VARIATION OF α-AMYLASE, β-AMYLASE, β-GLUCANASE, PULLULANASE, PROTEINASE AND CHITINASE ACTIVITY IN GERMINATED SAMPLES OF THE WILD PROGENITOR OF BARLEY

Variation in barley (1 → 3, 1 → 4)-β-glucan endohydrolases reveals novel allozymes with increased thermostability

Novel barley (1 → 3, 1 → 4)-β-glucan endohydrolases with increased thermostability. Rapid and reliable degradation of (1 → 3, 1 → 4)-β-glucan to produce low viscosity wort is an essential requirement for malting barley. The (1 → 3, 1 → 4)-β-glucan endohyrolases are responsible for the primary hydrolysis of cell wall β-glucan. The variation in β-glucanase genes HvGlb1 and HvGlb2 that encode EI and EII, respectively, were examined in elite and exotic germplasm. Six EI and 14 EII allozymes were identified, and significant variation was found in β-glucanase from Hordeum vulgare ssp. spontaneum (wild barley), the progenitor of modern cultivated barley. Allozymes were examined using prediction methods; the change in Gibbs free energy of the identified amino acid substitutions to predict changes in enzyme stability and homology modelling to examine the structure of the novel allozymes using the existing solved EII structure. Two EI and four EII allozymes in wild barley accessions were predicted to have improved barley β-glucanase thermostability. One novel EII candidate was identified in existing backcross lines with contrasting HvGlb2 alleles from wild barley and cv Flagship. The contrasting alleles in selected near isogenic lines were examined in β-glucanase thermostability analyses. The EII from wild barley exhibited a significant increase in β-glucanase thermostability conferred by the novel HvGlb2 allele. Increased β-glucanase thermostability is heritable and candidates identified in wild barley could improve malting and brewing quality in new varieties.

Detection and verification of malting quality QTLs using wild barley introgression lines

A malting quality quantitative trait locus (QTL) study was conducted using a set of 39 wild barley introgression lines (hereafter abbreviated with S42ILs). Each S42IL harbors a single marker-defined chromosomal segment from the wild barley accession 'ISR 42-8' (Hordeum vulgare ssp. spontaneum) within the genetic background of the elite spring barley cultivar 'Scarlett' (Hordeum vulgare ssp. vulgare). The aim of the study was (1) to verify genetic effects previously identified in the advanced backcross population S42, (2) to detect new QTLs, and (3) to identify S42ILs exhibiting multiple QTL effects. For this, grain samples from field tests in three different environments were subjected to micro malting. Subsequently, a line x phenotype association study was performed with the S42ILs in order to localize putative QTL effects. A QTL was accepted if the trait value of a particular S42IL was significantly (P < 0.05) different from the recurrent parent as a control, either across all tested environments or in a particular environment. For eight malting quality traits, altogether 40 QTLs were localized, among which 35 QTLs (87.5%) were stable across all environments. Six QTLs (15.0%) revealed a trait improving wild barley effect. Out of 36 QTLs detected in a previous advanced backcross QTL study with the parent BC(2)DH population S42, 18 QTLs (50.0%) could be verified with the S42IL set. For the quality parameters alpha-amylase activity and Hartong 45 degrees C, all QTLs assessed in population S42 were verified by S42ILs. In addition, eight new QTL effects and 17 QTLs affecting two newly investigated traits were localized. Two QTL clusters harboring simultaneous effects on eight and six traits, respectively, were mapped to chromosomes 1H and 4H. In future, fine-mapping of these QTL regions will be conducted in order to shed further light on the genetic basis of the most interesting QTLs.

Mutants and duplication in chromosome 7 (syn. 5H) in the barley line HA21: duplications may enhance QTLs and serve to make constant linear cis-heterozygosity

Cytological and linkage data indicate a duplication in the short arm of chromosome 7 (syn. 5H) in the mutant line HA21 (barley, Hordeum vulgare, cv. 'Pirkka'). The associated mutant (ha21) shows a weighted average linkage of 22.1 cM with pld, hitherto an ignored anthocyaninless gene, of cv. Pirkka. Some crosses produce F2 segregants with an exaggerated ha21 phenotype which may represent position effect or increased dosage of the mutant gene through recombination. Compared with cv. Pirkka, HA21 has changes in grain chemistry (alpha- and beta-amylase, beta-glucanase), which may be caused by changed QTL dosage or QTL position effect due to duplication. The use of duplication in creating constant +m/+ m or m+/m+ linear cis-heterozygotes is suggested. Linear cis-heterozygotes may produce stable heterosis or attenuate the undesired effects of drastic mutants.

Allele-dependent barley grain beta-amylase activity

The wild ancestor of cultivated barley, Hordeum vulgare subsp. spontaneum (K. Koch) A. & Gr. (H. spontaneum), is a source of wide genetic diversity, including traits that are important for malting quality. A high beta-amylase trait was previously identified in H. spontaneum strains from Israel, and transferred into the backcross progeny of a cross with the domesticated barley cv Adorra. We have used Southern-blot analysis and beta-amy1 gene characterization to demonstrate that the high beta-amylase trait in the backcross line is co-inherited with the beta-amy1 gene from the H. spontaneum parent. We have analyzed the beta-amy1 gene organization in various domesticated and wild-type barley strains and identified three distinct beta-amy1 alleles. Two of these beta-amy1 alleles were present in modern barley, one of which was specifically found in good malting barley cultivars. The third allele, linked with high grain beta-amylase activity, was found only in a H. spontaneum strain from the Judean foothills in Israel. The sequences of three isolated beta-amy1 alleles are compared. The involvement of specific intron III sequences, in particular a 126-bp palindromic insertion, in the allele-dependent expression of beta-amylase activity in barley grain is proposed.

Polymorphisms in the α-amy1 gene of wild and cultivated barley revealed by the polymerase chain reaction

α-Amylases are the key enzymes involved in the hydrolysis of starch in plants. The polymerase chain reaction (PCR) was used to detect polymorphisms in the length of amplified sequences between the annealing sites of two primers derived from published α-amy1 gene sequences in barley. These two primers (Bsw1 and Bsw7), flanking the promoter region and the first exon, amplified two PCR fragments in barley. One of the amplified products, with the expected length of 820 bp, appeared together with another shorter PCR band of around 750 bp. This 750-bp fragment seems to be derived from an α-amylase gene not reported previously. Both of the PCR products could be amplified from the two-rowed barley varieties tested, including cv Himalaya from which the sequence information was obtained. Five of the six-rowed barley varieties also have the two PCR fragments whereas another two have only the long fragment. These two fragments seem to be unique to barley, neither of them could be amplified from other cereals; for example, wheat, rye or sorghum. These two α-amylase fragments were mapped to the long arm of 6H, the location of the α-amy1 genes, using wheat-barley addition lines. Amplification of genomic DNA from wild barley accessions with primers Bsw1 and Bsw7 indicated that both of the fragments could be present, or the long and short fragments could be present alone. The results also demonstrated that the genes specifying these two fragments could be independent from each other in barley. The conserved banding pattern of these two fragments in the two-rowed barley varieties implies that artificial selection from these genes may have played an important role in the evolution of cultivated barley from wild barley.