Malting Cultivars Research Articles

Markers polymorphic among malting barley ( Hordeum vulgare L.) cultivars of a narrow gene pool associated with key QTLs.

Barley used for malting is a fine-tuned organism, and it requires breeding within narrow gene pools for realistic cultivar enhancement. Significant phenotypic advance within such narrow gene pools has been achieved and the necessary genetic variability for breeding progress has been documented, but it was not well understood. This study was conducted to further characterize detectable genetic variability present within a select set of four closely related malting barley cultivars using three types of molecular markers: RFLP, PCR-RAPD and AFLP. The markers that identified polymorphism among the select malting cultivars tended to link with each other and to map in chromosomal regions associated with quantitative trait loci (QTLs) for agronomic and malting quality traits that differed among the four cultivars. Although RFLPs identified the least amount of polymorphism, the differences detected by the RFLPs best fit the chronology of the cultivars. These results indicate that a large amount of the genetic variability necessary for cultivar improvement may have originally been present in the breeding gene pool, but does not rule out de novo variation. Study of the populations from crosses within this narrow germplasm is needed to further elucidate the basis of the phenotypic variability found among these select barley cultivars.

Grain weight and malting quality in barley as affected by brief periods of increased spike temperature under field conditions

High temperature is usually one of the most important stresses during grain filling affecting both yield and quality in barley crops. In the present study, an attempt was made to assess in the field the effects of short periods of high temperature, using transparent boxes covering only the spikes, with thermostatically controlled electric resistance for increasing the temperature. Treatments consisted of 2 malting cultivars and 5 heat treatments of high temperatures (8�C above the environmental temperature for 6 h/day for 5 consecutive days) over different periods during grain filling. Final grain weight was reduced by 2–14%, depending on the timing of heat stress and the genotype. There was a significant increase in grain nitrogen percentage in both cultivars, and grain β-glucans decreased with high temperatures in Logan and were unchanged in Beka. The resulting malt extract was reduced with exposure to high temperatures, depending on the cultivar, implying that even mild heat stress may change malting performance.

Transformation of barley scutellum protoplasts: regeneration of fertile transgenic plants.

A system for barley transformation via polyethyleneglycol-mediated DNA uptake into protoplasts isolated directly from scutella and the regeneration of transgenic plants is reported. Scutellum protoplasts (cv. Clipper, an Australian malting cultivar) were co-transformed with plasmids Act 1-DGUS, containing the marker uidA gene, and pCaIneo, which contains the selectable marker neomycin phosphotransferase gene. Protoplast-derived calluses were selected on medium containing the antibiotic G418 (25 and 15 mg.l-1) and macroscopic antibiotic resistant colonies were recovered. Fertile plants were regenerated from a callus line and molecular analysis confirmed transgene integration.

THE EFFECT OF CULTIVAR MIXTURES ON MALTING QUALITY IN WINTER BARLEY

A range of winter barley cultivars was grown, either as pure stands or as components of mixtures, in a trial in 1995–96. For malting quality characters, mean values of mixtures did not differ from mean values of the appropriate monocultures, except for decreases in homogeneity, as determined by a fluorescence test of cell wall modification. When disease pressure was modified by fungicide, hot water extract was not significantly altered, although this may have been due to the restriction of malting to grain retained by a 2.5 mm sieve. One mixture, comprised of three related winter malting cultivars, gave higher hot water extracts than its components, as pure stands, with no adverse effects on homogeneity. This was not simply attributable to lower grain nitrogen content.

Genetic and Environmental Variation in Malting and Feed Quality of Barley

Five barley cultivars (Hordeum vulgareL.) covering a wide range in adaptation pattern, row type, growth habit and malting quality were grown in two harvest years at six agro-ecologically contrasting locations across Spain in order to study the occurrence of genotype×environment (GE) interaction for a set of malting and chicken feeding quality parameters. There was no GE interaction for the nutritional and malting characters studied, except in the case of barley protein content. The nutritional characteristics and malt extract yield showed high broad-sense heritabilities. There were significant correlations between most of the malting and feeding characters studied. In particular, extract yield and apparent metabolisable energy, the main malting and feeding characters, showed a high significant correlation. The best malting cultivars were the best feed cultivars over years and locations. Similarly, the poorest feeding cultivars were also the worst for malting, thus there is no contradiction between malting and feeding quality for either breeding or end use.

