Barley Crosses Research Articles

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.

Genetic analysis of heading date and other agronomic characters in barley (Hordeum vulgare L.)

Genetic analyses of heading date, tiller number, plant height, grain yield, kernel weight, and plump and thin kernels were made in three six-rowed barley crosses (Hordeum vulgare L.) involving four cultivars. Six populations, P1 , P2 , F1 , F2 , BC1 , and BC2 , from each cross were grown and evaluated at Fargo and Prosper, North Dakota, 1982. Parental means within crosses generally were different except for tiller number. Comparison of generation means suggested that late heading was dominant to early, high kernel weight was dominant to low, and kernel plumpness was influenced by additive gene action. The relationship between yield and heading date was not consistent among crosses and positive r values were quite low. It should be possible to select early maturing, high yielding segregates with plump kernels. Heterosis over the mid-parent was quite similar among crosses for heading date, but there was no heterosis over the high parent. Inbreeding depression was fairly constant for heading date, but was less consistent for yield. The lack of uniformity for estimates of inbreeding depression can be related to environmental variation and to its influence on type of gene action. The ratio of additive to dominance variance was inconsistent among crosses for heading date and yield. These data suggest selection for these characters should be delayed past the F 2 generation. Broad sense heritabilities for heading date ranged from 42 to 86%. Values obtained for grain yield were more consistent among broad sense than narrow sense estimates. Genetic advance estimates were low due to lack of additive variance.

Identification of a QTL decreasing yield in barley linked to Mlo powdery mildew resistance

A molecular marker map, including Mlo mildew resistance, of the spring barley cross Derkado (Mlo-resistant) × B83-12/21/5 (Mlo-susceptible) was scanned for yield QTLs to determine whether the association of Mlo resistance with reduced yield was due to linkage or pleiotropy. Over the mapped portion of the genome of the cross, the QTL with the greatest effect upon yield was located within a 22 cM region between mlo and the simple sequence repeat HVM67 on chromosome 4(4H). The association of Mlo resistance with lower yield was therefore due to a repulsion linkage. Analysis of yield component characters revealed QTL alleles for reduced grain number and earlier heading date in the same region, also associated with Mlo resistance. Genotyping of a range of cultivars and sources of Mlo resistance with the HVM67 simple sequence repeat showed that the Derkado HVM67 allele was rare as it was found only in one other cultivar and four land-races or sources of disease resistance. Grannenlose Zweizeilige, the source, and Salome, the carrier of Mlo resistance in Derkado, have the same HVM67 genotype, although Salome was a mixture of two genotypes. The entire mlo-HVM67 chromosomal segment from Grannenlose Zweizeilige is therefore thought to have been transmitted to Derkado, possibly through joint selection for Mlo resistance and early heading. L92, synonym EP79, was another source of Mlo resistance with the same HVM67 allele as Derkado but recombination must have occurred during the breeding of Atem as it possesses a different HVM67 allele which is present in all the other Mlo sources and cultivars surveyed. Abbreviations: GN, grains per main stem ear; HD, heading date; MSTGW, thousand grain weight derived from GN and MSY; MSY, yield of grain on the main stem; PY, yield of grain from the whole plot; sCIM, simplified compound interval mapping; SIM, simple interval mapping; SPY, single plant yield; S-SAP, sequence-specific amplification polymorphism; TGW, thousand grain weight derived from bulk of plot seed; TN, number of fertile stems per plant.

Genetic analysis of a two-row × six-row cross of barley using doubled-haploid lines

A study was conducted on a two-row/six-row cross of barley to (1) determine the yield potential, (2) detect epistasis and genetic correlations, (3) estimate the heritabilities of six agronomic traits, and (4) study the effect of the V locus on the agronomic traits in the barley cross. The effects of five other marker loci (Re2, s, R, Est1, and Est5) on the six agronomic traits were also studied. One hundred and ninety doubled-haploid (DH) lines were derived from a ‘Leger’/CI9831 cross using the bulbosum method. The DH lines and the two parents were tested for grain yield, test weight, seed weight, plant height, lodging, and heading/maturity at two locations in Eastern Canada in 1993. Additive×additive epistasis and genetic correlations were detected for some of the agronomic traits. Many of the heritability estimates were high; however, significant progress in yield improvement would be difficult to achieve because of a low mean yield of the DH lines. Under the growing conditions in Eastern Canada, six-row lines outyielded two-row by 20–27%. Six-row lines, however, were associated with low test weight, low seed weight, and severe lodging. Some two-row lines yielded higher than the two-row parent CI9831, but none of the six-row lines yielded higher than the six-row parent ‘Leger’. The R, s, and Est5 loci were associated with the six agronomic traits, but the Est1 locus was apparently not associated with the agronomic traits. The effect of the Re2 locus was probably due to its close linkage with the V locus. Further studies are needed to determine if superior six-row lines can be developed from two-row/six-row crosses.

