Near infrared reflectance spectroscopy as a potential surrogate method forthe analysis of Delta C-13 in mature kernels of durum wheat

Carbon isotope discrimination (Delta C-13) in grain is a potentially useful trait in breeding programs that aim to increase the yield of wheat and oth er cereals. Near infrared reflectance spectroscopy (NIRS) is used in routin e assays to determine grain and flour quality. This study assesses the abil ity of NIRS to predict Delta C-13 in mature kernels of durum wheat. Plants were grown in north-west Syria as this location provided 3 distinct Mediter ranean trials that covered a wide range for Delta C-13 values in grains (fr om about 12.9 parts per thousand to 17.6 parts per thousand). We measured t he spectral reflectance signature between 1100 and 2500 nm in samples from the same flour used in the conventional (i.e. mass spectrometry) determinat ions of Delta C-13. By using principal components regression and partial le ast squares regression (PLSR), a model of the association between conventio nal laboratory analysis and these spectra was produced. Global regressions, which included samples from all 3 trials, and local models, which used sam ples from only one trial, were built and then validated with sample sets no t included in calibration procedures. In global models, strong significant correlations (P < 0.001) were found between NIRS-predicted <Delta>C-13 and measured Delta C-13 values. PLSR gave r(2) values of 0.86 and 0.82 for cali bration and validation sets, respectively. Although less strongly correlate d, all local models selected for a subset of samples with significantly hig her Delta C-13 values. Local models also performed well when selecting samp les from the other 2 trials. The advantages and possible limitations of NIR S are further discussed.