Identification of Reproducible PCR-RAPD Markers that Enable the Differentiation of Closely Related Six-Rowed Malting Barley (Hordeum VulgareL.) Cultivars

Varietal purity of barley seed and malt lots is important to the malting and brewing industries. This study was conducted to see if a modified polymerase chain reaction (PCR) technique using random DNA primers (PCR-RAPD) could generate repeatable polymorphisms among the closely related six-rowed malting cultivars Morex, Robust, Stander, Excel, and elite breeding line M77. From a total of 80, 30 random 10-mer primers were selected based on their ability to generate reproducible polymorphisms between the cultivars Steptoe and Morex. Bulked DNA isolated from the leaves of 10–12 plants of each cultivar was amplified using the Stoffel fragment of recombinant Thermus aquaticus DNA polymerase and one primer per PCR. Nine of the 30 primers detected repeatable polymorphisms among the malting lines. Each cultivar or line could be distinguished from another with the exception of Stander and M77. The results of six primers were reproduced in a second laboratory. It was concluded that this PCR-RAPD technique could be useful for distinguishing the four six-rowed malting barley cultivars. A faster version of the technique may be required for practical cultivar identification by the barley processing industry.

Variation in starch, protein, and fibre of Canadian barley cultivars

Barley (Hordeum vulgare L.) is a major feed in the Maritime region of Canada, but information on the chemical composition of barley cultivars grown in the Maritimes is lacking. Therefore, a study was undertaken to determine if starch, protein, neutral-detergent fibre (NDF), and acid-detergent fibre (ADF) of barley vary from region to region in Canada and to determine if barley cultivars that originated from Eastern Canada exhibit different chemical composition than those that originated from Western Canada. The chemical composition of two-row and six-row, covered and hulless, and feed and malting cultivars were also compared. Seventy-five cultivars were tested in eight environments (i.e. Charlottetown, Ottawa, Brandon, and Bentley in 1991 and 1992). These cultivars were classified into eight classes in four comparisons: eastern vs. western, two-row vs. six-row, hulless vs. covered, and feed vs. malting. Charlottetown grains were relatively low in protein, high in starch, and intermediate in NDF and ADF in comparison with grains produced at the other three locations. This suggests that more research in cultivar development and crop management is needed to increase the protein concentration of barley in the Maritimes. On average, two-row cultivars contained more starch and less fibre than six-row cultivars. Eastern two-row cultivars contained more protein than western two-row cultivars. As expected, hulless barleys contained more starch and protein, but less fibre than covered barleys. Canadian barley cultivars exhibited considerable variation in chemical composition. The cultivar x environment interaction was much smaller than the cultivar effect. Therefore, it is important to identify barley cultivars with high nutritional quality for use in commercial production. Key words: Barley, Hordeum vulgare L., cultivars, starch, protein, fibre

Effect of the ANT-13 locus (Proanthocyanidin-free) on the Malting Quality and Agronomic Performance of Barley

Proanthocyanidin (ant)-free barley may be used to brew beer with excellent haze stability, but economically competitive ant-free malting cultivars adapted to the western United States have not been developed. Two experimental lines derived from a cross of ANT-13 517 and the cultivar Harrington that were initially selected as ant-free were observed to be segregating for the ant-free character in advanced generations. Reselections (sublines) from these lines were studied to determine the effect of the ant-free character on agronomic performance and malting quality. Ant-free and ant-containing (normal) sublines from the lines 85Y22 and 85Y27 were evaluated in replicated field trials at two locations in two years. The agronomic performance and malting quality of the normal sublines was competitive with Harrington, whereas the ant-free sublines were markedly poorer. However, the ant-free sublines were improved relative to the ANT-13 517 parent. These results indicated that the ant-free character derived from ANT-13 517 is negatively associated with significant determinants of commercial acceptability. Additional hybridization to malting cultivars may break these relationships, and allow the development of commercially acceptable ant-free malting cultivars adapted to the western United States.

