Peter W. Gous

QTL associated with barley (Hordeum vulgare) feed quality traits measured through in situ digestion

Barley (Hordeum vulgare) is a major feed source for the intensive livestock industry. Competitiveness against other cereal grains depends largely on the price per unit of expressed feed quality. The traits which contribute to feed quality in barley are largely quantitative in nature but little is known about their genetic control. A study to identify the quantitative trait loci (QTLs) associated with feed quality was performed using a F6-derived recombinant inbred barley population. Samples from each line were incubated in the rumen of fistulated cattle, recovered, washed and dried for determination of in situ dry matter digestibility. Additionally, both pre- and post-digestion samples were analysed to quantify the content of key quality components relating to acid detergent fibre, total starch and protein. The data was used to identify trait-associated QTLs. Genetic analysis identified significant QTLs on chromosomes 2H, 5H and 7H. Genetic markers linked to these QTL should provide an effective tool for the selection and improvement of feed barley in the future.

Near infrared spectral assessment of stay-green barley genotypes under heat stress

This research aimed to correlate near infrared (NIR) spectral data to physiological and biochemical responses associated with stay-green (SG) traits expression in barley (Hordeum vulgare L.) plants experiencing heat stress. One hundred lines were randomly sub-sampled from a doubled haploid ND24260 × Flagship population consisting of 334 lines. A glasshouse trial with partial sample duplication was grown under terminal heat stress to induce SG expression during grain-fill. The “greenness” of the first leaves under the flag leaf (FL-1) was assessed using NIR spectra. A handheld NIR spectrometer was used to understand and describe some of the physiological and biochemical mechanisms and responses related to SG expression and vice versa which cannot be observed using visual assessments. The use of NIR spectroscopy made it possible both to differentiate between cosmetic (changes in pigments with senescence of spike but no functional chlorophyll affects) and functional (effects on chlorophyll catabolism) SG expression and also to differentiate between the two groups of functional SG. The delayed onset and reduced rate of leaf senescence was linked to plant moisture (water) and plant maturity, which is dependent on the level of SG expression. Variance in the dominant water peak at 1450 nm in the NIR spectrum can be used to differentiate between cosmetic and functional SG expression. The spectral data from the leaves showed significant correlation, with protein (R2 = 0.62) and starch (R2 = 0.70) composition of the grain. The use of NIR spectroscopy allows for the rapid, non-destructive analysis of leaves; enabling multiple traits to be assessed with a single measurement. Understanding the relationship between spectra and SG expression may help develop NIR spectroscopy as a rapid, high-throughput methodology for phenotyping breeding populations, with a view to improve drought resistant barley cultivars.

Drought-Proofing Barley (Hordeum vulgare): The Effects of Stay Green on Starch and Amylose Structure

The identification of the plant physiological trait called stay green (SG) was first identified in sorghum (Sorghum bicolor L. Moench), followed by other cereals, including barley. The effects of this drought tolerance trait on starch biosynthesis, structure, and properties have not been extensively investigated. Using size-exclusion chromatography, the impact of SG expression on starch molecular structure in barley (Hordeum vulgare L.) under heat- and water-stress conditions was examined. Differences were found in total starch and amylose contents within and between the treatments. The chain-length distribution of the amylose in a heat-stressed doubled haploid, ND24260 × Flagship population expressing SG showed significant differences (P < 0.05), whereas no such differences were observed in the water-stressed samples. However, significant differences (P < 0.05) in protein content were observed corresponding to SG expression, with higher levels of SG expression having higher protein content. These differe...