QTL Mapping of Diffuse Reflectance Indices of Leaves in Hexaploid Bread Wheat (Triticum aestivum L.)

Quantitative trait loci (QTL) mapping of diffuse reflectance indices of laminas in bread wheat (Triticum aestivum L.) has been first performed under controlled conditions of a regulated agroecobiological testing ground in the presence or absence of nitrogen fertilizers. Indices chosen for the study determine a range of important characteristics, such as the content of chlorophylls and anthocyanins, carotenoid/chlorophyll ratio, photochemical activity of the photosynthetic apparatus, light scattering on a lamina, assimilating leaf surface area, and grain productivity. In total, 31 QTLs have been mapped. A significant correlation has been revealed between the introduction of a nitrogen fertilizer and the five of six optical characteristics of the photosynthetic apparatus activity in bread wheat. The only exception is the reflectance index for near-infrared radiation (800 nm), which depends on the structural features of leaf tissues. No statistically significant correlation has been revealed between the thousand-grain weight and spectral characteristics of the diffuse reflectance of the lamina measured at the booting stage. However, a significant correlation between the number of grains formed in the spike of the main stalk and the traits characterizing activity of the photosynthetic apparatus (reflectance indices, leaf area) has been observed. Results of the performed variance, correlation, and QTL analyses confirm each other indicating reliability of the revealed effect of nitrogen nutrition level on the manifestation of the studied reflectance indices in bread wheat under strictly controlled conditions of an agroecobiological testing ground. Application of noninvasive optical methods provides a high-throughput assessment of photosynthetic intensity in plants and, therefore, can be used for efficient selection of promising wheat genotypes with high grain productivity under both controlled and field conditions.