Diversity among North American Spring Barley Cultivars Based on Coefficients of Parentage

Maintenance of genetic diversity is an important safeguard against vulnerability to biotic and abiotic stresses. The coefficients of parentage, r, among cultivars computed from known pedigree information can be used as an index of genetic diversity. Because of the emphasis placed on developing barley (Hordeum vulgare L.) cultivars for the malting and brewing industry, it seemed likely that barley may have a narrower gene pool than other crop species where less emphasis has been placed on quality traits. Our objective was to examine the diversity among North American spring barley cultivars and the contribution of major ancestors to the two‐ and six‐rowed barley gene pools using the coefficient of parentage as an index of diversity. Coefficients of parentage were computed for all pairs of 167 spring barley cultivars. Mean r with major ancestors was computed for cultivars categorized by row type and era of release. A cluster analysis, performed on the coefficient of parentage matrix, produced 30 disjoint clusters. The five ancestors with highest mean r with cultivars contributed 45 and 62% of the germplasm to the early and recent two‐rowed cultivars and 52 and 44% of the germplasm pool in the six‐rowed cultivars for the two respective time periods. Mean r within the two‐ and six‐rowed cultivars was 0.11 and 0.10, respectively. Mean r within cultivars increased 180% in the two‐rowed and 36% in the six‐rowed cultivar groups from the early to recent cultivar groups. Cultivar groups formed by the cluster analysis produced mean within‐cluster r values ranging from 0.29 to 0.57. Principal coordinate analysis of the between cluster matrix showed that the two‐ and six‐rowed gene pools are essentially unrelated. Major six‐rowed malting cultivars grouped into two clusters and the major two‐rowed malting cultivars grouped into one cluster. These results show that malting barley cultivars are based on a limited sample of germplasm.

The consequences, for malting quality, of Hordeum laevigatum as a source of mildew resistance in barley breeding

SUMMARYBarley cultivars which include Hordeum laevigatum in their pedigree, have harder endosperms, higher β‐glucan and lower α‐amylase levels than do other cultivars of poor malting quality. Good malting cultivars are characterised by high hot water extracts, soft endosperms, low β‐glucan and high α‐amylase levels. Introgressions of exotic genes for mildew resistance, into breeding populations, may be accompanied by factors adversely affecting malting quality.

Yield improvement in high lysine barley

Twenty-three barley genotypes were grown in field plots and the seed-yield components and seed composition were investigated. Ten malting and feed cultivars and waxy endosperm selection lines had the standard concentration of lysine in their seed protein. The other genotypes were five different natural or induced high-lysine mutants and/or selection lines developed from them. High-lysine lines were lower yielding than the most productive normal lysine cultivars because of a decrease in weight per seed, accompanied by a reduced content of the carbohydrates extractable with dimethyl sulfoxide. Ris� mutant no. 7 was exceptional in having fewer seeds per unit area and a normal carbohydrate content. Within the group of lys 3 homozygotes derived from Ris� no. 1508, the higher yielding lines had more seeds per unit area, higher concentrations of extractable carbohydrates, and lower concentrations of crude protein. Similar trends with yield also occurred among the lines homozygous for the lys gene from Hiproly. The yields of the most productive lys and lys 3 homozygotes approached that of Clipper, the leading Australian malting cultivar, but were 25% lower than that of the most productive feed barley, Cutter. The other mutants, Ris� no. 7, Ris� no. 29 and Clipper 500, were lower yielding than the better lys and lys 3 selections. The possibilities for improving the yield and energy content of the latter two high-lysine types by selection are discussed.