Mapping of QTL controlling NIR predicted hot water extract and grain nitrogen content in a spring barley cross using marker‐regression

AbstractA restriction fragment length polymorphism (RFLP) map constructed from 99 doubled haploid lines of a cross between two spring barley varieties (‘;Blenheim’בKym’) was used to map QTL controlling hot water extract and grain nitrogen content (predicted by analysis with near‐infrared reflectance spectroscopy). Eight QTL affecting predicted hot water extract were identified by a marker‐regression approach. The largest effects were found on chromosomes 3HL, associated with the denso dwarfing gene which is present in‘Blenheim’and conferred poorer predicted hot water extract quality, and 4HL. Other QTL were detected on chromosomes IHS. IHL. 2HS, 2HL. 5HL and 6HS. Analysis of single markers by analysis of variance detected an additional effect on chromosome 1H. Eight QTL affecting predicted grain nitrogen content were identified by marker‐regression, on chromosomes 1HS, 1HL. 2HL. 5HS, 6H, 7HS and 7HL. There was also evidence for an additional QTL on chromosome 5HL. The positions of the grain nitrogen content QTL on 5HS and 5HL are comparable to QTL on wheat chromosomes 5A and 5D that affect grain protein content. The denso gene had no detectable effect on grain nitrogen content.

Regions of the Genome That Affect Grain and Malt Quality in a North American Two‐Row Barley Cross

Malting is an important end use of barley (Hordeum vulgare L.). The suitability of barley for malting depends on numerous quality characteristics, all of which are affected by genetic and environmental variation and many of which are inter‐related. Here, our objective was to use genome mapping to improve knowledge about the genetic basis for variation and covariation in grain and malt quality characteristics. Kernel plumpness, kernel weight, grain protein, fine‐grind extract, fine‐coarse difference, soluble protein, extract β‐glucan, extract viscosity, diastatic power, and a‐amylase activity were measured on grain produced in six field environments, from parents and doubledhaploid progeny of a two‐row barley cross, ‘Harrington’/‘TR306’. Quantitative trait loci and QTL × environment interactions were detected by means of 127 mapped markers and two methods of QTL analysis: simple interval mapping (SIM) and simplified composite interval mapping (sCIM). Each trait was affected by two to four primary QTL (those detected using both SIM and sCIM) and similar numbers of secondary QTL (those detected by only one of SIM or sCIM). Together, these QTL explained 21 to 67% of the phenotypic variance per trait. The numbers, effects, and relative positions of these QTL were in concordance with the quantitative trait distributions and with correlations among traits. All chromosomes, except chromosome 2, contained regions with at least one important QTL. Several genomic regions affected multiple traits. Most QTL interacted with environment, but many showed effects consistent enough that they might serve as targets for marker‐assisted selection. There was little similarity in the QTL positions detected here and those detected previously for the same traits in crosses representing other germplasm groups.

Genetic analysis of the components of winterhardiness in barley (Hordeum vulgare L.)

Winterhardiness in cereals is the consequence of a number of complex and interacting components: cold tolerance, vernalization requirement and photoperiod sensitivity. An understanding of the genetic basis of these component traits should allow for more effective selection. Genome map-based analyses hold considerable promise for dissecting complex phenotypes. A 74-point linkage map was developed from one hundred double haploid lines derived from a winter x spring barley cross and used as the basis for quantitative trait locus (QTL) analyses to determine the chromosome location of genes controlling components of winterhardiness. Despite the greater genome coverage provided by the current map, a previously-reported interval on chromosome 7 remains the only region where significant QTL effects for winter survival were detected in this population. QTLs for heading date under 24 h light map to the same region. A QTL for heading date under this photoperiod regime also maps to chromosome 2. A distinct set of QTLs mapping to chromosomes 1, 2, 3 and 5 determined heading date under 8 h light. Patterns of differential QTL expression underscore the complexity of Winterhardiness.

