. The results indicated that the malt Kolbach index (KI), alpha-amylase activity (αAA) and wort soluble nitrogen (Wort-N) are controlled by both embryo genetic effects and endosperm genetic effects. Variance of the endosperm additive effects was obviously larger than that of the embryo additive effects. In the contribution of the embryo genetic effects to variation in malt αAA and Wort-N, the dominance effects were considerably larger than the additive effects. The endosperm dominance effects constituted a major part of the total genetic effect on the KI. Significant endosperm GE interactions were also detected in the malt traits concerned. Endosperm general heritability (h ² _e ) tended to be larger than interaction heritability (h ² _oE or h ² _eE ) for all the traits. Endosperm heterosis was observed to be significantly positive for αAA but negative for Wort-N in the F₂ seed generation. Prediction of main gene effects for seven parents showed that ‘Ganmu 2’ and ‘Supi1’ were suitable parental varieties for malt αAA and Wort-N improvement. Our genetic model for malting quality traits and its application in breeding are discussed. Received: 5 August 1997 / Accepted: 11 September 1997