Accumulation of mixed linkage (1 → 3) (1 → 4)-β-d-glucan during grain filling in barley: A vibrational spectroscopy study

The accumulation of mixed linkage barley (1 → 3) (1 → 4)-β-d-glucan (BG) during grain filling at eight stages was studied using standard reference methods and infrared spectroscopy. Two mutant barley genotypes having higher (starch mutant lys5f) and lower (high lysine mutant lys3a) BG content than the normal control Cork were studied. The Cork and lys3a genotypes showed a linear BG accumulation throughout the grain filling to reach a maximum of approximately 6 and 4% BG (w/w) dry matter, respectively. However, lys5f mutant exhibited an exponential increase in BG synthesis to a maximum of approximately 18% BG (w/w) dry matter 30 days after flowering (DAF), seemingly compensating for a decreased synthesis of starch.The spectral information of the barley flour was compared to pure BG spectra and partial least squares regression (PLS) models were constructed for calibration to BG content. Informative regions in the near-infrared (NIR) and the infrared (IR) spectra were identified for separation of temporal and genetic differences. Interval PLS yielded good calibration models to BG (R2 = 0.94 for NIR in the region 1194–1240 nm, whereas the global PLS gave correlations with BG with R2 = 0.92 for IR).