INCUBATION OF BARLEY KERNEL SECTIONS WITH PURIFIED CELL WALL DEGRADING ENZYMES

The effects of purified Trichoderma reesei endo-xylanase, XYN II and endoglucanases, EG I and EG II on the cell walls of embedded barley cross sections were studied. The cell walls were stained with Calcofluor which is specific for (1–3)(1–4)-β-D-glucans (mixed-linked β-glucans) in histochemical applications. Whereas endosperm cell walls remained highly fluorescent after incubation with buffer, the aleurone cell walls were only weakly fluorescent. Both EG I and EG II were effective in degrading the outer endosperm cell walls, but had little or no effect on the inner endosperm and aleurone cell walls. Corresponding sections incubated with XYN II showed highly intensive fluorescence of aleurone cell walls suggesting that the surface of alaurone cell walls contains a high level of xylan which is removed by xylanase treatment exposing a layer rich in mixed linked β-glucans. This indicates that arabinoxylans and β-glucans in the aleurone cell walls of barley exist as separate, macroscopic layers. Xylanase did not have any Influence on the microstructure of endosperm cell walls which are rich in mixed linked β-glucans. However, incubation with EG II after xylanase treatment caused the aleurone cell walls to become very thin.

Genetic studies on net blotch resistance in a barley cross

An investigation was initiated to study the genetics of resistance to three isolates of Pyrenophora teres (WRS102, WRS858, and WRS857), which have been routinely used for screening for net blotch resistance in Canada. The F1, F2, and doubled-haploid lines were derived from a Leger/CI9831 cross of barley (Hordeum vulgare L.). These materials, along with their parents, were inoculated with each of the three isolates at the three-leaf stage in growth chambers. Results showed that resistance to WRS102 was controlled by three recessive genes, resistance to WRS858 by one recessive gene, and resistance to WRS857 by either one dominant gene or two complementary genes. One of the WRS102-resistance genes appeared to be on chromosome 2 and another linked to the WRS858-resistance gene. Resistance to these three isolates was not associated with awn type, esterase 1, and esterase 5. Selection for resistance to WRS102 and WRS858 would be more effective than selection for resistance to WRS857 in a conventional breeding program. Key words: Barley, Hordeum vulgare, net blotch, Pyrenophora teres, haploids

Marker regression mapping of QTL controlling flowering time and plant height in a spring barley (Hordeum vulgare L.) cross

An RFLP map was constructed from 99 doubled haploid lines of a cross between two spring barley varieties (Blenheim × Kym) and used to map quantative trait loci (QTL) controlling ear emergence time and plant height using a marker-regression approach. Three QTL affecting plant height were identified. The largest effect was from the denso dwarfing gene, present in Blenheim, on chromosome 3(3H)L. Two other effects were found, one on 7(5H)L and one on 1(7H)L. The denso gene also had a major effect on ear emergence time. However, eight additional QTL for ear emergence were also identified. Two of these were in regions previously identified as carrying the Sh and Sh2 vernalization response genes, suggesting that allelic variation at these genes may affect ear emergence time in spring barley crosses. Comparisons with maps of related species show conservation and collinearity of markers and genes.

Marker regression mapping of QTL controlling flowering time and plant height in a spring barley (Hordeum vulgare L.) cross

An RFLP map was constructed from 99 doubled haploid lines of a cross between two spring barley varieties (Blenheim × Kym) and used to map quantative trait loci (QTL) controlling ear emergence time and plant height using a marker-regression approach. Three QTL affecting plant height were identified. The largest effect was from the denso dwarfing gene, present in Blenheim, on chromosome 3(3H)L. Two other effects were found, one on 7(5H)L and one on 1(7H)L. The denso gene also had a major effect on ear emergence time. However, eight additional QTL for ear emergence were also identified. Two of these were in regions previously identified as carrying the Sh and Sh2 vernalization response genes, suggesting that allelic variation at these genes may affect ear emergence time in spring barley crosses. Comparisons with maps of related species show conservation and collinearity of markers and genes.

Regions of the Genome that Affect Agronomic Performance in Two‐Row Barley

Quantitative trait locus (QTL) main effects and QTL by environment (QTL × E) interactions for seven agronomic traits (grain yield, days to heading, days to maturity, plant height, lodging severity, kernel weight, and test weight) were investigated in a two‐row barley (Hordeum vulgare L.) cross, Harrington/TR306. A 127‐point base map was constructed from markers (mostly RFLP) scored in 146 random double‐haploid (DH) lines from the Harrington/TR306 cross. Field experiments involving the two parents and 145 random DH lines were grown in 1992 and/or 1993 at 17 locations in North America. Analysis of QTL was based on simple and composite interval mapping. Primary QTL were declared at positions where both methods gave evidence for QTL. The number of primary QTL ranged from three to six per trait, collectively explaining 34 to 52% of the genetic variance. None of these primary QTL showed major effects, but many showed effects that were consistent across environments. The addition of secondary QTL gave models that explained 39 to 80% of the genetic variance. The QTL were dispersed throughout the barley genome and some were detected in regions where QTL have been found in previous studies. Eight chromosome regions contained pleiotropic loci and/or linked clusters of loci that affected multiple traits. One region on chromosome 7 affected all traits except days to heading. This study was an intensive effort to evaluate QTL in a narrow‐base population grown in a large set of environments. The results reveal the types and distributions of QTL effects manipulated by plant breeders and provide opportunities for future testing of marker‐assisted selection.

