In situ study of water uptake by the seeds, endosperm and husk of barley using infrared spectroscopy.

Variations in the amount and rates of water uptake influence the seed hydration as well as the modification of the endosperm for industrial uses (e.g., malting). The aim of this study was to investigate and interpret absorption frequencies in the mid infrared (MIR) region associated with water uptake in whole seeds, husk and endosperm of barley seeds during the initial period of soaking in water. Partial least squares (PLS) regression models for the prediction of water uptake in the set of samples yield a coefficient of determination (R(2)) and a standard error in cross validation of 0.75 and 2.57 (% w/w), respectively. The biological implications of this study are that the first stages of germination can be monitored using the information derived from the MIR spectra. These results also demonstrated that whole seeds, endosperm and husk derived from the same variety or genotype have different patterns in the MIR region.

The role of total lipids and fatty acids profile on the water uptake of barley grain during steeping.

Steeping is the first operation of malting and its overall purpose is to increase the water content of the grain, as well as to activate the enzymatic pool in the endosperm. The aim of this study was to evaluate the effects of total lipids content and individual fatty acids on water uptake, by commercial barley varieties. The results from this study showed that unsaturated fatty acids, such as oleic acid (18:1-n9), have a role in controlling water uptake by the barley endosperm during steeping. When partial least squares (PLS) regression was used to relate total lipids, individual fatty acids and water uptake, oleic (18:1-n9) acid had a positive effect, while long chain unsaturated fatty acids such as arachidic (20:0) and lignoceric (24:0) acids had a negative effect on explaining 72% of the total variability in water uptake. Water uptake by the endosperm is just a component of the system that is responsible for the overall malt quality properties and chemical characteristics of a given material. In this context, both total lipids and individual fatty acids have a role on determining malt quality in barley.

A genetic map of 1,000 SSR and DArT markers in a wide barley cross.

A high-density genetic map was developed from an F1-derived doubled haploid population generated from a cross between cultivated barley (Hordeum vulgare) and the subspecies H. vulgare ssp. spontaneum. The map comprises 1,000 loci, amplified using 536 SSR (558 loci) and 442 DArT markers. Of the SSRs, 149 markers (153 loci) were derived from barley ESTs, and 7 from wheat ESTs. A high level of polymorphism ( approximately 70%) was observed, which facilitated the mapping of 197 SSRs for which genetic assignments had not been previously reported. Comparison with a published composite map showed a high level of co-linearity and telomeric coverage on all seven chromosomes. This map provides access to previously unmapped SSRs, improved genome coverage due to the integration of DArT and EST-SSRs and overcomes locus order issues of composite maps constructed from the alignment of several genetic maps.

QTL mapping of chromosomal regions conferring reproductive frost tolerance in barley ( Hordeum vulgare L.).

Spring radiation frost is a major abiotic stress in southern Australia, reducing yield potential and grain quality of barley by damaging sensitive reproductive organs in the latter stages of development. Field-based screening methods were developed, and genetic variation for reproductive frost tolerance was identified. Mapping populations that were segregating for reproductive frost tolerance were screened and significant QTL identified. QTL on chromosome 2HL were identified for frost-induced floret sterility in two different populations at the same genomic location. This QTL was not associated with previously reported developmental or stress-response loci. QTL on chromosome 5HL were identified for frost-induced floret sterility and frost-induced grain damage in all three of the populations studied. The locations of QTL were coincident with previously reported vegetative frost tolerance loci close to the vrn- H1 locus. This locus on chromosome 5HL has now been associated with response to cold stress at both vegetative and reproductive developmental stages in barley. This study will allow reproductive frost tolerance to be seriously pursued as a breeding objective by facilitating a change from difficult phenotypic selection to high-throughput genotypic selection.

Removal of the four C-terminal glycine-rich repeats enhances the thermostability and substrate binding affinity of barley beta-amylase.

Barley beta-amylase undergoes proteolytic cleavage in the C-terminal region after germination. The implication of the cleavage in the enzyme's characteristics is unclear. With purified native beta-amylases from both mature barley grain and germinated barley, we found that the beta-amylase from germinated barley had significantly higher thermostability and substrate binding affinity for starch than that from mature barley grain. To better understand the effect of the proteolytic cleavage on the enzyme's thermostability and substrate binding affinity for starch, recombinant barley beta-amylases with specific deletions at the C-terminal tail were generated. The complete deletion of the four C-terminal glycine-rich repeats significantly increased the enzyme's thermostability, but an incomplete deletion with one repeat remaining did not change the thermostability. Although different C-terminal deletions affect the thermostability differently, they all increased the enzyme's affinity for starch. The possible reasons for the increased thermostability and substrate binding affinity, due to the removal of the four C-terminal glycine-rich repeats, are discussed in terms of the three-dimensional structure of beta-amylase.