Background: Photosynthesis is the primary energy for biosphere, and is the foundation for life on earth. Leaf color mutations are widely used to study chloroplast structure and development, biosynthesis and metabolism of chlorophyll and plant photosynthesis, such as in rice and maize, with many genes be mapped and cloned. By comparison, there is few researches on the leaf color mutants in wheat. More and more studies have demonstrated that photosynthesis is involved in plant-pathogen interaction, whether leaf color mutations affect plant-pathogen interactions are rarely reported.Results: In this study, a leaf color mutant, NAU31, which has fewer tillers, dwarfed plant and improved powdery mildew resistance was identified from regenerated plant of common wheat cv. Yangmai158. Inheritance analysis of NAU31 showed that the above mutant traits were significantly correlated and controlled by a dominant gene, named Tatyd. Linkage analysis of a mapping population between NAU31 and a synthesized wheat W7984 using SSR markers, the Tatyd was preliminary mapped to 2DS. By BSA and linkage analysis using a 55K wheat SNP array, the Tatyd was fine mapped to the terminal region of 2DS, flanked by markers ZH47 and gwm296 and corresponding to a physical interval of 0.76 Mb. Genome-wide gene expression analysis indicated that the impairing of photosynthesis may be responsible for plant yellowing in NAU31. Photosynthetic physiological analysis showed varied chloroplast inner structure in the mesophyll cells of the mutant, and this may lead to reduced chlorophyll content (chlorophyll “a”, Chlorophyll “b”, total chlorophyll and carotenoid), as well as decreased maximum quantum efficiency of photosystem II (Fv/Fm) and Net photosynthetic rate.Conclusions: A mutant with few-tiller, plant yellowish, dwarfness and improved powdery mildew resistance was identified, and the mutated locus Tatyd was fine mapped to a 0.76 Mb genome region of wheat chromosome 2D. The yellowing trait of NAU31 may be attributed to its reduced photosynthesis ability due to changes of the chloroplast inner structure. The cloning of Tatyd will facilitate dissection of the mechanism involved in chloroplast development of wheat and the regulation of plant development and disease resistance.