Quantitative Trait Loci for Germination and Malting Quality Characters in a Spring Barley Cross

Absence of dormancy and good malting quality are significant targets of many barley (Hordeum vulgare L.) breeding programs. Expression of dormancy is strongly affected by the environment, and malting quality assays are expensive. Both groups of characters would therefore be suitable for marker‐assisted selection. The objective of this study was to identify quantitative trait loci (QTL) controlling germination and malting quality characters in a cross between the spring barley genotypes ‘Blenheim’ and E224/3 as an initial step in the development of a marker‐assisted selection scheme. The characters were measured on a random sample of doubled haploid lines from the cross grown in replicated trials each year from 1989 to 1992. The QTL were revealed by regression analysis of the data with marker scores from 120 mapped polymorphic loci. The QTL controlling hot water extract were located on barley Chromosomes 2, 3, and 7. Milling energy was largely controlled by a factor on Chromosome 7, a region also associated with extract viscosity. The denso dwarfing gene on Chromosome 3 was associated with a reduction in grain N but this was found to be a dilution effect as the locus had previously been found to be associated with an increase in grain yield. The germination characters showed little relationship with each other, possibly reflecting different mechanisms of control.

Identification of RAPD markers for common root rot and spot blotch (Cochliobolus sativus) resistance in barley.

The identification of RAPD markers associated with genes for resistance to Cochliobolus sativus in barley would increase the efficiency of gene manipulation by reducing the number of lines that must be evaluated from a resistant by susceptible cross and by allowing selection during the off season. Two barley crosses consisting of resistant and susceptible parent genotypes ('Virden' x 'Ellice' and Fr926-77 x 'Deuce', both 2 row x 6 row crosses) and more than 140 homozygous progeny lines were rated for their reactions in field nurseries to common root rot and in a controlled environment for spot blotch. Putative RAPD markers were identified using bulked segregant analysis followed by individual progeny line analyses. Polymorphisms associated with disease reaction were detected between bulked segregant samples as differences in the band intensity of DNA fragments. The bulked segregant samples were screened against 186 RAPD primers (decamers) using the polymerase chain reaction. For the cross Fr926-77 x 'Deuce', one RAPD marker was obtained that did not segregate as expected but was associated with both diseases. For the cross 'Virden' x 'Ellice', a single RAPD marker was obtained that did not have the expected segregation ratio but was associated with spot blotch reaction. One RAPD marker linked to 2-rowed and 6-rowed spike locus was obtained in each cross, and both the marker and row type were associated with common root rot and spot blotch reactions. For the cross 'Virden' x 'Ellice', a linkage group consisting of three RAPD markers was associated with common root rot and spot blotch reaction. The genes associated with these markers condition significant levels of resistance to C. sativus and may be used to increase the speed and precision of resistance gene manipulation in barley germplasm.

Detection of quantitative trait loci for agronomic, yield, grain and disease characters in spring barley (Hordeum vulgare L.)

Quantitative trait loci (QTLs) have been revealed for characters in a segregating population from a spring barley cross between genotypes adapted to North-West Europe. Transgressive segregation was found for all the characters, which was confirmed by the regular detection of positive and negative QTLs from both parents. A QTL for all the agronomic, yield and grain characters measured except thousand grain weight was found in the region of the denso dwarfing gene locus. There were considerable differences between the location of QTLs found in the present study and those found in previous studies of North American germ plasm, revealing the diversity between the two gene pools. Thirty-one QTLs were detected in more than one environment for the 13 characters studied, although many more were detected in just one environment. Whilst biometrical analyses suggested the presence of epistasis in the genetic control of some characters, there was little evidence of interactions between the QTLs apart from those associated with yield. QTLs of large effect sometimes masked the presence of QTLs of smaller effect.

A barley RFLP map: alignment of three barley maps and comparisons to Gramineae species

Several gene linkage maps have been produced for cultivated barley. We have produced a new linkage map for barley, based on a cross between Hordeum vulgare subsp. spontaneum and Hordeum vulgare subsp. vulgare (Hvs x Hvv), having a higher level of polymorphism than most of the previous barley crosses used for RFLP mapping. Of 133 markers mapped in the Hvs x Hvv F2 population, 69 were previously mapped on other barley maps, and 26 were mapped in rice, maize, or wheat. Two known gene clones were mapped as well as two morphological markers. The distributions of previously mapped markers were compared with their respective barley maps to align the different maps into one consensus map. The distributions of common markers among barley, wheat, rice and maize were also compared, indicating colinear linkage groups among these species.

