The outermost wax layer protects plants from such as drought, phytophagous insects, pathogens, solar radiation, and freezing temperatures. One of the most important roles of the cuticle is 
to limit transpiration to reduce water loss and this provides a key mechanism for plant survival in water-limited environments, such as deserts, high mountains, saline-alkali lands, and coastal ecosystems. Worldwide, bread wheat is one of the most important food sources for human beings. The wheat leaf, stem and, in some cases, spike surfaces are coated with cuticular waxes that confer a glaucousness characteristic. Physiological studies in wheat by Johnson et al. and Richards et al. showed that glaucousness reduces transpiration and increased water use efficiency. More recently Zhang et al. demonstrated that glaucousness reduced cuticle permeability in the terms of nonstomatal water loss and chlorophyll efflux. Bread wheat cultivars with non-glaucousness traits exhibit significant yield increases with reduced solar radiation losses that enable continued photosynthesis during the grain filling period, and the trait may also provide resistance to aphids. Glaucousness and non-glaucousness are parallel variations in wheat and its relatives. Classical SAR131675 molecular weight Genetic studies have shown that both the glaucousness and the non-glaucousness stem and leaf phenotypes are controlled by two sets of loci; the wax production genes W1 and W2 and the wax inhibitor genes Iw1 and Iw2, respectively. The Iw1 and Iw2 non-glaucousness loci function as inhibitors of the W1 and W2 glaucousness loci, and could also inhibit other wax production genes in the wax pathway. Genetic analyses have indicated that the W1 wax production gene and the Iw1 wax inhibition gene are located on chromosome 2BS with a genetic distance of 2 cM. However, W2 and Iw2 are separated on chromosome 2DS where the W2 locus is close to the centromere. Two loci, Iw3 and Ws, were also reported conditioning wax on spikes in wheat. Non-glaucousness locus Iw3 was mapped on chromosome 1BS and the Ws gene on the short arm of chromosome 1AS is responsible for glaucous spikes. In addition to these genes, a major QTL that accounts for up to 52 percent of the flag leaf glaucousness variation has been detected in a doubled-haploid population. Molecular mapping and cloning of genes controlling epicuticular wax in wheat is of great interests for understanding interactions between none-glaucousness genes and glaucousness genes, as well as their effects on yield, and biotic and abiotic stresses. The Iw1 locus originating in wild emmer is closely linked to the Xcdo456 RFLP marker at the end of chromosome arm 2BS. Liu et al. found that the Iw1 locus is 18.77 cM away from the powdery mildew resistance gene MlIW170 on chromosome 2BS. Simmonds et al. also reported that the Iw1 gene conditioning a non-glaucousness phenotype maps to chromosome 2BS. In a tetraploid wheat background, Yoshiya et al., have found that W1 is linked to Iw1Dic, but the relationship between Iw1 and Iw1Dic was not confirmed, and in an Ae. tauschii F2 segregating population, the non-glaucous locus Iw2 was located on chromosome 2DS. In another report, the dominant non-glaucous locus Iw3672 derived from a AZ 960 synthetic hexaploid wheat also mapped on 2DS by simple sequence repeat and expressed sequence tag markers. During development of a wheat genetic linkage map with a doubled haploid population derived from the TA4152�C60 synthetic hexaploid wheat line and the ND495 common wheat line, Chu et al., also located a dominant wax inhibitor Iw2 on chromosome 2DS. Compared to studies on the Iw nonglaucousness loci, little work has been done to map the W glaucousness loci in wheat, aside from W1, which has been mapped on chromosome 2BS and the Ws glaucous spike allele that is located at the terminus of chromosome 1AS.