Molecular Mapping and Characterization of Flag Leaf Wax in Wheat (Triticum aestivum L.).

Plant leaf waxes play a role in abiotic and biotic stress tolerance. A fundamental understanding of the molecular and physiological basis of improved adaptation conferred by the presence of leaf cuticular waxes is important to develop stress adapted wheat lines. The objective of this study was to identify QTLs and characterize flag leaf waxes in wheat. We evaluated a set of 120 recombinant inbred line population derived from a cross of Karl 92 and Halberd for 2 years in the greenhouse. Flag leaf wax was characterized at 10 days after pollination via the estimation of the flag leaf wax content, Scanning Electron Microscopy (SEM) imaging of the cuticular layer and leaf surface reflectance. Leaf temperature was also recorded.  The flag leaf wax content and the total reflectance was significantly higher in the Halberd than Karl 92. A wider cuticle layer was observed in Halberd than Karl 92 through SEM imaging. Yield and leaf temperature depression was positively correlated with the flag leaf wax content.  QTL analysis identified 5 QTLs associated with flag leaf wax content.  The QTL on 5D (LOD –3.5) contributed to increased leaf wax content and was present in both the years 2008 and 2009. Another significant QTL on 2A (LOD – 6.5, R2– 0.186) was identified in year 2009. A QTL identified on 1B (LOD-4.7, R2 – 0.12) was related to reduced wax content in both years 2008 and 2009.  Thus we identify genomic regions in wheat that are associated with leaf wax production in wheat and can be further studied for fine mapping purposes.