Technical Abstract: Plant architecture includes branching (tillering) pattern, plant height, leaf shape and angle, and the structure of reproductive organs. These structures are of major agronomic importance as they determine the adaptability of a plant to various methods of cultivation, which in turn influence harvest index and grain yield. We detected a recessive mutant from the aromatic cultivar 'Khao Dawk Mali 105' (KDM105), which exhibits a plant architecture with shorter height, shorter and more erect leaves and panicles than the wild type. The short and erect rice (ser) mutation was induced by 30 kilorads of gamma ray irradiation. The ser had 104.6 degree smaller angle of the flag leaf to the panicle culm, compared to the KDM105 wild type. For the leaf below the flag leaf, the ser mutant was 46.2 degrees more erect than the wild type. The length of the flag, 2nd and 3rd leaf of the ser was 21.8, 24.4 and 16.3 cm shorter than the wild type, respectively. Plant height as measured from soil surface to flag leaf tip was reduced 43.5 cm, and the height measured from soil to panicle tip was reduced 28.5 cm in the ser in comparison with its wild type. Characterization of the ser, wild type and their reciprocal F1s confirmed these changes with no cytoplasmic effect. The ser was identical to the wild type and their F1 hybrid for 11 SSR markers over 7 chromosomes, indicating a true mutation. In the F2 generation, a ratio of 3 wild type: 1 ser resulted in a Chi Square of 0.067 (p=0.795) for a single gene segregation, demonstrating a recessive mutation. The ser will be an ideal material for studying pleiotropy and metabolic functions.