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

This research aimed to correlate near infrared (MR) spectral data to physiological and biochemical responses associated with stay-green (SO) traits expression in barley (Hordeum vulgare L.) plants experiencing heat stress. One hundred Lines were randomly sub-sampled from a doubled haploid ND24260 x 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 (R-2 = 0.62) and starch (R-2 = 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.