RELATIONSHIP OF GLAUCOUSNESS AND EPICUTICULAR WAX QUANTITY OF WHEAT

The quantity of epicuticular waxes of crops such as wheat (Triticum sp p.) influences water relations, wettability by pesticide sprays, and r esistance to insects and diseases. Determination of wax quantity for s election purposes is difficult, whereas visual selection for degree of glaucousness would be simple. However, the relationship between wax q uantity and glaucousness is unclear. Common (T. aestivum L.) and durum (T. turgidum L. var. durum) inbred genotypes, nonglaucous/glaucous is ogenics, and segregating families were grown under field conditions ne ar Swift Current, Saskatchewan. Waxes were extracted with petroleum et her and determined gravimetrically for flag leaf sheaths, blades or sp ikes sampled 1-2 wk post-anthesis, and compared with visual glaucousne ss ratings. Wax quantity was generally lower for nonglaucous than for glaucous genotypes, but there was some overlap of observed quantities for the two groups. On average, wax was 44% greater for glaucous than for nonglaucous durum genotypes, and 32% greater for glaucous than for nonglaucous common wheat genotypes. Visual selection for glaucousness is thus likely to produce differences in epicuticular wax quantity, b ut the quantity difference would have to be verified at advanced gener ations.