RFLP mapping of five major genes and eight quantitative trait loci controlling flowering time in a winter × spring barley (Hordeum vulgareL.) cross

A genetic map of 92 RFLP loci and two storage protein loci was made using 94 doubled-haploid lines from a cross between the winter barley variety Igri and the spring variety Triumph. The markers were combined with data from two field experiments (one spring sown and one autumn (fall) sown) and a glasshouse experiment to locate a total of 13 genes (five major genes and eight quantitative trait loci (QTL)) controlling flowering time. Two photoperiod response genes were found; Ppd-H1 on chromosome 2(2H)S regulated flowering time under long days, while Ppd-H2 on chromosome 5(1H)L was detected only under short days. In the field experiments Ppd-H1 strongly affected flowering time from spring and autumn sowings, while Ppd-H2 was detected only in the autumn sowing. The glasshouse experiment also located two vernalization response genes, probably Sh and Sh2, on chromosomes 4(4H)L and 7(5H)L, respectively. The vernalization response genes had little effect on flowering time in the field. Variation in flowering time was also affected by nine additional genes, whose effects were not specifically dependent on photoperiod or vernalization. One was the denso dwarfing gene on chromosome 3(3H)L. The remaining eight were QTLs of smaller effect. One was located on chromosome 2(2H), one on 3(3H), one on 4(4H), one on 7(5H), two on 6(6H), and two on 1(7H). Model fitting showed that the 13 putative genes, and their interactions, could account for all the observed genetical variation from both spring and autumn sowings, giving a complete model for the control of flowering time in this cross.

Genetic analysis of the components of winterhardiness in barley (Hordeum vulgare L.)

Winterhardiness in cereals is the consequence of a number of complex and interacting component characters: cold tolerance, vernalization requirement, and photoperiod sensitivity. An understanding of the genetic basis of these component traits should allow for more-effective selection. Genome map-based analyses hold considerable promise for dissecting complex phenotypes. A 74-point linkage map was developed from 100 doubled haploid lines derived from a winter x spring barley cross and used as the basis for quantitative trait locus (QTL) analyses to determine the chromosome location of genes controlling components of winterhardiness. Despite the greater genome coverage provided by the current map, a previously-reported interval on chromosome 7 remains the only region where significant QTL effects for winter survival were detected in this population. QTLs for growth habit and heading date, under 16 h and 24 h light, map to the same region. A QTL for heading date under these photoperiod regimes also maps to chromosome 2. Contrasting alleles at these loci interact in an epistatic fashion. A distinct set of QTLs mapping to chromosomes 1, 2, 3, and 5 determined heading date under 8 h of light. Under field conditions, all QTLs identified under controlled environment conditions were determinants of heading date. Patterns of differential QTL expression, coupled with additive and additive x additive QTL effects, underscore the complexity of winterhardiness. The presence of unique phenotype combinations in the mapping population suggests that coincident QTLs for heading date and winter survival represent the effects of linkage rather than pleiotropy.

Genetic relationships between reaction to common root rot and yield in the progeny of a barley cross

Genetic relationships between reaction to common root rot and yield in the progeny of a barley cross

Genetic analysis of a photoperiod response gene on the short arm of chromosome 2(2H) of Hordeum vulgare (barley)

RFLP mapping of 94 doubled haploid lines from a winter x spring barley cross (Igri x Triumph) identified a previously undescribed major photoperiod response locus (Ppd-H1) on the short arm of barley chromosome 2(2H). Lines with the Igri allele (winter parent) flowered 10 days earlier under long days in a glasshouse experiment. The Ppd-H1 locus also had a major effect in field experiments, giving differences of 12 days (spring sowing) and 7 days (autumn sowing). The Ppd-H1 locus accounted for 60 per cent of the genetic variation in flowering time in the spring sowing and 46 per cent in the autumn sowing. The most likely location of Ppd-H1 was in the 6 cM interval between the RFLP loci XMWG858 and XpsrB9, 1 cM proximal to XMWG858. The map position of Ppd-H1 suggests that it may be a homoeoallele of the wheat photoperiod response gene Ppdl. Field data also showed that the barley Ppd-H1 locus was associated with highly significant effects on plant height, biomass and yield components which were probably the direct results of the variation in flowering time. Flowering time and other agronomic characters were also significantly affected by an additional developmental rate gene on the same chromosome.