NIRS analysis reveals temporal trends in the chemical composition of French bread wheat accessions cultivated between 1800 and 2000

To improve the quality of wheat, information is needed on the genetic resources available and on the structure and evolution of its diversity. Whole spectra obtained by Near Infrared Reflectance Spectroscopy (NIRS) were used to follow the evolution of four groups of wheat components (proteins, minerals, fatty acids and carbohydrates) in a set of 539 French bread wheat accessions released and cultivated during the last two centuries in France. Specific wavelengths in the NIRS spectra revealed that, on an average, variations in α-helix and β-turn protein conformations were opposed; specific wavelengths for some amino acids indicated that gliadins decreased while glutenins increased. The content of magnesium and potassium increased, and fatty acids changed from poly-unsaturated to mono-unsaturated and saturated types. Soluble carbohydrates decreased, probably due to negative selection for amylolytic activity and positive selection for grain yield. These results are discussed and linked with the different selection events and changes in breeding targets over the two last centuries. Whole NIRS spectra provided a useful tool for describing the global evolution of the chemical composition of the grain of French wheat.